UpdateCallback.java

private void startUpdatingCallbackWithPosition() {
   if (mExecutor == null) {
       mExecutor = Executors.newSingleThreadScheduledExecutor();
   }
   if (mSeekBarPositionUpdateTask == null) {
       mSeekBarPositionUpdateTask = new Runnable() {
           @Override
           public void run() {
               updateProgressCallbackTask();
           }
       };
   }
   mExecutor.scheduleAtFixedRate(
           mSeekBarPositionUpdateTask,
           0,
           PLAYBACK_POSITION_REFRESH_INTERVAL_MS,
           TimeUnit.MILLISECONDS
   );
}

private void stopUpdatingCallbackWithPosition(boolean resetUIPlaybackPosition) {
   if (mExecutor != null) {
       mExecutor.shutdownNow();
       mExecutor = null;
       mSeekBarPositionUpdateTask = null;
       if (resetUIPlaybackPosition && mPlaybackInfoListener != null) {
           mPlaybackInfoListener.onPositionChanged(0);
       }
   }
}

private void updateProgressCallbackTask() {
   if (mMediaPlayer != null && mMediaPlayer.isPlaying()) {
       int currentPosition = mMediaPlayer.getCurrentPosition();
       if (mPlaybackInfoListener != null) {
           mPlaybackInfoListener.onPositionChanged(currentPosition);
       }
   }
}

@Override
public void initializeProgressCallback() {
   final int duration = mMediaPlayer.getDuration();
   if (mPlaybackInfoListener != null) {
       mPlaybackInfoListener.onDurationChanged(duration);
       mPlaybackInfoListener.onPositionChanged(0);
       logToUI(String.format("firing setPlaybackDuration(%d sec)",
                             TimeUnit.MILLISECONDS.toSeconds(duration)));
       logToUI("firing setPlaybackPosition(0)");
   }
}