diff --git a/DemoTest/Pages/DefaultTestPage.xaml.cs b/DemoTest/Pages/DefaultTestPage.xaml.cs
index a2644db..2373de5 100644
--- a/DemoTest/Pages/DefaultTestPage.xaml.cs
+++ b/DemoTest/Pages/DefaultTestPage.xaml.cs
@@ -35,7 +35,7 @@ public DefaultTestPage()
             VerticalScrollBarVisibility = ScrollBarVisibility.Always,
             HeightExpansionFactor = OperatingSystem.IsIOS()? 0:0,
             SelectionMode = SelectionMode.Multiple,
-            CanDrag = true,
+            //CanDrag = true,
         };
         tableView.ItemsLayout = new CollectionViewFlatListLayout(tableView)
         {
diff --git a/MauiUICollectionView/Layouts/CollectionViewFlatListLayout.cs b/MauiUICollectionView/Layouts/CollectionViewFlatListLayout.cs
index a03aeb5..47b6b7c 100644
--- a/MauiUICollectionView/Layouts/CollectionViewFlatListLayout.cs
+++ b/MauiUICollectionView/Layouts/CollectionViewFlatListLayout.cs
@@ -28,16 +28,16 @@ protected override double MeasureItems(double top, Rect inRect, Rect visibleRect
                 isScrollingTo == false &&
                 !HasOperation)
             {
-                //MeasureItemsWhenScroll(inRect, availablePreparedItems);
-                MeasureItems(top, inRect, availablePreparedItems, false);
+                Fill(inRect, AnalysisBaseline(top), availablePreparedItems, false);
             }
             else
             {
-                MeasureItems(top, inRect, availablePreparedItems);
+                Fill(inRect, AnalysisBaseline(top), availablePreparedItems, true);
+
                 if (isScrollingTo)
                     isScrollingTo = false;
-                if (BaseLineItemUsually != null)
-                    BaseLineItemUsually = null;
+                if (ItemLayoutBaseline != null)
+                    ItemLayoutBaseline = null;
             }
 
             // store some bounds
@@ -90,22 +90,20 @@ protected override double MeasureItems(double top, Rect inRect, Rect visibleRect
         /// <summary>
         /// When not touch scrolling, we use it to remeasure all prepared items.
         /// </summary>
-        /// <param name="inRect"></param>
         /// <param name="top"></param>
-        /// <param name="availablePreparedItems"></param>
-        protected virtual void MeasureItems(double top, Rect inRect, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availablePreparedItems, bool isRemeasureAll = true)
+        protected virtual LayoutInfor AnalysisBaseline(double top)
         {
-            if (BaseLineItemUsually != null)// use specify baseline to layout
+            if (ItemLayoutBaseline != null)// use specify baseline to layout
             {
-                OnLayoutChildren(inRect, BaseLineItemUsually.Copy(), availablePreparedItems, isRemeasureAll);
+                return ItemLayoutBaseline.Copy();
             }
             else if (OldPreparedItems.StartItem != null)// use last layout item as baseline to layout
             {
-                OnLayoutChildren(inRect, new LayoutInfor()
+                return new LayoutInfor()
                 {
                     StartItem = OldPreparedItems.StartItem,
                     StartBounds = OldPreparedItems.StartBounds
-                }, availablePreparedItems, isRemeasureAll);
+                };
             }
             else //use header's bottom as baseline to layout, this will be called when start a new collectionview or error(because fast scroll, scrollto, drag scrollbar)
             {
@@ -118,31 +116,30 @@ protected virtual void MeasureItems(double top, Rect inRect, Dictionary<NSIndexP
                             var rect = StartBoundsCache[i];
                             if (rect.Contains(0, CollectionView.ScrollY))
                             {
-                                OnLayoutChildren(inRect, new LayoutInfor()
+                                return new LayoutInfor()
                                 {
                                     StartItem = NSIndexPath.FromRowSection(i, 0),
                                     StartBounds = new Rect(0, rect.Top, 0, 0),
-                                }, availablePreparedItems, isRemeasureAll);
+                                };
                             }
                         }
                     }
                     else//estimate scrolly to fix 
                     {
-                        OnLayoutChildren(inRect, new LayoutInfor()
+                        return new LayoutInfor()
                         {
-                            StartItem = EstimateItem(0, CollectionView.ScrollY),
+                            StartItem = ItemAtPoint(new Point(0, CollectionView.ScrollY)),
                             StartBounds = new Rect(0, CollectionView.ScrollY, 0, 0),
-                        }, availablePreparedItems, isRemeasureAll);
+                        };
                     }
                 }
-                else// when header is visible, use first item
+
+                // if we can't easy solve error, try use first item
+                return new LayoutInfor()
                 {
-                    OnLayoutChildren(inRect, new LayoutInfor()
-                    {
-                        StartItem = NSIndexPath.FromRowSection(0, 0),
-                        StartBounds = new Rect(0, top, 0, 0),
-                    }, availablePreparedItems, isRemeasureAll);
-                }
+                    StartItem = NSIndexPath.FromRowSection(0, 0),
+                    StartBounds = new Rect(0, top, 0, 0),
+                };
             }
         }
 
