Unity 鼠标拖拽功能

继承3个处理拖拽方法的接口IBeginDragHandler, IDragHandler, IEndDragHandler

 /// <summary>
    /// 实现接口的OnBeginDrag方法,处理开始拖拽时要做的事情
    /// </summary>
    /// <param name="eventData"></param>
    public void OnBeginDrag(PointerEventData eventData)
    {
        startPosition = transform.position;//获取初始位置
        imageFather = transform.parent;//获取父物体的transform
        transform.SetParent(canvas.transform);//将物品放在canvas最下方，确保不会被遮挡
        canvasGroup.blocksRaycasts = false;//射线可以穿透物体
    }

/// <summary>
    /// 实现接口的OnDrag方法,处理拖动中要做的事情
    /// </summary>
    /// <param name="eventData"></param>
    public void OnDrag(PointerEventData eventData)
    {
        transform.position = screenPositionToWorldPositionBy_Z(Input.mousePosition, transform.position);
    }

/// <summary>
    /// 通过基准点的Z点坐标，转化屏幕坐标为世界坐标
    /// &