ScrollVIEW 2000个ITEM不会卡

using UnityEngine;
using System.Collections.Generic;

public class UIWrapGrid : MonoBehaviour
{
	Transform mTrans;
	UIPanel mPanel;
	UIScrollView mScroll;
    bool mHorizontal = false;
	bool mFirstTime = true;
	List<Transform> mChildren = new List<Transform>();

	/// <summary>
	/// Initialize everything and register a callback with the UIPanel to be notified when the clipping region moves.
	/// </summary>

	protected virtual void Start () {
        InitGrid();
		mFirstTime = false;
	}

    /// <summary>
    /// Cache the scroll view and return 'false' if the scroll view is not found.
    /// </summary>
    public void InitGrid() {
        mTrans = transform;
        mPanel = NGUITools.FindInParents<UIPanel>(gameObject);
        mScroll = mPanel.GetComponent<UIScrollView>();

        if (mScroll != null) {
            mScroll.GetComponent<UIPanel>().onClipMove = OnMove;
        }

        mChildren.Clear();
        for (int i = 0; i < mTrans.childCount; ++i)
            mChildren.Add(mTrans.GetChild(i));

        // Sort the list of children so that they are in order
        mChildren.Sort(UIGrid.SortByName);

        if (mScroll == null) return;
        if (mScroll.movement == UIScrollView.Movement.Horizontal) mHorizontal = true;
        else if (mScroll.movement == UIScrollView.Movement.Vertical) mHorizontal = false;

        WrapContent();
    }

	/// <summary>
	/// Callback triggered by the UIPanel when its clipping region moves (for example when it's being scrolled).
	/// </summary>

	protected virtual void OnMove (UIPanel panel) { WrapContent(); }

    void WrapContent() {
        Vector3[] corners = mPanel.worldCorners;

        for (int i = 0; i < 4; ++i) {
            Vector3 v = corners[i];
            v = mTrans.InverseTransformPoint(v);
            corners[i] = v;
        }
        Vector3 center = Vector3.Lerp(corners[0], corners[2], 0.5f);

        if (mHorizontal) {  //横向
            for (int i = 0, imax = mChildren.Count; i < imax; ++i) {
                Transform t = mChildren[i];
                float distance = t.localPosition.x - center.x;
                float min = corners[0].x - 100;
                float max = corners[2].x + 100;

                distance += mPanel.clipOffset.x - mTrans.localPosition.x;
                if (!UICamera.IsPressed(t.gameObject)) {
                    NGUITools.SetActive(t.gameObject, (distance > min && distance < max), false);
                }
            }
        } else {            //竖向
            for (int i = 0, imax = mChildren.Count; i < imax; ++i) {
                Transform t = mChildren[i];
                float distance = t.localPosition.y - center.y;
                float min = corners[0].y - 100;
                float max = corners[2].y + 100;

                distance += mPanel.clipOffset.y - mTrans.localPosition.y;
                if (!UICamera.IsPressed(t.gameObject)) {
                    bool active = t.gameObject.activeSelf;
                    bool willactive = distance > min && distance < max;
                    if (active == willactive) continue;
                    NGUITools.SetActive(t.gameObject, willactive, false);
                }
            }
        }
    }
}