@@ -155,34 +152,6 @@ protected virtual double EstimateAverageHeight()
             return (StartBoundsCache.Last().Bottom - StartBoundsCache.First().Top) / StartBoundsCache.Count;
         }
 
-        /// <summary>
-        /// Estimate the item displayed when scrolling to a certain position.
-        /// </summary>
-        /// <param name="y"></param>
-        /// <returns></returns>
-        protected virtual NSIndexPath EstimateItem(double x, double y)
-        {
-            var firstItemBounds = StartBoundsCache.First();
-            double averageHeight = EstimateAverageHeight();
-
-            var numberOfSections = CollectionView.NumberOfSections();
-            double allHeight = 0;
-            for (var section = 0; section < numberOfSections; section++)
-            {
-                var rowsInSection = CollectionView.NumberOfItemsInSection(section);
-                if (y - firstItemBounds.Top < allHeight + rowsInSection * averageHeight)
-                {
-                    return NSIndexPath.FromRowSection((int)((y - firstItemBounds.Top - allHeight) / averageHeight), section);
-                }
-                else
-                {
-                    allHeight += rowsInSection * averageHeight;
-                }
-            }
-            //maybe scrolly is very big
-            return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
-        }
-
         /// <summary>
         /// Arrange items from above or below to fill a given rectangle. 
         /// </summary>
@@ -190,7 +159,7 @@ protected virtual NSIndexPath EstimateItem(double x, double y)
         /// <param name="baselineInfor">according to it to layout other items</param>
         /// <param name="availableCells"></param>
         /// <exception cref="NotImplementedException"></exception>
-        protected virtual void OnLayoutChildren(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
+        protected virtual void Fill(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
         {
             /*
              * from top to bottom, means we have a top value of item, we base on it to calculate bounds of items below.
@@ -393,7 +362,7 @@ protected virtual void ScrollToItem(NSIndexPath targetIndexPath)
             if (targetIndexPath > lastPreparedItem.Key)//The target item is at the bottom of the visible area, laid out from the bottom up.
             {
                 itemsOffset += CollectionView.ItemCountInRange(lastPreparedItem.Key, targetIndexPath) * lastPreparedItem.Value.ItemBounds.Height;
-                BaseLineItemUsually = new LayoutInfor()
+                ItemLayoutBaseline = new LayoutInfor()
                 {
                     EndBounds = new Rect(0, 0, 0, CollectionView.ScrollY + itemsOffset + CollectionView.Bounds.Height), //set this item at bottom of visible area.
                     EndItem = targetIndexPath
@@ -406,7 +375,7 @@ protected virtual void ScrollToItem(NSIndexPath targetIndexPath)
                 var itemsCountFromTargetToFirstPrepared = CollectionView.ItemCountInRange(targetIndexPath, firstPreparedItem.Key) + 1;
                 var itemsCountFromFirstToFirstPrepared = CollectionView.ItemCountInRange(NSIndexPath.FromRowSection(0, 0), firstPreparedItem.Key) + 1;
                 var distanceFromTargetToFirstPrepared = (firstPreparedItem.Value.ItemBounds.Top - StartBoundsCache[0].Top) * itemsCountFromTargetToFirstPrepared / itemsCountFromFirstToFirstPrepared + (CollectionView.ScrollY - firstPreparedItem.Value.ItemBounds.Top);
-                BaseLineItemUsually = new LayoutInfor()
+                ItemLayoutBaseline = new LayoutInfor()
                 {
                     StartBounds = new Rect(0, CollectionView.ScrollY - distanceFromTargetToFirstPrepared, 0, 0),
                     StartItem = targetIndexPath
@@ -476,7 +445,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
                             var targetBounds = StartBoundsCache[visibleFirst.Row];
                             if (CollectionView.PreparedItems[visibleFirst].ItemBounds != targetBounds)
                             {
-                                BaseLineItemUsually = new LayoutInfor()
+                                ItemLayoutBaseline = new LayoutInfor()
                                 {
                                     StartBounds = new Rect(0, targetBounds.Top, 0, 0),
                                     StartItem = visibleFirst
@@ -489,7 +458,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
                         {
                             var targetTop = CollectionView.PreparedItems[visibleFirst].ItemBounds.Bottom + CollectionView.ItemCountInRange(lastCache, visibleFirst) * EstimateAverageHeight();
 
