Merge remote-tracking branch 'aosp/upstream-master' into merge

Also: add meta files

Bug: 213332338
Test: TH
Change-Id: Ib83f22bb728cf459fbebf5af7f8bfdcb42387b70

91 files changed, 5424 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..91f681f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,9 @@
+.DS_Store
+.gradle/
+.idea/
+build/
+
+*.iml
+*.pro
+bintray.properties
+local.properties
diff --git a/CHANGELOG b/CHANGELOG
new file mode 100644
index 0000000..489a2f1
--- /dev/null
+++ b/CHANGELOG
@@ -0,0 +1,31 @@
+1.3.1:
+  - Migrate from android.support to androidx library
+  - Add a default close() method
+  - Support for long arrays as parameters
+  - Use newer Notification methods for Android O and above
+  - Various minor fixes
+
+1.3.0:
+  - Support for RPC scheduling
+  - Support for custom converters of non-primitive types
+  - Support for JSONArray parsing of parameters
+  - Various minor fixes and cleanups
+
+1.2.0:
+  - New startup protocol:
+    - Snippet protocol is now versionated and reported to instrumentation output
+    - Snippet startup progress can now be monitored via output
+    - Server port can now be allocated on device and reported via output
+  - Improvements to help() output
+  - Allow close() methods to throw exceptions
+
+1.1.0:
+  - Support for asynchronous RPCs
+  - Add an optional annotation to cause RPCs to be invoked on the main thread
+  - Log tags are now configurable in the manifest
+
+1.0.1:
+  - Ignore regular JUnit tests linked into the snippet lib
+  - Improved exception handling and reporting
+
+1.0.0: Initial release of Mobly Snippet Lib with some examples
diff --git a/CONTRIBUTING b/CONTRIBUTING
new file mode 100644
index 0000000..1a09deb
--- /dev/null
+++ b/CONTRIBUTING
@@ -0,0 +1,27 @@
+Want to contribute? Great! First, read this page (including the small print at the end).
+
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+(https://cla.developers.google.com/about/google-corporate).
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..d645695
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,202 @@
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diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..ee44373
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,17 @@
+name: "mobly-snippet-lib"
+description:
+    "Mobly Snippet Lib is a library for triggering device-side code from host-side Mobly tests."
+
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://github.com/google/mobly-snippet-lib"
+  }
+  url {
+    type: GIT
+    value: "https://github.com/google/mobly-snippet-lib"
+  }
+  version: "1.3.1"
+  last_upgrade_date { year: 2022 month: 1 day: 4 }
+  license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..0854447
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,3 @@
+jdesprez@google.com
+frankfeng@google.com
+murj@google.com
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..f4447c3
--- /dev/null
+++ b/README.md
@@ -0,0 +1,66 @@
+# Getting Started with Snippets for Mobly
+
+Mobly Snippet Lib is a library for triggering device-side code from host-side
+[Mobly](http://github.com/google/mobly) tests. This tutorial teaches you how to
+use the snippet lib to trigger custom device-side actions.
+
+Note: Mobly and the snippet lib are not official Google products.
+
+
+## Prerequisites
+
+-   These examples and tutorials assume basic familiarity with the Mobly
+    framework, so please follow the
+    [Mobly tutorial](http://github.com/google/mobly) before doing this one.
+-   You should know how to create an Android app and build it with gradle. If
+    not, follow the
+    [Android app tutorial](https://developer.android.com/training/basics/firstapp/index.html).
+
+
+## Overview
+
+The Mobly Snippet Lib allows you to write Java methods that run on Android
+devices, and trigger the methods from inside a Mobly test case. The Java methods
+invoked this way are called `snippets`.
+
+The `snippet` code can either be written in its own standalone apk, or as a
+[product flavor](https://developer.android.com/studio/build/build-variants.html#product-flavors)
+of an existing apk. This allows you to write snippets that instrument or
+automate another app.
+
+
+## Under The Hood
+
+A snippet is launched by an `am instrument` call. Snippets use a custom
+`InstrumentationTestRunner` derived from `AndroidJUnitRunner`. This allows
+for snippets that interact with a main app's classes, such as Espresso snippets,
+and allows you to get either the test app's or the main app's context from
+`InstrumentationRegistry`.
+
+Once started, the special runner starts a web server which listens for requests
+to trigger snippets. The server's handler locates the corresponding methods by
+reflection, runs them, and returns results over the TCP socket. All common
+built-in variable types are supported as arguments.
+
+
+## Usage
+
+The [examples/](examples/) folder contains examples of how to use the
+mobly snippet lib along with detailed tutorials.
+
+*   [ex1_standalone_app](examples/ex1_standalone_app): Basic example of a
+    snippet which is compiled into its own standalone apk.
+*   [ex2_espresso](examples/ex2_espresso): Example of a snippet which
+    instruments a primary app to drive its UI using
+    [Espresso](https://google.github.io/android-testing-support-library/docs/espresso/).
+*   [ex3_async_event](examples/ex3_async_event): Example of how to use the
+    @AsyncRpc annotation to handle asynchronous callbacks.
+*   [ex4_uiautomator](examples/ex4_uiautomator): Example of how to create
+    snippets that automate the UI actions using UIAutomator. Unlike Espresso
+    UIAutomator works even without access to app source code.
+*   [ex5_schedule_rpc](examples/ex5_schedule_rpc): Example of how to use the
+    'scheduleRpc' RPC to execute another RPC at a later time, potentially after
+    device disconnection.
+*   [ex6_complex_type_conversion](examples/ex6_complex_type_conversion): Example of how to pass a
+    non-primitive type to the Rpc methods and return non-primitive type from Rpc methods by
+    supplying a type converter.
diff --git a/build.gradle b/build.gradle
new file mode 100644
index 0000000..dcd6e86
--- /dev/null
+++ b/build.gradle
@@ -0,0 +1,28 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+// For android studio 2.3 and plugin 2.3.3
+
+buildscript {
+    repositories {
+        mavenCentral()
+        google()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:7.0.2'
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        mavenCentral()
+        google()
+    }
+    gradle.projectsEvaluated {
+        tasks.withType(JavaCompile) {
+            options.compilerArgs << "-Xlint:all"
+        }
+    }
+}
+
diff --git a/examples/ex1_standalone_app/README.md b/examples/ex1_standalone_app/README.md
new file mode 100644
index 0000000..5d68e34
--- /dev/null
+++ b/examples/ex1_standalone_app/README.md
@@ -0,0 +1,108 @@
+# Standalone Snippet App Example
+
+This tutorial shows you how to create a standalone Mobly snippet app. To create
+a snippet app that controls (instruments) another app under test, please see
+[Example 2](../ex2_espresso/README.md).
+
+## Tutorial
+
+1.  Use Android Studio to create a new app project.
+
+1.  Link against Mobly Snippet Lib in your `build.gradle` file
+
+    ```
+    dependencies {
+      implementation 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    }
+    ```
+
+1.  Write a Java class implementing `Snippet` and add methods to trigger the
+    behaviour that you want. Annotate them with `@Rpc`
+
+    ```java
+    package com.my.app;
+    ...
+    public class ExampleSnippet implements Snippet {
+      @Rpc(description='Returns a string containing the given number.')
+      public String getFoo(Integer input) {
+        return "foo " + input;
+      }
+
+      @Override
+      public void shutdown() {}
+    }
+    ```
+
+1.  Add any classes that implement the `Snippet` interface in your
+    `AndroidManifest.xml` application section as `meta-data`
+
+    ```xml
+    <manifest
+        xmlns:android="http://schemas.android.com/apk/res/android"
+        package="com.my.app">
+      <application>
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.my.app.test.MySnippet1,
+                           com.my.app.test.MySnippet2" />
+        ...
+    ```
+
+
+1.  Add an `instrumentation` tag to your `AndroidManifest.xml` so that the
+    framework can launch your server through an `instrument` command.
+
+    ```xml
+    <manifest
+        xmlns:android="http://schemas.android.com/apk/res/android"
+        package="com.my.app">
+      <application>...</application>
+      <instrumentation
+          android:name="com.google.android.mobly.snippet.ServerRunner"
+          android:targetPackage="com.my.app" />
+    </manifest>
+    ```
+
+1.  Build your apk and install it on your phone
+
+1.  In your Mobly python test, connect to your snippet .apk in `setup_class`
+
+    ```python
+    class HelloWorldTest(base_test.BaseTestClass):
+      def setup_class(self):
+        self.ads = self.register_controller(android_device)
+        self.dut1 = self.ads[0]
+        self.dut1.load_snippet(name='snippet', package='com.my.app.test')
+    ```
+
+6.  Invoke your needed functionality within your test
+
+    ```python
+    def test_get_foo(self):
+      actual_foo = self.dut1.snippet.getFoo(5)
+      asserts.assert_equal("foo 5", actual_foo)
+    ```
+
+## Running the example code
+
+This folder contains a fully working example of a standalone snippet apk.
+
+1.  Compile the example
+
+        ./gradlew examples:ex1_standalone_app:assembleDebug
+
+1.  Install the apk on your phone
+
+        adb install -r ./examples/ex1_standalone_app/build/outputs/apk/debug/ex1_standalone_app-debug.apk
+
+1.  Use `snippet_shell` from mobly to trigger `getFoo()`:
+
+        snippet_shell.py com.google.android.mobly.snippet.example1
+
+        >>> print(s.help())
+        Known methods:
+          getBar(String) returns String  // Returns the given string with the prefix "bar"
+          getFoo(Integer) returns String  // Returns the given integer with the prefix "foo"
+
+        >>> s.getFoo(5)
+        u'foo 5'
diff --git a/examples/ex1_standalone_app/build.gradle b/examples/ex1_standalone_app/build.gradle
new file mode 100644
index 0000000..ee60dc1
--- /dev/null
+++ b/examples/ex1_standalone_app/build.gradle
@@ -0,0 +1,27 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 31
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example1"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.1"
+    }
+    lintOptions {
+        abortOnError false
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardwareIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+}
+
+dependencies {
+    // The 'implementation project' dep is to compile against the snippet lib source in
+    // this repo. For your own snippets, you'll want to use the regular
+    // 'implementation' dep instead:
+    //implementation 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    implementation project(':mobly-snippet-lib')
+}
diff --git a/examples/ex1_standalone_app/src/main/AndroidManifest.xml b/examples/ex1_standalone_app/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..90ebdea
--- /dev/null
+++ b/examples/ex1_standalone_app/src/main/AndroidManifest.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example1">
+
+    <application android:allowBackup="false">
+        <!-- Required: list of all classes with @Rpc methods. -->
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example1.ExampleSnippet,
+                           com.google.android.mobly.snippet.example1.ExampleSnippet2" />
+
+        <!-- Optional: tag which will be used for logs through the snippet lib's logger.
+             If specified, log lines will look like this:
+             MoblySnippetLibExample1.JsonRpcServer:84: Got shutdown signal
+
+             If not specified, log lines will look like this
+             com.google.android.mobly.snippet.example1.JsonRpcServer:84: Got shutdown signal -->
+        <meta-data
+          android:name="mobly-log-tag"
+          android:value="MoblySnippetLibExample1" />
+    </application>
+
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example1" />
+</manifest>
diff --git a/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet.java b/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet.java
new file mode 100644
index 0000000..46c55ba
--- /dev/null
+++ b/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example1;
+
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+
+public class ExampleSnippet implements Snippet {
+    @Rpc(description = "Returns the given integer with the prefix \"foo\"")
+    public String getFoo(Integer input) {
+        return "foo " + input;
+    }
+
+    @Override
+    public void shutdown() {}
+}
diff --git a/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet2.java b/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet2.java
new file mode 100644
index 0000000..61c3e0a
--- /dev/null
+++ b/examples/ex1_standalone_app/src/main/java/com/google/android/mobly/snippet/example1/ExampleSnippet2.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example1;
+
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+
+import com.google.android.mobly.snippet.rpc.RunOnUiThread;
+
+import org.json.JSONArray;
+
+import java.io.IOException;
+
+public class ExampleSnippet2 implements Snippet {
+    @Rpc(description = "Returns the given string with the prefix \"bar\"")
+    public String getBar(String input) {
+        return "bar " + input;
+    }
+
+    @Rpc(description = "Returns the given JSON array with the prefix \"bar\"")
+    public String getJSONArray(JSONArray input) {
+        return "bar " + input;
+    }
+
+    @Rpc(description = "Throws an exception")
+    public String throwSomething() throws IOException {
+        throw new IOException("Example exception from throwSomething()");
+    }
+
+    @Rpc(description = "Throws an exception from the main thread")
+    // @RunOnUiThread makes this method execute on the main thread, but only has effect when
+    // invoked as an RPC. It does not affect how this method executes if invoked directly in Java.
+    // This annotation can also be applied to the constructor and the shutdown() method.
+    @RunOnUiThread
+    public String throwSomethingFromMainThread() throws IOException {
+        throw new IOException("Example exception from throwSomethingFromMainThread()");
+    }
+
+    @Override
+    public void shutdown() {}
+}
diff --git a/examples/ex2_espresso/README.md b/examples/ex2_espresso/README.md
new file mode 100644
index 0000000..c9422a5
--- /dev/null
+++ b/examples/ex2_espresso/README.md
@@ -0,0 +1,128 @@
+# Espresso Snippet Example
+
+This tutorial shows you how to create snippets that automate the UI of another
+app using Espresso.
+
+The same approach can be used to create any snippet app that needs to access
+the classes or resources of any other single app.
+
+## Overview
+
+To build a snippet that instruments another app, you have to create a new
+[product flavor](https://developer.android.com/studio/build/build-variants.html#product-flavors)
+of your existing app with the snippet code built in.
+
+The snippet code cannot run from a regular test apk because it requires a custom
+`testInstrumentationRunner`.
+
+## Tutorial
+
+1.  In the `build.gradle` file of your existing app, create a new product flavor called `snippet`.
+
+    ```
+    android {
+      defaultConfig { ... }
+      productFlavors {
+        main {}
+        snippet {}
+      }
+    }
+    ```
+
+1.  Link against Mobly Snippet Lib in your `build.gradle` file
+
+    ```
+    dependencies {
+      snippetCompile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    }
+    ```
+
+1.  Create a new source tree called `src/snippet` where you will place the
+    snippet code.
+
+1.  In Android Studio, use the `Build Variants` tab in the left hand pane to
+    switch to the snippetDebug build variant. This will let you edit code in the
+    new tree.
+
+1.  Write your snippet code in a new class under `src/snippet/java`
+
+    ```java
+    package com.my.app;
+    ...
+    public class EspressoSnippet implements Snippet {
+      @Rpc(description="Pushes the main app button.")
+      public void pushMainButton() {
+        onView(withId(R.id.main_button)).perform(click());
+      }
+
+      @Override
+      public void shutdown() {}
+    }
+    ```
+
+1.  Create `src/snippet/AndroidManifest.xml` containing an `<instrument>` block
+    and any classes that implement the `Snippet` interface in `meta-data`
+
+    ```xml
+    <?xml version="1.0" encoding="utf-8"?>
+    <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+      <application>
+        <meta-data
+          android:name="mobly-snippets"
+          android:value="com.my.app.EspressoSnippet" />
+      </application>
+
+      <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.my.app" />
+    </manifest>
+    ```
+
+1.  Build your apk by invoking the new `assembleSnippetDebug` target.
+
+1.  Install the apk on your phone. You do not need to install the main app's
+    apk; the snippet-enabled apk is a complete replacement for your app.
+
+1.  In your Mobly python test, connect to your snippet .apk in `setup_class`
+
+    ```python
+    class HelloWorldTest(base_test.BaseTestClass):
+      def setup_class(self):
+        self.ads = self.register_controller(android_device)
+        self.dut1 = self.ads[0]
+        self.dut1.load_snippet(name='snippet', package='com.my.app')
+    ```
+
+6.  Invoke your needed functionality within your test
+
+    ```python
+    def test_click_button(self):
+      self.dut1.snippet.pushMainButton()
+    ```
+
+## Running the example code
+
+This folder contains a fully working example of a snippet apk that uses espresso
+to automate a simple app.
+
+1.  Compile the example
+
+        ./gradlew examples:ex2_espresso:assembleSnippetDebug
+
+1.  Install the apk on your phone
+
+        adb install -r ./examples/ex2_espresso/build/outputs/apk/snippet/debug/ex2_espresso-snippet-debug.apk
+
+1.  Use `snippet_shell` from mobly to trigger `pushMainButton()`:
+
+        snippet_shell.py com.google.android.mobly.snippet.example2
+
+        >>> print(s.help())
+        Known methods:
+          pushMainButton(boolean) returns void  // Pushes the main app button, and checks the label if this is the first time.
+          startMainActivity() returns void  // Opens the main activity of the app
+
+        >>> s.startMainActivity()
+        >>> s.pushMainButton(True)
+
+1. Press ctrl+d to exit the shell and terminate the app.
diff --git a/examples/ex2_espresso/build.gradle b/examples/ex2_espresso/build.gradle
new file mode 100644
index 0000000..4479e1b
--- /dev/null
+++ b/examples/ex2_espresso/build.gradle
@@ -0,0 +1,56 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 31
+    flavorDimensions "examples"
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example2"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.1"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    productFlavors {
+        original {
+            dimension "examples"
+        }
+        snippet {
+            testApplicationId "com.google.android.mobly.snippet.example2.snippet"
+            dimension "examples"
+        }
+    }
+
+    lintOptions {
+        abortOnError true
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardcodedText', 'UnusedIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+}
+
+dependencies {
+    implementation 'androidx.appcompat:appcompat:1.4.0-beta01'
+    implementation 'androidx.test:runner:1.4.0'
+
+    // The androidTest package is not for snippet support; it shows an example
+    // of an instrumentation test coexisting with a snippet in the same
+    // codebase.
+    androidTestImplementation 'androidx.annotation:annotation:1.2.0'
+    androidTestImplementation 'androidx.test:runner:1.4.0'
+    androidTestImplementation('androidx.test.espresso:espresso-core:3.4.0', {
+        exclude group: 'com.android.support', module: 'support-annotations'
+    })
+
+    // The 'snippetCompile project' dep is to compile against the snippet lib
+    // source in this repo. For your own snippets, you'll want to use the
+    // regular 'snippetCompile' dep instead:
+    //snippetCompile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    snippetImplementation project(':mobly-snippet-lib')
+
+    snippetImplementation 'androidx.annotation:annotation:1.2.0'
+    snippetImplementation 'androidx.test:rules:1.4.0'
+    snippetImplementation 'androidx.test.espresso:espresso-core:3.4.0'
+}
diff --git a/examples/ex2_espresso/src/androidTest/AndroidManifest.xml b/examples/ex2_espresso/src/androidTest/AndroidManifest.xml
new file mode 100644
index 0000000..0dc87bc
--- /dev/null
+++ b/examples/ex2_espresso/src/androidTest/AndroidManifest.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example2.test">
+    <application>
+        <uses-library android:name="android.test.runner" />
+    </application>
+
+    <instrumentation
+        android:name="androidx.test.runner.AndroidJUnitRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example2" />
+</manifest>
diff --git a/examples/ex2_espresso/src/androidTest/java/com/google/android/mobly/snippet/example2/EspressoTest.java b/examples/ex2_espresso/src/androidTest/java/com/google/android/mobly/snippet/example2/EspressoTest.java
new file mode 100644
index 0000000..f41374e
--- /dev/null
+++ b/examples/ex2_espresso/src/androidTest/java/com/google/android/mobly/snippet/example2/EspressoTest.java
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example2;
+
+import androidx.test.espresso.action.ViewActions;
+import androidx.test.rule.ActivityTestRule;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static androidx.test.espresso.Espresso.onView;
