FairyGUI.GList.HandleScroll2 C# (CSharp) Method

        void HandleScroll2(bool forceUpdate)
        {
            enterCounter++;
            if (enterCounter > 3)
                return;

            float pos = scrollPane.scrollingPosX;
            float max = pos + scrollPane.viewWidth;
            bool end = pos == scrollPane.contentWidth;//这个标志表示当前需要滚动到最末，无论内容变化大小

            //寻找当前位置的第一条项目
            int newFirstIndex = GetIndexOnPos2(ref pos, forceUpdate);
            if (newFirstIndex == _firstIndex && !forceUpdate)
            {
                enterCounter--;
                return;
            }

            int oldFirstIndex = _firstIndex;
            _firstIndex = newFirstIndex;
            int curIndex = newFirstIndex;
            bool forward = oldFirstIndex > newFirstIndex;
            int oldCount = this.numChildren;
            int lastIndex = oldFirstIndex + oldCount - 1;
            int reuseIndex = forward ? lastIndex : oldFirstIndex;
            float curX = pos, curY = 0;
            bool needRender;
            float deltaSize = 0;
            float firstItemDeltaSize = 0;
            string url = defaultItem;

            itemInfoVer++;
            while (curIndex < _realNumItems && (end || curX < max))
            {
                ItemInfo ii = _virtualItems[curIndex];

                if (ii.obj == null || forceUpdate)
                {
                    if (itemProvider != null)
                    {
                        url = itemProvider(curIndex % _numItems);
                        if (url == null)
                            url = defaultItem;
                    }

                    if (ii.obj != null && ii.obj.resourceURL != url)
                    {
                        RemoveChildToPool(ii.obj);
                        ii.obj = null;
                    }
                }

                if (ii.obj == null)
                {
                    if (forward)
                    {
                        for (int j = reuseIndex; j >= oldFirstIndex; j--)
                        {
                            ItemInfo ii2 = _virtualItems[j];
                            if (ii2.obj != null && ii2.updateFlag != itemInfoVer && ii2.obj.resourceURL == url)
                            {
                                ii.obj = ii2.obj;
                                ii2.obj = null;
                                if (j == reuseIndex)
                                    reuseIndex--;
                                break;
                            }
                        }
                    }
                    else
                    {
                        for (int j = reuseIndex; j <= lastIndex; j++)
                        {
                            ItemInfo ii2 = _virtualItems[j];
                            if (ii2.obj != null && ii2.updateFlag != itemInfoVer && ii2.obj.resourceURL == url)
                            {
                                ii.obj = ii2.obj;
                                ii2.obj = null;
                                if (j == reuseIndex)
                                    reuseIndex++;
                                break;
                            }
                        }
                    }

                    if (ii.obj != null)
                    {
                        SetChildIndex(ii.obj, forward ? curIndex - newFirstIndex : numChildren);
                    }
                    else
                    {
                        ii.obj = _pool.GetObject(url);
                        if (forward)
                            this.AddChildAt(ii.obj, curIndex - newFirstIndex);
                        else
                            this.AddChild(ii.obj);
                    }
                    if (ii.obj is GButton)
                        ((GButton)ii.obj).selected = false;

                    needRender = true;
                }
                else
                    needRender = forceUpdate;

                if (needRender)
                {
                    itemRenderer(curIndex % _numItems, ii.obj);
                    if (curIndex % _curLineItemCount == 0)
                    {
                        deltaSize += Mathf.CeilToInt(ii.obj.size.x) - ii.size.x;
                        if (curIndex == newFirstIndex && oldFirstIndex > newFirstIndex)
                        {
                            //当内容向下滚动时，如果新出现的一个项目大小发生变化，需要做一个位置补偿，才不会导致滚动跳动
                            firstItemDeltaSize = Mathf.CeilToInt(ii.obj.size.x) - ii.size.x;
                        }
                    }
                    ii.size.x = Mathf.CeilToInt(ii.obj.size.x);
                    ii.size.y = Mathf.CeilToInt(ii.obj.size.y);
                }

                ii.updateFlag = itemInfoVer;
                ii.obj.SetXY(curX, curY);
                if (curIndex == newFirstIndex) //要显示多一条才不会穿帮
                    max += ii.size.x;

                curY += ii.size.y + _lineGap;

                if (curIndex % _curLineItemCount == _curLineItemCount - 1)
                {
                    curY = 0;
                    curX += ii.size.x + _columnGap;
                }
                curIndex++;
            }

            for (int i = 0; i < oldCount; i++)
            {
                ItemInfo ii = _virtualItems[oldFirstIndex + i];
                if (ii.updateFlag != itemInfoVer && ii.obj != null)
                {
                    RemoveChildToPool(ii.obj);
                    ii.obj = null;
                }
            }

            if (deltaSize != 0 || firstItemDeltaSize != 0)
                this.scrollPane.ChangeContentSizeOnScrolling(deltaSize, 0, firstItemDeltaSize, 0);

            if (curIndex > 0 && this.numChildren > 0 && this.container.x < 0 && GetChildAt(0).x > -this.container.x)//最后一页没填满！
                HandleScroll2(false);

            enterCounter--;
        }