More Compositional

.vscode/launch.json

@@ -0,0 +1,14 @@
+{
+	// Use IntelliSense to learn about possible attributes.
+	// Hover to view descriptions of existing attributes.
+	// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"name": ".NET MAUI",
+			"type": "maui",
+			"request": "launch",
+			"preLaunchTask": "maui: Build"
+		}
+	]
+}

Sample/VirtualListViewSample/ObservableCollectionPage.xaml

@@ -18,10 +18,6 @@
 					<Label HorizontalOptions="Center" VerticalOptions="Center" Text="EMPTY!!!" />
 				</Grid>
 			</vlv:VirtualListView.EmptyView>
-			<vlv:VirtualListView.GlobalHeader>
-				<Label Text="HEADER"/>
-
-			</vlv:VirtualListView.GlobalHeader>
 			<vlv:VirtualListView.ItemTemplate>
 				<DataTemplate>
 					<vlv:VirtualViewCell>

Sample/VirtualListViewSample/ObservableCollectionPage.xaml.cs

@@ -26,14 +26,14 @@ protected override void OnAppearing()
 	{
 		base.OnAppearing();
 
-		Task.Delay(1000).ContinueWith(t =>
-		{
-			this.Dispatcher.Dispatch(() =>
-			{
-				Items.Add("Item 11");
-				Items.Add("Item 12");
-			});
-		});
+		// Task.Delay(1000).ContinueWith(t =>
+		// {
+		// 	this.Dispatcher.Dispatch(() =>
+		// 	{
+		// 		Items.Add("Item 11");
+		// 		Items.Add("Item 12");
+		// 	});
+		// });
 	}
 	private void Button_Clicked(object sender, EventArgs e)
 	{

VirtualListView/Adapters/IVirtualListViewAdapter.cs

@@ -1,4 +1,45 @@
-namespace Microsoft.Maui.Adapters;
+
+namespace Microsoft.Maui.Adapters;
+
+internal class EmptyViewSelector : IVirtualListViewSelector
+{
+    public IView CreateView(PositionInfo position, object data)
+		=> null;
+
+    public string GetReuseId(PositionInfo position, object data)
+    	=> "ITEM";
+
+    public void RecycleView(PositionInfo position, object data, IView view)
+    {
+    }
+
+    public bool SectionHasFooter(int sectionIndex)
+    	=> false;
+
+    public bool SectionHasHeader(int sectionIndex)
+    	=> false;
+}
+
+internal class EmptyAdapter : IVirtualListViewAdapter
+{
+	public int GetNumberOfSections()
+		=> 0;
+
+	public object GetSection(int sectionIndex)
+		=> null;
+
+	public int GetNumberOfItemsInSection(int sectionIndex)
+		=> 0;
+
+	public object GetItem(int sectionIndex, int itemIndex)
+		=> null;
+
+	public event EventHandler OnDataInvalidated;
+
+	public void InvalidateData()
+	{
+	}
+}
 
 public interface IVirtualListViewAdapter
 {

VirtualListView/Adapters/ObservableCollectionAdapter.cs

@@ -21,6 +21,9 @@ void CollectionChanged(object sender, System.Collections.Specialized.NotifyColle
 	public override TItem GetItem(int sectionIndex, int itemIndex)
 		=> Items[itemIndex];
 
+	public override int GetNumberOfSections()
+		=> 1;
+
 	public override int GetNumberOfItemsInSection(int sectionIndex)
 		=> Items.Count;
 

VirtualListView/Apple/CvCell.ios.maccatalyst.cs

@@ -96,12 +96,12 @@ public override UICollectionViewLayoutAttributes PreferredLayoutAttributesFittin
 
 		var preferredAttributes = base.PreferredLayoutAttributesFittingAttributes(layoutAttributes);
 
-		if (Handler?.VirtualView is not null)
+		if (VirtualView.TryGetTarget(out var virtualView))
 		{
 			if (Handler.VirtualView.Orientation == ListOrientation.Vertical)
 			{
 				var measure =
-					Handler.VirtualView.Measure(preferredAttributes.Size.Width, double.PositiveInfinity);
+					virtualView.Measure(preferredAttributes.Size.Width, double.PositiveInfinity);
 
 				preferredAttributes.Frame =
 					new CGRect(preferredAttributes.Frame.X, preferredAttributes.Frame.Y,
@@ -110,7 +110,7 @@ public override UICollectionViewLayoutAttributes PreferredLayoutAttributesFittin
 			else
 			{
 				var measure =
-					Handler.VirtualView.Measure(double.PositiveInfinity, preferredAttributes.Size.Height);
+					virtualView.Measure(double.PositiveInfinity, preferredAttributes.Size.Height);
 
 				preferredAttributes.Frame =
 					new CGRect(preferredAttributes.Frame.X, preferredAttributes.Frame.Y,

VirtualListView/Apple/CvDataSource.ios.maccatalyst.cs

@@ -20,37 +20,18 @@ public CvDataSource(VirtualListViewHandler handler)
 	readonly ReusableIdManager sectionFooterIdManager = new ReusableIdManager("SectionFooter", new NSString("SectionFooter"));
 
 	public override nint NumberOfSections(UICollectionView collectionView)
-		=> 1;
-
+		=> Handler.Adapter.GetNumberOfSections();
 
 	public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
 	{
-		var info = PositionInfo.ForItem();
-
-		object? data = null;
-
-		var nativeReuseId = CvCell.ReuseIdUnknown;
+		var sectionIndex = indexPath.Section;
+		var itemIndex = indexPath.Item.ToInt32();
+		var info = Handler.PlatformController.GetInfo(sectionIndex, itemIndex);
+
+		object? data = Handler.Adapter.DataFor(PositionKind.Item, sectionIndex, itemIndex);
+		var reuseId = Handler.VirtualView.ViewSelector?.GetReuseId(info, data);
+		var nativeReuseId = itemIdManager.GetReuseId(collectionView, reuseId);
 