+import static androidx.test.espresso.assertion.ViewAssertions.matches;
+import static androidx.test.espresso.matcher.ViewMatchers.withId;
+import static androidx.test.espresso.matcher.ViewMatchers.withText;
+
+/**
+ * This test is not part of the snippet code. It's a regular espresso instrumentation test which
+ * shows how regular tests can coexist with snippets in the source tree.
+ */
+@RunWith(AndroidJUnit4.class)
+public class EspressoTest {
+    @Rule
+    public ActivityTestRule<MainActivity> mActivityRule =
+            new ActivityTestRule<>(MainActivity.class);
+
+    @Test
+    public void espressoTest() {
+        onView(withId(R.id.main_text_view)).check(matches(withText("Hello World!")));
+        onView(withId(R.id.main_button)).perform(ViewActions.click());
+        onView(withId(R.id.main_text_view)).check(matches(withText("Button pressed 1 times.")));
+    }
+}
diff --git a/examples/ex2_espresso/src/main/AndroidManifest.xml b/examples/ex2_espresso/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..33f853f
--- /dev/null
+++ b/examples/ex2_espresso/src/main/AndroidManifest.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example2">
+
+    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>
diff --git a/examples/ex2_espresso/src/main/java/com/google/android/mobly/snippet/example2/MainActivity.java b/examples/ex2_espresso/src/main/java/com/google/android/mobly/snippet/example2/MainActivity.java
new file mode 100644
index 0000000..0cc0b54
--- /dev/null
+++ b/examples/ex2_espresso/src/main/java/com/google/android/mobly/snippet/example2/MainActivity.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example2;
+
+import java.util.Locale;
+import androidx.appcompat.app.AppCompatActivity;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.TextView;
+
+public class MainActivity extends AppCompatActivity {
+    private TextView mTextView;
+    private Button mButton;
+    private int mNumPressed;
+
+    /**
+     * Attaches a simple listener that increments the text in the textbox whenever the button is
+     * pressed.
+     */
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        mTextView = (TextView) findViewById(R.id.main_text_view);
+        mButton = (Button) findViewById(R.id.main_button);
+        mButton.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                mNumPressed++;
+                mTextView.setText(String.format(Locale.ROOT, "Button pressed %d times.", mNumPressed));
+            }
+        });
+    }
+}
diff --git a/examples/ex2_espresso/src/main/res/layout/activity_main.xml b/examples/ex2_espresso/src/main/res/layout/activity_main.xml
new file mode 100644
index 0000000..e190302
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/layout/activity_main.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
+    android:layout_width="match_parent" android:layout_height="match_parent"
+    android:paddingBottom="@dimen/activity_vertical_margin"
+    android:paddingLeft="@dimen/activity_horizontal_margin"
+    android:paddingRight="@dimen/activity_horizontal_margin"
+    android:paddingTop="@dimen/activity_vertical_margin"
+    tools:context="com.google.android.mobly.snippet.example2.MainActivity">
+
+<TextView
+    android:id="@+id/main_text_view"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:layout_gravity="center_horizontal"
+    android:text="Hello World!" />
+
+<Button
+    android:id="@+id/main_button"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:text="Push the button!" />
+</RelativeLayout>
diff --git a/examples/ex2_espresso/src/main/res/mipmap-hdpi/ic_launcher.png b/examples/ex2_espresso/src/main/res/mipmap-hdpi/ic_launcher.png
new file mode 100644
index 0000000..cde69bc
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/mipmap-hdpi/ic_launcher.png
diff --git a/examples/ex2_espresso/src/main/res/mipmap-mdpi/ic_launcher.png b/examples/ex2_espresso/src/main/res/mipmap-mdpi/ic_launcher.png
new file mode 100644
index 0000000..c133a0c
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/mipmap-mdpi/ic_launcher.png
diff --git a/examples/ex2_espresso/src/main/res/mipmap-xhdpi/ic_launcher.png b/examples/ex2_espresso/src/main/res/mipmap-xhdpi/ic_launcher.png
new file mode 100644
index 0000000..bfa42f0
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/mipmap-xhdpi/ic_launcher.png
diff --git a/examples/ex2_espresso/src/main/res/mipmap-xxhdpi/ic_launcher.png b/examples/ex2_espresso/src/main/res/mipmap-xxhdpi/ic_launcher.png
new file mode 100644
index 0000000..324e72c
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/mipmap-xxhdpi/ic_launcher.png
diff --git a/examples/ex2_espresso/src/main/res/mipmap-xxxhdpi/ic_launcher.png b/examples/ex2_espresso/src/main/res/mipmap-xxxhdpi/ic_launcher.png
new file mode 100644
index 0000000..aee44e1
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/mipmap-xxxhdpi/ic_launcher.png
diff --git a/examples/ex2_espresso/src/main/res/values-w820dp/dimens.xml b/examples/ex2_espresso/src/main/res/values-w820dp/dimens.xml
new file mode 100644
index 0000000..63fc816
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/values-w820dp/dimens.xml
@@ -0,0 +1,6 @@
+<resources>
+    <!-- Example customization of dimensions originally defined in res/values/dimens.xml
+         (such as screen margins) for screens with more than 820dp of available width. This
+         would include 7" and 10" devices in landscape (~960dp and ~1280dp respectively). -->
+    <dimen name="activity_horizontal_margin">64dp</dimen>
+</resources>
diff --git a/examples/ex2_espresso/src/main/res/values/colors.xml b/examples/ex2_espresso/src/main/res/values/colors.xml
new file mode 100644
index 0000000..3ab3e9c
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/values/colors.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#3F51B5</color>
+    <color name="colorPrimaryDark">#303F9F</color>
+    <color name="colorAccent">#FF4081</color>
+</resources>
diff --git a/examples/ex2_espresso/src/main/res/values/dimens.xml b/examples/ex2_espresso/src/main/res/values/dimens.xml
new file mode 100644
index 0000000..47c8224
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/values/dimens.xml
@@ -0,0 +1,5 @@
+<resources>
+    <!-- Default screen margins, per the Android Design guidelines. -->
+    <dimen name="activity_horizontal_margin">16dp</dimen>
+    <dimen name="activity_vertical_margin">16dp</dimen>
+</resources>
diff --git a/examples/ex2_espresso/src/main/res/values/strings.xml b/examples/ex2_espresso/src/main/res/values/strings.xml
new file mode 100644
index 0000000..c46b9d8
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/values/strings.xml
@@ -0,0 +1,3 @@
+<resources>
+    <string name="app_name">Mobly Snippet Espresso Example</string>
+</resources>
diff --git a/examples/ex2_espresso/src/main/res/values/styles.xml b/examples/ex2_espresso/src/main/res/values/styles.xml
new file mode 100644
index 0000000..daa2a5c
--- /dev/null
+++ b/examples/ex2_espresso/src/main/res/values/styles.xml
@@ -0,0 +1,11 @@
+<resources>
+
+    <!-- Base application theme. -->
+    <style name="AppTheme" parent="Theme.AppCompat">
+        <!-- Customize your theme here. -->
+        <item name="colorPrimary">@color/colorPrimary</item>
+        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
+        <item name="colorAccent">@color/colorAccent</item>
+    </style>
+
+</resources>
diff --git a/examples/ex2_espresso/src/snippet/AndroidManifest.xml b/examples/ex2_espresso/src/snippet/AndroidManifest.xml
new file mode 100644
index 0000000..85797ce
--- /dev/null
+++ b/examples/ex2_espresso/src/snippet/AndroidManifest.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <application>
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example2.EspressoSnippet" />
+    </application>
+
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example2" />
+
+</manifest>
diff --git a/examples/ex2_espresso/src/snippet/java/com/google/android/mobly/snippet/example2/EspressoSnippet.java b/examples/ex2_espresso/src/snippet/java/com/google/android/mobly/snippet/example2/EspressoSnippet.java
new file mode 100644
index 0000000..8ea7c21
--- /dev/null
+++ b/examples/ex2_espresso/src/snippet/java/com/google/android/mobly/snippet/example2/EspressoSnippet.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example2;
+
+import static androidx.test.espresso.Espresso.onView;
+import static androidx.test.espresso.assertion.ViewAssertions.matches;
+import static androidx.test.espresso.matcher.ViewMatchers.withId;
+import static androidx.test.espresso.matcher.ViewMatchers.withText;
+
+import androidx.test.espresso.action.ViewActions;
+import androidx.test.rule.ActivityTestRule;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+import org.junit.Rule;
+
+public class EspressoSnippet implements Snippet {
+    @Rule
+    public ActivityTestRule<MainActivity> mActivityRule =
+            new ActivityTestRule<>(MainActivity.class);
+
+    @Rpc(description="Opens the main activity of the app")
+    public void startMainActivity() {
+        mActivityRule.launchActivity(null /* startIntent */);
+    }
+
+    @Rpc(description="Pushes the main app button, and checks the label if this is the first time.")
+    public void pushMainButton(boolean checkFirstRun) {
+        if (checkFirstRun) {
+            onView(withId(R.id.main_text_view)).check(matches(withText("Hello World!")));
+        }
+        onView(withId(R.id.main_button)).perform(ViewActions.click());
+        if (checkFirstRun) {
+            onView(withId(R.id.main_text_view)).check(matches(withText("Button pressed 1 times.")));
+        }
+    }
+
+    @Override
+    public void shutdown() {
+        mActivityRule.getActivity().finish();
+    }
+}
diff --git a/examples/ex3_async_event/README.md b/examples/ex3_async_event/README.md
new file mode 100644
index 0000000..edb4fbd
--- /dev/null
+++ b/examples/ex3_async_event/README.md
@@ -0,0 +1,41 @@
+# Async Event RPC Example
+
+This example shows you how to use the @AsyncRpc annotation of Mobly snippet lib
+to handle asynchronous callbacks.
+
+See the source code in `ExampleAsyncSnippet.java` for details.
+
+## Running the example code
+
+This folder contains a fully working example of a standalone snippet apk.
+
+1.  Compile the example
+
+        ./gradlew examples:ex3_async_event:assembleDebug
+
+1.  Install the apk on your phone
+
+        adb install -r ./examples/ex3_async_event/build/outputs/apk/debug/ex3_async_event-debug.apk
+
+1.  Use `snippet_shell` from mobly to trigger `tryEvent()`:
+
+        snippet_shell.py com.google.android.mobly.snippet.example3
+
+        >>> handler = s.tryEvent(42)
+        >>> print("Not blocked, can do stuff here")
+        >>> event = handler.waitAndGet('AsyncTaskResult') # Blocks until the event is received
+
+        Now let's see the content of the event
+
+        >>> import pprint
+        >>> pprint.pprint(event)
+        {
+            'callbackId': '2-1',
+            'name': 'AsyncTaskResult',
+            'time': 20460228696,
+            'data': {
+                'exampleData': "Here's a simple event.",
+                'successful': True,
+                'secretNumber': 12
+            }
+        }
diff --git a/examples/ex3_async_event/build.gradle b/examples/ex3_async_event/build.gradle
new file mode 100644
index 0000000..7327fc4
--- /dev/null
+++ b/examples/ex3_async_event/build.gradle
@@ -0,0 +1,26 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 31
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example3"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.1"
+    }
+    lintOptions {
+        abortOnError false
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardwareIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+}
+
+dependencies {
+    // The 'compile project' dep is to compile against the snippet lib source in
+    // this repo. For your own snippets, you'll want to use the regular 'compile' dep instead:
+    // compile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    implementation project(':mobly-snippet-lib')
+}
diff --git a/examples/ex3_async_event/src/main/AndroidManifest.xml b/examples/ex3_async_event/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..dcc724b
--- /dev/null
+++ b/examples/ex3_async_event/src/main/AndroidManifest.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example3">
+
+    <application android:allowBackup="false">
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example3.ExampleAsyncSnippet" />
+    </application>
+
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example3" />
+
+</manifest>
diff --git a/examples/ex3_async_event/src/main/java/com/google/android/mobly/snippet/example3/ExampleAsyncSnippet.java b/examples/ex3_async_event/src/main/java/com/google/android/mobly/snippet/example3/ExampleAsyncSnippet.java
new file mode 100644
index 0000000..a2b22fa
--- /dev/null
+++ b/examples/ex3_async_event/src/main/java/com/google/android/mobly/snippet/example3/ExampleAsyncSnippet.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example3;
+
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.event.EventCache;
+import com.google.android.mobly.snippet.event.SnippetEvent;
+import com.google.android.mobly.snippet.rpc.AsyncRpc;
+import com.google.android.mobly.snippet.util.Log;
+
+public class ExampleAsyncSnippet implements Snippet {
+
+    private final EventCache mEventCache = EventCache.getInstance();
+
+    /**
+     * This is a sample asynchronous task.
+     *
+     * In real world use cases, it can be a {@link android.content.BroadcastReceiver}, a Listener,
+     * or any other kind asynchronous callback class.
+     */
+    public class AsyncTask implements Runnable {
+
+        private final String mCallbackId;
+        private final int mSecretNumber;
+
+        public AsyncTask(String callbackId, int secreteNumber) {
+            this.mCallbackId = callbackId;
+            this.mSecretNumber = secreteNumber;
+        }
+
+        /**
+         * Sleeps for 10s then post a {@link SnippetEvent} with some data.
+         *
+         * If the sleep is interrupted, a {@link SnippetEvent} signaling failure will be posted instead.
+         */
+        public void run() {
+            Log.d("Sleeping for 10s before posting an event.");
+            SnippetEvent event = new SnippetEvent(mCallbackId, "AsyncTaskResult");
+            try {
+                Thread.sleep(10000);
+            } catch (InterruptedException e) {
+                event.getData().putBoolean("successful", false);
+                event.getData().putString("reason", "Sleep was interrupted.");
+                mEventCache.postEvent(event);
+            }
+            event.getData().putBoolean("successful", true);
+            event.getData().putString("exampleData", "Here's a simple event.");
+            event.getData().putInt("secretNumber", mSecretNumber);
+            mEventCache.postEvent(event);
+        }
+    }
+
+    /**
+     * An Rpc method demonstrating the async event mechanism.
+     *
+     * This call returns immediately, but starts a task in a separate thread which will post an
+     * event 10s after the task was started.
+     *
+     * Expect to see an event on the client side that looks like:
+     *
+     *    {
+     *        'callbackId': '2-1',
+     *        'name': 'AsyncTaskResult',
+     *        'time': 20460228696,
+     *        'data': {
+     *            'exampleData': "Here's a simple event.",
+     *            'successful': True,
+     *            'secretNumber': 12
+     *        }
+     *    }
+     *
+     * @param callbackId The ID that should be used to tag {@link SnippetEvent} objects triggered by
+     *                   this method.
+     * @throws InterruptedException
+     */
+    @AsyncRpc(description = "This triggers an async event and returns.")
+    public void tryEvent(String callbackId, int secretNumber) throws InterruptedException {
+        Runnable asyncTask = new AsyncTask(callbackId, secretNumber);
+        Thread thread = new Thread(asyncTask);
+        thread.start();
+    }
+    @Override
+    public void shutdown() {}
+}
diff --git a/examples/ex4_uiautomator/README.md b/examples/ex4_uiautomator/README.md
new file mode 100644
index 0000000..10fb144
--- /dev/null
+++ b/examples/ex4_uiautomator/README.md
@@ -0,0 +1,45 @@
+# UIAutomator Snippet Example
+
+This example shows you how to create snippets that control the UI of a device
+across system and multiple app views using UIAutomator. Unlike Espresso-based
+UI automation, it does not require access to app source code.
+
+This snippet is written as a [standalone snippet](../ex1_standalone_app/README.md)
+and does not target another app. In particular, it doesn't need to target the
+app under test, so it doesn't need its classpath or to be signed with the same
+key.
+
+See the [Espresso snippet tutorial](../ex2_espresso/README.md) for more
+information about the app this example automates.
+
+## Running the example code
+
+This folder contains a fully working example of a snippet apk that uses
+UIAutomator to automate a simple app.
+
+1.  Compile the main app and automation. The main app of ex2 (espresso) is used
+    as the app to automate. Unlike espresso, the uiautomator test does not
+    depend on this apk and does not use its source or classpath, so you must
+    compile and install the app separately.
+
+        ./gradlew examples:ex2_espresso:assembleDebug examples:ex4_uiautomator:assembleDebug
+
+1.  Install the apks on your phone
+
+        adb install -r ./examples/ex2_espresso/build/outputs/apk/debug/ex2_espresso-main-debug.apk
+        adb install -r ./examples/ex4_uiautomator/build/outputs/apk/debug/ex4_uiautomator-debug.apk
+
+1.  Use `snippet_shell` from mobly to trigger `pushMainButton()`:
+
+        snippet_shell.py com.google.android.mobly.snippet.example4
+
+        >>> print(s.help())
+        Known methods:
+          pushMainButton(boolean) returns void  // Pushes the main app button, and checks the label if this is the first time.
+          startMainActivity() returns void  // Opens the main activity of the app
+          uiautomatorDump() returns String  // Perform a UIAutomator dump
+
+        >>> s.startMainActivity()
+        >>> s.pushMainButton(True)
+
+1. Press ctrl+d to exit the shell and terminate the app.
diff --git a/examples/ex4_uiautomator/build.gradle b/examples/ex4_uiautomator/build.gradle
new file mode 100644
index 0000000..b071e1b
--- /dev/null
+++ b/examples/ex4_uiautomator/build.gradle
@@ -0,0 +1,32 @@
+apply plugin: 'com.android.application'
+
+android {
+    // This has to match what the appcompat dep expects.
+    compileSdkVersion 31
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example4"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.2"
+    }
+    lintOptions {
+        abortOnError false
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardwareIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+}
+
+dependencies {
+    // The 'compile project' dep is to compile against the snippet lib source in
+    // this repo. For your own snippets, you'll want to use the regular
+    // 'compile' dep instead:
+    //compile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    implementation project(':mobly-snippet-lib')
+    implementation 'junit:junit:4.13.2'
+    implementation 'androidx.test:runner:1.4.0'
+    implementation 'androidx.appcompat:appcompat:1.4.0-beta01'
+    implementation 'androidx.test.uiautomator:uiautomator:2.2.0'
+}
diff --git a/examples/ex4_uiautomator/src/main/AndroidManifest.xml b/examples/ex4_uiautomator/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..89d5276
--- /dev/null
+++ b/examples/ex4_uiautomator/src/main/AndroidManifest.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example4">
+
+    <application android:allowBackup="false">
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example4.UiAutomatorSnippet" />
+    </application>
+
+    <!-- This snippet does NOT target ex2 (which is the main app the code
+         automates). The instrumentation target is itself which creates a
+         standalone snippet. -->
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example4" />
+
+</manifest>
diff --git a/examples/ex4_uiautomator/src/main/java/com/google/android/mobly/snippet/example4/UiAutomatorSnippet.java b/examples/ex4_uiautomator/src/main/java/com/google/android/mobly/snippet/example4/UiAutomatorSnippet.java
new file mode 100644
index 0000000..9fc01b2
--- /dev/null
+++ b/examples/ex4_uiautomator/src/main/java/com/google/android/mobly/snippet/example4/UiAutomatorSnippet.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example4;
+
+import static org.junit.Assert.assertEquals;
+
+import android.content.Context;
+import android.content.Intent;
+
+import androidx.test.platform.app.InstrumentationRegistry;
+import androidx.test.uiautomator.By;
+import androidx.test.uiautomator.UiDevice;
+import androidx.test.uiautomator.UiObject2;
+import androidx.test.uiautomator.Until;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.Charset;
+
+/**
+ * Demonstrates how to drive an app using UIAutomator without access to the app's source code or
+ * classpath.
+ *
+ * <p>Drives the Espresso example app from ex2 without instrumenting it.
+ */
+public class UiAutomatorSnippet implements Snippet {
+    private static final class UiAutomatorSnippetException extends Exception {
+        private static final long serialVersionUID = 1;
+
+        public UiAutomatorSnippetException(String message) {
+            super(message);
+        }
+    }
+
+    private static final String MAIN_PACKAGE = "com.google.android.mobly.snippet.example2";
+    private static final int LAUNCH_TIMEOUT = 5000;
+
+    private final Context mContext;
+    private final UiDevice mDevice;
+