-                            BaseLineItemUsually = new LayoutInfor()
+                            ItemLayoutBaseline = new LayoutInfor()
                             {
                                 StartBounds = new Rect(0, targetTop, 0, 0),
                                 StartItem = visibleFirst
@@ -508,7 +477,7 @@ void FitBoundsWhenCloseHeader(LayoutInfor visibleItems)
                     if (firstItemRect.Top > StartBoundsCache[0].Top && //There is space  
                         CollectionView.ScrollY < (firstItemRect.Bottom - firstItemRect.Height * 4 / 5))//when close to first item top
                     {
-                        BaseLineItemUsually = new LayoutInfor()
+                        ItemLayoutBaseline = new LayoutInfor()
                         {
                             StartBounds = new Rect(0, StartBoundsCache[0].Top, 0, 0),
                             StartItem = firstItem
@@ -594,6 +563,57 @@ public override Rect RectForItem(NSIndexPath indexPath)
             return rect;
         }
 
+        #region ItemAtPoint
+
+        public override NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true)
+        {
+            if (!baseOnContent)
+            {
+                var contentOffset = CollectionView.ScrollY;
+                point.Y = point.Y + contentOffset;//convert to base on content
+            }
+
+            foreach (var item in CollectionView.PreparedItems)
+            {
+                if (item.Value.ItemBounds.Contains(point))
+                {
+                    return item.Key;
+                }
+            }
+
+            return EstimateItem(point.X, point.Y);
+        }
+
+        /// <summary>
+        /// Estimate the item displayed when scrolling to a certain position.
+        /// </summary>
+        /// <param name="y"></param>
+        /// <returns></returns>
+        NSIndexPath EstimateItem(double x, double y)
+        {
+            var firstItemBounds = StartBoundsCache.First();
+            double averageHeight = EstimateAverageHeight();
+
+            var numberOfSections = CollectionView.NumberOfSections();
+            double allHeight = 0;
+            for (var section = 0; section < numberOfSections; section++)
+            {
+                var rowsInSection = CollectionView.NumberOfItemsInSection(section);
+                if (y - firstItemBounds.Top < allHeight + rowsInSection * averageHeight)
+                {
+                    return NSIndexPath.FromRowSection((int)((y - firstItemBounds.Top - allHeight) / averageHeight), section);
+                }
+                else
+                {
+                    allHeight += rowsInSection * averageHeight;
+                }
+            }
+            //maybe scrolly is very big
+            return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
+        }
+
+        #endregion
+
         #endregion
     }
 }
diff --git a/MauiUICollectionView/Layouts/CollectionViewGridLayout.cs b/MauiUICollectionView/Layouts/CollectionViewGridLayout.cs
index 3f6453a..b775725 100644
--- a/MauiUICollectionView/Layouts/CollectionViewGridLayout.cs
+++ b/MauiUICollectionView/Layouts/CollectionViewGridLayout.cs
@@ -14,100 +14,11 @@ public CollectionViewGridLayout(MAUICollectionView collectionView) : base(collec
         /// </summary>
         public int ColumnCount { get; set; } = 2;
 
