public ChooserDialog withOnLastBackPressedListener(OnBackPressedListener listener) {
        if (this._onBackPressed instanceof defBackPressed) {
            ((defBackPressed) this._onBackPressed)._onLastBackPressed = listener;
        }
        return this;
    }
called if {@link KeyEvent#KEYCODE_BACK} is caught,
and current directory is the root of Primary/SdCard storage.
android-file-chooser/src/main/java/com/obsez/android/lib/filechooser/ChooserDialog.java