+    public UiAutomatorSnippet() {
+        mContext = InstrumentationRegistry.getInstrumentation().getContext();
+        mDevice = UiDevice.getInstance(InstrumentationRegistry.getInstrumentation());
+    }
+
+    @Rpc(description="Opens the main activity of the app")
+    public void startMainActivity() throws UiAutomatorSnippetException {
+        // Send the launch intent
+        Intent intent = mContext.getPackageManager().getLaunchIntentForPackage(MAIN_PACKAGE);
+        if (intent == null) {
+            throw new UiAutomatorSnippetException(
+                "Unable to create launch intent for " + MAIN_PACKAGE + "; is the app installed?");
+        }
+        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
+        mContext.startActivity(intent);
+
+        // Wait for the app to appear
+        mDevice.wait(Until.hasObject(By.pkg(MAIN_PACKAGE).depth(0)), LAUNCH_TIMEOUT);
+    }
+
+    @Rpc(description="Pushes the main app button, and checks the label if this is the first time.")
+    public void pushMainButton(boolean checkFirstRun) {
+        if (checkFirstRun) {
+            assertEquals(
+                "Hello World!",
+                // Example of finding object by id.
+                mDevice.findObject(By.res(MAIN_PACKAGE, "main_text_view")).getText());
+        }
+        // Example of finding a button by text. Finding by ID is also possible, as above.
+        UiObject2 button = mDevice.findObject(By.text("PUSH THE BUTTON!"));
+        button.click();
+        if (checkFirstRun) {
+            assertEquals(
+                "Button pressed 1 times",
+                mDevice.findObject(By.res(MAIN_PACKAGE, "main_text_view")).getText());
+        }
+    }
+
+    @Rpc(description="Perform a UIAutomator dump")
+    public String uiautomatorDump() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        try {
+            mDevice.dumpWindowHierarchy(baos);
+            byte[] dumpBytes = baos.toByteArray();
+            String dumpStr = new String(dumpBytes, Charset.forName("UTF-8"));
+            return dumpStr;
+        } finally {
+            baos.close();
+        }
+    }
+
+    @Override
+    public void shutdown() throws IOException {
+        mDevice.executeShellCommand("am force-stop " + MAIN_PACKAGE);
+    }
+}
diff --git a/examples/ex5_schedule_rpc/README.md b/examples/ex5_schedule_rpc/README.md
new file mode 100644
index 0000000..4ccd10f
--- /dev/null
+++ b/examples/ex5_schedule_rpc/README.md
@@ -0,0 +1,62 @@
+# Scheduling RPCs Example
+
+This example shows you how to use `scheduleRpc` which is built into
+Mobly snippet lib to handle RPC scheduling.
+
+## Why this is needed?
+
+Some tests may need a snippet RPC to execute when the snippet client is unable
+to reach the device, e.g., performing test actions while USB is disconnected.
+For example, for battery testing (with Monsoon devices), we may want to measure
+power consumed during certain test actions (e.g., phone calls). However
+a Monsoon device turns off USB during battery data measurement, and a regular
+snippet RPC won't work when the client is not connected to the device.
+Therefore, prior to starting the Monsoon measurement we need to schedule a phone
+call RPC prior to soccur during the measurement period.
+
+In this scenario, the test steps would be:
+
+1. Schedule the `makePhoneCall('123456')` to execute after (e.g., 10 seconds):
+
+        s.scheduleRpc('makePhoneCall', 10000, ['123456'])
+
+2. Start a Monsoon device to collect battery data, while simultaneously USB is
+   turned off.
+3. After 10 seconds, the phone call starts while USB is off.
+4. Finally, after the phone call is finished, Monsoon data collection completes
+   and USB is re-enabled.
+5. The test retrieves any cached events or data from the device.
+
+
+
+See the source code ExampleScheduleRpcSnippet.java for details.
+
+## Running the example code
+
+This folder contains a fully working example of a standalone snippet apk.
+
+1.  Compile the example
+
+        ./gradlew examples:ex5_schedule_rpc:assembleDebug
+
+1.  Install the apk on your phone
+
+        adb install -r ./examples/ex5_schedule_rpc/build/outputs/apk/debug/ex5_schedule_rpc-debug.apk
+
+1.  Use `snippet_shell` from mobly to trigger `tryEvent()`:
+
+        snippet_shell.py com.google.android.mobly.snippet.example5
+
+        >>> callback = s.scheduleRpc('makeToast', 5000, ['message'])
+
+        Wait for the message to show up on the screen (sync RPC call)
+
+        >>> callback.waitAndGet('makeToast').data
+        {u'callback': u'null', u'error': u'null', u'result': u'OK', u'id': u'0'}
+
+        >>> callback = s.scheduleRpc('asyncMakeToast', 5000, ['message'])
+
+        Wait for the message to show up on the screen (async RPC call)
+
+        >>> callback.waitAndGet('asyncMakeToast').data
+        {u'callback': u'1-1', u'error': u'null', u'result': u'null', u'id': u'0'}
diff --git a/examples/ex5_schedule_rpc/build.gradle b/examples/ex5_schedule_rpc/build.gradle
new file mode 100644
index 0000000..f5aa15c
--- /dev/null
+++ b/examples/ex5_schedule_rpc/build.gradle
@@ -0,0 +1,27 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 31
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example5"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.1"
+    }
+    lintOptions {
+        abortOnError false
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardwareIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+}
+
+dependencies {
+    // The 'compile project' dep is to compile against the snippet lib source in
+    // this repo. For your own snippets, you'll want to use the regular 'compile' dep instead:
+    // compile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    implementation project(':mobly-snippet-lib')
+    implementation 'androidx.test:runner:1.4.0'
+}
diff --git a/examples/ex5_schedule_rpc/src/main/AndroidManifest.xml b/examples/ex5_schedule_rpc/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..9a3271c
--- /dev/null
+++ b/examples/ex5_schedule_rpc/src/main/AndroidManifest.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example5">
+
+    <application android:allowBackup="false">
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example5.ExampleScheduleRpcSnippet" />
+    </application>
+
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example5" />
+
+</manifest>
diff --git a/examples/ex5_schedule_rpc/src/main/java/com/google/android/mobly/snippet/example5/ExampleScheduleRpcSnippet.java b/examples/ex5_schedule_rpc/src/main/java/com/google/android/mobly/snippet/example5/ExampleScheduleRpcSnippet.java
new file mode 100644
index 0000000..a94d68a
--- /dev/null
+++ b/examples/ex5_schedule_rpc/src/main/java/com/google/android/mobly/snippet/example5/ExampleScheduleRpcSnippet.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example5;
+
+import android.content.Context;
+import android.os.Handler;
+import androidx.test.InstrumentationRegistry;
+import android.widget.Toast;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.event.EventCache;
+import com.google.android.mobly.snippet.event.SnippetEvent;
+import com.google.android.mobly.snippet.rpc.AsyncRpc;
+import com.google.android.mobly.snippet.rpc.Rpc;
+import com.google.android.mobly.snippet.util.Log;
+
+/**
+ * Demonstrates how to schedule an RPC.
+ */
+public class ExampleScheduleRpcSnippet implements Snippet {
+
+    /**
+     * This is a sample asynchronous task.
+     *
+     * In real world use cases, it can be a {@link android.content.BroadcastReceiver}, a Listener,
+     * or any other kind asynchronous callback class.
+     */
+    public class AsyncTask implements Runnable {
+
+        private final String mCallbackId;
+        private final String mMessage;
+
+        public AsyncTask(String callbackId, String message) {
+            this.mCallbackId = callbackId;
+            this.mMessage = message;
+        }
+
+        /**
+         * Sleeps for 10s then make toast and post a {@link SnippetEvent} with some data.
+         *
+         * <p>If the sleep is interrupted, a {@link SnippetEvent} signaling failure will be posted
+         * instead.
+         */
+        @Override
+        public void run() {
+            Log.d("Sleeping for 10s before posting an event.");
+            SnippetEvent event = new SnippetEvent(mCallbackId, mMessage);
+            try {
+                Thread.sleep(10000);
+                showToast(mMessage);
+            } catch (InterruptedException e) {
+                event.getData().putBoolean("successful", false);
+                event.getData().putString("reason", "Sleep was interrupted.");
+                mEventCache.postEvent(event);
+            }
+            event.getData().putBoolean("successful", true);
+            event.getData().putString("eventName", mMessage);
+            mEventCache.postEvent(event);
+        }
+    }
+
+    private final Context mContext;
+    private final EventCache mEventCache = EventCache.getInstance();
+
+    /**
+     * Since the APIs here deal with UI, most of them have to be called in a thread that has called
+     * looper.
+     */
+    private final Handler mHandler;
+
+    public ExampleScheduleRpcSnippet() {
+        mContext = InstrumentationRegistry.getContext();
+        mHandler = new Handler(mContext.getMainLooper());
+    }
+
+    @Rpc(description = "Make a toast on screen.")
+    public String makeToast(String message) throws InterruptedException {
+        showToast(message);
+        return "OK";
+    }
+
+    @AsyncRpc(description = "Make a toast on screen after some time.")
+    public void asyncMakeToast(String callbackId, String message)
+        throws Throwable {
+        Runnable asyncTask = new AsyncTask(callbackId, "asyncMakeToast");
+        Thread thread = new Thread(asyncTask);
+        thread.start();
+    }
+
+    @Override
+    public void shutdown() {}
+
+    private void showToast(final String message) {
+        mHandler.post(
+            new Runnable() {
+                @Override
+                public void run() {
+                    Toast.makeText(mContext, message, Toast.LENGTH_LONG).show();
+                }
+            });
+    }
+}
+
diff --git a/examples/ex6_complex_type_conversion/README.md b/examples/ex6_complex_type_conversion/README.md
new file mode 100644
index 0000000..104d91b
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/README.md
@@ -0,0 +1,108 @@
+# Complex Type Conversion in Snippet Example
+
+This tutorial shows you how to use a custom object in Snippet Lib.
+
+This example assumes basic familiarity with Snippet Lib as demonstrated in
+[Example 1](../ex1_standalone_app/README.md).
+
+## Tutorial
+
+1.  Use Android Studio to create a new app project, similar to
+    [Example 1](../ex1_standalone_app/README.md).
+
+1.  Create a complex type in Java:
+    ```java
+    public class CustomType {
+        private String myValue;
+        CustomType(String value) {
+            myValue = value;
+        }
+    
+        String getMyValue() {
+            return myValue;
+        }
+        public void setMyValue(String newValue) {
+            myValue = newValue;
+        }
+    }
+    ```
+1.  Create a Java class implementing `SnippetObjectConverter`, which defines how the complex type
+    should be converted against `JSONObject`:
+    ```java
+    public class ExampleObjectConverter implements SnippetObjectConverter {
+        @Override
+        public JSONObject serialize(Object object) throws JSONException {
+            JSONObject result = new JSONObject();
+            if (object instanceof CustomType) {
+                CustomType input = (CustomType) object;
+                result.put("Value", input.getMyValue());
+                return result;
+            }
+            return null;
+        }
+    
+        @Override
+        public Object deserialize(JSONObject jsonObject, Type type) throws JSONException {
+            if (type == CustomType.class) {
+                return new CustomType(jsonObject.getString("Value"));
+            }
+            return null;
+        }
+    }
+    ```
+1.  Write a Java class implementing `Snippet` and add Rpc methods that takes your complex type as
+    a parameter and another Rpc method that returns the complext type directly.
+
+    ```java
+    package com.my.app;
+    ...
+    public class ExampleSnippet implements Snippet {
+        @Rpc(description = "Pass a complex type as a snippet parameter.")
+        public String passComplexTypeToSnippet(CustomType input) {
+            Log.i("Old value is: " + input.getMyValue());
+            return "The value in CustomType is: " + input.getMyValue();
+        }
+      
+        @Rpc(description = "Returns a complex type from snippet.")
+        public CustomType returnComplexTypeFromSnippet(String value) {
+            return new CustomType(value);
+        }
+        @Override
+        public void shutdown() {}
+    }
+    ```
+
+1.  In `AndroidManifest.xml`, specify the converter class as a `meta-data` named
+    `mobly-object-converter`
+
+    ```xml
+    <manifest
+        xmlns:android="http://schemas.android.com/apk/res/android"
+        package="com.my.app">
+      <application>
+        <meta-data
+            android:name="mobly-object-converter"
+            android:value="com.my.app.ExampleObjectConverter" />
+        ...
+    ```
+
+## Running the example code
+
+This folder contains a fully working example of a standalone snippet apk.
+
+1.  Compile the example
+
+        ./gradlew examples:ex6_complex_type_conversion:assembleDebug
+
+1.  Install the apk on your phone
+
+        adb install -r ./examples/ex6_complex_type_conversion/build/outputs/apk/debug/ex6_complex_type_conversion-debug.apk
+
+1.  Use Mobly's `snippet_shell` from mobly to trigger the Rpc methods:
+
+        snippet_shell.py com.google.android.mobly.snippet.example6
+
+        >>> s.passComplexTypeToSnippet({'Value': 'Hello'})
+        'The value in CustomType is: Hello'
+        >>> s.returnComplexTypeFromSnippet('Bye')
+        {'Value': 'Bye'}
diff --git a/examples/ex6_complex_type_conversion/build.gradle b/examples/ex6_complex_type_conversion/build.gradle
new file mode 100644
index 0000000..b6039b0
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/build.gradle
@@ -0,0 +1,27 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 31
+    buildToolsVersion '31.0.0'
+
+    defaultConfig {
+        applicationId "com.google.android.mobly.snippet.example6"
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode 1
+        versionName "0.0.1"
+    }
+    lintOptions {
+        abortOnError true
+        checkAllWarnings true
+        warningsAsErrors true
+    }
+}
+
+dependencies {
+    // The 'implementation project' dep is to compile against the snippet lib source in
+    // this repo. For your own snippets, you'll want to use the regular
+    // 'implementation' dep instead:
+    //implementation 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
+    implementation project(':mobly-snippet-lib')
+}
diff --git a/examples/ex6_complex_type_conversion/src/main/AndroidManifest.xml b/examples/ex6_complex_type_conversion/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..c1548e7
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/src/main/AndroidManifest.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet.example6">
+
+    <application>
+        <!-- Required: list of all classes with @Rpc methods. -->
+        <meta-data
+            android:name="mobly-snippets"
+            android:value="com.google.android.mobly.snippet.example6.ExampleSnippet" />
+        <!-- Optional: a class used for converting Java objects to/from JSON. -->
+        <meta-data
+            android:name="mobly-object-converter"
+            android:value="com.google.android.mobly.snippet.example6.ExampleObjectConverter" />
+        <meta-data
+          android:name="mobly-log-tag"
+          android:value="MoblySnippetLibExample6" />
+    </application>
+
+    <instrumentation
+        android:name="com.google.android.mobly.snippet.SnippetRunner"
+        android:targetPackage="com.google.android.mobly.snippet.example6" />
+</manifest>
diff --git a/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/CustomType.java b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/CustomType.java
new file mode 100644
index 0000000..223b63e
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/CustomType.java
@@ -0,0 +1,21 @@
+package com.google.android.mobly.snippet.example6;
+
+/**
+ * A data class that defines a non-primitive type.
+ *
+ * This type is used to demonstrate serialization and de-serialization of complex type objects in
+ * Mobly Snippet Lib for Android.
+ */
+public class CustomType {
+    private String myValue;
+    CustomType(String value) {
+        myValue = value;
+    }
+
+    String getMyValue() {
+        return myValue;
+    }
+    public void setMyValue(String newValue) {
+        myValue = newValue;
+    }
+}
diff --git a/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleObjectConverter.java b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleObjectConverter.java
new file mode 100644
index 0000000..eea8831
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleObjectConverter.java
@@ -0,0 +1,34 @@
+package com.google.android.mobly.snippet.example6;
+
+import com.google.android.mobly.snippet.SnippetObjectConverter;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.lang.reflect.Type;
+
+
+/**
+ * Example showing how to supply custom object converter to Mobly Snippet Lib.
+ */
+
+public class ExampleObjectConverter implements SnippetObjectConverter {
+    @Override
+    public JSONObject serialize(Object object) throws JSONException {
+        JSONObject result = new JSONObject();
+        if (object instanceof CustomType) {
+            CustomType input = (CustomType) object;
+            result.put("Value", input.getMyValue());
+            return result;
+        }
+        return null;
+    }
+
+    @Override
+    public Object deserialize(JSONObject jsonObject, Type type) throws JSONException {
+        if (type == CustomType.class) {
+            return new CustomType(jsonObject.getString("Value"));
+        }
+        return null;
+    }
+}
diff --git a/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleSnippet.java b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleSnippet.java
new file mode 100644
index 0000000..3306f85
--- /dev/null
+++ b/examples/ex6_complex_type_conversion/src/main/java/com/google/android/mobly/snippet/example6/ExampleSnippet.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.example6;
+
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+import com.google.android.mobly.snippet.util.Log;
+
+import java.util.ArrayList;
+
+/**
+ * Example snippet showing converting complex type objects using custom logic.
+ *
+ * For complex types in Java, one can supply a custom object converter to Snippet Lib to specify how
+ * each complex type should be serialized/de-serialized. With this, users don't have to explicitly
+ * call a serializer or de-serializer in every single Rpc method, which simplifies code.
+ */
+public class ExampleSnippet implements Snippet {
+    @Rpc(description = "Pass a complex type as a snippet parameter.")
+    public String passComplexTypeToSnippet(CustomType input) {
+        Log.i("Old value is: " + input.getMyValue());
+        return "The value in CustomType is: " + input.getMyValue();
+    }
+
+    @Rpc(description = "Returns a complex type from snippet.")
+    public CustomType returnComplexTypeFromSnippet(String value) {
+        return new CustomType(value);
+    }
+
+    /**
+     * Demonstrates serialization/de-serialization of a collection of custom type objects.
+     */
+    @Rpc(description = "Update values for multiple CustomType objects.")
+    public ArrayList<CustomType> updateValues(ArrayList<CustomType> objects, String newValue) {
+        for (CustomType obj : objects) {
+            obj.setMyValue(newValue);
+        }
+        return objects;
+    }
+
+    @Override
+    public void shutdown() {}
+}
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 0000000..ec6a751
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1,29 @@
+# Project-wide Gradle settings.
+
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx1536m
+
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+# org.gradle.parallel=true
+
+android.useAndroidX=true
+android.enableJetifier=true
+
+# Key for signing the release
+signing.keyId=<your-key-id>
+signing.password=<your-key-password>
+signing.secretKeyRingFile=<path-to-your-secret-key-ring-file>
+
+# Credentials for OSSRH
+ossrhUsername=<your-jira-username>
+ossrhPassword=<your-jira-password>
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..13372ae
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.jar
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..cc8de8e
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Tue Oct 05 19:50:22 PDT 2021
+distributionBase=GRADLE_USER_HOME
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
+distributionPath=wrapper/dists
+zipStorePath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
diff --git a/gradlew b/gradlew
new file mode 100755
index 0000000..9d82f78
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,160 @@
+#!/usr/bin/env bash
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn ( ) {
+    echo "$*"
+}
+
+die ( ) {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+esac
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules
+function splitJvmOpts() {
+    JVM_OPTS=("$@")
+}
+eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS
+JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME"
+
+exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 0000000..aec9973
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,90 @@
+@if "%DEBUG%" == "" @echo off

