Android - 是否可以找出哪个应用程序具有音频焦点？

Question

我的手机上有一个应用程序可以持续获取音频焦点，即使没有播放声音也是如此。我想知道作为应用开发者，我是否能够告知用户它是哪个应用，或者我是否可以判断我的应用是否具有音频焦点？

Answer 1

我非常怀疑是否有任何公共(public) API 可以告诉您当前焦点是哪个应用。

您可以通过请求跟踪您的应用是否具有音频焦点，例如:

AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
boolean requestGranted = AudioManager.AUDIOFOCUS_REQUEST_GRANTED == audioManager.requestAudioFocus(listener, AudioManager.STREAM_MUSIC,
                    AudioManager.AUDIOFOCUS_GAIN);
if(requestGranted){
   // you now has the audio focus
}

当您请求和放弃焦点时，您应该确保维护一个单个 监听器实例，see my answer here解决音频焦点的常见问题

下面是一个onAudioFocusChange()的例子:

@Override
public void onAudioFocusChange(int focus) {

  switch (focus) {
    case AudioManager.AUDIOFOCUS_LOSS:
        Log.d(TAG,"AUDIOFOCUS_LOSS");
        // stop and release your player
        break;
    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
        Log.d(TAG,"AUDIOFOCUS_LOSS_TRANSIENT");
        // pause your player
        break;
    case AudioManager.AUDIOFOCUS_GAIN:
        Log.d(TAG,"AUDIOFOCUS_GAIN");
        // restore volume and resume player if needed
        break;
    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
        Log.d(TAG,"AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK");
        // Lower volume
        break;
   }
}