-        /// <summary>
-        /// The default height to apply to all items
-        /// </summary>
-        public Size AspectRatio { get; set; } = new Size(1, 1);
-
         protected override double MeasureItems(double top, Rect inRect, Rect visibleRect, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availablePreparedItems)
         {
-            double measureItem(NSIndexPath indexPath, Rect itemRect, bool unknowItemHeight)
-            {
-                //如果在可见区域, 就详细测量
-                if (itemRect.IntersectsWith(inRect))
-                {
-                    //获取Cell, 优先获取之前已经被显示的, 这里假定已显示的数据没有变化
-                    MAUICollectionViewViewHolder cell = null;
-                    if (availablePreparedItems.ContainsKey(indexPath))
-                    {
-                        cell = availablePreparedItems[indexPath];
-                        availablePreparedItems.Remove(indexPath);
-                        if (CollectionView.IsScrolling && !HasOperation)
-                        {
-                            //return cell.BoundsInLayout.Height;
-                        }
-                    }
-                    cell = CollectionView.Source.ViewHolderForItem(CollectionView, indexPath, cell, inRect.Width);
-
-                    if (cell != null)
-                    {
-                        //将Cell添加到正在显示的Cell字典
-                        CollectionView.PreparedItems.Add(indexPath, cell);
-
-                        //添加到ScrollView, 必须先添加才有测量值
-                        if (!CollectionView.ContentView.Children.Contains(cell))
-                            CollectionView.AddSubview(cell);
-                        //测量高度
-                        cell.WidthRequest = itemRect.Width;
-                        cell.HeightRequest = unknowItemHeight ? -1 : itemRect.Height;
-                        var measureSize = cell.MeasureSelf(itemRect.Width, unknowItemHeight ? double.PositiveInfinity : itemRect.Height).Request;
-                        var bounds = new Rect(itemRect.X, itemRect.Y, measureSize.Width, measureSize.Height);
-
-                        if (cell.Operation == (int)OperateItem.OperateType.Move && // move
-                            HasOperation && // anim
-                            bounds != cell.ItemBounds) // diff bounds
-                        {
-                            cell.OldItemBounds = cell.ItemBounds;
-                            cell.ItemBounds = bounds;
-                        }
-                        else
-                        {
-                            if (cell.Operation == (int)OperateItem.OperateType.Move &&
-                                HasOperation)
-                                cell.OldItemBounds = Rect.Zero;
-                            cell.ItemBounds = bounds;
-                        }
-
-                        //here have a chance to change appearance of this item
-                        CollectionView.Source?.DidPrepareItem?.Invoke(CollectionView, indexPath, cell, Edge.Top | Edge.Left);
-
-                        cell.IndexPath = indexPath;
-
-                        return cell.ItemBounds.Height;
-                    }
-                    else
-                    {
-                        throw new NotImplementedException($"Get ViewHolder is null of {indexPath} from {nameof(MAUICollectionViewSource.ViewHolderForItem)}.");
-                    }
-                }
-                else// if don't in prepared rect
-                {
-                    if (availablePreparedItems.ContainsKey(indexPath))//we want store bounds info for invisible item, because maybe we need it to make animation
-                    {
-                        var cell = availablePreparedItems[indexPath];
-
-                        if (cell.Operation == (int)OperateItem.OperateType.Move
-                            && HasOperation
-                            && itemRect != cell.ItemBounds)//move + anim + diff bounds
-                        {
-                            cell.OldItemBounds = cell.ItemBounds;//move operate need old position to make animation
-                            cell.ItemBounds = itemRect;
-                        }
-                        else
-                        {
-                            cell.ItemBounds = itemRect;
-                        }
-                    }
-
-                    return itemRect.Height;
-                }
-            }
-
             base.MeasureItems(top, inRect, visibleRect, availablePreparedItems);
 
             double itemsHeight = 0;
-            var itemWidth = inRect.Width / ColumnCount;
-            var itemHeight = itemWidth * AspectRatio.Height / AspectRatio.Width;
             int numberOfSections = CollectionView.NumberOfSections();
 
             //根据已知的最后一个Item来估计总高度
@@ -178,74 +89,7 @@ protected override double EstimateAverageHeight()
             return totalH / StartBoundsCache.Count;
         }
 
