add UiDevice for global actions

add UiAutomationDriver#clearAccessibilityNodeInfoCache
to work around an Accessibility bug

Change-Id: I42db1d61944240520cc34f1ccb4537f572adecf9

17 files changed, 289 insertions, 33 deletions

diff --git a/src/com/google/android/droiddriver/DroidDriver.java b/src/com/google/android/droiddriver/DroidDriver.java
index 6daed71..d43e982 100644
--- a/src/com/google/android/droiddriver/DroidDriver.java
+++ b/src/com/google/android/droiddriver/DroidDriver.java
@@ -20,6 +20,9 @@ import com.google.android.droiddriver.exceptions.ElementNotFoundException;
 import com.google.android.droiddriver.exceptions.TimeoutException;
 import com.google.android.droiddriver.finders.Finder;
 
+/**
+ * The entry interface for using droiddriver.
+ */
 public interface DroidDriver {
   /**
    * Returns whether a matching element exists without polling. Use this if the
@@ -106,6 +109,11 @@ public interface DroidDriver {
   void setPoller(Poller poller);
 
   /**
+   * Returns a {@link UiDevice} for device-wide interaction.
+   */
+  UiDevice getUiDevice();
+
+  /**
    * Dumps the UiElement tree to a file to help debug. The tree is based on the
    * last used root UiElement if it exists. Screenshot is always current. If
    * they do not match, the UiElement tree must be stale, indicating that you
diff --git a/src/com/google/android/droiddriver/UiDevice.java b/src/com/google/android/droiddriver/UiDevice.java
new file mode 100644
index 0000000..381aeab
--- /dev/null
+++ b/src/com/google/android/droiddriver/UiDevice.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2013 DroidDriver committers
+ *
+ * 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.droiddriver;
+
+import com.google.android.droiddriver.actions.Action;
+
+/**
+ * Interface for device-wide interaction.
+ */
+public interface UiDevice {
+  /**
+   * Returns whether the screen is on.
+   */
+  boolean isScreenOn();
+
+  /** Wakes up device if the screen is off */
+  void wakeUp();
+
+  /** Puts device to sleep if the screen is on */
+  void sleep();
+
+  /**
+   * Executes a global action without the context of a certain UiElement.
+   *
+   * @param action The action to execute
+   * @return true if the action is successful
+   */
+  boolean perform(Action action);
+}
diff --git a/src/com/google/android/droiddriver/actions/KeyAction.java b/src/com/google/android/droiddriver/actions/KeyAction.java
index 1cafe0e..1855b21 100644
--- a/src/com/google/android/droiddriver/actions/KeyAction.java
+++ b/src/com/google/android/droiddriver/actions/KeyAction.java
@@ -16,11 +16,23 @@
 
 package com.google.android.droiddriver.actions;
 
+import com.google.android.droiddriver.UiElement;
+import com.google.android.droiddriver.exceptions.ActionException;
+
 /**
  * Base class for {@link Action} that injects key events.
  */
 public abstract class KeyAction extends BaseAction {
-  protected KeyAction(long timeoutMillis) {
+  private final boolean checkFocused;
+
+  protected KeyAction(long timeoutMillis, boolean checkFocused) {
     super(timeoutMillis);
+    this.checkFocused = checkFocused;
+  }
+
+  protected void maybeCheckFocused(UiElement element) {
+    if (checkFocused && element != null && !element.isFocused()) {
+      throw new ActionException(element + " is not focused");
+    }
   }
 }
diff --git a/src/com/google/android/droiddriver/actions/PressKeyAction.java b/src/com/google/android/droiddriver/actions/PressKeyAction.java
index 14fd060..a08dbef 100644
--- a/src/com/google/android/droiddriver/actions/PressKeyAction.java
+++ b/src/com/google/android/droiddriver/actions/PressKeyAction.java
@@ -25,25 +25,39 @@ import com.google.android.droiddriver.util.Events;
 import com.google.common.base.Objects;
 
