@Override
  public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    ArrayList<Boolean> states = mUserIdsAdapter.getCheckStates();
    // no proper parceling method available :(
    outState.putSerializable(ARG_CHECK_STATES, states);
  }
 @Override
 public void onSaveInstanceState(Bundle outState) {
   super.onSaveInstanceState(outState);
   outState.putBoolean(ARG_USE_COMPRESSION, mUseCompression);
 }