/** {@inheritDoc} */
  @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
      mContainerActivity = (ContainerActivity) activity;

    } catch (ClassCastException e) {
      throw new ClassCastException(
          activity.toString()
              + " must implement "
              + FileFragment.ContainerActivity.class.getSimpleName());
    }
  }