Question

I have a ContentObserver registered to android.provider.Settings.System that should observe changes of any audio volume. It is notified as expected when clicking the hardware volume buttons but is not notified when I change the audio volume via AudioManager.setStreamVolume or AudioManager.adjustStreamVolume.

Here’s how my ContentObserver looks like:

// this is a Service
this.getApplicationContext().getContentResolver().registerContentObserver(
  android.provider.Settings.System.CONTENT_URI, 
  true, new ContentObserver(new Handler()) {
    public void onChange(boolean selfChange) {
      Log.d("ContentObserver", "got notified");
    }
});

And here my call to AudioManager.adjustStreamVolume:

// this.context is the activities context
this.context.getSystemService(Context.AUDIO_SERVICE).adjustStreamVolume(
  AudioManager.STREAM_RING, AudioManager.ADJUST_LOWER,
  AudioManager.FLAG_SHOW_UI);

I have read this and that post and the AudioManager and Settings.System documentation and can not find a reason why the Observer is notified when changing the volume with the volume buttons but not when changing it with the AudioManager.

Thanks for the help!

Answer 1

The AudioManager does broadcast an intent

android.media.VOLUME_CHANGED_ACTION`

But this is not part of the official documentation. So this might change in future releases. But you could use this atleast for gingerbread devices.

you can find more about the extras in the intent from here