+@rem ##########################################################################

+@rem

+@rem  Gradle startup script for Windows

+@rem

+@rem ##########################################################################

+

+@rem Set local scope for the variables with windows NT shell

+if "%OS%"=="Windows_NT" setlocal

+

+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.

+set DEFAULT_JVM_OPTS=

+

+set DIRNAME=%~dp0

+if "%DIRNAME%" == "" set DIRNAME=.

+set APP_BASE_NAME=%~n0

+set APP_HOME=%DIRNAME%

+

+@rem Find java.exe

+if defined JAVA_HOME goto findJavaFromJavaHome

+

+set JAVA_EXE=java.exe

+%JAVA_EXE% -version >NUL 2>&1

+if "%ERRORLEVEL%" == "0" goto init

+

+echo.

+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

+echo.

+echo Please set the JAVA_HOME variable in your environment to match the

+echo location of your Java installation.

+

+goto fail

+

+:findJavaFromJavaHome

+set JAVA_HOME=%JAVA_HOME:"=%

+set JAVA_EXE=%JAVA_HOME%/bin/java.exe

+

+if exist "%JAVA_EXE%" goto init

+

+echo.

+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%

+echo.

+echo Please set the JAVA_HOME variable in your environment to match the

+echo location of your Java installation.

+

+goto fail

+

+:init

+@rem Get command-line arguments, handling Windowz variants

+

+if not "%OS%" == "Windows_NT" goto win9xME_args

+if "%@eval[2+2]" == "4" goto 4NT_args

+

+:win9xME_args

+@rem Slurp the command line arguments.

+set CMD_LINE_ARGS=

+set _SKIP=2

+

+:win9xME_args_slurp

+if "x%~1" == "x" goto execute

+

+set CMD_LINE_ARGS=%*

+goto execute

+

+:4NT_args

+@rem Get arguments from the 4NT Shell from JP Software

+set CMD_LINE_ARGS=%$

+

+:execute

+@rem Setup the command line

+

+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar

+

+@rem Execute Gradle

+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%

+

+:end

+@rem End local scope for the variables with windows NT shell

+if "%ERRORLEVEL%"=="0" goto mainEnd

+

+:fail

+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of

+rem the _cmd.exe /c_ return code!