-        protected override NSIndexPath EstimateItem(double x, double y)
-        {
-            var firstItemBounds = StartBoundsCache.First();
-            double averageHeight = EstimateAverageHeight();
-
-            var numberOfSections = CollectionView.NumberOfSections();
-            double allHeight = 0;
-            for (var section = 0; section < numberOfSections; section++)
-            {
-                double headerH = 0;
-                var firstItem = NSIndexPath.FromRowSection(0, section);
-                var firstItemRowColumn = GetRowAndColumnOfItem(firstItem);
-                if (firstItemRowColumn.row == -1)// is header
-                {
-                    var wantH = CollectionView.Source.HeightForItem(CollectionView, firstItem);
-                    if (wantH == MAUICollectionViewViewHolder.AutoSize)
-                        headerH = averageHeight;
-                    else
-                        headerH = wantH;
-                    // in header item
-                    if (y - firstItemBounds.Top < allHeight + headerH)
-                    {
-                        return NSIndexPath.FromRowSection(0, section);
-                    }
-                }
-                var indexCountInSection = CollectionView.NumberOfItemsInSection(section);
-                int rowOfLastDataItem = 0;
-                var lastItem = NSIndexPath.FromRowSection(indexCountInSection - 1, section);
-                var lastItemRowColumn = GetRowAndColumnOfItem(lastItem);
-                if (lastItemRowColumn.row == -2)
-                {
-                    rowOfLastDataItem = GetRowAndColumnOfItem(NSIndexPath.FromRowSection(indexCountInSection - 1, section)).row;
-                }
-                else
-                {
-                    rowOfLastDataItem = lastItemRowColumn.row;
-                }
-
-                // in data items
-                if (y - firstItemBounds.Top < allHeight + headerH + rowOfLastDataItem * averageHeight)
-                {
-                    var firstItemIndexAtTargetRow = (int)((y - firstItemBounds.Top - allHeight - headerH) / averageHeight) * ColumnCount;
-                    var column = (int)( x / (CollectionView.ContentSize.Width / ColumnCount));
-                    return NSIndexPath.FromRowSection(firstItemIndexAtTargetRow + column, section);
-                }
-
-                double footerH = 0;
-                if (lastItemRowColumn.row == -2)
-                {
-                    var wantH = CollectionView.Source.HeightForItem(CollectionView, lastItem);
-                    if (wantH == MAUICollectionViewViewHolder.AutoSize)
-                        footerH = averageHeight;
-                    else
-                        footerH = wantH;
-                    // in footer item
-                    if (y - firstItemBounds.Top < allHeight + headerH + rowOfLastDataItem * averageHeight + footerH)
-                    {
-                        return NSIndexPath.FromRowSection(indexCountInSection - 1, section);
-                    }
-                }
-
-                allHeight += headerH + rowOfLastDataItem * averageHeight + footerH;
-            }
-            //maybe scrolly is very big
-            return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
-        }
-
-        protected override void OnLayoutChildren(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
+        protected override void Fill(Rect inRect, LayoutInfor baselineInfor, Dictionary<NSIndexPath, MAUICollectionViewViewHolder> availableCells, bool isRemeasureAll = true)
         {
             void LayoutFromTopToBottom(LayoutInfor topBaselineInfor)
             {
@@ -387,55 +231,96 @@ void LayoutFromBottomToTop(LayoutInfor bottomBaselineInfor)
             }
         }
 
-        /// <summary>
-        /// ViewHolder分成几列时, 判断下一个分在哪一列, header或者footer返回-1, 其它基于0递增.
-        /// </summary>
-        /// <param name="front"></param>
-        /// <param name="currentBounds"></param>
-        /// <param name="nextItem"></param>
-        /// <returns></returns>
-        int NextItemColumn(bool front, double singleColumnWidth, Rect currentBounds, NSIndexPath nextItem)
+        #region ItemAtPoint
+
+        public override NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true)
         {
-            if (CollectionView.Source.IsSectionItem(CollectionView, nextItem))
+            if (!baseOnContent)
             {
-                return -1;
+                var contentOffset = CollectionView.ScrollY;
+                point.Y = point.Y + contentOffset;//convert to base on content
             }
-            else
+
+            foreach (var item in CollectionView.PreparedItems)
             {
-                //判断当前在哪一列
-                var currentColumn = (int)(currentBounds.Center.X / singleColumnWidth);
-                if (front)
-                {
-                    if (currentColumn == 0)
-                        return ColumnCount - 1;
-                    else
-                        return currentColumn - 1;
-                }
-                else
+                if (item.Value.ItemBounds.Contains(point))
                 {
-                    if (currentColumn == (ColumnCount - 1))
-                        return 0;
-                    else
-                        return currentColumn + 1;
+                    return item.Key;
                 }
             }
+
+            return EstimateItem(point.X, point.Y);
         }
 
-        public override NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true)
+        NSIndexPath EstimateItem(double x, double y)
         {
-            var visibleIndexPath = base.ItemAtPoint(point, baseOnContent);
-            if (visibleIndexPath != null)
-                return visibleIndexPath;
+            var firstItemBounds = StartBoundsCache.First();
+            double averageHeight = EstimateAverageHeight();
 
