Unity,UI拖拽（跟随手指移动）

public class UIDrag : MonoBehaviour, IPointerDownHandler, IDragHandler, IEndDragHandler
{

    #region 字段
    public RectTransform canvas;
    private RectTransform imgRect;
    Vector2 offest = new Vector2();
    #endregion

    private void Start()
    {
        imgRect = this.GetComponent<RectTransform>();
        canvas = this.transform.parent.GetComponent<RectTransform>();
    }

    #region  接口
    public void OnDrag(PointerEventData eventData)
    {
        Vector2 mouseDrag = eventData.position;
        Vector2 uguiPos = new Vector2();

        //RectTransformUtility.ScreenPointToLocalPointInRectangle() 把屏幕坐标转换成UI坐标
        //canvas 为当前物体的父物体的RectTransform
        bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas,mouseDrag,eventData.enterEventCamera,out uguiPos);
        if (isRect)
        {
            imgRect.anchoredPosition = offest + uguiPos;
        }
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        offest = Vector2.zero;
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        Debug.Log("按下");
        Vector2 mouseDown = eventData.position;   //鼠标按下时的屏幕坐标
        Vector2 mouseUguiPos = new Vector2();   //返回的UGUI坐标
        bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas,mouseDown,eventData.enterEventCamera,out mouseUguiPos);
        if (isRect)
        {
            offest = imgRect.anchoredPosition - mouseUguiPos;     //计算点击在UI上但是没点击在UI正中心
            Debug.Log(offest);
        }
    }

    #endregion
}

Unity,UI拖拽（跟随手指移动）

public class UIDrag : MonoBehaviour, IPointerDownHandler, IDragHandler, IEndDragHandler
{

    #region 字段
    public RectTransform canvas;
    private RectTransform imgRect;
    Vector2 offest = new Vector2();
    #endregion

    private void Start()
    {
        imgRect = this.GetComponent<RectTransform>();
        canvas = this.transform.parent.GetComponent<RectTransform>();
    }

    #region  接口
    public void OnDrag(PointerEventData eventData)
    {
        Vector2 mouseDrag = eventData.position;
        Vector2 uguiPos = new Vector2();

        //RectTransformUtility.ScreenPointToLocalPointInRectangle() 把屏幕坐标转换成UI坐标
        //canvas 为当前物体的父物体的RectTransform
        bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas,mouseDrag,eventData.enterEventCamera,out uguiPos);
        if (isRect)
        {
            imgRect.anchoredPosition = offest + uguiPos;
        }
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        offest = Vector2.zero;
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        Debug.Log("按下");
        Vector2 mouseDown = eventData.position;   //鼠标按下时的屏幕坐标
        Vector2 mouseUguiPos = new Vector2();   //返回的UGUI坐标
        bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas,mouseDown,eventData.enterEventCamera,out mouseUguiPos);
        if (isRect)
        {
            offest = imgRect.anchoredPosition - mouseUguiPos;     //计算点击在UI上但是没点击在UI正中心
            Debug.Log(offest);
        }
    }

    #endregion
}