private void unbind() {
   assert (!(mCurrentLayer == null ^ mCurrentPlayer == null));
   if (mCurrentLayer == null) return;
   mCurrentPlayer.unRegisterPlayListener(mCurrentLayer);
   mCurrentLayer.onPause();
   mCurrentLayer.setPlayer(null);
   mCurrentLayer.setData(null);
   mCurrentPlayer = null;
   mCurrentLayer = null;
 }
 private void bind(Player player, Layer layer, MediaData data) {
   assert (player != null && layer != null && data != null);
   mCurrentLayer = layer;
   mCurrentPlayer = player;
   mCurrentLayer.setPlayer(player);
   mCurrentLayer.setData(data);
   mCurrentPlayer.registerPlayListener(mCurrentLayer);
   mCurrentLayer.onPrepareOptionsMenu(mOptionsMenu);
   mCurrentLayer.onResume(mIsFilmMode);
 }