+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1

+exit /b 1

+

+:mainEnd

+if "%OS%"=="Windows_NT" endlocal

+

+:omega

diff --git a/settings.gradle b/settings.gradle
new file mode 100644
index 0000000..08025db
--- /dev/null
+++ b/settings.gradle
@@ -0,0 +1,9 @@
+include (
+    ':mobly-snippet-lib',
+    ':examples:ex1_standalone_app',
+    ':examples:ex2_espresso',
+    ':examples:ex3_async_event',
+    ':examples:ex4_uiautomator',
+    ':examples:ex5_schedule_rpc',
+    ':examples:ex6_complex_type_conversion')
+project(":mobly-snippet-lib").projectDir = file('third_party/sl4a')
diff --git a/third_party/sl4a/LICENSE b/third_party/sl4a/LICENSE
new file mode 100644
index 0000000..a095299
--- /dev/null
+++ b/third_party/sl4a/LICENSE
@@ -0,0 +1,154 @@
+Copied from http://www.apache.org/licenses/LICENSE-2.0:
+
+Apache License
+
+Version 2.0, January 2004
+
+http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+"License" shall mean the terms and conditions for use, reproduction, and
+distribution as defined by Sections 1 through 9 of this document.
+
+"Licensor" shall mean the copyright owner or entity authorized by the copyright
+owner that is granting the License.
+
+"Legal Entity" shall mean the union of the acting entity and all other entities
+that control, are controlled by, or are under common control with that entity.
+For the purposes of this definition, "control" means (i) the power, direct or
+indirect, to cause the direction or management of such entity, whether by
+contract or otherwise, or (ii) ownership of fifty percent (50%) or more of the
+outstanding shares, or (iii) beneficial ownership of such entity.
+
+"You" (or "Your") shall mean an individual or Legal Entity exercising
+permissions granted by this License.
+
+"Source" form shall mean the preferred form for making modifications, including
+but not limited to software source code, documentation source, and configuration
+files.
+
+"Object" form shall mean any form resulting from mechanical transformation or
+translation of a Source form, including but not limited to compiled object code,
+generated documentation, and conversions to other media types.
+
+"Work" shall mean the work of authorship, whether in Source or Object form, made
+available under the License, as indicated by a copyright notice that is included
+in or attached to the work (an example is provided in the Appendix below).
+
+"Derivative Works" shall mean any work, whether in Source or Object form, that
+is based on (or derived from) the Work and for which the editorial revisions,
+annotations, elaborations, or other modifications represent, as a whole, an
+original work of authorship. For the purposes of this License, Derivative Works
+shall not include works that remain separable from, or merely link (or bind by
+name) to the interfaces of, the Work and Derivative Works thereof.
+
+"Contribution" shall mean any work of authorship, including the original version
+of the Work and any modifications or additions to that Work or Derivative Works
+thereof, that is intentionally submitted to Licensor for inclusion in the Work
+by the copyright owner or by an individual or Legal Entity authorized to submit
+on behalf of the copyright owner. For the purposes of this definition,
+"submitted" means any form of electronic, verbal, or written communication sent
+to the Licensor or its representatives, including but not limited to
+communication on electronic mailing lists, source code control systems, and
+issue tracking systems that are managed by, or on behalf of, the Licensor for
+the purpose of discussing and improving the Work, but excluding communication
+that is conspicuously marked or otherwise designated in writing by the copyright
+owner as "Not a Contribution."
+
+"Contributor" shall mean Licensor and any individual or Legal Entity on behalf
+of whom a Contribution has been received by Licensor and subsequently
+incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of this
+License, each Contributor hereby grants to You a perpetual, worldwide, non-
+exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce,
+prepare Derivative Works of, publicly display, publicly perform, sublicense, and
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+
+3. Grant of Patent License. Subject to the terms and conditions of this License,
+each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-
+charge, royalty-free, irrevocable (except as stated in this section) patent
+license to make, have made, use, offer to sell, sell, import, and otherwise
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+Contribution(s) alone or by combination of their Contribution(s) with the Work
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+alleging that the Work or a Contribution incorporated within the Work
+constitutes direct or contributory patent infringement, then any patent licenses
+granted to You under this License for that Work shall terminate as of the date
+such litigation is filed.
+
+4. Redistribution. You may reproduce and distribute copies of the Work or
+Derivative Works thereof in any medium, with or without modifications, and in
+Source or Object form, provided that You meet the following conditions:
+
+You must give any other recipients of the Work or Derivative Works a copy of
+this License; and You must cause any modified files to carry prominent notices
+stating that You changed the files; and You must retain, in the Source form of
+any Derivative Works that You distribute, all copyright, patent, trademark, and
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+includes a "NOTICE" text file as part of its distribution, then any Derivative
+Works that You distribute must include a readable copy of the attribution
+notices contained within such NOTICE file, excluding those notices that do not
+pertain to any part of the Derivative Works, in at least one of the following
+places: within a NOTICE text file distributed as part of the Derivative Works;
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+Works; or, within a display generated by the Derivative Works, if and wherever
+such third-party notices normally appear. The contents of the NOTICE file are
+for informational purposes only and do not modify the License. You may add Your
+own attribution notices within Derivative Works that You distribute, alongside
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+additional attribution notices cannot be construed as modifying the License. 
+
+You may add Your own copyright statement to Your modifications and may provide
+additional or different license terms and conditions for use, reproduction, or
+distribution of Your modifications, or for any such Derivative Works as a whole,
+provided Your use, reproduction, and distribution of the Work otherwise complies
+with the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise, any
+Contribution intentionally submitted for inclusion in the Work by You to the
+Licensor shall be under the terms and conditions of this License, without any
+additional terms or conditions. Notwithstanding the above, nothing herein shall
+supersede or modify the terms of any separate license agreement you may have
+executed with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade names,
+trademarks, service marks, or product names of the Licensor, except as required
+for reasonable and customary use in describing the origin of the Work and
+reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or agreed to in
+writing, Licensor provides the Work (and each Contributor provides its
+Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied, including, without limitation, any warranties
+or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+PARTICULAR PURPOSE. You are solely responsible for determining the
+appropriateness of using or redistributing the Work and assume any risks
+associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory, whether in
+tort (including negligence), contract, or otherwise, unless required by
+applicable law (such as deliberate and grossly negligent acts) or agreed to in
+writing, shall any Contributor be liable to You for damages, including any
+direct, indirect, special, incidental, or consequential damages of any character
+arising as a result of this License or out of the use or inability to use the
+Work (including but not limited to damages for loss of goodwill, work stoppage,
+computer failure or malfunction, or any and all other commercial damages or
+losses), even if such Contributor has been advised of the possibility of such
+damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing the Work or
+Derivative Works thereof, You may choose to offer, and charge a fee for,
+acceptance of support, warranty, indemnity, or other liability obligations
+and/or rights consistent with this License. However, in accepting such
+obligations, You may act only on Your own behalf and on Your sole
+responsibility, not on behalf of any other Contributor, and only if You agree to
+indemnify, defend, and hold each Contributor harmless for any liability incurred
+by, or claims asserted against, such Contributor by reason of your accepting any
+such warranty or additional liability.
diff --git a/third_party/sl4a/README.google b/third_party/sl4a/README.google
new file mode 100644
index 0000000..1efc19f
--- /dev/null
+++ b/third_party/sl4a/README.google
@@ -0,0 +1,22 @@
+URL: https://android.googlesource.com/platform/external/sl4a/+archive/f0a094f3709187319222e64d8434f168ad8ffac9.tar.gz
+Version: f0a094f3709187319222e64d8434f168ad8ffac9
+License: Apache 2.0
+License File: LICENSE
+
+Description:
+Originally authored by Damon Kohler, Scripting Layer for Android, SL4A, is an
+automation toolset for calling Android APIs in a platform-independent manner. It
+supports both remote automation via ADB as well as execution of scripts from
+on-device via a series of lightweight translation layers.
+
+This version of sl4a is heavily modified to act as an RPC library for
+third-party facades (called code snippets). It no longer has much in common with
+the original sl4a project.
+
+
+Local Modifications:
+- LICENSE file has been created for compliance purposes. Not included in
+  original distribution.
+- This version of sl4a has been extensively refactored to remove all Android
+  facades and scripting interpreters. Only the RPC layer and facade registration
+  engine remain. This is to facilitate its use as a library in user projects.
diff --git a/third_party/sl4a/build.gradle b/third_party/sl4a/build.gradle
new file mode 100644
index 0000000..48446b4
--- /dev/null
+++ b/third_party/sl4a/build.gradle
@@ -0,0 +1,163 @@
+buildscript {
+    repositories {
+        mavenCentral()
+        google()
+    }
+}
+
+plugins {
+    id 'com.github.sherter.google-java-format' version '0.9'
+    id 'maven-publish'
+    id 'signing'
+}
+
+apply plugin: 'com.android.library'
+
+android {
+    compileSdkVersion 31
+
+    defaultConfig {
+        minSdkVersion 26
+        targetSdkVersion 31
+        versionCode VERSION_CODE.toInteger()
+        versionName VERSION_NAME
+
+        // Need to set up some project properties to publish to bintray.
+        project.group = GROUP_ID
+        project.archivesBaseName = ARTIFACT_ID
+        project.version = VERSION_NAME
+    }
+
+    splits {
+        abi {
+          enable true
+          reset()
+          // Specifies a list of ABIs that Gradle should create APKs for.
+          include "arm64-v8a", "armeabi-v7a", "armeabi"
+          universalApk true
+        }
+    }
+
+    lintOptions {
+        abortOnError false
+        checkAllWarnings true
+        warningsAsErrors true
+        disable 'HardwareIds','MissingApplicationIcon','GoogleAppIndexingWarning','InvalidPackage','OldTargetApi'
+    }
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+}
+
+dependencies {
+    implementation 'junit:junit:4.13.2'
+    implementation 'androidx.test:runner:1.4.0'
+}
+
+googleJavaFormat {
+    options style: 'AOSP'
+}
+
+task sourcesJar(type: Jar) {
+    from android.sourceSets.main.java.srcDirs
+    classifier = 'sources'
+}
+
+task javadoc(type: Javadoc) {
+    source = android.sourceSets.main.java.srcDirs
+    classpath += project.files(android.getBootClasspath().join(File.pathSeparator))
+    options.addStringOption('Xdoclint:none', '-quiet')
+    options.addStringOption('encoding', 'UTF-8')
+    options.addStringOption('charSet', 'UTF-8')
+    failOnError false
+}
+
+task javadocJar(type: Jar, dependsOn: javadoc) {
+    classifier = 'javadoc'
+    from javadoc.destinationDir
+}
+
+artifacts {
+    archives javadocJar
+    archives sourcesJar
+}
+
+
+afterEvaluate {
+    publishing {
+        publications {
+            release(MavenPublication) {
+                groupId GROUP_ID
+                artifactId ARTIFACT_ID
+                version VERSION_NAME
+                from components.release
+
+                artifact sourcesJar
+                artifact javadocJar
+
+                pom {
+                    name = ARTIFACT_ID
+                    description = 'Android library for triggering device-side ' +
+                                  'code from host-side Mobly tests.'
+                    url = 'https://github.com/google/mobly-snippet-lib'
+                    licenses {
+                        license {
+                            name = 'The Apache Software License, Version 2.0'
+                            url = 'http://www.apache.org/licenses/LICENSE-2.0.txt'
+                            distribution = 'repo'
+                        }
+                    }
+                    developers {
+                        developer {
+                            name = 'The Mobly Team'
+                        }
+                    }
+                    scm {
+                        connection = 'https://github.com/google/mobly-snippet-lib.git'
+                        url = 'https://github.com/google/mobly-snippet-lib'
+                    }
+                }
+            }
+        }
+
+        repositories {
+            maven {
+                def releasesRepoUrl = 'https://oss.sonatype.org/service/local/staging/deploy/maven2/'
+                def snapshotsRepoUrl = 'https://oss.sonatype.org/content/repositories/snapshots/'
+                url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
+                credentials {
+                    username ossrhUsername
+                    password ossrhPassword
+                }
+            }
+        }
+    }
+    signing {
+        sign publishing.publications.release
+    }
+}
+
+// Open lint's HTML report in your default browser or viewer.
+task openLintReport(type: Exec) {
+    def lint_report = "build/reports/lint-results-debug.html"
+    def cmd = "cat"
+    def platform = System.getProperty('os.name').toLowerCase(Locale.ROOT)
+    if (platform.contains("linux")) {
+        cmd = "xdg-open"
+    } else if (platform.contains("mac os x")) {
+        cmd = "open"
+    } else if (platform.contains("windows")) {
+        cmd = "launch"
+    }
+    commandLine cmd, lint_report
+}
+
+task presubmit {
+    dependsOn { ['googleJavaFormat', 'lint', 'openLintReport'] }
+    doLast {
+        println "Fix any lint issues you see. When it looks good, submit the pull request."
+    }
+}
+
diff --git a/third_party/sl4a/gradle.properties b/third_party/sl4a/gradle.properties
new file mode 100644
index 0000000..86f8068
--- /dev/null
+++ b/third_party/sl4a/gradle.properties
@@ -0,0 +1,6 @@
+# This version code implements the versioning recommendations in:
+# https://blog.jayway.com/2015/03/11/automatic-versioncode-generation-in-android-gradle/
+VERSION_CODE=1030199
+VERSION_NAME=1.3.1
+GROUP_ID=com.google.android.mobly
+ARTIFACT_ID=mobly-snippet-lib
diff --git a/third_party/sl4a/src/main/AndroidManifest.xml b/third_party/sl4a/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..5b6c4cf
--- /dev/null
+++ b/third_party/sl4a/src/main/AndroidManifest.xml
@@ -0,0 +1,4 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.android.mobly.snippet">
+    <uses-permission android:name="android.permission.INTERNET" />
+</manifest>
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/Snippet.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/Snippet.java
new file mode 100644
index 0000000..646a3d9
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/Snippet.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet;
+
+public interface Snippet {
+    /** Invoked when the receiver is shut down. */
+    default void shutdown() throws Exception {}
+    ;
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetObjectConverter.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetObjectConverter.java
new file mode 100644
index 0000000..b9a101b
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetObjectConverter.java
@@ -0,0 +1,39 @@
+package com.google.android.mobly.snippet;
+
+import java.lang.reflect.Type;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Interface for a converter that serializes and de-serializes objects.
+ *
+ * <p>Classes implementing this interface are meant to provide custom serialization/de-serialization
+ * logic for complex types.
+ *
+ * <p>Serialization here means converting a Java object to {@link JSONObject}, which can be
+ * transported over Snippet's Rpc protocol. De-serialization is this process in reverse.
+ */
+public interface SnippetObjectConverter {
+    /**
+     * Serializes a complex type object to {@link JSONObject}.
+     *
+     * <p>Return null to signify the complex type is not supported.
+     *
+     * @param object The object to convert to "serialize".
+     * @return A JSONObject representation of the input object, or `null` if the input object type
+     *     is not supported.
+     * @throws JSONException
+     */
+    JSONObject serialize(Object object) throws JSONException;
+
+    /**
+     * Deserializes a {@link JSONObject} to a Java complex type object.
+     *
+     * @param jsonObject A {@link JSONObject} passed from the Rpc client.
+     * @param type The expected {@link Type} of the Java object.
+     * @return A Java object of the specified {@link Type}, or `null` if the {@link Type} is not
+     *     supported.
+     * @throws JSONException
+     */
+    Object deserialize(JSONObject jsonObject, Type type) throws JSONException;
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetRunner.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetRunner.java
new file mode 100644
index 0000000..36d1348
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/SnippetRunner.java
@@ -0,0 +1,199 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.android.mobly.snippet;
+
+import android.app.Instrumentation;
+import android.app.Notification;
+import android.app.NotificationChannel;
+import android.app.NotificationManager;
+import android.content.Context;
+import android.os.Build;
+import android.os.Bundle;
+import android.os.Process;
+import androidx.test.runner.AndroidJUnitRunner;
+import com.google.android.mobly.snippet.rpc.AndroidProxy;
+import com.google.android.mobly.snippet.util.EmptyTestClass;
+import com.google.android.mobly.snippet.util.Log;
+import com.google.android.mobly.snippet.util.NotificationIdFactory;
+import java.io.IOException;
+import java.net.SocketException;
+import java.util.Locale;
+
+/**
+ * A launcher that starts the snippet server as an instrumentation so that it has access to the
+ * target app's context.
+ *
+ * <p>We have to extend some subclass of {@link androidx.test.runner.AndroidJUnitRunner} because
+ * snippets are launched with 'am instrument', and snippet APKs need to access {@link
+ * androidx.test.platform.app.InstrumentationRegistry}.
+ *
+ * <p>The launch and communication protocol between snippet and client is versionated and reported
+ * as follows:
+ *
+ * <ul>
+ *   <li>v0 (not reported):
+ *       <ul>
+ *         <li>Launch as Instrumentation with SnippetRunner.
+ *         <li>No protocol-specific messages reported through instrumentation output.
+ *         <li>'stop' action prints 'OK (0 tests)'
+ *         <li>'start' action prints nothing.
+ *       </ul>
+ *   <li>v1.0: New instrumentation output added to track bringup process
+ *       <ul>
+ *         <li>"SNIPPET START, PROTOCOL &lt;major&gt; &lt;minor&gt;" upon snippet start
+ *         <li>"SNIPPET SERVING, PORT &lt;port&gt;" once server is ready
+ *       </ul>
+ * </ul>
+ */
+public class SnippetRunner extends AndroidJUnitRunner {
+
+    /**
+     * Major version of the launch and communication protocol.
+     *
+     * <p>Incrementing this means that compatibility with clients using the older version is broken.
+     * Avoid breaking compatibility unless there is no other choice.
+     */
+    public static final int PROTOCOL_MAJOR_VERSION = 1;
+
+    /**
+     * Minor version of the launch and communication protocol.
+     *
+     * <p>Increment this when new features are added to the launch and communication protocol that
+     * are backwards compatible with the old protocol and don't break existing clients.
+     */
+    public static final int PROTOCOL_MINOR_VERSION = 0;
+
+    private static final String ARG_ACTION = "action";
+    private static final String ARG_PORT = "port";
+
+    /**
+     * Values needed to create a notification channel. This applies to versions > O (26).
+     */
+    private static final String NOTIFICATION_CHANNEL_ID = "msl_channel";
+    private static final String NOTIFICATION_CHANNEL_DESC = "Channel reserved for mobly-snippet-lib.";
+    private static final CharSequence NOTIFICATION_CHANNEL_NAME = "msl";
+
+    private enum Action {
+        START,
+        STOP
+    };
+
+    private static final int NOTIFICATION_ID = NotificationIdFactory.create();
+
+    private Bundle mArguments;
+    private NotificationManager mNotificationManager;
+    private Notification mNotification;
+
+    @Override
+    public void onCreate(Bundle arguments) {
+        mArguments = arguments;
+
+        // First-run static setup
+        Log.initLogTag(getContext());
+
+        // First order of business is to report HELLO to instrumentation output.
+        sendString(
+                "SNIPPET START, PROTOCOL " + PROTOCOL_MAJOR_VERSION + " " + PROTOCOL_MINOR_VERSION);
+
+        // Prevent this runner from triggering any real JUnit tests in the snippet by feeding it a
+        // hardcoded empty test class.
+        mArguments.putString("class", EmptyTestClass.class.getCanonicalName());
+        mNotificationManager =
+                (NotificationManager)
+                        getTargetContext().getSystemService(Context.NOTIFICATION_SERVICE);
+        super.onCreate(mArguments);
+    }
+
+    @Override
+    public void onStart() {
+        String actionStr = mArguments.getString(ARG_ACTION);
+        if (actionStr == null) {
+            throw new IllegalArgumentException("\"--e action <action>\" was not specified");
+        }
+        Action action = Action.valueOf(actionStr.toUpperCase(Locale.ROOT));
+        switch (action) {
+            case START:
+                String servicePort = mArguments.getString(ARG_PORT);
+                int port = 0 /* auto chosen */;
+                if (servicePort != null) {
+                    port = Integer.parseInt(servicePort);
+                }
+                startServer(port);
+                break;
+            case STOP:
+                mNotificationManager.cancel(NOTIFICATION_ID);
+                mNotificationManager.cancelAll();
+                super.onStart();
+        }
+    }
+
+    private void startServer(int port) {
+        AndroidProxy androidProxy = new AndroidProxy(getContext());
+        try {
+            androidProxy.startLocal(port);
+        } catch (SocketException e) {
+            if ("Permission denied".equals(e.getMessage())) {
+                throw new RuntimeException(
+                        "Failed to start server. No permission to create a socket. Does the *MAIN* "
+                                + "app manifest declare the INTERNET permission?",
+                        e);
+            }
+            throw new RuntimeException("Failed to start server", e);
+        } catch (IOException e) {
+            throw new RuntimeException("Failed to start server", e);
+        }
+        createNotification();
+        int actualPort = androidProxy.getPort();
+        sendString("SNIPPET SERVING, PORT " + actualPort);
+        Log.i("Snippet server started for process " + Process.myPid() + " on port " + actualPort);
+    }
+
+    @SuppressWarnings("deprecation") // Depreciated calls needed for versions < O (26)
+    private void createNotification() {
+        Notification.Builder builder;
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
+            builder = new Notification.Builder(getTargetContext());
+            builder.setSmallIcon(android.R.drawable.btn_star)
+                    .setTicker(null)
+                    .setWhen(System.currentTimeMillis())
+                    .setContentTitle("Snippet Service");
+            mNotification = builder.getNotification();
+        } else {
+            // Create a new channel for notifications. Needed for versions >= O
+            NotificationChannel channel = new NotificationChannel(
+                    NOTIFICATION_CHANNEL_ID, NOTIFICATION_CHANNEL_NAME, NotificationManager.IMPORTANCE_DEFAULT);
+            channel.setDescription(NOTIFICATION_CHANNEL_DESC);
+            mNotificationManager.createNotificationChannel(channel);
+
+            // Build notification
+            builder = new Notification.Builder(getTargetContext(), NOTIFICATION_CHANNEL_ID);
+            builder.setSmallIcon(android.R.drawable.btn_star)
+                    .setTicker(null)
+                    .setWhen(System.currentTimeMillis())
+                    .setContentTitle("Snippet Service");
+            mNotification = builder.build();
+        }
+        mNotification.flags = Notification.FLAG_NO_CLEAR | Notification.FLAG_ONGOING_EVENT;
+        mNotificationManager.notify(NOTIFICATION_ID, mNotification);
+    }
+
+    private void sendString(String string) {
+        Log.i("Sending protocol message: " + string);
+        Bundle bundle = new Bundle();
+        bundle.putString(Instrumentation.REPORT_KEY_STREAMRESULT, string + "\n");
+        sendStatus(0, bundle);
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventCache.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventCache.java
new file mode 100644
index 0000000..a3106f5
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventCache.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.event;
+
+import com.google.android.mobly.snippet.util.Log;
+import java.util.Deque;
+import java.util.HashMap;
+import java.util.Locale;
+import java.util.Map;
+import java.util.concurrent.LinkedBlockingDeque;
+
+/**
+ * Manage the event queue.
+ *
+ * <p>EventCache APIs interact with the SnippetEvent cache - a data structure that holds {@link
+ * SnippetEvent} objects posted from snippet classes. The SnippetEvent cache provides a useful means
+ * of recording background events (such as sensor data) when the phone is busy with foreground
+ * activities.
+ */
+public class EventCache {
+    private static final String EVENT_DEQUE_ID_TEMPLATE = "%s|%s";
+    private static final int EVENT_DEQUE_MAX_SIZE = 1024;
+
+    // A Map with each value being the queue for a particular type of event, and the key being the
+    // unique ID of the queue. The ID is composed of a callback ID and an event's name.
+    private final Map<String, LinkedBlockingDeque<SnippetEvent>> mEventDeques = new HashMap<>();
+
+    private static volatile EventCache mEventCache;
+
+    private EventCache() {}
+
+    public static EventCache getInstance() {
+        if (mEventCache == null) {
+            synchronized (EventCache.class) {
+                if (mEventCache == null) {
+                    mEventCache = new EventCache();
+                }
+            }
+        }
+        return mEventCache;
+    }
+
+    public static String getQueueId(String callbackId, String name) {
+        return String.format(Locale.US, EVENT_DEQUE_ID_TEMPLATE, callbackId, name);
+    }
+
+    public LinkedBlockingDeque<SnippetEvent> getEventDeque(String qId) {
+        synchronized (mEventDeques) {
+            LinkedBlockingDeque<SnippetEvent> eventDeque = mEventDeques.get(qId);
+            if (eventDeque == null) {
+                eventDeque = new LinkedBlockingDeque<>(EVENT_DEQUE_MAX_SIZE);
+                mEventDeques.put(qId, eventDeque);
+            }
+            return eventDeque;