-            if (!baseOnContent)
+            var numberOfSections = CollectionView.NumberOfSections();
+            double allHeight = 0;
+            for (var section = 0; section < numberOfSections; section++)
             {
-                var contentOffset = CollectionView.ScrollY;
-                point.Y = point.Y + contentOffset;//convert to base on content
-            }
+                double headerH = 0;
+                var firstItem = NSIndexPath.FromRowSection(0, section);
+                var firstItemRowColumn = GetRowAndColumnOfItem(firstItem);
+                if (firstItemRowColumn.row == -1)// is header
+                {
+                    var wantH = CollectionView.Source.HeightForItem(CollectionView, firstItem);
+                    if (wantH == MAUICollectionViewViewHolder.AutoSize)
+                        headerH = averageHeight;
+                    else
+                        headerH = wantH;
+                    // in header item
+                    if (y - firstItemBounds.Top < allHeight + headerH)
+                    {
+                        return NSIndexPath.FromRowSection(0, section);
+                    }
+                }
+                var indexCountInSection = CollectionView.NumberOfItemsInSection(section);
+                int rowOfLastDataItem = 0;
+                var lastItem = NSIndexPath.FromRowSection(indexCountInSection - 1, section);
+                var lastItemRowColumn = GetRowAndColumnOfItem(lastItem);
+                if (lastItemRowColumn.row == -2)
+                {
+                    rowOfLastDataItem = GetRowAndColumnOfItem(NSIndexPath.FromRowSection(indexCountInSection - 1, section)).row;
+                }
+                else
+                {
+                    rowOfLastDataItem = lastItemRowColumn.row;
+                }
 
-            return EstimateItem(point.X, point.Y);
+                // in data items
+                if (y - firstItemBounds.Top < allHeight + headerH + rowOfLastDataItem * averageHeight)
+                {
+                    var firstItemIndexAtTargetRow = (int)((y - firstItemBounds.Top - allHeight - headerH) / averageHeight) * ColumnCount;
+                    var column = (int)(x / (CollectionView.ContentSize.Width / ColumnCount));
+                    return NSIndexPath.FromRowSection(firstItemIndexAtTargetRow + column, section);
+                }
+
+                double footerH = 0;
+                if (lastItemRowColumn.row == -2)
+                {
+                    var wantH = CollectionView.Source.HeightForItem(CollectionView, lastItem);
+                    if (wantH == MAUICollectionViewViewHolder.AutoSize)
+                        footerH = averageHeight;
+                    else
+                        footerH = wantH;
+                    // in footer item
+                    if (y - firstItemBounds.Top < allHeight + headerH + rowOfLastDataItem * averageHeight + footerH)
+                    {
+                        return NSIndexPath.FromRowSection(indexCountInSection - 1, section);
+                    }
+                }
+
+                allHeight += headerH + rowOfLastDataItem * averageHeight + footerH;
+            }
+            //maybe scrolly is very big
+            return NSIndexPath.FromRowSection(CollectionView.NumberOfItemsInSection(numberOfSections - 1), numberOfSections - 1);
         }
 
+        #endregion
+
         public override Rect RectForItem(NSIndexPath indexPath)
         {
             if (CollectionView.PreparedItems.ContainsKey(indexPath))
@@ -488,7 +373,7 @@ protected override void ScrollToItem(NSIndexPath targetIndexPath)
             {
                 itemsOffset += CollectionView.ItemCountInRange(lastPreparedItem.Key, targetIndexPath) / ColumnCount * EstimateAverageHeight();
                 
-                BaseLineItemUsually = new LayoutInfor()
+                ItemLayoutBaseline = new LayoutInfor()
                 {
                     EndBounds = new Rect(0, 0, 0, lastPreparedItem.Value.ItemBounds.Bottom + itemsOffset + CollectionView.Bounds.Height),
                     EndItem = targetIndexPath
@@ -501,7 +386,7 @@ protected override void ScrollToItem(NSIndexPath targetIndexPath)
                 var rowCountFromTargetToFirstPrepared = (CollectionView.ItemCountInRange(targetIndexPath, firstPreparedItem.Key) + 1) / ColumnCount;
                 var rowCountFromFirstToFirstPrepared = (CollectionView.ItemCountInRange(NSIndexPath.FromRowSection(0, 0), firstPreparedItem.Key) + 1) / ColumnCount;
                 var distanceFromTargetToFirstPrepared = (firstPreparedItem.Value.ItemBounds.Top - StartBoundsCache[0].Top) * rowCountFromTargetToFirstPrepared / rowCountFromFirstToFirstPrepared + (CollectionView.ScrollY - firstPreparedItem.Value.ItemBounds.Top);
-                BaseLineItemUsually = new LayoutInfor()
+                ItemLayoutBaseline = new LayoutInfor()
                 {
                     StartBounds = new Rect(0, CollectionView.ScrollY - distanceFromTargetToFirstPrepared, 0, 0),
                     StartItem = targetIndexPath
diff --git a/MauiUICollectionView/Layouts/CollectionViewLayout.LayoutInfor.cs b/MauiUICollectionView/Layouts/CollectionViewLayout.LayoutInfor.cs
new file mode 100644
index 0000000..0cbd03e
--- /dev/null
+++ b/MauiUICollectionView/Layouts/CollectionViewLayout.LayoutInfor.cs
@@ -0,0 +1,24 @@
+namespace MauiUICollectionView.Layouts
+{
+    public abstract partial class CollectionViewLayout
+    {
+        public class LayoutInfor
+        {
+            public NSIndexPath StartItem;
+            public NSIndexPath EndItem;
+            public Rect StartBounds;
+            public Rect EndBounds;
+
+            public LayoutInfor Copy()
+            {
+                return new LayoutInfor()
+                {
+                    StartItem = this.StartItem,
+                    EndItem = this.EndItem,
+                    StartBounds = this.StartBounds,
+                    EndBounds = this.EndBounds
+                };
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/MauiUICollectionView/Layouts/CollectionViewLayout.cs b/MauiUICollectionView/Layouts/CollectionViewLayout.cs
index c33d66f..b99b250 100644
--- a/MauiUICollectionView/Layouts/CollectionViewLayout.cs
+++ b/MauiUICollectionView/Layouts/CollectionViewLayout.cs
@@ -6,7 +6,7 @@ namespace MauiUICollectionView.Layouts
     /// <summary>
     /// layout content.
     /// </summary>
-    public abstract class CollectionViewLayout : IDisposable
+    public abstract partial class CollectionViewLayout : IDisposable
     {
         public CollectionViewLayout(MAUICollectionView collectionView)
         {
@@ -45,7 +45,23 @@ public ItemsLayoutOrientation ScrollDirection
         /// </summary>
         protected bool HasOperation = false;
 
