/// <summary>

    /// 对UI做出限制

    /// 将UI限制在屏幕内

    /// </summary>

    private void UIAstrict()

    {

        // 世界空间

        Vector2 minworld = transform.TransformPoint(rect.rect.min);

        Vector2 maxworld = transform.TransformPoint(rect.rect.max);

        Vector2 sizeworld = maxworld - minworld;

        // 保持最小的位置在屏幕边界-大小

        maxworld = new Vector2(Screen.width, Screen.height) - sizeworld;

        // 保持位置在(0,0)和maxworld之间

        float y = Mathf.Clamp(minworld.y, 0, maxworld.y);

        float x = Mathf.Clamp(minworld.x, 0, maxworld.x);

        // set new position to xy(=local) + offset(=world)设置新位置为xy(=本地)+偏移量(=世界)

        Vector2 offset = (Vector2)transform.position - minworld;

        transform.position = new Vector2(x, y) + offset;

    }