public class Item : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler

    {

        public RectTransform rt;

        public void OnBeginDrag(PointerEventData eventData)

        {

            //RectTransformUtility.ScreenPointToLocalPointInRectangle(btn.GetComponent<RectTransform>(), eventData.position, Camera.main, null);

        }

        public void OnDrag(PointerEventData eventData)

        {

            Vector3 globalMousePos;

            if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, eventData.position, null, out globalMousePos))

            {

                rt.position = globalMousePos;

            }

        }

        public void OnEndDrag(PointerEventData eventData)

        {

        }

        /// <summary>

        /// 更新UI的位置

        /// </summary>

        private void SetDraggedPosition(PointerEventData eventData)

        {

            Vector3 globalMousePos;

            if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, eventData.position, null, out globalMousePos))

            {

                rt.position = globalMousePos;

            }

        }

    }

 private void Init(Transform mParent, Transform mChild)

        {

            Vector3 targetPos = mParent.localPosition;

            Vector3 curPos = mChild.localPosition;

            line.rectTransform.sizeDelta = new Vector2(8, Vector3.Distance(targetPos, curPos));

            double angle = Math.Atan2(targetPos.y - curPos.y, targetPos.x - curPos.x) * 180 / Math.PI;

            line.transform.rotation = Quaternion.Euler(0, 0, (float)angle + 270);

            line.transform.localPosition = new Vector3((targetPos.x + curPos.x) / 2, (targetPos.y + curPos.y) / 2, targetPos.z);

        }