Модифицируем плеер Vanilla Music под Android

/**
	 * Execute the given action.
	 *
	 * @param action The action to execute.
	 * @param receiver Optional. If non-null, update the PlaybackActivity with
	 * new song or state from the executed action. The activity will still be
	 * updated by the broadcast if not passed here; passing it just makes the
	 * update immediate.
	 */
	public void performAction(Action action, PlaybackActivity receiver)
	{
		switch (action) {
		case Nothing:
			break;
		case Library:
			Intent intent = new Intent(this, LibraryActivity.class);
			intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
			startActivity(intent);
			break;
		case PlayPause: {
			int state = playPause();
			if (receiver != null)
				receiver.setState(state);
			break;
		}
		case NextSong: {
			Song song = shiftCurrentSong(SongTimeline.SHIFT_NEXT_SONG);
			if (receiver != null)
				receiver.setSong(song);
			break;
		}
		case PreviousSong: {
			Song song = shiftCurrentSong(SongTimeline.SHIFT_PREVIOUS_SONG);
			if (receiver != null)
				receiver.setSong(song);
			break;
		}
		case NextAlbum: {
			Song song = shiftCurrentSong(SongTimeline.SHIFT_NEXT_ALBUM);
			if (receiver != null)
				receiver.setSong(song);
			break;
		}
		case PreviousAlbum: {
			Song song = shiftCurrentSong(SongTimeline.SHIFT_PREVIOUS_ALBUM);
			if (receiver != null)
				receiver.setSong(song);
			break;
		}
		case Repeat: {
			int state = cycleFinishAction();
			if (receiver != null)
				receiver.setState(state);
			break;
		}
		case Shuffle: {
			int state = cycleShuffle();
			if (receiver != null)
				receiver.setState(state);
			break;
		}
		case EnqueueAlbum:
			enqueueFromCurrent(MediaUtils.TYPE_ALBUM);
			break;
		case EnqueueArtist:
			enqueueFromCurrent(MediaUtils.TYPE_ARTIST);
			break;
		case EnqueueGenre:
			enqueueFromCurrent(MediaUtils.TYPE_GENRE);
			break;
		case ClearQueue:
			clearQueue();
			Toast.makeText(this, R.string.queue_cleared, Toast.LENGTH_SHORT).show();
			break;
		case ShowQueue:
			Intent intentShowQueue = new Intent(this, ShowQueueActivity.class);
			intentShowQueue.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
			startActivity(intentShowQueue);
			break;
		case ToggleControls:
			// Handled in FullPlaybackActivity.performAction
			break;
		case SeekForward:
			if (mCurrentSong != null) {
				mPendingSeekSong = mCurrentSong.id;
				mPendingSeek = getPosition() + 10000;
				// We 'abuse' setCurrentSong as it will stop the playback and restart it
				// at the new position, taking care of the ui update
				setCurrentSong(0);
			}
			break;
		case SeekBackward:
			if (mCurrentSong != null) {
				mPendingSeekSong = mCurrentSong.id;
				mPendingSeek = getPosition() - 10000;
				if (mPendingSeek < 1) mPendingSeek = 1; // must at least be 1
				setCurrentSong(0);
			}
			break;
		default:
			throw new IllegalArgumentException("Invalid action: " + action);
		}
	}

	public class SettingsContentObserver extends ContentObserver {
		Context context;

		public SettingsContentObserver(Context c, Handler handler) {
			super(handler);
			context = c;
		}

		@Override
		public boolean deliverSelfNotifications() {
			return super.deliverSelfNotifications();
		}

		@Override
		public void onChange(boolean selfChange) {
			super.onChange(selfChange);
		}
}

	//   for a catch volume change
public class SettingsContentObserver extends ContentObserver {
	int previousVolume;
	Context context;
	int prevdelta=0;

	public SettingsContentObserver(Context c, Handler handler) {
		super(handler);
		context = c;

		AudioManager audio = mAudioManager;
		previousVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);
	}

	@Override
	public boolean deliverSelfNotifications() {
		return super.deliverSelfNotifications();
	}

	@Override
	public void onChange(boolean selfChange) {
		super.onChange(selfChange);

		AudioManager audio = mAudioManager;
		int currentVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);

		if(isproximity && enable_vol_track_select) { // isproximity , enable_vol_track_select - признаки что сработал датчик приближения
// и активирована опция переключения треков клавишами регулировки звука

			long now = SystemClock.elapsedRealtime();
			if (now - mLastVolChangeTime > MIN_SHAKE_PERIOD * 8)
			{
				// запускаем отдельный    handler , который вернет уровень громкости обратно
				undo_volume_change();

				delta = previousVolume - currentVolume;
				mLastVolChangeTime = now;
				if (delta > 0) {
					performAction(Action.NextSong, null); // переключение трека на следующий

					previousVolume = currentVolume;
				} else if (delta <= 0) {
					performAction(Action.PreviousSong, null); // переключение трека на предыдущий
					previousVolume = currentVolume;
				}

				prevdelta = delta;
			} else {
				int difvol = currentVolume - audio.getStreamVolume(AudioManager.STREAM_MUSIC);
				previousVolume = difvol + currentVolume;
			}

		}else delta=0;
	}
}

void undo_volume_change()
{
 //  undo volume change afer next-prev comand
	android.os.Handler h = new Handler() {
		int currentVolume;
		public void handleMessage(android.os.Message msg) {
			switch (msg.what)
			{
				case 1:
					currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
				break;
				case 2:
					if(isproximity)
					{
						if(mMediaPlayer.isPlaying()    )
						{
							if(Math.abs(delta)==1)
							{
								mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, currentVolume + delta, AudioManager.FLAG_SHOW_UI);
								Log.d("PLEER", " setStreamVolume  Volume=" + String.valueOf(currentVolume));
							}

						}
					}
					else
					{
						delta=0;
						currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);

					}
					break;

			}

		};
	};
	h.sendEmptyMessage(1);
	h.sendEmptyMessageDelayed(2,1000);

}