NGUI对象跟随鼠标拖拽移动

public Camera WNGUICamera;
    Vector3 _WoldPosition;//指针的初始位置
    // Vector3 _WoldAng;
    Vector3 WscreenSpace;
    Vector3 Woffset;
    Vector3 WcurScreenSpace;
    Vector3 WcurPosition;

    //工具跟随鼠标拖拽移动
    IEnumerator fnOnMouseDown()
    {

        WscreenSpace = WNGUICamera.WorldToScreenPoint(transform.position);
        Woffset = transform.position - WNGUICamera.ScreenToWorldPoint(new Vector3(Input.mousePosition.x,Input.mousePosition.y, WscreenSpace.z));

        while (Input.GetMouseButton(0))
        {
            //DrawLineScript.isMoveLine = true;
            if (Input.mousePosition.x > 0 && Input.mousePosition.x < Screen.width && Input.mousePosition.y > 0 && Input.mousePosition.y < Screen.height)
            {
                WcurScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, WscreenSpace.z);
                WcurPosition = WNGUICamera.ScreenToWorldPoint(WcurScreenSpace) + Woffset;
                transform.position = new Vector3(WcurPosition.x, WcurPosition.y, 0f);
            }
            yield return new WaitForFixedUpdate();
        }
    }