code: private void setPlaying(boolean isPlaying) {
          if (isPlaying) {
              mPlayPause.setImageResource(R.drawable.ic_pause_white);
          } else {
              mPlayPause.setImageResource(R.drawable.ic_play_white);
          }
      }
docs: Used to update the play/pause button.
  <p/>
  Should be synchronize with the player playing state.
  See also : {@link CheerleaderPlayer#isPlaying()}.
  
  @param isPlaying true if a track is currently played.