1 files changed, 52 insertions, 0 deletions
diff --git a/src/com/android/musicfx/KeepAliveService.java b/src/com/android/musicfx/KeepAliveService.java
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+++ b/src/com/android/musicfx/KeepAliveService.java
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+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * 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.android.musicfx;
+
+import android.app.Service;
+import android.content.Intent;
+import android.os.Binder;
+import android.os.IBinder;
+import android.util.Log;
+
+/**
+ * This Service provides a way for client to bind to MusicFx, so that MusicFx can run at same
+ * Process State (see @ProcessStateEnum) as the client.
+ *
+ * Currently, MusicFx does not run in a high priority state (often in CACHED_EMPTY) and can be
+ * easily killed by the LowMemoryKiller. However, its users (music apps, for example) are usually
+ * in a higher priority state, which means they are less likely to be killed. This can lead to
+ * MusicFx and its users being out of sync. To avoid this, framework side will keep record of all
+ * active MusicFx audio sessions, promote the procstate of MusicFx to foreground with the first
+ * audio session open, and remove the foreground procstate delegate with the last audio session
+ * close, or the last user of MusicFx is gone.
+ *
+ * MusicFx user APPs do not need to do anything.
+ *
+ */
+public class KeepAliveService extends Service {
+    private final String TAG = "MusicFxKeepAliveService";
+
+    // Binder given to clients with onBind() callback, the client app receive it as IBinder
+    // parameter of onServiceConnected which can not be used.
+    private final IBinder mBinder = new Binder();
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        Log.i(TAG, "onBind with intent " + intent);
+        return mBinder;
+    }
+}