 /**
- * An action to press a single key. TODO: rename to SingleKeyAction
+ * An action to press a single key. While it is convenient for navigating the
+ * UI, do not overuse it -- the application may interpret key codes in a custom
+ * way and, more importantly, application users may not have access to it
+ * because the device (physical or virtual keyboard) may not support all key
+ * codes. TODO: rename to SingleKeyAction
  */
 public class PressKeyAction extends KeyAction {
+  /**
+   * Common instances for convenience and memory preservation.
+   */
+  public static final PressKeyAction MENU = new PressKeyAction(KeyEvent.KEYCODE_MENU);
+  public static final PressKeyAction SEARCH = new PressKeyAction(KeyEvent.KEYCODE_SEARCH);
+  public static final PressKeyAction BACK = new PressKeyAction(KeyEvent.KEYCODE_BACK);
+  public static final PressKeyAction DELETE = new PressKeyAction(KeyEvent.KEYCODE_DEL);
+
   private final int keyCode;
 
   /**
-   * Defaults timeoutMillis to 0.
+   * Defaults timeoutMillis to 100.
    */
   public PressKeyAction(int keyCode) {
-    this(keyCode, 0L);
+    this(keyCode, 100L, false);
   }
 
-  public PressKeyAction(int keyCode, long timeoutMillis) {
-    super(timeoutMillis);
+  public PressKeyAction(int keyCode, long timeoutMillis, boolean checkFocused) {
+    super(timeoutMillis, checkFocused);
     this.keyCode = keyCode;
   }
 
   @Override
   public boolean perform(InputInjector injector, UiElement element) {
+    maybeCheckFocused(element);
+
     final long downTime = SystemClock.uptimeMillis();
     KeyEvent downEvent = Events.newKeyEvent(downTime, KeyEvent.ACTION_DOWN, keyCode);
     KeyEvent upEvent = Events.newKeyEvent(downTime, KeyEvent.ACTION_UP, keyCode);
diff --git a/src/com/google/android/droiddriver/actions/SwipeAction.java b/src/com/google/android/droiddriver/actions/SwipeAction.java
index 433f6de..a7ea7ea 100644
--- a/src/com/google/android/droiddriver/actions/SwipeAction.java
+++ b/src/com/google/android/droiddriver/actions/SwipeAction.java
@@ -24,20 +24,43 @@ import com.google.android.droiddriver.InputInjector;
 import com.google.android.droiddriver.UiElement;
 import com.google.android.droiddriver.exceptions.ActionException;
 import com.google.android.droiddriver.util.Events;
+import com.google.common.base.Objects;
+import com.google.common.base.Objects.ToStringHelper;
 
 /**
  * A {@link ScrollAction} that swipes the touch screen.
  */
 public class SwipeAction extends ScrollAction {
+  /** Common instances for convenience */
+  public static final SwipeAction SCROLL_UP = new SwipeAction(ScrollDirection.UP, false);
+  public static final SwipeAction SCROLL_DOWN = new SwipeAction(ScrollDirection.DOWN, false);
+  public static final SwipeAction SCROLL_LEFT = new SwipeAction(ScrollDirection.LEFT, false);
+  public static final SwipeAction SCROLL_RIGHT = new SwipeAction(ScrollDirection.RIGHT, false);
+
+  /** Gets canned common instances */
+  public static SwipeAction toScroll(ScrollDirection direction) {
+    switch (direction) {
+      case UP:
+        return SCROLL_UP;
+      case DOWN:
+        return SCROLL_DOWN;
+      case LEFT:
+        return SCROLL_LEFT;
+      case RIGHT:
+        return SCROLL_RIGHT;
+      default:
+        throw new ActionException("Unknown scroll direction: " + direction);
+    }
+  }
 
   private final ScrollDirection direction;
   private final boolean drag;
 
   /**
-   * Defaults timeoutMillis to 0.
+   * Defaults timeoutMillis to 1000.
    */
   public SwipeAction(ScrollDirection direction, boolean drag) {
-    this(direction, drag, 0L);
+    this(direction, drag, 1000L);
   }
 
   public SwipeAction(ScrollDirection direction, boolean drag, long timeoutMillis) {
@@ -106,4 +129,13 @@ public class SwipeAction extends ScrollAction {
     Events.touchUp(injector, downTime, endX, endY);
     return true;
   }
+
+  @Override
+  public String toString() {
+    ToStringHelper toStringHelper = Objects.toStringHelper(this).addValue(direction);
+    if (drag) {
+      toStringHelper.addValue("drag");
+    }
+    return toStringHelper.toString();
+  }
 }
diff --git a/src/com/google/android/droiddriver/actions/TypeAction.java b/src/com/google/android/droiddriver/actions/TypeAction.java
index 55e8dea..912b58f 100644
--- a/src/com/google/android/droiddriver/actions/TypeAction.java
+++ b/src/com/google/android/droiddriver/actions/TypeAction.java
@@ -37,19 +37,21 @@ public class TypeAction extends KeyAction {
   private final String text;
 