+        }
+    }
+
+    /**
+     * Post an {@link SnippetEvent} object to the Event cache.
+     *
+     * <p>Snippet classes should use this method to post events. If EVENT_DEQUE_MAX_SIZE is reached,
+     * the oldest elements will be retired until the new event could be posted.
+     *
+     * @param snippetEvent The snippetEvent to post to {@link EventCache}.
+     */
+    public void postEvent(SnippetEvent snippetEvent) {
+        String qId = getQueueId(snippetEvent.getCallbackId(), snippetEvent.getName());
+        Deque<SnippetEvent> q = getEventDeque(qId);
+        synchronized (q) {
+            while (!q.offer(snippetEvent)) {
+                SnippetEvent retiredEvent = q.removeFirst();
+                Log.v(
+                        String.format(
+                                Locale.US,
+                                "Retired event %s due to deque reaching the size limit (%s).",
+                                retiredEvent,
+                                EVENT_DEQUE_MAX_SIZE));
+            }
+        }
+        Log.v(String.format(Locale.US, "Posted event(%s)", qId));
+    }
+
+    /** Clears all cached events. */
+    public void clearAll() {
+        synchronized (mEventDeques) {
+            mEventDeques.clear();
+        }
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventSnippet.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventSnippet.java
new file mode 100644
index 0000000..4cebb74
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/EventSnippet.java
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.event;
+
+import androidx.annotation.Nullable;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.Rpc;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.TimeUnit;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public class EventSnippet implements Snippet {
+    private static class EventSnippetException extends Exception {
+        private static final long serialVersionUID = 1L;
+
+        public EventSnippetException(String msg) {
+            super(msg);
+        }
+    }
+
+    private static final int DEFAULT_TIMEOUT_MILLISECOND = 60 * 1000;
+    private final EventCache mEventCache = EventCache.getInstance();
+
+    @Rpc(
+            description =
+                    "Blocks until an event of a specified type has been received. The returned event is removed from the cache. Default timeout is 60s.")
+    public JSONObject eventWaitAndGet(
+            String callbackId, String eventName, @Nullable Integer timeout)
+            throws InterruptedException, JSONException, EventSnippetException {
+        // The server side should never wait forever, so we'll use a default timeout is one is not
+        // provided.
+        if (timeout == null) {
+            timeout = DEFAULT_TIMEOUT_MILLISECOND;
+        }
+        String qId = EventCache.getQueueId(callbackId, eventName);
+        LinkedBlockingDeque<SnippetEvent> q = mEventCache.getEventDeque(qId);
+        SnippetEvent result = q.pollFirst(timeout, TimeUnit.MILLISECONDS);
+        if (result == null) {
+            throw new EventSnippetException("timeout.");
+        }
+        return result.toJson();
+    }
+
+    @Rpc(
+            description =
+                    "Gets and removes all the events of a certain name that have been received so far. "
+                            + "Non-blocking. Potentially racey since it does not guarantee no event of "
+                            + "the same name will occur after the call.")
+    public List<JSONObject> eventGetAll(String callbackId, String eventName)
+            throws InterruptedException, JSONException {
+        String qId = EventCache.getQueueId(callbackId, eventName);
+        LinkedBlockingDeque<SnippetEvent> q = mEventCache.getEventDeque(qId);
+        ArrayList<JSONObject> results = new ArrayList<>(q.size());
+        ArrayList<SnippetEvent> buffer = new ArrayList<>(q.size());
+        q.drainTo(buffer);
+        for (SnippetEvent snippetEvent : buffer) {
+            results.add(snippetEvent.toJson());
+        }
+        if (results.size() == 0) {
+            return Collections.emptyList();
+        }
+        return results;
+    }
+
+    @Override
+    public void shutdown() {
+        mEventCache.clearAll();
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/SnippetEvent.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/SnippetEvent.java
new file mode 100644
index 0000000..a90d9eb
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/event/SnippetEvent.java
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.event;
+
+import android.os.Bundle;
+import com.google.android.mobly.snippet.rpc.JsonBuilder;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/** Class used to store information from a callback event. */
+public class SnippetEvent {
+
+    // The ID used to associate an event to a callback object on the client side.
+    private final String mCallbackId;
+    // The name of this event, e.g. startXxxServiceOnSuccess.
+    private final String mName;
+    // The content of this event. We use Android's Bundle because it adheres to Android convention
+    // and adding data to it does not throw checked exceptions, which makes the world a better
+    // place.
+    private final Bundle mData = new Bundle();
+
+    private final long mCreationTime;
+
+    /**
+     * Constructs an {@link SnippetEvent} object.
+     *
+     * <p>The object is used to store information from a callback method associated with a call to
+     * an {@link com.google.android.mobly.snippet.rpc.AsyncRpc} method.
+     *
+     * @param callbackId The callbackId passed to the {@link
+     *     com.google.android.mobly.snippet.rpc.AsyncRpc} method.
+     * @param name The name of the event.
+     */
+    public SnippetEvent(String callbackId, String name) {
+        if (callbackId == null) {
+            throw new IllegalArgumentException("SnippetEvent's callback ID shall not be null.");
+        }
+        if (name == null) {
+            throw new IllegalArgumentException("SnippetEvent's name shall not be null.");
+        }
+        mCallbackId = callbackId;
+        mName = name;
+        mCreationTime = System.currentTimeMillis();
+    }
+
+    public String getCallbackId() {
+        return mCallbackId;
+    }
+
+    public String getName() {
+        return mName;
+    }
+
+    /**
+     * Get the internal bundle of this event.
+     *
+     * <p>This is the only way to add data to the event, because we can't inherit Bundle type and we
+     * don't want to dup all the getter and setters of {@link Bundle}.
+     *
+     * @return The Bundle that holds user data for this {@link SnippetEvent}.
+     */
+    public Bundle getData() {
+        return mData;
+    }
+
+    public long getCreationTime() {
+        return mCreationTime;
+    }
+
+    public JSONObject toJson() throws JSONException {
+        JSONObject result = new JSONObject();
+        result.put("callbackId", getCallbackId());
+        result.put("name", getName());
+        result.put("time", getCreationTime());
+        result.put("data", JsonBuilder.build(mData));
+        return result;
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/future/FutureResult.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/future/FutureResult.java
new file mode 100644
index 0000000..5e6edd3
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/future/FutureResult.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.future;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+/** FutureResult represents an eventual execution result for asynchronous operations. */
+public class FutureResult<T> implements Future<T> {
+
+    private final CountDownLatch mLatch = new CountDownLatch(1);
+    private volatile T mResult = null;
+
+    public void set(T result) {
+        mResult = result;
+        mLatch.countDown();
+    }
+
+    @Override
+    public boolean cancel(boolean mayInterruptIfRunning) {
+        return false;
+    }
+
+    @Override
+    public T get() throws InterruptedException {
+        mLatch.await();
+        return mResult;
+    }
+
+    @Override
+    public T get(long timeout, TimeUnit unit) throws InterruptedException {
+        mLatch.await(timeout, unit);
+        return mResult;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return false;
+    }
+
+    @Override
+    public boolean isDone() {
+        return mResult != null;
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetManager.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetManager.java
new file mode 100644
index 0000000..7707de2
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetManager.java
@@ -0,0 +1,290 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.manager;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.os.Build;
+import android.os.Bundle;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.SnippetObjectConverter;
+import com.google.android.mobly.snippet.event.EventSnippet;
+import com.google.android.mobly.snippet.rpc.MethodDescriptor;
+import com.google.android.mobly.snippet.rpc.RpcMinSdk;
+import com.google.android.mobly.snippet.rpc.RunOnUiThread;
+import com.google.android.mobly.snippet.schedulerpc.ScheduleRpcSnippet;
+import com.google.android.mobly.snippet.util.Log;
+import com.google.android.mobly.snippet.util.MainThread;
+import com.google.android.mobly.snippet.util.SnippetLibException;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.TreeSet;
+import java.util.concurrent.Callable;
+
+public class SnippetManager {
+    /**
+     * Name of the XML tag specifying what snippet classes to look for RPCs in.
+     *
+     * <p>Comma delimited list of full package names for classes that implements the Snippet
+     * interface.
+     */
+    private static final String TAG_NAME_SNIPPET_LIST = "mobly-snippets";
+    /** Name of the XML tag specifying the custom object converter class to use. */
+    private static final String TAG_NAME_OBJECT_CONVERTER = "mobly-object-converter";
+
+    private final Map<Class<? extends Snippet>, Snippet> mSnippets;
+    /** A map of strings to known RPCs. */
+    private final Map<String, MethodDescriptor> mKnownRpcs;
+
+    private static SnippetManager sInstance = null;
+    private boolean mShutdown = false;
+
+    private SnippetManager(Collection<Class<? extends Snippet>> classList) {
+        // Synchronized for multiple connections on the same session. Can't use ConcurrentHashMap
+        // because we have to put in a value of 'null' before the class is constructed, but
+        // ConcurrentHashMap does not allow null values.
+        mSnippets = Collections.synchronizedMap(new HashMap<Class<? extends Snippet>, Snippet>());
+        Map<String, MethodDescriptor> knownRpcs = new HashMap<>();
+        for (Class<? extends Snippet> receiverClass : classList) {
+            mSnippets.put(receiverClass, null);
+            Collection<MethodDescriptor> methodList = MethodDescriptor.collectFrom(receiverClass);
+            for (MethodDescriptor m : methodList) {
+                if (knownRpcs.containsKey(m.getName())) {
+                    // We already know an RPC of the same name. We don't catch this anywhere because
+                    // this is a programming error.
+                    throw new RuntimeException(
+                            "An RPC with the name " + m.getName() + " is already known.");
+                }
+                knownRpcs.put(m.getName(), m);
+            }
+        }
+        // Does not need to be concurrent because this map is read only, so it is safe to access
+        // from multiple threads. Wrap in an unmodifiableMap to enforce this.
+        mKnownRpcs = Collections.unmodifiableMap(knownRpcs);
+    }
+
+    public static synchronized SnippetManager initSnippetManager(Context context) {
+        if (sInstance != null) {
+            throw new IllegalStateException("SnippetManager should not be re-initialized");
+        }
+        // Add custom object converter if user provided one.
+        Class<? extends SnippetObjectConverter> converterClazz =
+                findSnippetObjectConverterFromMetadata(context);
+        if (converterClazz != null) {
+            Log.d("Found custom converter class, adding...");
+            SnippetObjectConverterManager.addConverter(converterClazz);
+        }
+        Collection<Class<? extends Snippet>> classList = findSnippetClassesFromMetadata(context);
+        sInstance = new SnippetManager(classList);
+        return sInstance;
+    }
+
+    public static SnippetManager getInstance() {
+        if (sInstance == null) {
+            throw new IllegalStateException("getInstance() called before init()");
+        }
+        if (sInstance.isShutdown()) {
+            throw new IllegalStateException("shutdown() called before getInstance()");
+        }
+        return sInstance;
+    }
+
+    public MethodDescriptor getMethodDescriptor(String methodName) {
+        return mKnownRpcs.get(methodName);
+    }
+
+    public SortedSet<String> getMethodNames() {
+        return new TreeSet<>(mKnownRpcs.keySet());
+    }
+
+    public Object invoke(Class<? extends Snippet> clazz, Method method, Object[] args)
+            throws Throwable {
+        if (method.isAnnotationPresent(RpcMinSdk.class)) {
+            int requiredSdkLevel = method.getAnnotation(RpcMinSdk.class).value();
+            if (Build.VERSION.SDK_INT < requiredSdkLevel) {
+                throw new SnippetLibException(
+                        String.format(
+                                Locale.US,
+                                "%s requires API level %d, current level is %d",
+                                method.getName(),
+                                requiredSdkLevel,
+                                Build.VERSION.SDK_INT));
+            }
+        }
+        Snippet object;
+        try {
+            object = get(clazz);
+            return invoke(object, method, args);
+        } catch (InvocationTargetException e) {
+            throw e.getCause();
+        }
+    }
+
+    public void shutdown() throws Exception {
+        for (final Entry<Class<? extends Snippet>, Snippet> entry : mSnippets.entrySet()) {
+            if (entry.getValue() == null) {
+                continue;
+            }
+            Method method = entry.getKey().getMethod("shutdown");
+            if (method.isAnnotationPresent(RunOnUiThread.class)) {
+                Log.d("Shutting down " + entry.getKey().getName() + " on the main thread");
+                MainThread.run(
+                        new Callable<Void>() {
+                            @Override
+                            public Void call() throws Exception {
+                                entry.getValue().shutdown();
+                                return null;
+                            }
+                        });
+            } else {
+                Log.d("Shutting down " + entry.getKey().getName());
+                entry.getValue().shutdown();
+            }
+        }
+        mSnippets.clear();
+        mKnownRpcs.clear();
+        mShutdown = true;
+    }
+
+    public boolean isShutdown() {
+        return mShutdown;
+    }
+
+    private static Bundle findMetadata(Context context) {
+        ApplicationInfo appInfo;
+        try {
+            appInfo =
+                    context.getPackageManager()
+                            .getApplicationInfo(
+                                    context.getPackageName(), PackageManager.GET_META_DATA);
+        } catch (PackageManager.NameNotFoundException e) {
+            throw new IllegalStateException(
+                    "Failed to find ApplicationInfo with package name: "
+                            + context.getPackageName());
+        }
+        return appInfo.metaData;
+    }
+
+    private static Class<? extends SnippetObjectConverter> findSnippetObjectConverterFromMetadata(
+            Context context) {
+        String className = findMetadata(context).getString(TAG_NAME_OBJECT_CONVERTER);
+        if (className == null) {
+            Log.i("No object converter provided.");
+            return null;
+        }
+        try {
+            return Class.forName(className).asSubclass(SnippetObjectConverter.class);
+        } catch (ClassNotFoundException | ClassCastException e) {
+            Log.e("Failed to find class " + className);
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static Set<Class<? extends Snippet>> findSnippetClassesFromMetadata(Context context) {
+        String snippets = findMetadata(context).getString(TAG_NAME_SNIPPET_LIST);
+        if (snippets == null) {
+            throw new IllegalStateException(
+                    "AndroidManifest.xml does not contain a <metadata> tag with "
+                            + "name=\""
+                            + TAG_NAME_SNIPPET_LIST
+                            + "\"");
+        }
+        String[] snippetClassNames = snippets.split("\\s*,\\s*");
+        Set<Class<? extends Snippet>> receiverSet = new HashSet<>();
+        /** Add the event snippet class which is provided within the Snippet Lib. */
+        receiverSet.add(EventSnippet.class);
+        /** Add the schedule RPC snippet class which is provided within the Snippet Lib. */
+        receiverSet.add(ScheduleRpcSnippet.class);
+        for (String snippetClassName : snippetClassNames) {
+            try {
+                Log.i("Trying to load Snippet class: " + snippetClassName);
+                Class<? extends Snippet> snippetClass =
+                        Class.forName(snippetClassName).asSubclass(Snippet.class);
+                receiverSet.add(snippetClass);
+            } catch (ClassNotFoundException | ClassCastException e) {
+                Log.e("Failed to find class " + snippetClassName);
+                throw new RuntimeException(e);
+            }
+        }
+        if (receiverSet.isEmpty()) {
+            throw new IllegalStateException("Found no subclasses of Snippet.");
+        }
+        return receiverSet;
+    }
+
+    private Snippet get(Class<? extends Snippet> clazz) throws Exception {
+        Snippet snippetImpl = mSnippets.get(clazz);
+        if (snippetImpl == null) {
+            // First time calling an RPC for this snippet; construct an instance under lock.
+            synchronized (clazz) {
+                snippetImpl = mSnippets.get(clazz);
+                if (snippetImpl == null) {
+                    final Constructor<? extends Snippet> constructor = clazz.getConstructor();
+                    if (constructor.isAnnotationPresent(RunOnUiThread.class)) {
+                        Log.d("Constructing " + clazz + " on the main thread");
+                        snippetImpl =
+                                MainThread.run(
+                                        new Callable<Snippet>() {
+                                            @Override
+                                            public Snippet call() throws Exception {
+                                                return constructor.newInstance();
+                                            }
+                                        });
+                    } else {
+                        Log.d("Constructing " + clazz);
+                        snippetImpl = constructor.newInstance();
+                    }
+                    mSnippets.put(clazz, snippetImpl);
+                }
+            }
+        }
+        return snippetImpl;
+    }
+
+    private Object invoke(final Snippet snippetImpl, final Method method, final Object[] args)
+            throws Exception {
+        if (method.isAnnotationPresent(RunOnUiThread.class)) {
+            Log.d(
+                    "Invoking RPC method "
+                            + method.getDeclaringClass()
+                            + "#"
+                            + method.getName()
+                            + " on the main thread");
+            return MainThread.run(
+                    new Callable<Object>() {
+                        @Override
+                        public Object call() throws Exception {
+                            return method.invoke(snippetImpl, args);
+                        }
+                    });
+        } else {
+            Log.d("Invoking RPC method " + method.getDeclaringClass() + "#" + method.getName());
+            return method.invoke(snippetImpl, args);
+        }
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetObjectConverterManager.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetObjectConverterManager.java
new file mode 100644
index 0000000..df8af53
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/manager/SnippetObjectConverterManager.java
@@ -0,0 +1,65 @@
+package com.google.android.mobly.snippet.manager;
+
+import com.google.android.mobly.snippet.SnippetObjectConverter;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Type;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Manager for classes that implement {@link SnippetObjectConverter}.
+ *
+ * <p>This class is created to separate how Snippet Lib handles object conversion internally from
+ * how the conversion scheme for complex types is defined for users.
+ *
+ * <p>Snippet Lib can pull in the custom serializers and deserializers through here in various
+ * stages of execution, whereas users can have a clean interface for supplying these methods without
+ * worrying about internal states of Snippet Lib.
+ *
+ * <p>This gives us the flexibility of changing Snippet Lib internal structure or expanding support
+ * without impacting users. E.g. we can support multiple converter classes in the future.
+ */
+public class SnippetObjectConverterManager {
+    private static SnippetObjectConverter mConverter;
+    private static volatile SnippetObjectConverterManager mManager;
+
+    private SnippetObjectConverterManager() {}
+
+    public static synchronized SnippetObjectConverterManager getInstance() {
+        if (mManager == null) {
+            mManager = new SnippetObjectConverterManager();
+        }
+        return mManager;
+    }
+
+    static void addConverter(Class<? extends SnippetObjectConverter> converterClass) {
+        if (mConverter != null) {
+            throw new RuntimeException("A converter has been added, cannot add again.");
+        }
+        try {
+            mConverter = converterClass.getConstructor().newInstance();
+        } catch (NoSuchMethodException e) {
+            throw new RuntimeException("No default constructor found for the converter class.");
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException(e);
+        } catch (InvocationTargetException e) {
+            throw new RuntimeException(e.getCause());
+        } catch (InstantiationException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public Object objectToJson(Object object) throws JSONException {
+        if (mConverter == null) {
+            return null;
+        }
+        return mConverter.serialize(object);
+    }
+
+    public Object jsonToObject(JSONObject jsonObject, Type type) throws JSONException {
+        if (mConverter == null) {
+            return null;
+        }
+        return mConverter.deserialize(jsonObject, type);
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AndroidProxy.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AndroidProxy.java
new file mode 100644
index 0000000..9428c82
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AndroidProxy.java
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import android.content.Context;
+import java.io.IOException;
+
+public class AndroidProxy {
+
+    private final JsonRpcServer mJsonRpcServer;
+
+    public AndroidProxy(Context context) {
+        mJsonRpcServer = new JsonRpcServer(context);
+    }
+
+    public void startLocal(int port) throws IOException {
+        mJsonRpcServer.startLocal(port);
+    }
+
+    public int getPort() {
+        return mJsonRpcServer.getPort();
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AsyncRpc.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AsyncRpc.java
new file mode 100644
index 0000000..6bdd8ca
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/AsyncRpc.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * The {@link AsyncRpc} annotation is used to annotate server-side implementations of RPCs that
+ * trigger asynchronous events. This behaves generally the same as {@link Rpc}, but methods that are
+ * annotated with {@link AsyncRpc} are expected to take the extra parameter which is the ID to use
+ * when posting async events.
+ *
+ * <p>Sample Usage:
+ *
+ * <pre>{@code
+ * {@literal @}AsyncRpc(description = "An example showing the usage of AsyncRpc")
+ * public void doSomethingAsync(String callbackId, ...) {
+ *     // start some async operation and post a Snippet Event object with the given callbackId.
+ * }
+ * }</pre>
+ *
+ * AsyncRpc methods can still return serializable values, which will be transported in the regular
+ * return value field of the Rpc protocol.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+@Documented
+public @interface AsyncRpc {
+    /** Returns brief description of the function. Should be limited to one or two sentences. */
+    String description();
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonBuilder.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonBuilder.java
new file mode 100644
index 0000000..a1d3425
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonBuilder.java
@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import android.content.ComponentName;
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.ParcelUuid;
+import com.google.android.mobly.snippet.manager.SnippetObjectConverterManager;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public class JsonBuilder {
+
+    private JsonBuilder() {}
+
+    @SuppressWarnings("unchecked")
+    public static Object build(Object data) throws JSONException {
+        if (data == null) {
+            return JSONObject.NULL;
+        }
+        if (data instanceof Integer) {
+            return data;
+        }
+        if (data instanceof Float) {
+            return data;
+        }
+        if (data instanceof Double) {
+            return data;
+        }
+        if (data instanceof Long) {
+            return data;
+        }
+        if (data instanceof String) {
+            return data;
+        }
+        if (data instanceof Boolean) {
+            return data;
+        }
+        if (data instanceof JsonSerializable) {
+            return ((JsonSerializable) data).toJSON();
+        }
+        if (data instanceof JSONObject) {
+            return data;
+        }
+        if (data instanceof JSONArray) {
+            return data;
+        }
+        if (data instanceof Set<?>) {
+            List<Object> items = new ArrayList<>((Set<?>) data);
+            return buildJsonList(items);
+        }
+        if (data instanceof Collection<?>) {
+            List<Object> items = new ArrayList<>((Collection<?>) data);
+            return buildJsonList(items);
+        }
+        if (data instanceof List<?>) {
+            return buildJsonList((List<?>) data);
+        }
+        if (data instanceof Bundle) {
+            return buildJsonBundle((Bundle) data);
+        }
+        if (data instanceof Intent) {
+            return buildJsonIntent((Intent) data);
+        }
+        if (data instanceof Map<?, ?>) {
+            // TODO(damonkohler): I would like to make this a checked cast if possible.
+            return buildJsonMap((Map<String, ?>) data);
+        }
+        if (data instanceof ParcelUuid) {
+            return data.toString();
+        }
+        // TODO(xpconanfan): Deprecate the following default non-primitive type builders.
+        if (data instanceof InetSocketAddress) {
+            return buildInetSocketAddress((InetSocketAddress) data);
+        }
+        if (data instanceof InetAddress) {
+            return buildInetAddress((InetAddress) data);
+        }
+        if (data instanceof URL) {
+            return buildURL((URL) data);
+        }
+        if (data instanceof byte[]) {
+            JSONArray result = new JSONArray();
+            for (byte b : (byte[]) data) {
+                result.put(b & 0xFF);
+            }
+            return result;
+        }
+        if (data instanceof Object[]) {
+            return buildJSONArray((Object[]) data);
+        }
+        // Try with custom converter provided by user.
+        Object result = SnippetObjectConverterManager.getInstance().objectToJson(data);
+        if (result != null) {
+            return result;
+        }
