Android P按键静音流程

静音流程"/>

Android P按键静音流程

今天跟了一下Android系统按键静音的流程，Android实现了在系统层面静音。输出给底层的音量为0。

按键使用注入按键方式实现，静音按键值：

public static final int KEYCODE_VOLUME_MUTE     = 164;

注入方式：

KeyEvent k = new KeyEvent(KeyEvent.ACTION_DOWN,KeyEvent.KEYCODE_VOLUME_MUTE);
InputManager.getInstance().injectInputEvent(key, 0);

或者：

simulateKey(KeyEvent.KEYCODE_VOLUME_MUTE);public static void simulateKey(final int KeyCode) {new Thread() {@Overridepublic void run() {try {Instrumentation inst = new Instrumentation();inst.sendKeyDownUpSync(KeyCode);} catch (Exception e) {Log.e("hello", e.toString());}}}.start();
}

调用流程：
DecorView.java --> PhoneWindow.java --> MediaSessionService.java

窗口监听Key消息的过程省略过，在Input输入系统中已经分析过。

\frameworks\base\services\core\java\com\android\server\media\MediaSessionService.java
dispatchVolumeKeyEvent()
dispatchVolumeKeyEventLocked()

\frameworks\base\services\core\java\com\android\server\audio\AudioService.java
adjustSuggestedStreamVolume()

private void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags,String callingPackage, String caller, int uid) {//省略一部分代码//...// mute为truefinal boolean isMute = isMuteAdjust(direction);ensureValidStreamType(streamType);final int resolvedStream = mStreamVolumeAlias[streamType];// Play sounds on STREAM_RING only.if ((flags & AudioManager.FLAG_PLAY_SOUND) != 0 &&resolvedStream != AudioSystem.STREAM_RING) {flags &= ~AudioManager.FLAG_PLAY_SOUND;}// For notifications/ring, show the ui before making any adjustments// Don't suppress mute/unmute requestsif (mVolumeController.suppressAdjustment(resolvedStream, flags, isMute)) {direction = 0;flags &= ~AudioManager.FLAG_PLAY_SOUND;flags &= ~AudioManager.FLAG_VIBRATE;if (DEBUG_VOL) Log.d(TAG, "Volume controller suppressed adjustment");}adjustStreamVolume(streamType, direction, flags, callingPackage, caller, uid);
}
protected void adjustStreamVolume(int streamType, int direction, int flags,String callingPackage, String caller, int uid) {//省略一部分代码//...//省略一部分代码//...if (isMuteAdjust) {boolean state;if (direction == AudioManager.ADJUST_TOGGLE_MUTE) {state = !streamState.mIsMuted;} else {state = direction == AudioManager.ADJUST_MUTE;}if (streamTypeAlias == AudioSystem.STREAM_MUSIC) {setSystemAudioMute(state