   /**
-   * Defaults timeoutMillis to 0.
+   * Defaults timeoutMillis to 100.
    */
   public TypeAction(String text) {
-    this(text, 0L);
+    this(text, 100L, false);
   }
 
-  public TypeAction(String text, long timeoutMillis) {
-    super(timeoutMillis);
+  public TypeAction(String text, long timeoutMillis, boolean checkFocused) {
+    super(timeoutMillis, checkFocused);
     this.text = Preconditions.checkNotNull(text);
   }
 
   @Override
   public boolean perform(InputInjector injector, UiElement element) {
+    maybeCheckFocused(element);
+
     // TODO: recycle events?
     KeyEvent[] events = KEY_CHAR_MAP.getEvents(text.toCharArray());
     boolean success = false;
diff --git a/src/com/google/android/droiddriver/base/AbstractContext.java b/src/com/google/android/droiddriver/base/AbstractContext.java
index 2c831ee..a0b8b4a 100644
--- a/src/com/google/android/droiddriver/base/AbstractContext.java
+++ b/src/com/google/android/droiddriver/base/AbstractContext.java
@@ -16,18 +16,33 @@
 
 package com.google.android.droiddriver.base;
 
+import android.app.Instrumentation;
+
 import com.google.android.droiddriver.InputInjector;
 
 /**
  * Internal helper for managing all instances.
  */
 public abstract class AbstractContext {
+  protected final Instrumentation instrumentation;
+  protected final AbstractDroidDriver driver;
   protected final InputInjector injector;
 
-  protected AbstractContext(InputInjector injector) {
+  protected AbstractContext(Instrumentation instrumentation, AbstractDroidDriver driver,
+      InputInjector injector) {
+    this.instrumentation = instrumentation;
+    this.driver = driver;
     this.injector = injector;
   }
 
+  public Instrumentation getInstrumentation() {
+    return instrumentation;
+  }
+
+  public AbstractDroidDriver getDriver() {
+    return driver;
+  }
+
   public InputInjector getInjector() {
     return injector;
   }
diff --git a/src/com/google/android/droiddriver/base/AbstractDroidDriver.java b/src/com/google/android/droiddriver/base/AbstractDroidDriver.java
index ed78b46..0b0f9c6 100644
--- a/src/com/google/android/droiddriver/base/AbstractDroidDriver.java
+++ b/src/com/google/android/droiddriver/base/AbstractDroidDriver.java
@@ -16,7 +16,6 @@
 
 package com.google.android.droiddriver.base;
 
-import android.app.Instrumentation;
 import android.graphics.Bitmap;
 import android.graphics.Bitmap.CompressFormat;
 import android.util.Log;
@@ -32,7 +31,6 @@ import com.google.android.droiddriver.finders.Finder;
 import com.google.android.droiddriver.util.DefaultPoller;
 import com.google.android.droiddriver.util.FileUtils;
 import com.google.android.droiddriver.util.Logs;
-import com.google.common.base.Preconditions;
 
 import java.io.BufferedOutputStream;
 
@@ -42,14 +40,9 @@ import java.io.BufferedOutputStream;
  */
 public abstract class AbstractDroidDriver implements DroidDriver, Screenshotter {
 
-  protected final Instrumentation instrumentation;
   private Poller poller = new DefaultPoller();
   private AbstractUiElement rootElement;
 
-  protected AbstractDroidDriver(Instrumentation instrumentation) {
-    this.instrumentation = Preconditions.checkNotNull(instrumentation);
-  }
-
   @Override
   public UiElement find(Finder finder) {
     Logs.call(this, "find", finder);
diff --git a/src/com/google/android/droiddriver/base/AbstractUiElement.java b/src/com/google/android/droiddriver/base/AbstractUiElement.java
index 65048f2..780d4ac 100644
--- a/src/com/google/android/droiddriver/base/AbstractUiElement.java
+++ b/src/com/google/android/droiddriver/base/AbstractUiElement.java
@@ -90,7 +90,6 @@ public abstract class AbstractUiElement implements UiElement {
 
