函数的调用顺序:
这段代码进入ShowMask()中, 再调用 t.OnComplete(ExitSceneComplete);,进行了currentSceneState.EnterScene()操作  ,为何currentSceneState 此时已经变为了baseSceneState ,我认为现在 应该还没执行完ShowMask()函数,请老师解释一哈这个回调方法OnComplete()为何是在        currentSceneState = baseSceneState;后面执行的

   public void ChanegSceneState(IBaseSceneState baseSceneState)
    {
        lastSceneState = currentSceneState;
        ShowMask();
        currentSceneState = baseSceneState;
    }
    //显示遮罩
    public void ShowMask()
    {
        Tween t = DOTween.To(() => maskImage.color, toColor => maskImage.color = toColor, new Color(0, 0, 0, 1), 2f);
        t.OnComplete(ExitSceneComplete);//在tween动画完成时回调ExitSceneComplete()函数
    }
    //离开当前场景
    private void ExitSceneComplete()
    {
        lastSceneState.ExitScene();
        currentSceneState.EnterScene();
        HideMask();
    }

    //隐藏遮罩
    public void HideMask()
    {
        DOTween.To(() => maskImage.color, toColor => maskImage.color = toColor, new Color(0, 0, 0,0), 2f);
    }