在拖拽物體上繫結的本指令碼中，重寫一下UGUI的drag相關事件，調ScrollRect的drag等方法

public class DragScrollView : EventTriggerListener

{
    /// <summary>
    /// Reference to the scroll view that will be dragged by the script.
    /// </summary>

    public ScrollRect scrollView;

    // Legacy functionality, kept for backwards compatibility. Use 'scrollView' instead.
    [HideInInspector]
    [SerializeField]
    ScrollRect draggablePanel;

    Transform mTrans;
    ScrollRect mScroll;
    bool mAutoFind = false;
    bool mStarted = false;

    /// <summary>
    /// Automatically find the scroll view if possible.
    /// </summary>

    void OnEnable()
    {
        mTrans = transform;

        // Auto-upgrade
        if (scrollView == null && draggablePanel != null) {
            scrollView = draggablePanel;
            draggablePanel = null;
        }

        if (mStarted && (mAutoFind || mScroll == null))
            FindScrollView();
    }


    /// <summary>
    /// Find the scroll view.
    /// </summary>

    void Start()
    {
        mStarted = true;
        FindScrollView();
    }

    /// <summary>
    /// Find the scroll view to work with.
    /// </summary>

    void FindScrollView()
    {
        // If the scroll view is on a parent, don't try to remember it (as we want it to be dynamic in case of re-parenting)
        ScrollRect sv = mTrans.GetComponentInParent<ScrollRect>();


        if (scrollView == null) {
            scrollView = sv;
            mAutoFind = true;
        } else if (scrollView == sv) {
            mAutoFind = true;
        }
        mScroll = scrollView;

    }

public override void OnDrag(UnityEngine.EventSystems.PointerEventData eventData)
    {
        scrollView.OnDrag(eventData);
    }
    public override void OnInitializePotentialDrag(PointerEventData eventData)
    {
        scrollView.OnInitializePotentialDrag(eventData);
    }
    public override void OnBeginDrag(PointerEventData eventData)
    {
        scrollView.OnBeginDrag(eventData);
    }
    public override void OnEndDrag(PointerEventData eventData)
    {
        scrollView.OnEndDrag(eventData);
    }
}