Merge branch 'main' of https://github.com/Redth/Maui.VirtualListView

.gitignore

@@ -350,4 +350,4 @@ MigrationBackup/
 .ionide/
 .DS_Store
 
-.idea/
+.idea/

README.md

@@ -1,7 +1,7 @@
 # VirtualListView for .NET MAUI
 This is an experiment in creating a virtualized ListView control for .NET MAUI to support simple, fast, multi-templated, uneven item sized lists by not adding too many bells and whistles and using an adapter pattern data source.
 
-![Nuget: Redth.Maui.VirtualListView](https://img.shields.io/nuget/vpre/Redth.Maui.VirtualListView?logo=nuget&label=Redth.Maui.VirtualListView&color=004880&link=https%3A%2F%2Fwww.nuget.org%2Fpackages%2FRedth.Maui.VirtualListView%2F)
+[![Nuget: Redth.Maui.VirtualListView](https://img.shields.io/nuget/vpre/Redth.Maui.VirtualListView?logo=nuget&label=Redth.Maui.VirtualListView&color=004880&link=https%3A%2F%2Fwww.nuget.org%2Fpackages%2FRedth.Maui.VirtualListView%2F)](https://www.nuget.org/packages/Redth.Maui.VirtualListView)
 
 
 ## Vroooom!

Sample/VirtualListViewSample/MusicLibraryPage.xaml

@@ -72,6 +72,15 @@
 				<Label Padding="20" Text="That's all folks!" TextColor="White" HorizontalOptions="Center" />
 			</Grid>
 		</vlv:VirtualListView.GlobalFooter>
+
+		<vlv:VirtualListView.EmptyView>
+			<Grid>
+				<Label
+					VerticalOptions="Center"
+					HorizontalOptions="Center"
+					Text="No Items" />
+			</Grid>
+		</vlv:VirtualListView.EmptyView>
 	</vlv:VirtualListView>
 
 </ContentPage>

Sample/VirtualListViewSample/SectionedAdapterPage.xaml

@@ -10,6 +10,8 @@
 		<vlv:VirtualListView
 			Grid.Row="0"
 			Grid.Column="0" Grid.ColumnSpan="3"
+			IsRefreshEnabled="False"
+			OnRefresh="Vlv_OnOnRefresh"
 			x:Name="vlv"
 			OnSelectedItemsChanged="vlv_SelectedItemsChanged"
 			SelectionMode="Single">

Sample/VirtualListViewSample/SectionedAdapterPage.xaml.cs

@@ -47,4 +47,10 @@ private void vlv_SelectedItemsChanged(object sender, SelectedItemsChangedEventAr
 		}
 
 	}
+
+	private async void Vlv_OnOnRefresh(object sender, RefreshEventArgs e)
+	{
+		await Task.Delay(3000);
+		e.Complete();
+	}
 }

VirtualListView/Adapters/VirtualListViewAdapterBase.cs

@@ -2,7 +2,12 @@
 
 public abstract class VirtualListViewAdapterBase<TSection, TItem> : IVirtualListViewAdapter
 {
-	public virtual int GetNumberOfSections() => 1;
+	// This adapter assumes we only ever have 1 section
+	// however we really want to return 0 if there's no items at all
+	// So, ask the derived class how many items might be in the first
+	// section and if any, we return 1 section otherwise 0
+	public virtual int GetNumberOfSections() =>
+		GetNumberOfItemsInSection(0) > 0 ? 1 : 0;
 
 	public event EventHandler OnDataInvalidated;
 

VirtualListView/Apple/CvCell.ios.maccatalyst.cs

@@ -9,6 +9,8 @@ namespace Microsoft.Maui;
 
 internal class CvCell : UICollectionViewCell
 {
+	internal const string ReuseIdUnknown = "UNKNOWN";
+
 	public VirtualListViewHandler Handler { get; set; }
 
 	public WeakReference<NSIndexPath> IndexPath { get; set; }

VirtualListView/Apple/CvDataSource.ios.maccatalyst.cs

@@ -1,4 +1,5 @@
-using Foundation;
+#nullable enable
+using Foundation;
 using UIKit;
 
 namespace Microsoft.Maui;
@@ -20,54 +21,74 @@ public CvDataSource(VirtualListViewHandler handler)
 
 	public override nint NumberOfSections(UICollectionView collectionView)
 		=> 1;
-
+	
 	public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
 	{
 		var info = Handler?.PositionalViewSelector?.GetInfo(indexPath.Item.ToInt32());
 
-		var data = Handler?.PositionalViewSelector?.Adapter?.DataFor(info.Kind, info.SectionIndex, info.ItemIndex);
-
-		var reuseId = Handler?.PositionalViewSelector?.ViewSelector?.GetReuseId(info, data);
+		object? data = null;
 