-		if (info is not null)
-		{
-			data = Handler?.Adapter?.DataFor(info.Kind, info.SectionIndex, info.ItemIndex);
-
-			nativeReuseId = info.Kind switch
-			{
-				var reuseId = Handler?.VirtualView?.ViewSelector?.GetReuseId(info, data);
-
-				nativeReuseId = info.Kind switch
-				{
-					PositionKind.Item => itemIdManager.GetReuseId(collectionView, reuseId),
-					PositionKind.SectionHeader => sectionHeaderIdManager.GetReuseId(collectionView, reuseId),
-					PositionKind.SectionFooter => sectionFooterIdManager.GetReuseId(collectionView, reuseId),
-					PositionKind.Header => globalIdManager.GetReuseId(collectionView, reuseId),
-					PositionKind.Footer => globalIdManager.GetReuseId(collectionView, reuseId),
-					_ => CvCell.ReuseIdUnknown,
-				};
-			}
-		}
-
 		var nativeCell = collectionView.DequeueReusableCell(nativeReuseId, indexPath);
 		if (nativeCell is not CvCell cell)
 			return (UICollectionViewCell)nativeCell;
@@ -62,50 +43,48 @@ public override UICollectionViewCell GetCell(UICollectionView collectionView, NS
 		cell.ReuseCallback = new WeakReference<Action<IView>>((rv) =>
 		{
 			if (info is not null && (cell.VirtualView?.TryGetTarget(out var cellView) ?? false))
-				Handler?.VirtualView?.ViewSelector?.ViewDetached(info, cellView);
+				Handler.VirtualView.ViewSelector?.ViewDetached(info, cellView);
 		});
 
 		if (info is not null)
 		{
 			if (info.SectionIndex < 0 || info.ItemIndex < 0)
 				info.IsSelected = false;
 			else
-				info.IsSelected = Handler?.IsItemSelected(info.SectionIndex, info.ItemIndex) ?? false;
+				info.IsSelected = Handler.IsItemSelected(info.SectionIndex, info.ItemIndex);
 
 			if (cell.NeedsView)
 			{
-				var view = Handler?.PositionalViewSelector?.ViewSelector?.CreateView(info, data);
+				var view = Handler.ViewSelector?.CreateView(info, data);
+				if (view is not null)
+					cell.SetupView(view);
+			}
+
+			if (cell.NeedsView)
+			{
+				var view = Handler.VirtualView.ViewSelector?.CreateView(info, data);
 				if (view is not null)
 					cell.SetupView(view);
 			}
 
-		if (cell.NeedsView && info is not null && data is not null)
-		{
-			var view = Handler?.VirtualView?.ViewSelector?.CreateView(info, data);
-			if (view is not null)
-				cell.SetupView(view);
-		}
-
-		if (info is not null)
-		{
 			cell.UpdatePosition(info);
 
-			if (cell.VirtualView?.TryGetTarget(out var cellVirtualView) ?? false)
+			if (cell.VirtualView.TryGetTarget(out var cellVirtualView))
 			{
-				Handler?.VirtualView?.ViewSelector?.RecycleView(info, data, cellVirtualView);
+				Handler.VirtualView.ViewSelector?.RecycleView(info, data, cellVirtualView);
 
-				Handler?.VirtualView?.ViewSelector?.ViewAttached(info, cellVirtualView);
+				Handler.VirtualView.ViewSelector?.ViewAttached(info, cellVirtualView);
 			}
 		}
 
 		return cell;
 	}
 
-	public override UICollectionReusableView GetViewForSupplementaryElement(UICollectionView collectionView, NSString elementKind,
-		NSIndexPath indexPath)
-	{
-		return base.GetViewForSupplementaryElement(collectionView, elementKind, indexPath);
-	}
+	// public override UICollectionReusableView GetViewForSupplementaryElement(UICollectionView collectionView, NSString elementKind,
+	// 	NSIndexPath indexPath)
+	// {
+	// 	return base.GetViewForSupplementaryElement(collectionView, elementKind, indexPath);
+	// }
 
 	void TapCellHandler(CvCell cell)
 	{
@@ -114,13 +93,11 @@ void TapCellHandler(CvCell cell)
 		cell.PositionInfo.IsSelected = !cell.PositionInfo.IsSelected;
 
 		if (cell.PositionInfo.IsSelected)
-			Handler?.VirtualView?.SelectItem(p);
+			Handler.VirtualView.SelectItem(p);
 		else
-			Handler?.VirtualView?.DeselectItem(p);
+			Handler.VirtualView.DeselectItem(p);
 	}
 
 	public override nint GetItemsCount(UICollectionView collectionView, nint section)
-	{
-		return Handler?.PositionalViewSelector?.TotalCount ?? 0;
-	}
+		=> Handler.Adapter.GetNumberOfItemsInSection(section.ToInt32());
 }