Unity 鼠标拖拽功能

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

 /// 
    /// 实现接口的OnBeginDrag方法,处理开始拖拽时要做的事情
    /// 
    /// 
    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
    }

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

/// 
    /// 通过基准点的Z点坐标，转化屏幕坐标为世界坐标
    /// 
    /// 需要转化的屏幕坐标
    /// 基准点(需要它的z点坐标做转换)
    Vector3 screenPositionToWorldPositionBy_Z(Vector3 needToFixedScreenPosition, Vector3 baseWorldPosition)
    {
        Vector3 baseScreenPosition = Camera.main.WorldToScreenPoint(baseWorldPosition);
        needToFixedScreenPosition.z = baseScreenPosition.z;
        return Camera.main.ScreenToWorldPoint(needToFixedScreenPosition);
    } 

/// 
    /// 实现接口的OnEndDrag方法,处理结束时的方法
    /// 
    /// 
    public void OnEndDrag(PointerEventData eventData )
    {
        //获取鼠标下的物体
        GameObject go = eventData.pointerCurrentRaycast.gameObject;
        //交换物品
        if (go.tag.Equals(Enum_Tags.InventoryItemGird)) ExchangeOfGoods(go);
        //复原
        else
        {
            transform.SetParent(imageFather);
            transform.position = startPosition;
        }
        canvasGroup.blocksRaycasts = true;//ui事件穿透：置为不能穿透
 
    }

/// 
    /// 将一个物体放在另一个物体下
    /// 
    /// 作为子物体
    /// 作为父物体
    private void SetParentAndPosition(Transform child, Transform parent)
    {
        child.SetParent(parent);
        child.position = parent.position;
    }

   /// 
    /// 格子内的物品进行交换
    /// 
    /// 鼠标结束位置的格子
    private void ExchangeOfGoods(GameObject go)
    {
        Transform[] childrens = go.GetComponentsInChildren();
        bool isHaveChildren= childrens.Length > 1;
        if (isHaveChildren)
        {
            Transform child = go.transform.GetChild(0);
            SetParentAndPosition(child, imageFather);
          
        }
        SetParentAndPosition(gameObject.transform, go.transform);
        
    }

Vector3 screenPositionToWorldPositionBy_Z(Vector3 needToFixedScreenPosition, Vector3 baseWorldPosition)
    {
        Vector3 baseScreenPosition = Camera.main.WorldToScreenPoint(baseWorldPosition);
        needToFixedScreenPosition.z = baseScreenPosition.z;
        return Camera.main.ScreenToWorldPoint(needToFixedScreenPosition);
    }