-		var nativeReuseId = info.Kind switch
+		var nativeReuseId = CvCell.ReuseIdUnknown;
+
+		if (info is not null)
 		{
-			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),
-			_ => "UNKNOWN",
-		};
-
-		var cell = (collectionView.DequeueReusableCell(nativeReuseId, indexPath) as CvCell)!;
+			data = Handler?.PositionalViewSelector?.Adapter?.DataFor(info.Kind, info.SectionIndex, info.ItemIndex);
+
+			if (data is not null)
+			{
+				var reuseId = Handler?.PositionalViewSelector?.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;
+
 		cell.SetTapHandlerCallback(TapCellHandler);
 		cell.Handler = Handler;
 		cell.IndexPath = new WeakReference<NSIndexPath>(indexPath);
 
 		cell.ReuseCallback = new WeakReference<Action<IView>>((rv) =>
 		{
-			if (cell?.VirtualView?.TryGetTarget(out var cellVirtualView) ?? false)
-				Handler.VirtualView.ViewSelector.ViewDetached(info, cellVirtualView);
+			if (info is not null && (cell.VirtualView?.TryGetTarget(out var cellView) ?? false))
+				Handler?.VirtualView?.ViewSelector?.ViewDetached(info, cellView);
 		});
 
-		if (info.SectionIndex < 0 || info.ItemIndex < 0)
-			info.IsSelected = false;
-		else
-			info.IsSelected = Handler?.IsItemSelected(info.SectionIndex, info.ItemIndex) ?? false;
+		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;
+		}
 
-		if (cell.NeedsView)
+		if (cell.NeedsView && info is not null && data is not null)
 		{
 			var view = Handler?.PositionalViewSelector?.ViewSelector?.CreateView(info, data);
-			cell.SetupView(view);
+			if (view is not null)
+				cell.SetupView(view);
 		}
 
-		cell.UpdatePosition(info);
-
-		if (cell.VirtualView.TryGetTarget(out var cellVirtualView))
+		if (info is not null)
 		{
-			Handler?.PositionalViewSelector?.ViewSelector?.RecycleView(info, data, cellVirtualView);
+			cell.UpdatePosition(info);
+
+			if (data is not null && (cell.VirtualView?.TryGetTarget(out var cellVirtualView) ?? false))
+			{
+				Handler?.PositionalViewSelector?.ViewSelector?.RecycleView(info, data, cellVirtualView);
 
-			Handler.VirtualView.ViewSelector.ViewAttached(info, cellVirtualView);
+				Handler?.VirtualView?.ViewSelector?.ViewAttached(info, cellVirtualView);
+			}
 		}
 
 		return cell;

VirtualListView/Apple/CvDelegate.ios.maccatalyst.cs

@@ -11,12 +11,13 @@ public CvDelegate(VirtualListViewHandler handler, UICollectionView collectionVie
 	{
 		Handler = handler;
 		NativeCollectionView = new WeakReference<UICollectionView>(collectionView);
+		collectionView.RegisterClassForCell(typeof(CvCell), CvCell.ReuseIdUnknown);
 	}
 
 	internal readonly WeakReference<UICollectionView> NativeCollectionView;
 	internal readonly VirtualListViewHandler Handler;
 
-	public WeakReference<Action<NFloat, NFloat>> ScrollHandler { get; set; }
+	public Action<NFloat, NFloat> ScrollHandler { get; set; }
 
 	public override void ItemSelected(UICollectionView collectionView, NSIndexPath indexPath)
 		=> HandleSelection(collectionView, indexPath, true);
@@ -27,27 +28,28 @@ public override void ItemDeselected(UICollectionView collectionView, NSIndexPath
 	void HandleSelection(UICollectionView collectionView, NSIndexPath indexPath, bool selected)
 	{
 		//UIView.AnimationsEnabled = false;
-		var selectedCell = collectionView.CellForItem(indexPath) as CvCell;
-
-		if ((selectedCell?.PositionInfo?.Kind ?? PositionKind.Header) == PositionKind.Item)
+		if (collectionView.CellForItem(indexPath) is CvCell selectedCell
+		    && (selectedCell.PositionInfo?.Kind ?? PositionKind.Header) == PositionKind.Item)
 		{
 			selectedCell.UpdateSelected(selected);
 
-			var itemPos = new ItemPosition(
-				selectedCell.PositionInfo.SectionIndex,
-				selectedCell.PositionInfo.ItemIndex);
+			if (selectedCell.PositionInfo is not null)
+			{
+				var itemPos = new ItemPosition(
+					selectedCell.PositionInfo.SectionIndex,
+					selectedCell.PositionInfo.ItemIndex);
 