   @Override
   public void setText(String text) {
-    // TODO: Define common actions as a const.
     perform(new TypeAction(text));
     // TypeAction may not be effective immediately and reflected bygetText(),
     // so the following will fail.
@@ -120,7 +119,7 @@ public abstract class AbstractUiElement implements UiElement {
 
   @Override
   public void scroll(ScrollDirection direction) {
-    perform(new SwipeAction(direction, false));
+    perform(SwipeAction.toScroll(direction));
   }
 
   @Override
diff --git a/src/com/google/android/droiddriver/base/BaseUiDevice.java b/src/com/google/android/droiddriver/base/BaseUiDevice.java
new file mode 100644
index 0000000..29320b2
--- /dev/null
+++ b/src/com/google/android/droiddriver/base/BaseUiDevice.java
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2013 DroidDriver committers
+ *
+ * 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.droiddriver.base;
+
+import android.app.Service;
+import android.os.PowerManager;
+import android.view.KeyEvent;
+
+import com.google.android.droiddriver.UiDevice;
+import com.google.android.droiddriver.actions.Action;
+import com.google.android.droiddriver.actions.PressKeyAction;
+
+/**
+ * Base implementation of {@link UiDevice}.
+ */
+public class BaseUiDevice implements UiDevice {
+  // power off may not trigger new events
+  private static final PressKeyAction POWER_OFF = new PressKeyAction(KeyEvent.KEYCODE_POWER, 0,
+      false);
+  // power on should always trigger new events
+  private static final PressKeyAction POWER_ON = new PressKeyAction(KeyEvent.KEYCODE_POWER, 1000L,
+      false);
+
+  private final AbstractContext abstractContext;
+
+  public BaseUiDevice(AbstractContext abstractContext) {
+    this.abstractContext = abstractContext;
+  }
+
+  @Override
+  public boolean isScreenOn() {
+    PowerManager pm =
+        (PowerManager) abstractContext.instrumentation.getTargetContext().getSystemService(
+            Service.POWER_SERVICE);
+    return pm.isScreenOn();
+  }
+
+  @Override
+  public void wakeUp() {
+    if (!isScreenOn()) {
+      perform(POWER_ON);
+    }
+  }
+
+  @Override
+  public void sleep() {
+    if (isScreenOn()) {
+      perform(POWER_OFF);
+    }
+  }
+
+  @Override
+  public boolean perform(Action action) {
+    return abstractContext.driver.getRootElement().perform(action);
+  }
+}
diff --git a/src/com/google/android/droiddriver/finders/XPaths.java b/src/com/google/android/droiddriver/finders/XPaths.java
index c401582..b671aca 100644
--- a/src/com/google/android/droiddriver/finders/XPaths.java
+++ b/src/com/google/android/droiddriver/finders/XPaths.java
@@ -95,6 +95,11 @@ public class XPaths {
     return attr(Attribute.TEXT, value);
   }
 
+  /** Shorthand for {@link #attr}{@code (Attribute.RESOURCE_ID, value)} */
+  public static String resourceId(String value) {
+    return attr(Attribute.RESOURCE_ID, value);
+  }
+
   /**
    * Adapted from http://stackoverflow.com/questions/1341847/.
    * <p>
diff --git a/src/com/google/android/droiddriver/instrumentation/InstrumentationContext.java b/src/com/google/android/droiddriver/instrumentation/InstrumentationContext.java
index 0c4e9dc..3ed7e20 100644
--- a/src/com/google/android/droiddriver/instrumentation/InstrumentationContext.java
+++ b/src/com/google/android/droiddriver/instrumentation/InstrumentationContext.java
@@ -35,8 +35,8 @@ import java.util.Map;
 public class InstrumentationContext extends AbstractContext {
   private final Map<View, ViewElement> map = new MapMaker().weakKeys().weakValues().makeMap();
 
-  InstrumentationContext(final Instrumentation instrumentation) {
-    super(new InputInjector() {
+  InstrumentationContext(final Instrumentation instrumentation, InstrumentationDriver driver) {
+    super(instrumentation, driver, new InputInjector() {
       @Override
       public boolean injectInputEvent(InputEvent event) {
         if (event instanceof MotionEvent) {
diff --git a/src/com/google/android/droiddriver/instrumentation/InstrumentationDriver.java b/src/com/google/android/droiddriver/instrumentation/InstrumentationDriver.java
index c4f1fbb..078c4bf 100644
--- a/src/com/google/android/droiddriver/instrumentation/InstrumentationDriver.java
+++ b/src/com/google/android/droiddriver/instrumentation/InstrumentationDriver.java
@@ -22,9 +22,12 @@ import android.graphics.Bitmap;
 import android.os.SystemClock;
 import android.view.View;
 
