Handling Changes in Audio Output

Besides responding to your UI controls and media buttons, an audio app should also react to other Android events that can affect its sound. This page describes how to handle these cases:

• Change the volume when the user adjusts a hardware volume control
• Stop playing if the headphones are disconnected while in use

Honor the volume controls

When a user presses a volume key in a game or music app the volume should change, even if the player is paused between songs or there’s no music for the current game location.

Android uses separate audio streams for playing music, alarms, notifications, the incoming call ringer, system sounds, in-call volume, and DTMF tones. This allows users to control the volume of each stream independently.

By default, pressing the volume control modifies the volume of the active audio stream. If your app isn't currently playing anything, hitting the volume keys adjusts the ringer volume.

Unless your app is a replacement alarm clock, you probably play audio using the STREAM_MUSIC stream.

To ensure that volume controls adjust the correct stream, you should call setVolumeControlStream() passing in AudioManager.STREAM_MUSIC.

setVolumeControlStream(AudioManager.STREAM_MUSIC);

Make this call early in your app’s lifecycle, typically from the onCreate() method of the activity or fragment that controls your media. This connects the volume controls to STREAM_MUSIC whenever the target activity or fragment is visible.

Don't be noisy

Users have a number of alternatives when it comes to enjoying the audio from their Android devices. Most devices have a built-in speaker, headphone jacks for wired headsets, and many also feature Bluetooth connectivity and support for A2DP audio.

When a headset is unplugged or a Bluetooth device disconnected, the audio stream automatically reroutes to the built-in speaker. If you listen to music at a high volume, this can be a noisy surprise.

Luckily the system broadcasts an ACTION_AUDIO_BECOMING_NOISY intent when this happens. You should create a BroadcastReceiver that listens for this intent whenever you’re playing audio. In the case of music players, users typically expect the playback to be paused. For gaming apps, you may choose to significantly lower the volume instead. Your receiver should look like this:

private class BecomingNoisyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
      if (AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals(intent.getAction())) {
          // Pause the playback
      }
    }
}

Register the receiver when you begin playback, and unregister it when you stop. If you design your app as we describe in this guide, these calls should appear in the onPlay() and onStop() media session callbacks.

private IntentFilter intentFilter = new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
private BecomingNoisyReceiver myNoisyAudioStreamReceiver = new BecomingNoisyReceiver();

MediaSessionCompat.Callback callback = new
MediaSessionCompat.Callback() {
  @Override
  public void onPlay() {
    registerReceiver(myNoisyAudioStreamReceiver, intentFilter);
  }

  @Override
  public void onStop() {
    unregisterReceiver(myNoisyAudioStreamReceiver);
  }
}