-        public bool RunOperateAnimation = false;
+        /// <summary>
+        /// it start equal to true when <see cref="HasOperation"/> equal to, but it be false after start operation animation.
+        /// </summary>
+        protected bool RunOperateAnimation = false;
+
+        /// <summary>
+        /// it contain information about item and bounds, we layout item according to it. it's IndexPath is latest.
+        /// </summary>
+        public LayoutInfor ItemLayoutBaseline;
+
+        /// <summary>
+        /// current Visible items, it is different with <see cref="MAUICollectionView.PreparedItems"/>
+        /// </summary>
+        public LayoutInfor VisibleIndexPath { get; protected set; }
+        public LayoutInfor LastVisibleIndexPath { get; protected set; }
+
+        public LayoutInfor OldPreparedItems;
 
         /// <summary>
         /// Arrange Header, Items and Footer. They will be arranged according to <see cref="MAUICollectionViewViewHolder.ItemBounds"/>
@@ -91,32 +107,6 @@ public virtual void ArrangeContents()
             }
         }
 
-        public LayoutInfor OldPreparedItems;
-
-        public class LayoutInfor
-        {
-            public NSIndexPath StartItem;
-            public NSIndexPath EndItem;
-            public Rect StartBounds;
-            public Rect EndBounds;
-
-            public LayoutInfor Copy()
-            {
-                return new LayoutInfor()
-                {
-                    StartItem = this.StartItem,
-                    EndItem = this.EndItem,
-                    StartBounds = this.StartBounds,
-                    EndBounds = this.EndBounds
-                };
-            }
-        }
-
-        /// <summary>
-        /// it contain information about item and bounds, we layout item according to it. it's IndexPath is latest.
-        /// </summary>
-        public LayoutInfor BaseLineItemUsually;
-
         /// <summary>
         /// Measure size of Header, Items and Footer. It will load <see cref="MeasureHeader"/>, <see cref="MeasureItems"/>, <see cref="MeasureFooter"/>.
         /// </summary>
@@ -402,12 +392,6 @@ protected virtual double MeasureHeader(double top, double widthConstraint)
             return 0;
         }
 
-        /// <summary>
-        /// current Visible items, it is different with <see cref="MAUICollectionView.PreparedItems"/>
-        /// </summary>
-        public LayoutInfor VisibleIndexPath { get; protected set; }
-        public LayoutInfor LastVisibleIndexPath { get; protected set; }
-
         /// <summary>
         /// Measure items to fill target rect.
         /// </summary>
@@ -439,23 +423,7 @@ protected virtual double MeasureFooter(double top, double widthConstraint)
         /// <param name="point">the point in Content or CollectionView</param>
         /// <param name="baseOnContent"> specify point is base on Content or CollectionView</param>
         /// <returns></returns>
-        public virtual NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true)
-        {
-            if (!baseOnContent)
-            {
-                var contentOffset = CollectionView.ScrollY;
-                point.Y = point.Y + contentOffset;//convert to base on content
-            }
-
-            foreach (var item in CollectionView.PreparedItems)
-            {
-                if (item.Value.ItemBounds.Contains(point))
-                {
-                    return item.Key;
-                }
-            }
-            return null;
-        }
+        public abstract NSIndexPath ItemAtPoint(Point point, bool baseOnContent = true);
 