+        return data.toString();
+    }
+
+    private static Object buildInetAddress(InetAddress data) {
+        JSONArray address = new JSONArray();
+        address.put(data.getHostName());
+        address.put(data.getHostAddress());
+        return address;
+    }
+
+    private static Object buildInetSocketAddress(InetSocketAddress data) {
+        JSONArray address = new JSONArray();
+        address.put(data.getHostName());
+        address.put(data.getPort());
+        return address;
+    }
+
+    private static JSONArray buildJSONArray(Object[] data) throws JSONException {
+        JSONArray result = new JSONArray();
+        for (Object o : data) {
+            result.put(build(o));
+        }
+        return result;
+    }
+
+    private static JSONObject buildJsonBundle(Bundle bundle) throws JSONException {
+        JSONObject result = new JSONObject();
+        bundle.setClassLoader(JsonBuilder.class.getClassLoader());
+        for (String key : bundle.keySet()) {
+            result.put(key, build(bundle.get(key)));
+        }
+        return result;
+    }
+
+    private static JSONObject buildJsonIntent(Intent data) throws JSONException {
+        JSONObject result = new JSONObject();
+        result.put("data", data.getDataString());
+        result.put("type", data.getType());
+        result.put("extras", build(data.getExtras()));
+        result.put("categories", build(data.getCategories()));
+        result.put("action", data.getAction());
+        ComponentName component = data.getComponent();
+        if (component != null) {
+            result.put("packagename", component.getPackageName());
+            result.put("classname", component.getClassName());
+        }
+        result.put("flags", data.getFlags());
+        return result;
+    }
+
+    private static <T> JSONArray buildJsonList(final List<T> list) throws JSONException {
+        JSONArray result = new JSONArray();
+        for (T item : list) {
+            result.put(build(item));
+        }
+        return result;
+    }
+
+    private static JSONObject buildJsonMap(Map<String, ?> map) throws JSONException {
+        JSONObject result = new JSONObject();
+        for (Entry<String, ?> entry : map.entrySet()) {
+            String key = entry.getKey();
+            if (key == null) {
+                key = "";
+            }
+            result.put(key, build(entry.getValue()));
+        }
+        return result;
+    }
+
+    private static Object buildURL(URL data) throws JSONException {
+        JSONObject url = new JSONObject();
+        url.put("Authority", data.getAuthority());
+        url.put("Host", data.getHost());
+        url.put("Path", data.getPath());
+        url.put("Port", data.getPort());
+        url.put("Protocol", data.getProtocol());
+        return url;
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcResult.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcResult.java
new file mode 100644
index 0000000..90cf8f9
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcResult.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Represents a JSON RPC result.
+ *
+ * @see <a href="http://json-rpc.org/wiki/specification">http://json-rpc.org/wiki/specification</a>
+ */
+public class JsonRpcResult {
+
+    private JsonRpcResult() {
+        // Utility class.
+    }
+
+    public static JSONObject empty(int id) throws JSONException {
+        JSONObject json = new JSONObject();
+        json.put("id", id);
+        json.put("result", JSONObject.NULL);
+        json.put("callback", JSONObject.NULL);
+        json.put("error", JSONObject.NULL);
+        return json;
+    }
+
+    public static JSONObject result(int id, Object data) throws JSONException {
+        JSONObject json = new JSONObject();
+        json.put("id", id);
+        json.put("result", JsonBuilder.build(data));
+        json.put("callback", JSONObject.NULL);
+        json.put("error", JSONObject.NULL);
+        return json;
+    }
+
+    public static JSONObject callback(int id, Object data, String callbackId) throws JSONException {
+        JSONObject json = new JSONObject();
+        json.put("id", id);
+        json.put("result", JsonBuilder.build(data));
+        json.put("callback", callbackId);
+        json.put("error", JSONObject.NULL);
+        return json;
+    }
+
+    public static JSONObject error(int id, Throwable t) throws JSONException {
+        String stackTrace = getStackTrace(t);
+        JSONObject json = new JSONObject();
+        json.put("id", id);
+        json.put("result", JSONObject.NULL);
+        json.put("callback", JSONObject.NULL);
+        json.put("error", stackTrace);
+        return json;
+    }
+
+    public static String getStackTrace(Throwable throwable) {
+        StringWriter stackTraceWriter = new StringWriter();
+        stackTraceWriter.write("\n-------------- Java Stacktrace ---------------\n");
+        throwable.printStackTrace(new PrintWriter(stackTraceWriter));
+        stackTraceWriter.write("----------------------------------------------");
+        return stackTraceWriter.toString();
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcServer.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcServer.java
new file mode 100644
index 0000000..1dde423
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonRpcServer.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import android.content.Context;
+import com.google.android.mobly.snippet.manager.SnippetManager;
+import com.google.android.mobly.snippet.util.Log;
+import com.google.android.mobly.snippet.util.RpcUtil;
+import java.io.BufferedReader;
+import java.io.PrintWriter;
+import java.net.Socket;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/** A JSON RPC server that forwards RPC calls to a specified receiver object. */
+public class JsonRpcServer extends SimpleServer {
+    private static final String CMD_CLOSE_SESSION = "closeSl4aSession";
+    private static final String CMD_HELP = "help";
+
+    private final SnippetManager mSnippetManager;
+    private final RpcUtil mRpcUtil;
+
+    /** Construct a {@link JsonRpcServer} connected to the provided {@link SnippetManager}. */
+    public JsonRpcServer(Context context) {
+        mSnippetManager = SnippetManager.initSnippetManager(context);
+        mRpcUtil = new RpcUtil();
+    }
+
+    @Override
+    protected void handleRPCConnection(
+            Socket sock, Integer UID, BufferedReader reader, PrintWriter writer) throws Exception {
+        Log.d("UID " + UID);
+        String data;
+        while ((data = reader.readLine()) != null) {
+            Log.v("Session " + UID + " Received: " + data);
+            JSONObject request = new JSONObject(data);
+            int id = request.getInt("id");
+            String method = request.getString("method");
+            JSONArray params = request.getJSONArray("params");
+
+            // Handle builtin commands
+            if (method.equals(CMD_HELP)) {
+                help(writer, id, mSnippetManager, UID);
+                continue;
+            } else if (method.equals(CMD_CLOSE_SESSION)) {
+                Log.d("Got shutdown signal");
+                synchronized (writer) {
+                    // Shut down all RPC receivers.
+                    mSnippetManager.shutdown();
+
+                    // Shut down this client connection. As soon as this happens, the client will
+                    // kill us by triggering the 'stop' action from another instrumentation, so no
+                    // other cleanup steps are guaranteed to execute.
+                    send(writer, JsonRpcResult.empty(id), UID);
+                    reader.close();
+                    writer.close();
+                    sock.close();
+
+                    // Shut down this server.
+                    shutdown();
+                }
+                return;
+            }
+            JSONObject returnValue = mRpcUtil.invokeRpc(method, params, id, UID);
+            send(writer, returnValue, UID);
+        }
+    }
+
+    private void help(PrintWriter writer, int id, SnippetManager receiverManager, Integer UID)
+            throws JSONException {
+        // Create a map from class simple name to the methods inside it.
+        Map<String, Set<MethodDescriptor>> methods = new TreeMap<>();
+        for (String method : receiverManager.getMethodNames()) {
+            MethodDescriptor descriptor = receiverManager.getMethodDescriptor(method);
+            String snippetClassName = descriptor.getSnippetClass().getSimpleName();
+            Set<MethodDescriptor> snippetClassMethods = methods.get(snippetClassName);
+            if (snippetClassMethods == null) {
+                // Preserve insertion order (alphabetical)
+                snippetClassMethods = new LinkedHashSet<>();
+                methods.put(snippetClassName, snippetClassMethods);
+            }
+            snippetClassMethods.add(descriptor);
+        }
+        StringBuilder result = new StringBuilder();
+        for (Map.Entry<String, Set<MethodDescriptor>> entry : methods.entrySet()) {
+            result.append("\nRPCs provided by ").append(entry.getKey()).append(":\n");
+            for (MethodDescriptor descriptor : entry.getValue()) {
+                result.append("  ").append(descriptor.getHelp()).append("\n");
+            }
+        }
+        send(writer, JsonRpcResult.result(id, result), UID);
+    }
+
+    private void send(PrintWriter writer, JSONObject result, int UID) {
+        writer.write(result + "\n");
+        writer.flush();
+        Log.v("Session " + UID + " Sent: " + result);
+    }
+
+    @Override
+    protected void handleConnection(Socket socket) throws Exception {}
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonSerializable.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonSerializable.java
new file mode 100644
index 0000000..5871e01
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/JsonSerializable.java
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public interface JsonSerializable {
+    JSONObject toJSON() throws JSONException;
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/MethodDescriptor.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/MethodDescriptor.java
new file mode 100644
index 0000000..b9c8a7a
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/MethodDescriptor.java
@@ -0,0 +1,252 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import android.content.Intent;
+import android.net.Uri;
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.manager.SnippetManager;
+import com.google.android.mobly.snippet.manager.SnippetObjectConverterManager;
+import com.google.android.mobly.snippet.util.AndroidUtil;
+import java.lang.reflect.Method;
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Locale;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/** An adapter that wraps {@code Method}. */
+public final class MethodDescriptor {
+    private final Method mMethod;
+    private final Class<? extends Snippet> mClass;
+
+    private MethodDescriptor(Class<? extends Snippet> clazz, Method method) {
+        mClass = clazz;
+        mMethod = method;
+    }
+
+    @Override
+    public String toString() {
+        return mMethod.getDeclaringClass().getCanonicalName() + "." + mMethod.getName();
+    }
+
+    /** Collects all methods with {@code RPC} annotation from given class. */
+    public static Collection<MethodDescriptor> collectFrom(Class<? extends Snippet> clazz) {
+        List<MethodDescriptor> descriptors = new ArrayList<MethodDescriptor>();
+        for (Method method : clazz.getMethods()) {
+            if (method.isAnnotationPresent(Rpc.class)
+                    || method.isAnnotationPresent(AsyncRpc.class)) {
+                descriptors.add(new MethodDescriptor(clazz, method));
+            }
+        }
+        return descriptors;
+    }
+
+    /**
+     * Invokes the call that belongs to this object with the given parameters. Wraps the response
+     * (possibly an exception) in a JSONObject.
+     *
+     * @param parameters {@code JSONArray} containing the parameters
+     * @return result
+     * @throws Throwable the exception raised from executing the RPC method.
+     */
+    public Object invoke(SnippetManager manager, final JSONArray parameters) throws Throwable {
+        final Type[] parameterTypes = getGenericParameterTypes();
+        final Object[] args = new Object[parameterTypes.length];
+
+        if (parameters.length() > args.length) {
+            throw new RpcError("Too many parameters specified.");
+        }
+
+        for (int i = 0; i < args.length; i++) {
+            final Type parameterType = parameterTypes[i];
+            if (i < parameters.length()) {
+                args[i] = convertParameter(parameters, i, parameterType);
+            } else {
+                throw new RpcError("Argument " + (i + 1) + " is not present");
+            }
+        }
+
+        return manager.invoke(mClass, mMethod, args);
+    }
+
+    /** Converts a parameter from JSON into a Java Object. */
+    // TODO(damonkohler): This signature is a bit weird (auto-refactored). The obvious alternative
+    // would be to work on one supplied parameter and return the converted parameter. However,
+    // that's problematic because you lose the ability to call the getXXX methods on the JSON array.
+    // @VisibleForTesting
+    private static Object convertParameter(final JSONArray parameters, int index, Type type)
+            throws JSONException, RpcError {
+        try {
+            // We must handle null and numbers explicitly because we cannot magically cast them. We
+            // also need to convert implicitly from numbers to bools.
+            if (parameters.isNull(index)) {
+                return null;
+            } else if (type == Boolean.class || type == boolean.class) {
+                try {
+                    return parameters.getBoolean(index);
+                } catch (JSONException e) {
+                    return parameters.getInt(index) != 0;
+                }
+            } else if (type == Long.class || type == long.class) {
+                return parameters.getLong(index);
+            } else if (type == Double.class || type == double.class) {
+                return parameters.getDouble(index);
+            } else if (type == Integer.class || type == int.class) {
+                return parameters.getInt(index);
+            } else if (type == Intent.class) {
+                return buildIntent(parameters.getJSONObject(index));
+            } else if (type == String.class) {
+                return parameters.getString(index);
+            } else if (type == Integer[].class || type == int[].class) {
+                JSONArray list = parameters.getJSONArray(index);
+                Integer[] result = new Integer[list.length()];
+                for (int i = 0; i < list.length(); i++) {
+                    result[i] = list.getInt(i);
+                }
+                return result;
+            } else if (type == Long[].class || type == long[].class) {
+                JSONArray list = parameters.getJSONArray(index);
+                Long[] result = new Long[list.length()];
+                for (int i = 0; i < list.length(); i++) {
+                    result[i] = list.getLong(i);
+                }
+                return result;
+            } else if (type == Byte.class || type == byte[].class) {
+                JSONArray list = parameters.getJSONArray(index);
+                byte[] result = new byte[list.length()];
+                for (int i = 0; i < list.length(); i++) {
+                    result[i] = (byte) list.getInt(i);
+                }
+                return result;
+            } else if (type == String[].class) {
+                JSONArray list = parameters.getJSONArray(index);
+                String[] result = new String[list.length()];
+                for (int i = 0; i < list.length(); i++) {
+                    result[i] = list.getString(i);
+                }
+                return result;
+            } else if (type == JSONObject.class) {
+                return parameters.getJSONObject(index);
+            } else if (type == JSONArray.class) {
+                return parameters.getJSONArray(index);
+            } else {
+                // Try any custom converter provided.
+                Object object =
+                        SnippetObjectConverterManager.getInstance()
+                                .jsonToObject(parameters.getJSONObject(index), type);
+                if (object != null) {
+                    return object;
+                }
+                // Magically cast the parameter to the right Java type.
+                return ((Class<?>) type).cast(parameters.get(index));
+            }
+        } catch (ClassCastException e) {
+            throw new RpcError(
+                    "Argument "
+                            + (index + 1)
+                            + " should be of type "
+                            + ((Class<?>) type).getSimpleName()
+                            + ", but is of type "
+                            + parameters.get(index).getClass().getSimpleName());
+        }
+    }
+
+    private static Object buildIntent(JSONObject jsonObject) throws JSONException {
+        Intent intent = new Intent();
+        if (jsonObject.has("action")) {
+            intent.setAction(jsonObject.getString("action"));
+        }
+        if (jsonObject.has("data") && jsonObject.has("type")) {
+            intent.setDataAndType(
+                    Uri.parse(jsonObject.optString("data", null)),
+                    jsonObject.optString("type", null));
+        } else if (jsonObject.has("data")) {
+            intent.setData(Uri.parse(jsonObject.optString("data", null)));
+        } else if (jsonObject.has("type")) {
+            intent.setType(jsonObject.optString("type", null));
+        }
+        if (jsonObject.has("packagename") && jsonObject.has("classname")) {
+            intent.setClassName(
+                    jsonObject.getString("packagename"), jsonObject.getString("classname"));
+        }
+        if (jsonObject.has("flags")) {
+            intent.setFlags(jsonObject.getInt("flags"));
+        }
+        if (!jsonObject.isNull("extras")) {
+            AndroidUtil.putExtrasFromJsonObject(jsonObject.getJSONObject("extras"), intent);
+        }
+        if (!jsonObject.isNull("categories")) {
+            JSONArray categories = jsonObject.getJSONArray("categories");
+            for (int i = 0; i < categories.length(); i++) {
+                intent.addCategory(categories.getString(i));
+            }
+        }
+        return intent;
+    }
+
+    public String getName() {
+        return mMethod.getName();
+    }
+
+    private Type[] getGenericParameterTypes() {
+        return mMethod.getGenericParameterTypes();
+    }
+
+    public boolean isAsync() {
+        return mMethod.isAnnotationPresent(AsyncRpc.class);
+    }
+
+    Class<? extends Snippet> getSnippetClass() {
+        return mClass;
+    }
+
+    private String getAnnotationDescription() {
+        if (isAsync()) {
+            AsyncRpc annotation = mMethod.getAnnotation(AsyncRpc.class);
+            return annotation.description();
+        }
+        Rpc annotation = mMethod.getAnnotation(Rpc.class);
+        return annotation.description();
+    }
+    /**
+     * Returns a human-readable help text for this RPC, based on annotations in the source code.
+     *
+     * @return derived help string
+     */
+    String getHelp() {
+        StringBuilder paramBuilder = new StringBuilder();
+        Class<?>[] parameterTypes = mMethod.getParameterTypes();
+        for (int i = 0; i < parameterTypes.length; i++) {
+            if (i != 0) {
+                paramBuilder.append(", ");
+            }
+            paramBuilder.append(parameterTypes[i].getSimpleName());
+        }
+        return String.format(
+                Locale.US,
+                "%s %s(%s) returns %s  // %s",
+                isAsync() ? "@AsyncRpc" : "@Rpc",
+                mMethod.getName(),
+                paramBuilder,
+                mMethod.getReturnType().getSimpleName(),
+                getAnnotationDescription());
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/Rpc.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/Rpc.java
new file mode 100644
index 0000000..af321ba
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/Rpc.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * The {@link Rpc} annotation is used to annotate server-side implementations of RPCs. It describes
+ * meta-information (currently a brief documentation of the function), and marks a function as the
+ * implementation of an RPC.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+@Documented
+public @interface Rpc {
+    /** Returns brief description of the function. Should be limited to one or two sentences. */
+    String description();
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcError.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcError.java
new file mode 100644
index 0000000..0862673
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcError.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+@SuppressWarnings("serial")
+public class RpcError extends Exception {
+
+    public RpcError(String message) {
+        super(message);
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcMinSdk.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcMinSdk.java
new file mode 100644
index 0000000..f03fd2a
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RpcMinSdk.java
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** Use this annotation to specify minimum SDK level (if higher than 3). */
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface RpcMinSdk {
+    /** Minimum SDK Level. */
+    int value();
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RunOnUiThread.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RunOnUiThread.java
new file mode 100644
index 0000000..cde08f0
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/RunOnUiThread.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.android.mobly.snippet.rpc;
+
+import com.google.android.mobly.snippet.Snippet;
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * This annotation will cause the RPC to execute on the main app thread.
+ *
+ * <p>This annotation can be applied to:
+ *
+ * <ul>
+ *   <li>The constructor of a class implementing the {@link Snippet} interface.
+ *   <li>A method annotated with the {@link Rpc} or {@link AsyncRpc} annotation.
+ *   <li>The {@link Snippet#shutdown()} method.
+ * </ul>
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface RunOnUiThread {}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/SimpleServer.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/SimpleServer.java
new file mode 100644
index 0000000..db7255a
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/rpc/SimpleServer.java
@@ -0,0 +1,285 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.rpc;
+
+import com.google.android.mobly.snippet.util.Log;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.net.NetworkInterface;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/** A simple server. */
+public abstract class SimpleServer {
+    private static int threadIndex = 0;
+    private final ConcurrentHashMap<Integer, ConnectionThread> mConnectionThreads =
+            new ConcurrentHashMap<>();
+    private final List<SimpleServerObserver> mObservers = new ArrayList<>();
+    private volatile boolean mStopServer = false;
+    private ServerSocket mServer;
+    private Thread mServerThread;
+
+    public interface SimpleServerObserver {
+        void onConnect();
+
+        void onDisconnect();
+    }
+
+    protected abstract void handleConnection(Socket socket) throws Exception;
+
+    protected abstract void handleRPCConnection(
+            Socket socket, Integer UID, BufferedReader reader, PrintWriter writer) throws Exception;
+
+    /** Adds an observer. */
+    public void addObserver(SimpleServerObserver observer) {
+        mObservers.add(observer);
+    }
+
+    /** Removes an observer. */
+    public void removeObserver(SimpleServerObserver observer) {
+        mObservers.remove(observer);
+    }
+
+    private void notifyOnConnect() {
+        for (SimpleServerObserver observer : mObservers) {
+            observer.onConnect();
+        }
+    }
+
+    private void notifyOnDisconnect() {
+        for (SimpleServerObserver observer : mObservers) {
+            observer.onDisconnect();
+        }
+    }
+
+    private final class ConnectionThread extends Thread {
+        private final Socket mmSocket;
+        private final BufferedReader reader;
+        private final PrintWriter writer;
+        private final Integer UID;
+        private final boolean isRpc;
+
+        private ConnectionThread(
+                Socket socket,
+                boolean rpc,
+                Integer uid,
+                BufferedReader reader,
+                PrintWriter writer) {
+            setName("SimpleServer ConnectionThread " + getId());
+            mmSocket = socket;
+            this.UID = uid;
+            this.reader = reader;
+            this.writer = writer;
+            this.isRpc = rpc;
+        }
+
+        @Override
+        public void run() {
+            Log.v("Server thread " + getId() + " started.");
+            try {
+                if (isRpc) {
+                    Log.d("Handling RPC connection in " + getId());
+                    handleRPCConnection(mmSocket, UID, reader, writer);
+                } else {
+                    Log.d("Handling Non-RPC connection in " + getId());
+                    handleConnection(mmSocket);
+                }
+            } catch (Exception e) {
+                if (!mStopServer) {
+                    Log.e("Server error.", e);
+                }
+            } finally {
+                close();
+                mConnectionThreads.remove(this.UID);
+                notifyOnDisconnect();
+                Log.v("Server thread " + getId() + " stopped.");
+            }
+        }
+
+        private void close() {
+            if (mmSocket != null) {
+                try {
+                    mmSocket.close();
+                } catch (IOException e) {
+                    Log.e(e.getMessage(), e);
+                }
+            }
+        }
+    }
+
+    private InetAddress getPrivateInetAddress() throws UnknownHostException, SocketException {
+
+        InetAddress candidate = null;
+        Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
+        for (NetworkInterface netint : Collections.list(nets)) {
+            if (!netint.isLoopback() || !netint.isUp()) { // Ignore if localhost or not active
+                continue;
+            }
+            Enumeration<InetAddress> addresses = netint.getInetAddresses();
+            for (InetAddress address : Collections.list(addresses)) {
+                if (address instanceof Inet4Address) {
+                    Log.d("local address " + address);
+                    return address; // Prefer ipv4
+                }
+                candidate = address; // Probably an ipv6
+            }
+        }
+        if (candidate != null) {
+            return candidate; // return ipv6 address if no suitable ipv6
+        }
+        return InetAddress.getLocalHost(); // No damn matches. Give up, return local host.
+    }
+
+    /**
+     * Starts the RPC server bound to the localhost address.
+     *
+     * @param port the port to bind to or 0 to pick any unused port
+     * @throws IOException
+     */
+    public void startLocal(int port) throws IOException {
+        InetAddress address = getPrivateInetAddress();
+        mServer = new ServerSocket(port, 5 /* backlog */, address);
+        start();
+    }
+
+    public int getPort() {
+        return mServer.getLocalPort();
+    }
+
+    private void start() {
+        mServerThread =
+                new Thread() {
+                    @Override
+                    public void run() {
+                        while (!mStopServer) {
+                            try {
+                                Socket sock = mServer.accept();
+                                if (!mStopServer) {
+                                    startConnectionThread(sock);
+                                } else {
+                                    sock.close();
+                                }
+                            } catch (IOException e) {
+                                if (!mStopServer) {
+                                    Log.e("Failed to accept connection.", e);