+import com.google.android.droiddriver.UiDevice;
 import com.google.android.droiddriver.base.AbstractDroidDriver;
+import com.google.android.droiddriver.base.BaseUiDevice;
 import com.google.android.droiddriver.exceptions.TimeoutException;
 import com.google.android.droiddriver.util.ActivityUtils;
+import com.google.common.base.Preconditions;
 import com.google.common.primitives.Longs;
 
 /**
@@ -32,10 +35,13 @@ import com.google.common.primitives.Longs;
  */
 public class InstrumentationDriver extends AbstractDroidDriver {
   private final InstrumentationContext context;
+  private final Instrumentation instrumentation;
+  private final BaseUiDevice uiDevice;
 
   public InstrumentationDriver(Instrumentation instrumentation) {
-    super(instrumentation);
-    this.context = new InstrumentationContext(instrumentation);
+    this.instrumentation = Preconditions.checkNotNull(instrumentation);
+    this.context = new InstrumentationContext(instrumentation, this);
+    uiDevice = new BaseUiDevice(context);
   }
 
   @Override
@@ -102,4 +108,9 @@ public class InstrumentationDriver extends AbstractDroidDriver {
     instrumentation.runOnMainSync(screenshotRunnable);
     return screenshotRunnable.screenshot;
   }
+
+  @Override
+  public UiDevice getUiDevice() {
+    return uiDevice;
+  }
 }
diff --git a/src/com/google/android/droiddriver/scroll/DynamicSentinelStrategy.java b/src/com/google/android/droiddriver/scroll/DynamicSentinelStrategy.java
index c166c1e..779a41f 100644
--- a/src/com/google/android/droiddriver/scroll/DynamicSentinelStrategy.java
+++ b/src/com/google/android/droiddriver/scroll/DynamicSentinelStrategy.java
@@ -88,6 +88,15 @@ public class DynamicSentinelStrategy extends AbstractSentinelStrategy {
 
     @Override
     public boolean isSentinelUpdated(UiElement newSentinel, UiElement oldSentinel) {
+      // If the sentinel moved, scrolling has some effect. This is both an
+      // optimization - getBounds is cheaper than find - and necessary in
+      // certain cases, e.g. user is looking for a sibling of the unique string;
+      // the scroll is close to the end therefore the unique string does not
+      // change, but the target could be revealed.
+      if (!newSentinel.getBounds().equals(oldSentinel.getBounds())) {
+        return true;
+      }
+
       String newString = getUniqueStringFromSentinel(newSentinel);
       // If newString is null, newSentinel must be partially shown. In this case
       // we return true to allow further scrolling. But program error could also
diff --git a/src/com/google/android/droiddriver/uiautomation/UiAutomationContext.java b/src/com/google/android/droiddriver/uiautomation/UiAutomationContext.java
index 7efa48e..57a64d5 100644
--- a/src/com/google/android/droiddriver/uiautomation/UiAutomationContext.java
+++ b/src/com/google/android/droiddriver/uiautomation/UiAutomationContext.java
@@ -16,6 +16,7 @@
 
 package com.google.android.droiddriver.uiautomation;
 
+import android.app.Instrumentation;
 import android.app.UiAutomation;
 import android.view.InputEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
@@ -35,14 +36,14 @@ public class UiAutomationContext extends AbstractContext {
       .weakValues().makeMap();
   private final UiAutomation uiAutomation;
 
-  UiAutomationContext(final UiAutomation uiAutomation) {
-    super(new InputInjector() {
+  UiAutomationContext(final Instrumentation instrumentation, UiAutomationDriver driver) {
+    super(instrumentation, driver, new InputInjector() {
       @Override
       public boolean injectInputEvent(InputEvent event) {
-        return uiAutomation.injectInputEvent(event, true /* sync */);
+        return instrumentation.getUiAutomation().injectInputEvent(event, true /* sync */);
       }
     });
-    this.uiAutomation = uiAutomation;
+    this.uiAutomation = instrumentation.getUiAutomation();
   }
 
   public UiAutomationElement getUiElement(AccessibilityNodeInfo node) {
diff --git a/src/com/google/android/droiddriver/uiautomation/UiAutomationDriver.java b/src/com/google/android/droiddriver/uiautomation/UiAutomationDriver.java
index 7d21233..8b2baaf 100644
--- a/src/com/google/android/droiddriver/uiautomation/UiAutomationDriver.java
+++ b/src/com/google/android/droiddriver/uiautomation/UiAutomationDriver.java
@@ -16,13 +16,18 @@
 
 package com.google.android.droiddriver.uiautomation;
 
