private void prev() {
   if (--mCurrentItem < 0) {
     mCurrentItem = mItems.size() - 1;
   }
   if (mPlayPauseAction.getIndex() == PlayPauseAction.PLAY) {
     mCallback.onFragmentPlayPause(mItems.get(mCurrentItem), 0, false);
   } else {
     mCallback.onFragmentPlayPause(mItems.get(mCurrentItem), 0, true);
   }
   updatePlaybackRow(mCurrentItem);
 }
  private void next() {
    if (++mCurrentItem >= mItems.size()) {
      mCurrentItem = 0;
    }

    if (mPlayPauseAction.getIndex() == PlayPauseAction.PLAY) {
      mCallback.onFragmentPlayPause(mItems.get(mCurrentItem), 0, false);
    } else {
      mCallback.onFragmentPlayPause(mItems.get(mCurrentItem), 0, true);
    }
    updatePlaybackRow(mCurrentItem);
  }
 public void togglePlayback(boolean playPause) {
   if (playPause) {
     startProgressAutomation();
     setFadingEnabled(true);
     mCallback.onFragmentPlayPause(
         mItems.get(mCurrentItem), mPlaybackControlsRow.getCurrentTime(), true);
     mPlayPauseAction.setIcon(mPlayPauseAction.getDrawable(PlayPauseAction.PAUSE));
   } else {
     stopProgressAutomation();
     setFadingEnabled(false);
     mCallback.onFragmentPlayPause(
         mItems.get(mCurrentItem), mPlaybackControlsRow.getCurrentTime(), false);
     mPlayPauseAction.setIcon(mPlayPauseAction.getDrawable(PlayPauseAction.PLAY));
   }
   notifyChanged(mPlayPauseAction);
 }