+                                }
+                            } catch (JSONException e) {
+                                if (!mStopServer) {
+                                    Log.e("Failed to parse request.", e);
+                                }
+                            }
+                        }
+                    }
+                };
+        mServerThread.start();
+        Log.v("Bound to " + mServer.getInetAddress());
+    }
+
+    private void startConnectionThread(final Socket sock) throws IOException, JSONException {
+        BufferedReader reader =
+                new BufferedReader(new InputStreamReader(sock.getInputStream()), 8192);
+        PrintWriter writer = new PrintWriter(sock.getOutputStream(), true);
+        String data;
+        if ((data = reader.readLine()) != null) {
+            Log.v("Received: " + data);
+            JSONObject request = new JSONObject(data);
+            if (request.has("cmd") && request.has("uid")) {
+                String cmd = request.getString("cmd");
+                int uid = request.getInt("uid");
+                JSONObject result = new JSONObject();
+                if (cmd.equals("initiate")) {
+                    Log.d("Initiate a new session");
+                    threadIndex += 1;
+                    int mUID = threadIndex;
+                    ConnectionThread networkThread =
+                            new ConnectionThread(sock, true, mUID, reader, writer);
+                    mConnectionThreads.put(mUID, networkThread);
+                    networkThread.start();
+                    notifyOnConnect();
+                    result.put("uid", mUID);
+                    result.put("status", true);
+                    result.put("error", null);
+                } else if (cmd.equals("continue")) {
+                    Log.d("Continue an existing session");
+                    Log.d("keys: " + mConnectionThreads.keySet().toString());
+                    if (!mConnectionThreads.containsKey(uid)) {
+                        result.put("uid", uid);
+                        result.put("status", false);
+                        result.put("error", "Session does not exist.");
+                    } else {
+                        ConnectionThread networkThread =
+                                new ConnectionThread(sock, true, uid, reader, writer);
+                        mConnectionThreads.put(uid, networkThread);
+                        networkThread.start();
+                        notifyOnConnect();
+                        result.put("uid", uid);
+                        result.put("status", true);
+                        result.put("error", null);
+                    }
+                } else {
+                    result.put("uid", uid);
+                    result.put("status", false);
+                    result.put("error", "Unrecognized command.");
+                }
+                writer.write(result + "\n");
+                writer.flush();
+                Log.v("Sent: " + result);
+            } else {
+                ConnectionThread networkThread =
+                        new ConnectionThread(sock, false, 0, reader, writer);
+                mConnectionThreads.put(0, networkThread);
+                networkThread.start();
+                notifyOnConnect();
+            }
+        }
+    }
+
+    public void shutdown() throws Exception {
+        // Stop listening on the server socket to ensure that
+        // beyond this point there are no incoming requests.
+        mStopServer = true;
+        try {
+            mServer.close();
+        } catch (IOException e) {
+            Log.e("Failed to close server socket.", e);
+        }
+        // Since the server is not running, the mNetworkThreads set can only
+        // shrink from this point onward. We can just stop all of the running helper
+        // threads. In the worst case, one of the running threads will already have
+        // shut down. Since this is a CopyOnWriteList, we don't have to worry about
+        // concurrency issues while iterating over the set of threads.
+        for (ConnectionThread connectionThread : mConnectionThreads.values()) {
+            connectionThread.close();
+        }
+        for (SimpleServerObserver observer : mObservers) {
+            removeObserver(observer);
+        }
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/schedulerpc/ScheduleRpcSnippet.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/schedulerpc/ScheduleRpcSnippet.java
new file mode 100644
index 0000000..2042b7f
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/schedulerpc/ScheduleRpcSnippet.java
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.schedulerpc;
+
+import com.google.android.mobly.snippet.Snippet;
+import com.google.android.mobly.snippet.rpc.AsyncRpc;
+import com.google.android.mobly.snippet.util.RpcUtil;
+import org.json.JSONArray;
+
+/** Snippet that provides {@link AsyncRpc} to schedule other RPCs. */
+public class ScheduleRpcSnippet implements Snippet {
+
+    private final RpcUtil mRpcUtil;
+
+    public ScheduleRpcSnippet() {
+        mRpcUtil = new RpcUtil();
+    }
+
+    @AsyncRpc(description = "Delay the given RPC by provided milli-seconds.")
+    public void scheduleRpc(
+            String callbackId, String methodName, long delayTimerMs, JSONArray params)
+            throws Throwable {
+        mRpcUtil.scheduleRpc(callbackId, methodName, delayTimerMs, params);
+    }
+
+    @Override
+    public void shutdown() {}
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/AndroidUtil.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/AndroidUtil.java
new file mode 100644
index 0000000..46c4940
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/AndroidUtil.java
@@ -0,0 +1,199 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import android.content.Intent;
+import android.os.Bundle;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public final class AndroidUtil {
+    private AndroidUtil() {}
+
+    // TODO(damonkohler): Pull this out into proper argument deserialization and support
+    // complex/nested types being passed in.
+    public static void putExtrasFromJsonObject(JSONObject extras, Intent intent)
+            throws JSONException {
+        JSONArray names = extras.names();
+        for (int i = 0; i < names.length(); i++) {
+            String name = names.getString(i);
+            Object data = extras.get(name);
+            if (data == null) {
+                continue;
+            }
+            if (data instanceof Integer) {
+                intent.putExtra(name, (Integer) data);
+            }
+            if (data instanceof Float) {
+                intent.putExtra(name, (Float) data);
+            }
+            if (data instanceof Double) {
+                intent.putExtra(name, (Double) data);
+            }
+            if (data instanceof Long) {
+                intent.putExtra(name, (Long) data);
+            }
+            if (data instanceof String) {
+                intent.putExtra(name, (String) data);
+            }
+            if (data instanceof Boolean) {
+                intent.putExtra(name, (Boolean) data);
+            }
+            // Nested JSONObject
+            if (data instanceof JSONObject) {
+                Bundle nestedBundle = new Bundle();
+                intent.putExtra(name, nestedBundle);
+                putNestedJSONObject((JSONObject) data, nestedBundle);
+            }
+            // Nested JSONArray. Doesn't support mixed types in single array
+            if (data instanceof JSONArray) {
+                // Empty array. No way to tell what type of data to pass on, so skipping
+                if (((JSONArray) data).length() == 0) {
+                    Log.e("Empty array not supported in JSONObject, skipping");
+                    continue;
+                }
+                // Integer
+                if (((JSONArray) data).get(0) instanceof Integer) {
+                    Integer[] integerArrayData = new Integer[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        integerArrayData[j] = ((JSONArray) data).getInt(j);
+                    }
+                    intent.putExtra(name, integerArrayData);
+                }
+                // Double
+                if (((JSONArray) data).get(0) instanceof Double) {
+                    Double[] doubleArrayData = new Double[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        doubleArrayData[j] = ((JSONArray) data).getDouble(j);
+                    }
+                    intent.putExtra(name, doubleArrayData);
+                }
+                // Long
+                if (((JSONArray) data).get(0) instanceof Long) {
+                    Long[] longArrayData = new Long[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        longArrayData[j] = ((JSONArray) data).getLong(j);
+                    }
+                    intent.putExtra(name, longArrayData);
+                }
+                // String
+                if (((JSONArray) data).get(0) instanceof String) {
+                    String[] stringArrayData = new String[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        stringArrayData[j] = ((JSONArray) data).getString(j);
+                    }
+                    intent.putExtra(name, stringArrayData);
+                }
+                // Boolean
+                if (((JSONArray) data).get(0) instanceof Boolean) {
+                    Boolean[] booleanArrayData = new Boolean[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        booleanArrayData[j] = ((JSONArray) data).getBoolean(j);
+                    }
+                    intent.putExtra(name, booleanArrayData);
+                }
+            }
+        }
+    }
+
+    // Contributed by Emmanuel T
+    // Nested Array handling contributed by Sergey Zelenev
+    private static void putNestedJSONObject(JSONObject jsonObject, Bundle bundle)
+            throws JSONException {
+        JSONArray names = jsonObject.names();
+        for (int i = 0; i < names.length(); i++) {
+            String name = names.getString(i);
+            Object data = jsonObject.get(name);
+            if (data == null) {
+                continue;
+            }
+            if (data instanceof Integer) {
+                bundle.putInt(name, ((Integer) data).intValue());
+            }
+            if (data instanceof Float) {
+                bundle.putFloat(name, ((Float) data).floatValue());
+            }
+            if (data instanceof Double) {
+                bundle.putDouble(name, ((Double) data).doubleValue());
+            }
+            if (data instanceof Long) {
+                bundle.putLong(name, ((Long) data).longValue());
+            }
+            if (data instanceof String) {
+                bundle.putString(name, (String) data);
+            }
+            if (data instanceof Boolean) {
+                bundle.putBoolean(name, ((Boolean) data).booleanValue());
+            }
+            // Nested JSONObject
+            if (data instanceof JSONObject) {
+                Bundle nestedBundle = new Bundle();
+                bundle.putBundle(name, nestedBundle);
+                putNestedJSONObject((JSONObject) data, nestedBundle);
+            }
+            // Nested JSONArray. Doesn't support mixed types in single array
+            if (data instanceof JSONArray) {
+                // Empty array. No way to tell what type of data to pass on, so skipping
+                if (((JSONArray) data).length() == 0) {
+                    Log.e("Empty array not supported in nested JSONObject, skipping");
+                    continue;
+                }
+                // Integer
+                if (((JSONArray) data).get(0) instanceof Integer) {
+                    int[] integerArrayData = new int[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        integerArrayData[j] = ((JSONArray) data).getInt(j);
+                    }
+                    bundle.putIntArray(name, integerArrayData);
+                }
+                // Double
+                if (((JSONArray) data).get(0) instanceof Double) {
+                    double[] doubleArrayData = new double[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        doubleArrayData[j] = ((JSONArray) data).getDouble(j);
+                    }
+                    bundle.putDoubleArray(name, doubleArrayData);
+                }
+                // Long
+                if (((JSONArray) data).get(0) instanceof Long) {
+                    long[] longArrayData = new long[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        longArrayData[j] = ((JSONArray) data).getLong(j);
+                    }
+                    bundle.putLongArray(name, longArrayData);
+                }
+                // String
+                if (((JSONArray) data).get(0) instanceof String) {
+                    String[] stringArrayData = new String[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        stringArrayData[j] = ((JSONArray) data).getString(j);
+                    }
+                    bundle.putStringArray(name, stringArrayData);
+                }
+                // Boolean
+                if (((JSONArray) data).get(0) instanceof Boolean) {
+                    boolean[] booleanArrayData = new boolean[((JSONArray) data).length()];
+                    for (int j = 0; j < ((JSONArray) data).length(); ++j) {
+                        booleanArrayData[j] = ((JSONArray) data).getBoolean(j);
+                    }
+                    bundle.putBooleanArray(name, booleanArrayData);
+                }
+            }
+        }
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/EmptyTestClass.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/EmptyTestClass.java
new file mode 100644
index 0000000..ac1920f
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/EmptyTestClass.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import org.junit.Ignore;
+
+/**
+ * A stub JUnit class with no tests.
+ *
+ * <p>Used for 'safely' calling AndroidJUnitRunner methods on snippets that happen to have tests
+ * defined, to avoid actually calling those tests.
+ */
+@Ignore
+public class EmptyTestClass {}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/Log.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/Log.java
new file mode 100644
index 0000000..64f03e9
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/Log.java
@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.content.pm.PackageManager.NameNotFoundException;
+import android.os.Bundle;
+
+public final class Log {
+    public static volatile String apkLogTag = null;
+
+    private static final String MY_CLASS_NAME = Log.class.getName();
+    private static final String ANDROID_LOG_CLASS_NAME = android.util.Log.class.getName();
+
+    // Skip the first two entries in stack trace when trying to infer the caller.
+    // The first two entries are:
+    // - dalvik.system.VMStack.getThreadStackTrace(Native Method)
+    // - java.lang.Thread.getStackTrace(Thread.java:580)
+    // The {@code getStackTrace()} function returns the stack trace at where the trace is collected
+    // (inisde the JNI function {@code getThreadStackTrace()} instead of at where the {@code
+    // getStackTrace()} is called (althrought this is the natual expectation).
+    private static final int STACK_TRACE_WALK_START_INDEX = 2;
+
+    private Log() {}
+
+    public static synchronized void initLogTag(Context context) {
+        if (apkLogTag != null) {
+            throw new IllegalStateException("Logger should not be re-initialized");
+        }
+        String packageName = context.getPackageName();
+        PackageManager packageManager = context.getPackageManager();
+        ApplicationInfo appInfo;
+        try {
+            appInfo = packageManager.getApplicationInfo(packageName, PackageManager.GET_META_DATA);
+        } catch (NameNotFoundException e) {
+            throw new IllegalStateException(
+                    "Failed to find ApplicationInfo with package name: " + packageName);
+        }
+        Bundle bundle = appInfo.metaData;
+        apkLogTag = bundle.getString("mobly-log-tag");
+        if (apkLogTag == null) {
+            apkLogTag = packageName;
+            w(
+                    "AndroidManifest.xml does not contain metadata field named \"mobly-log-tag\". "
+                            + "Using package name for logging instead.");
+        }
+    }
+
+    private static String getTag() {
+        String logTag = apkLogTag;
+        if (logTag == null) {
+            throw new IllegalStateException("Logging called before initLogTag()");
+        }
+        StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();
+
+        boolean isCallerClassNameFound = false;
+        String fullClassName = null;
+        int lineNumber = 0;
+        // Walk up the stack and look for the first class name that is neither us nor
+        // android.util.Log: that's the caller.
+        // Do not used hard-coded stack depth: that does not work all the time because of proguard
+        // inline optimization.
+        for (int i = STACK_TRACE_WALK_START_INDEX; i < stackTraceElements.length; i++) {
+            StackTraceElement element = stackTraceElements[i];
+            fullClassName = element.getClassName();
+            if (!fullClassName.equals(MY_CLASS_NAME)
+                    && !fullClassName.equals(ANDROID_LOG_CLASS_NAME)) {
+                lineNumber = element.getLineNumber();
+                isCallerClassNameFound = true;
+                break;
+            }
+        }
+
+        if (!isCallerClassNameFound) {
+            // Failed to determine caller's class name, fall back the the minimal one.
+            return logTag;
+        } else {
+            String className = fullClassName.substring(fullClassName.lastIndexOf(".") + 1);
+            return logTag + "." + className + ":" + lineNumber;
+        }
+    }
+
+    public static void v(String message) {
+        android.util.Log.v(getTag(), message);
+    }
+
+    public static void v(String message, Throwable e) {
+        android.util.Log.v(getTag(), message, e);
+    }
+
+    public static void e(Throwable e) {
+        android.util.Log.e(getTag(), "Error", e);
+    }
+
+    public static void e(String message) {
+        android.util.Log.e(getTag(), message);
+    }
+
+    public static void e(String message, Throwable e) {
+        android.util.Log.e(getTag(), message, e);
+    }
+
+    public static void w(Throwable e) {
+        android.util.Log.w(getTag(), "Warning", e);
+    }
+
+    public static void w(String message) {
+        android.util.Log.w(getTag(), message);
+    }
+
+    public static void w(String message, Throwable e) {
+        android.util.Log.w(getTag(), message, e);
+    }
+
+    public static void d(String message) {
+        android.util.Log.d(getTag(), message);
+    }
+
+    public static void d(String message, Throwable e) {
+        android.util.Log.d(getTag(), message, e);
+    }
+
+    public static void i(String message) {
+        android.util.Log.i(getTag(), message);
+    }
+
+    public static void i(String message, Throwable e) {
+        android.util.Log.i(getTag(), message, e);
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/MainThread.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/MainThread.java
new file mode 100644
index 0000000..0e4ece5
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/MainThread.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import android.os.Handler;
+import android.os.Looper;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CountDownLatch;
+
+public class MainThread {
+    /**
+     * Wraps a {@link Callable} in a {@link Runnable} that has a way to get the return value and
+     * exception after the fact.
+     */
+    private static class CallableWrapper<T> implements Runnable {
+        private final Callable<T> mCallable;
+        private final CountDownLatch mLatch = new CountDownLatch(1);
+        private T mReturnValue;
+        private Throwable mException;
+
+        public CallableWrapper(Callable<T> callable) {
+            mCallable = callable;
+        }
+
+        @Override
+        public final void run() {
+            try {
+                mReturnValue = mCallable.call();
+            } catch (Throwable t) {
+                mException = t;
+            } finally {
+                mLatch.countDown();
+            }
+        }
+
+        public void awaitTermination() throws InterruptedException {
+            mLatch.await();
+        }
+
+        public T getReturnValue() {
+            return mReturnValue;
+        }
+
+        public Throwable getException() {
+            return mException;
+        }
+    }
+
+    private static final Handler sMainThreadHandler = new Handler(Looper.getMainLooper());
+
+    private MainThread() {
+        // Utility class.
+    }
+
+    /** Executed in the main thread. Returns the result of an execution or any exception thrown. */
+    public static <T> T run(final Callable<T> task) throws Exception {
+        CallableWrapper<T> wrapper = new CallableWrapper<>(task);
+        return runCallableWrapper(wrapper);
+    }
+
+    private static <T> T runCallableWrapper(CallableWrapper<T> wrapper) throws Exception {
+        sMainThreadHandler.post(wrapper);
+        wrapper.awaitTermination();
+        Throwable exception = wrapper.getException();
+        if (exception != null) {
+            if (exception instanceof RuntimeException) {
+                throw (RuntimeException) exception;
+            }
+            if (exception instanceof Error) {
+                throw (Error) exception;
+            }
+            throw (Exception) exception;
+        }
+        return wrapper.getReturnValue();
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/NotificationIdFactory.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/NotificationIdFactory.java
new file mode 100644
index 0000000..39cea5e
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/NotificationIdFactory.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Creates unique ids to identify the notifications created by the android scripting service and the
+ * trigger service.
+ */
+public final class NotificationIdFactory {
+    private static final AtomicInteger mNextId = new AtomicInteger(0);
+
+    public static int create() {
+        return mNextId.incrementAndGet();
+    }
+
+    private NotificationIdFactory() {}
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/RpcUtil.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/RpcUtil.java
new file mode 100644
index 0000000..4601e93
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/RpcUtil.java
@@ -0,0 +1,139 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+import com.google.android.mobly.snippet.event.EventCache;
+import com.google.android.mobly.snippet.event.SnippetEvent;
+import com.google.android.mobly.snippet.manager.SnippetManager;
+import com.google.android.mobly.snippet.rpc.JsonRpcResult;
+import com.google.android.mobly.snippet.rpc.MethodDescriptor;
+import com.google.android.mobly.snippet.rpc.RpcError;
+import java.util.Locale;
+import java.util.Timer;
+import java.util.TimerTask;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Class that implements APIs to schedule other RPCs.
+ *
+ * <p>If a device is required to be disconnected (e.g., USB power off), no RPCs can be made while
+ * device is offline.
+ *
+ * <p>However, We still need snippet continue to run and execute previously scheduled RPCs
+ *
+ * <p>The return value of the scheduled RPC is cached in {@link EventCache} and can be retrieved
+ * later after device is back online.
+ */
+public class RpcUtil {
+    // RPC ID is used for reporting responses back to the client. However, the results of
+    // scheduled RPCs are reported back to the client via events instead of through synchronous
+    // responses, so the RPC ID is unused. We pass an arbitrary value of 0.
+    private static final int DEFAULT_ID = 0;
+    private final SnippetManager mReceiverManager;
+    private final EventCache mEventCache = EventCache.getInstance();
+
+    public RpcUtil() {
+        mReceiverManager = SnippetManager.getInstance();
+    }
+
+    /**
+     * Schedule given RPC with some delay.
+     *
+     * @param callbackId The callback ID used to cache RPC results.
+     * @param methodName The RPC name to be scheduled.
+     * @param delayMs The delay in ms
+     * @param params Array of the parameters to the RPC
+     */
+    public void scheduleRpc(
+            final String callbackId,
+            final String methodName,
+            final long delayMs,
+            final JSONArray params)
+            throws Throwable {
+        Timer timer = new Timer();
+        TimerTask task =
+                new TimerTask() {
+                    @Override
+                    public void run() {
+                        SnippetEvent event = new SnippetEvent(callbackId, methodName);
+                        try {
+                            JSONObject obj = invokeRpc(methodName, params, DEFAULT_ID, callbackId);
+                            // Cache RPC method return value.
+                            for (int i = 0; i < obj.names().length(); i++) {
+                                String key = obj.names().getString(i);
+                                event.getData().putString(key, obj.get(key).toString());
+                            }
+                        } catch (JSONException e) {
+                            String stackTrace = JsonRpcResult.getStackTrace(e);
+                            event.getData().putString("error", stackTrace);
+                        } finally {
+                            mEventCache.postEvent(event);
+                        }
+                    }
+                };
+        timer.schedule(task, delayMs);
+    }
+
+    /**
+     * Invoke the RPC.
+     *
+     * @param methodName The RPC name to be invoked.
+     * @param params Array of the parameters to the RPC
+     * @param id The ID that identifies an RPC
+     * @param UID Globally unique session ID.
+     */
+    public JSONObject invokeRpc(String methodName, JSONArray params, int id, Integer UID)
+            throws JSONException {
+        return invokeRpc(methodName, params, id, String.format(Locale.US, "%d-%d", UID, id));
+    }
+
+    /**
+     * Invoke the RPC.
+     *
+     * @param methodName The RPC name to be invoked.
+     * @param params Array of the parameters to the RPC
+     * @param id The ID that identifies an RPC
+     * @param callbackId The callback ID used to cache RPC results.
+     */
+    public JSONObject invokeRpc(String methodName, JSONArray params, int id, String callbackId)
+            throws JSONException {
+        MethodDescriptor rpc = mReceiverManager.getMethodDescriptor(methodName);
+        if (rpc == null) {
+            return JsonRpcResult.error(id, new RpcError("Unknown RPC: " + methodName));
+        }
+        try {
+            JSONArray newParams = new JSONArray();
+            /** If calling an {@link AsyncRpc}, put the message ID as the first param. */
+            if (rpc.isAsync()) {
+                newParams.put(callbackId);
+                for (int i = 0; i < params.length(); i++) {
+                    newParams.put(params.get(i));
+                }
+                Object returnValue = rpc.invoke(mReceiverManager, newParams);
+                return JsonRpcResult.callback(id, returnValue, callbackId);
+            } else {
+                Object returnValue = rpc.invoke(mReceiverManager, params);
+                return JsonRpcResult.result(id, returnValue);
+            }
+        } catch (Throwable t) {
+            Log.e("Invocation error.", t);
+            return JsonRpcResult.error(id, t);
+        }
+    }
+}
diff --git a/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/SnippetLibException.java b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/SnippetLibException.java
new file mode 100644
index 0000000..e6f5af7
--- /dev/null
+++ b/third_party/sl4a/src/main/java/com/google/android/mobly/snippet/util/SnippetLibException.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.android.mobly.snippet.util;
+
+@SuppressWarnings("serial")
+public class SnippetLibException extends Exception {
+
+    public SnippetLibException(Exception e) {
+        super(e);
+    }
+
+    public SnippetLibException(String message) {
+        super(message);
+    }
+
+    public SnippetLibException(String message, Exception e) {
+        super(message, e);
+    }
+}