code: public ChooserDialog withOnLastBackPressedListener(OnBackPressedListener listener) {
          if (this._onBackPressed instanceof defBackPressed) {
              ((defBackPressed) this._onBackPressed)._onLastBackPressed = listener;
          }
          return this;
      }
docs: called if {@link KeyEvent#KEYCODE_BACK} is caught,
  and current directory is the root of Primary/SdCard storage.