void Start()
    {
        ClosureTest();
    }


    public Button[] btn;
    private void ClosureTest()
    {
        for (int i = 0; i < 5; i++)
        {
            int num = i;        //如果不在使用btn回调前声明变量并把i的值赋过去，i就会永远变成5..
            btn[i].onClick.AddListener(() =>
            {
                Debug.Log(num);
            });
        }

    }