-import android.app.UiAutomation;
 import android.app.Instrumentation;
+import android.app.UiAutomation;
+import android.content.Context;
 import android.graphics.Bitmap;
 import android.os.SystemClock;
+import android.view.accessibility.AccessibilityEvent;
+import android.view.accessibility.AccessibilityManager;
 import android.view.accessibility.AccessibilityNodeInfo;
 
+import com.google.android.droiddriver.UiDevice;
 import com.google.android.droiddriver.base.AbstractDroidDriver;
+import com.google.android.droiddriver.base.BaseUiDevice;
 import com.google.android.droiddriver.exceptions.TimeoutException;
 import com.google.common.primitives.Longs;
 
@@ -40,11 +45,12 @@ public class UiAutomationDriver extends AbstractDroidDriver {
 
   private final UiAutomationContext context;
   private final UiAutomation uiAutomation;
+  private final BaseUiDevice uiDevice;
 
   public UiAutomationDriver(Instrumentation instrumentation) {
-    super(instrumentation);
     this.uiAutomation = instrumentation.getUiAutomation();
-    this.context = new UiAutomationContext(uiAutomation);
+    this.context = new UiAutomationContext(instrumentation, this);
+    uiDevice = new BaseUiDevice(context);
   }
 
   @Override
@@ -84,4 +90,33 @@ public class UiAutomationDriver extends AbstractDroidDriver {
   protected Bitmap takeScreenshot() {
     return uiAutomation.takeScreenshot();
   }
+
+  /**
+   * Some widgets fail to trigger some AccessibilityEvent's after actions,
+   * resulting in stale AccessibilityNodeInfo's. As a work-around, force to
+   * clear the AccessibilityNodeInfoCache.
+   */
+  public void clearAccessibilityNodeInfoCache() {
+    uiDevice.sleep();
+    uiDevice.wakeUp();
+  }
+
+  /**
+   * {@link #clearAccessibilityNodeInfoCache} causes the screen to blink. This
+   * method clears the cache without blinking by employing an implementation
+   * detail of AccessibilityNodeInfoCache. This is a hack; use it at your own
+   * discretion.
+   */
+  public void clearAccessibilityNodeInfoCacheHack() {
+    AccessibilityManager accessibilityManager =
+        (AccessibilityManager) context.getInstrumentation().getTargetContext()
+            .getSystemService(Context.ACCESSIBILITY_SERVICE);
+    accessibilityManager.sendAccessibilityEvent(AccessibilityEvent
+        .obtain(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED));
+  }
+
+  @Override
+  public UiDevice getUiDevice() {
+    return uiDevice;
+  }
 }
diff --git a/src/com/google/android/droiddriver/uiautomation/UiAutomationElement.java b/src/com/google/android/droiddriver/uiautomation/UiAutomationElement.java
index a399360..a28498c 100644
--- a/src/com/google/android/droiddriver/uiautomation/UiAutomationElement.java
+++ b/src/com/google/android/droiddriver/uiautomation/UiAutomationElement.java
@@ -189,6 +189,13 @@ public class UiAutomationElement extends AbstractUiElement {
       // it is not reliable.
       // Exception is ignored here. Tests will fail anyways if this is
       // critical.
+      // Actions should usually trigger some AccessibilityEvent's, but some
+      // widgets fail to do so, resulting in stale AccessibilityNodeInfo's. As a
+      // work-around, force to clear the AccessibilityNodeInfoCache.
+      // A legitimate case of no AccessibilityEvent is when scrolling has
+      // reached the end, but we cannot tell whether it's legitimate or the
+      // widget has bugs, so clearAccessibilityNodeInfoCache anyways.
+      ((UiAutomationDriver) context.getDriver()).clearAccessibilityNodeInfoCacheHack();
     }
   }
 }