         /// <summary>
         /// Get <see cref="MAUICollectionViewViewHolder.ItemBounds"/> of item. If it in <see cref="MAUICollectionView.PreparedItems"/>, will return bounds, if not, return <see cref="Rect.Zero"/>.
diff --git a/MauiUICollectionView/MAUICollectionView.cs b/MauiUICollectionView/MAUICollectionView.cs
index 4770073..1069805 100644
--- a/MauiUICollectionView/MAUICollectionView.cs
+++ b/MauiUICollectionView/MAUICollectionView.cs
@@ -630,7 +630,7 @@ public void NotifyItemRangeRemoved(NSIndexPath indexPath, int count = 1)
                     baselineCurrentIndexPath = firstVisibleItem.Section == indexPath.Section ?
                         NSIndexPath.FromRowSection(firstVisibleItem.Row - count, firstVisibleItem.Section) ://row will change when same section 
                         firstVisibleItem;
-                    layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                    layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                     {
                         //indexpath maybe change
                         StartItem = baselineCurrentIndexPath,
@@ -645,7 +645,7 @@ public void NotifyItemRangeRemoved(NSIndexPath indexPath, int count = 1)
                         baselineLastIndexPath = firstVisibleItem;
                         baselineCurrentIndexPath = firstVisibleItem;
 
-                        layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                        layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                         {
                             StartItem = baselineCurrentIndexPath,
                             StartBounds = firstVisibleItemBounds
@@ -659,7 +659,7 @@ public void NotifyItemRangeRemoved(NSIndexPath indexPath, int count = 1)
                             NSIndexPath.FromRowSection(lastVisibleItem.Row - count, lastVisibleItem.Section) ://row will change when same section 
                             lastVisibleItem;
 
-                        layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                        layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                         {
                             StartItem = baselineCurrentIndexPath,
                             StartBounds = lastVisibleItemBounds
@@ -668,7 +668,7 @@ public void NotifyItemRangeRemoved(NSIndexPath indexPath, int count = 1)
                         //fix move first item will measure multiple times when remove top item
                         if (ItemCountInRange(NSIndexPath.FromRowSection(0, 0), baselineCurrentIndexPath) <= count)
                         {
-                            layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                            layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                             {
                                 StartItem = baselineCurrentIndexPath,
                                 StartBounds = new Rect(0, ScrollY, 0, 0)
@@ -686,7 +686,7 @@ public void NotifyItemRangeRemoved(NSIndexPath indexPath, int count = 1)
                             baselineCurrentIndexPath = next.Section == indexPath.Section ?
                                 NSIndexPath.FromRowSection(next.Row - count, next.Section) ://row will change when same section 
                                 next;
-                            layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                            layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                             {
                                 StartItem = baselineCurrentIndexPath,
                                 StartBounds = new Rect(0, ScrollY, 0, 0)
@@ -759,7 +759,7 @@ public void NotifyItemRangeInserted(NSIndexPath indexPath, int count = 1)
                 {
                     baselineCurrentIndexPath = firstVisibleItem;
                 }
-                layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                 {
                     StartItem = baselineCurrentIndexPath,
                     StartBounds = firstVisibleItemBounds
@@ -802,7 +802,7 @@ public void MoveItem(NSIndexPath indexPath, NSIndexPath toIndexPath)
                 NSIndexPath baselineLastIndexPath = firstVisibleItem;
                 NSIndexPath baselineCurrentIndexPath = firstVisibleItem;
                 bool moved = false;
-                layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                 {
                     StartItem = baselineCurrentIndexPath,
                     StartBounds = firstVisibleItemBounds
@@ -830,7 +830,7 @@ public void NotifyItemRangeChanged(NSIndexPath indexPath)
             if (layout != null)
             {
                 var firstVisibleItem = PreparedItems.FirstOrDefault();
-                layout.BaseLineItemUsually = new CollectionViewLayout.LayoutInfor()
+                layout.ItemLayoutBaseline = new CollectionViewLayout.LayoutInfor()
                 {
                     StartItem = firstVisibleItem.Key,
                     StartBounds = firstVisibleItem.Value.ItemBounds