FairyGUI.GList.HandleScroll3 C# (CSharp) Method

        void HandleScroll3(bool forceUpdate)
        {
            float pos = scrollPane.scrollingPosX;

            //寻找当前位置的第一条项目
            int newFirstIndex = GetIndexOnPos3(ref pos, forceUpdate);
            if (newFirstIndex == _firstIndex && !forceUpdate)
                return;

            int oldFirstIndex = _firstIndex;
            _firstIndex = newFirstIndex;

            //分页模式不支持不等高，所以渲染满一页就好了

            int reuseIndex = oldFirstIndex;
            int virtualItemCount = _virtualItems.Count;
            int pageSize = _curLineItemCount * _curLineItemCount2;
            int startCol = newFirstIndex % _curLineItemCount;
            float viewWidth = this.viewWidth;
            int page = (int)(newFirstIndex / pageSize);
            int startIndex = page * pageSize;
            int lastIndex = startIndex + pageSize * 2; //测试两页
            bool needRender;

            itemInfoVer++;

            //先标记这次要用到的项目
            for (int i = startIndex; i < lastIndex; i++)
            {
                if (i >= _realNumItems)
                    continue;

                int col = i % _curLineItemCount;
                if (i - startIndex < pageSize)
                {
                    if (col < startCol)
                        continue;
                }
                else
                {
                    if (col > startCol)
                        continue;
                }

                ItemInfo ii = _virtualItems[i];
                ii.updateFlag = itemInfoVer;
            }

            GObject lastObj = null;
            int insertIndex = 0;
            for (int i = startIndex; i < lastIndex; i++)
            {
                if (i >= _realNumItems)
                    continue;

                int col = i % _curLineItemCount;
                if (i - startIndex < pageSize)
                {
                    if (col < startCol)
                        continue;
                }
                else
                {
                    if (col > startCol)
                        continue;
                }

                ItemInfo ii = _virtualItems[i];
                if (ii.obj == null)
                {
                    //寻找看有没有可重用的
                    while (reuseIndex < virtualItemCount)
                    {
                        ItemInfo ii2 = _virtualItems[reuseIndex];
                        if (ii2.obj != null && ii2.updateFlag != itemInfoVer)
                        {
                            ii.obj = ii2.obj;
                            ii2.obj = null;
                            break;
                        }
                        reuseIndex++;
                    }

                    if (insertIndex == -1)
                        insertIndex = GetChildIndex(lastObj) + 1;

                    if (ii.obj == null)
                    {
                        ii.obj = _pool.GetObject(defaultItem);
                        this.AddChildAt(ii.obj, insertIndex);
                    }
                    else
                    {
                        insertIndex = SetChildIndexBefore(ii.obj, insertIndex);
                    }
                    insertIndex++;

                    if (ii.obj is GButton)
                        ((GButton)ii.obj).selected = false;

                    needRender = true;
                }
                else
                {
                    needRender = forceUpdate;
                    insertIndex = -1;
                    lastObj = ii.obj;
                }

                if (needRender)
                    itemRenderer(i % _numItems, ii.obj);

                ii.obj.SetXY((int)(i / pageSize) * viewWidth + col * (ii.size.x + _columnGap),
                    (int)(i / _curLineItemCount) % _curLineItemCount2 * (ii.size.y + _lineGap));
            }

            //释放未使用的
            for (int i = reuseIndex; i < virtualItemCount; i++)
            {
                ItemInfo ii = _virtualItems[i];
                if (ii.updateFlag != itemInfoVer && ii.obj != null)
                {
                    RemoveChildToPool(ii.obj);
                    ii.obj = null;
                }
            }
        }