-			if (selected)
-				Handler?.VirtualView?.SelectItem(itemPos);
-			else
-				Handler?.VirtualView?.DeselectItem(itemPos);
+				if (selected)
+					Handler?.VirtualView?.SelectItem(itemPos);
+				else
+					Handler?.VirtualView?.DeselectItem(itemPos);
+			}
 		}
 	}
 
 	public override void Scrolled(UIScrollView scrollView)
 	{
-		if (ScrollHandler?.TryGetTarget(out var handler) ?? false)
-			handler?.Invoke(scrollView.ContentOffset.X, scrollView.ContentOffset.Y);
+		ScrollHandler?.Invoke(scrollView.ContentOffset.X, scrollView.ContentOffset.Y);
 	}
 
 	public override bool ShouldSelectItem(UICollectionView collectionView, NSIndexPath indexPath)

VirtualListView/Apple/VirtualListViewHandler.ios.maccatalyst.cs

@@ -36,13 +36,21 @@ protected override UICollectionView CreatePlatformView()
 
 
 		refreshControl = new UIRefreshControl();
+		refreshControl.Enabled = VirtualView?.IsRefreshEnabled ?? false;
 		refreshControl.AddTarget(new EventHandler((s, a) =>
 		{
 			refreshControl.BeginRefreshing();
-			VirtualView?.Refresh(() => refreshControl.EndRefreshing());
+			try
+			{
+				VirtualView?.Refresh(() => refreshControl.EndRefreshing());
+			}
+			catch
+			{
+				refreshControl.EndRefreshing();
+			}
 		}), UIControlEvent.ValueChanged);
 
-		collectionView.AddSubview(refreshControl);
+		//collectionView.AddSubview(refreshControl);
 
 		collectionView.AlwaysBounceVertical = true;
 
@@ -62,8 +70,7 @@ protected override void ConnectHandler(UICollectionView nativeView)
 		dataSource = new CvDataSource(this);
 
 		cvdelegate = new CvDelegate(this, nativeView);
-		cvdelegate.ScrollHandler = new WeakReference<Action<System.Runtime.InteropServices.NFloat, System.Runtime.InteropServices.NFloat>>((x, y) =>
-			VirtualView?.Scrolled(x, y));
+		cvdelegate.ScrollHandler = (x, y) => VirtualView?.Scrolled(x, y);
 
 		nativeView.DataSource = dataSource;
 		nativeView.Delegate = cvdelegate;
@@ -176,8 +183,20 @@ public static void MapRefreshAccentColor(VirtualListViewHandler handler, IVirtua
 
 	public static void MapIsRefreshEnabled(VirtualListViewHandler handler, IVirtualListView virtualListView)
 	{
+		var isRefreshEnabled = virtualListView?.IsRefreshEnabled ?? false;
 		if (handler.refreshControl is not null)
-			handler.refreshControl.Enabled = virtualListView.IsRefreshEnabled;
+		{
+			if (isRefreshEnabled)
+			{
+				handler.PlatformView.AddSubview(handler.refreshControl);
+				handler.refreshControl.Enabled = true;
+			}
+			else
+			{
+				handler.refreshControl.Enabled = false;
+				handler.refreshControl.RemoveFromSuperview();
+			}
+		}
 	}
 
 
@@ -213,16 +232,26 @@ void UpdateEmptyView()
 		}
 	}
 
+	void UpdateVerticalScrollbarVisibility(ScrollBarVisibility scrollBarVisibility)
+	{
+		PlatformView.ShowsVerticalScrollIndicator = scrollBarVisibility == ScrollBarVisibility.Always || scrollBarVisibility == ScrollBarVisibility.Default;
+	}
+
+	void UpdateHorizontalScrollbarVisibility(ScrollBarVisibility scrollBarVisibility)
+	{
+		PlatformView.ShowsHorizontalScrollIndicator = scrollBarVisibility == ScrollBarVisibility.Always || scrollBarVisibility == ScrollBarVisibility.Default;
+	}
+
 	public void InvalidateData()
 	{
 		this.PlatformView.InvokeOnMainThread(() => {
-			layout?.InvalidateLayout();
+			//layout?.InvalidateLayout();
 
 			UpdateEmptyViewVisibility();
 
-			PlatformView?.SetNeedsLayout();
+			//PlatformView?.SetNeedsLayout();
 			PlatformView?.ReloadData();
-			PlatformView?.LayoutIfNeeded();
+			//PlatformView?.LayoutIfNeeded();
 		});
 
 	}