Unity UGUI實現鼠標拖動圖片

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
/// <summary>
/// **************************UGUI拖動圖片,腳本掛在Image上即可*********************************
/// </summary>
public class TuoDongWuPin : MonoBehaviour, IDragHandler, IBeginDragHandler, IEndDragHandler
{
    //需要被實例化的與制體
    //public GameObject YuSheWu;
    //實例化后的對象
    private Image img;
    Vector3 offPos;//存儲按下鼠標時的圖片-鼠標位置差
    Vector3 arragedPos; //保存經過整理后的向量，用於圖片移動
    /// <summary>
    /// 開始拖拽的時候
    /// </summary>
    /// <param name="eventData"></param>
    public void OnBeginDrag(PointerEventData eventData)
    {
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(transform.GetComponent<RectTransform>(), Input.mousePosition
     , eventData.enterEventCamera, out arragedPos))
        {
            offPos = transform.position - arragedPos;
        }
    }
    /// <summary>
    /// 拖拽中
    /// </summary>
    /// <param name="eventData"></param>
    public void OnDrag(PointerEventData eventData)
    {
        transform.position = offPos + Input.mousePosition;
    }
    /// <summary>
    /// 拖拽結束
    /// </summary>
    /// <param name="eventData"></param>
    public void OnEndDrag(PointerEventData eventData)
    {
        transform.position = transform.parent.transform.position;
    }
}