code: public void fadeOut (float time) {
  		if (fadeOutActionRunning) return;
  		fadeOutActionRunning = true;
  		final Touchable previousTouchable = getTouchable();
  		setTouchable(Touchable.disabled);
  		Stage stage = getStage();
  		if (stage != null && stage.getKeyboardFocus() != null && stage.getKeyboardFocus().isDescendantOf(this)) {
  			FocusManager.resetFocus(stage);
  		}
  		addAction(Actions.sequence(Actions.fadeOut(time, Interpolation.fade), new Action() {
  			@Override
  			public boolean act (float delta) {
  				setTouchable(previousTouchable);
  				remove();
  				getColor().a = 1f;
  				fadeOutActionRunning = false;
  				return true;
  			}
  		}));
  	}
docs: Fade outs this window, when fade out animation is completed, window is removed from Stage. Calling this for the
  second time won't have any effect if previous animation is still running.