Update StaggeredItemsViewLayout

Directory.Build.props

@@ -53,7 +53,7 @@
 
 	<PropertyGroup Condition="$([MSBuild]::IsOSPlatform('windows')) == 'false' and $([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios' and $(Configuration) == 'Debug'">
 		<RuntimeIdentifier>ios-arm64</RuntimeIdentifier>
-		<RuntimeIdentifier>iossimulator-x64</RuntimeIdentifier>
+		<RuntimeIdentifier>iossimulator-arm64</RuntimeIdentifier>
 		<CreatePackage>false</CreatePackage>
 	</PropertyGroup>
 

MauiStaggeredCollectionView/AppShell.xaml

@@ -8,7 +8,7 @@
     Title="MauiStaggeredCollectionView">
 
     <ShellContent
-        Title=".NET MAUI Staggeled CollectionView"
+        Title=".NET MAUI Staggered CollectionView"
         ContentTemplate="{DataTemplate local:MainPage}"
         Route="MainPage" />
 

MauiStaggeredCollectionView/MainPage.xaml.cs

@@ -51,7 +51,7 @@ private static void MapItemsLayout(StructuredItemsViewHandler<CollectionView> ha
 					platformView?.UpdateAdapter();
 					platformView?.SetLayoutManager(
 						new AndroidX.RecyclerView.Widget.StaggeredGridLayoutManager(
-							staggeredItemsLayout.Span, 
+							staggeredItemsLayout.Span,
 							staggeredItemsLayout.Orientation == ItemsLayoutOrientation.Horizontal ? AndroidX.RecyclerView.Widget.StaggeredGridLayoutManager.Horizontal : AndroidX.RecyclerView.Widget.StaggeredGridLayoutManager.Vertical));
 					break;
 				default:
@@ -68,7 +68,7 @@ protected override ItemsViewLayout SelectLayout()
 
 			if (itemsLayout is StaggeredItemsLayout staggeredItemsLayout)
 			{
-				return new StagLayout([(1d, 1d), (1d, 1d)], 0, staggeredItemsLayout, ItemSizingStrategy.MeasureAllItems);
+				return new StagerredItemsViewLayout(staggeredItemsLayout, ItemsView.ItemSizingStrategy);
 			}
 
 			return base.SelectLayout();
@@ -90,10 +90,10 @@ protected override Microsoft.UI.Xaml.Controls.ListViewBase SelectListViewBase()
 public class StaggeredItemsLayout(ItemsLayoutOrientation orientation) : ItemsLayout(orientation)
 {
 	public static readonly BindableProperty SpanProperty = BindableProperty.Create(nameof(Span), typeof(int), typeof(StaggeredItemsLayout), default(int));
-		
+
 	public StaggeredItemsLayout() : this(ItemsLayoutOrientation.Vertical)
 	{
-			
+
 	}
 
 	public int Span

MauiStaggeredCollectionView/Platforms/MacCatalyst/StagerredItemsViewLayout.cs

@@ -0,0 +1,92 @@
+namespace MauiStaggeredCollectionView;
+
+using CoreGraphics;
+using Foundation;
+using Microsoft.Maui.Controls.Handlers.Items;
+using UIKit;
+
+public class StagerredItemsViewLayout(StaggeredItemsLayout itemsLayout, ItemSizingStrategy sizingStrategy)
+	: ItemsViewLayout(itemsLayout, sizingStrategy)
+{
+	private readonly List<UICollectionViewLayoutAttributes> cache = new();
+
+	private float contentHeight;
+
+	public int ColumnCount { get; set; } = itemsLayout.Span;
+
+	public double MinCellHeight { get; set; } = 150;
+
+	public double MaxCellHeight { get; set; } = 250;
+
+	public override CGSize CollectionViewContentSize => new(CollectionView.Frame.Width, contentHeight);
+
+	public override void ConstrainTo(CGSize size)
+	{
+		ConstrainedDimension = ScrollDirection == UICollectionViewScrollDirection.Vertical ? size.Width : size.Height;
+		DetermineCellSize();
+	}
+
+	protected void OnItemsSourcePropertyChanged()
+	{
+		cache.Clear();
+	}
+
+	public override void PrepareLayout()
+	{
+		if (cache.Count > 0)
+		{
+			return;
+		}
+
+		contentHeight = 0;
+		var columnWidth = (float)CollectionView.Frame.Width / ColumnCount;
+		var xOffsets = new List<float>();
+		var yOffsets = new List<float>();
+		for (var i = 0; i < ColumnCount; i++)
+		{
+			xOffsets.Add(i * columnWidth);
+			yOffsets.Add(0);
+		}
+
+		var column = 0;
+
+		var itemsCount = CollectionView.NumberOfItemsInSection(0).ToInt32();
+		for (var i = 0; i < itemsCount; i++)
+		{
+			var indexPath = NSIndexPath.FromRowSection(i, 0);
+
+			var cellHeight = new Random().Next((int)MinCellHeight, (int)MaxCellHeight);
+
+			var frame = new CGRect(xOffsets[column], yOffsets[column], columnWidth, cellHeight);
+
+			var attrs = UICollectionViewLayoutAttributes.CreateForCell(indexPath);
+			attrs.Frame = frame;
+			cache.Add(attrs);
+
+			contentHeight = Math.Max(contentHeight, (float)frame.GetMaxY());
+			yOffsets[column] += cellHeight;
+
+			column = column == ColumnCount - 1 ? 0 : column + 1;
+		}
+	}
+
+	public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(CGRect rect)
+	{
+		var visibleLayoutAttributes = new List<UICollectionViewLayoutAttributes>();
+
+		foreach (var attr in cache)
+		{
+			if (attr.Frame.IntersectsWith(rect))
+			{
+				visibleLayoutAttributes.Add(attr);
+			}
+		}
+
+		return visibleLayoutAttributes.ToArray();
+	}
+
+	public override UICollectionViewLayoutAttributes LayoutAttributesForItem(NSIndexPath indexPath)
+	{
+		return cache[indexPath.Row];
+	}
+}