[ios/catalyst] fix memory leaks in *Cell

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/CellTableViewCell.cs

@@ -9,10 +9,19 @@ namespace Microsoft.Maui.Controls.Handlers.Compatibility
 {
 	public class CellTableViewCell : UITableViewCell, INativeElementView
 	{
-		Cell _cell;
+		WeakReference<Cell> _cell;
+		readonly WeakEventManager _weakEventManager = new();
 
+		// NOTE: internal callers can use InternalPropertyChanged
+		[Obsolete("To be removed in a future release.")]
 		public Action<object, PropertyChangedEventArgs> PropertyChanged;
 
+		internal event Action<object, PropertyChangedEventArgs> InternalPropertyChanged
+		{
+			add => _weakEventManager.AddEventHandler(value);
+			remove => _weakEventManager.RemoveEventHandler(value);
+		}
+
 		bool _disposed;
 
 		public CellTableViewCell(UITableViewCellStyle style, string key) : base(style, key)
@@ -21,30 +30,37 @@ public CellTableViewCell(UITableViewCellStyle style, string key) : base(style, k
 
 		public Cell Cell
 		{
-			get { return _cell; }
+			get => _cell?.GetTargetOrDefault();
 			set
 			{
-				if (_cell == value)
-					return;
-
-				if (_cell != null)
+				if (_cell is not null)
 				{
-					_cell.PropertyChanged -= HandlePropertyChanged;
-					BeginInvokeOnMainThread(_cell.SendDisappearing);
+					if (_cell.TryGetTarget(out var cell) && cell == value)
+						return;
+
+					if (cell is not null)
+					{
+						cell.PropertyChanged -= HandlePropertyChanged;
+						BeginInvokeOnMainThread(cell.SendDisappearing);
+					}
 				}
-				_cell = value;
 
-				if (_cell != null)
+				if (value is not null)
 				{
-					_cell.PropertyChanged += HandlePropertyChanged;
-					BeginInvokeOnMainThread(_cell.SendAppearing);
+					_cell = new(value);
+					value.PropertyChanged += HandlePropertyChanged;
+					BeginInvokeOnMainThread(value.SendAppearing);
+				}
+				else
+				{
+					_cell = null;
 				}
 			}
 		}
 
 		public Element Element => Cell;
 
-		public void HandlePropertyChanged(object sender, PropertyChangedEventArgs e) => PropertyChanged?.Invoke(sender, e);
+		public void HandlePropertyChanged(object sender, PropertyChangedEventArgs e) => _weakEventManager.HandleEvent(sender, e, nameof(InternalPropertyChanged));
 
 		internal static UITableViewCell GetPlatformCell(UITableView tableView, Cell cell, bool recycleCells = false, string templateId = "")
 		{
@@ -109,12 +125,10 @@ protected override void Dispose(bool disposing)
 
 			if (disposing)
 			{
-				PropertyChanged = null;
-
-				if (_cell != null)
+				if (Cell is Cell cell)
 				{
-					_cell.PropertyChanged -= HandlePropertyChanged;
-					CellRenderer.SetRealCell(_cell, null);
+					cell.PropertyChanged -= HandlePropertyChanged;
+					CellRenderer.SetRealCell(cell, null);
 				}
 				_cell = null;
 			}

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/EntryCellRenderer.cs

@@ -31,15 +31,15 @@ public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell,
 				tvc = new EntryCellTableViewCell(item.GetType().FullName);
 			else
 			{
-				tvc.PropertyChanged -= HandlePropertyChanged;
+				tvc.InternalPropertyChanged -= HandlePropertyChanged;
 				tvc.TextFieldTextChanged -= OnTextFieldTextChanged;
 				tvc.KeyboardDoneButtonPressed -= OnKeyBoardDoneButtonPressed;
 			}
 
 			SetRealCell(item, tvc);
 
 			tvc.Cell = item;
-			tvc.PropertyChanged += HandlePropertyChanged;
+			tvc.InternalPropertyChanged += HandlePropertyChanged;
 			tvc.TextFieldTextChanged += OnTextFieldTextChanged;
 			tvc.KeyboardDoneButtonPressed += OnKeyBoardDoneButtonPressed;
 

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/ImageCellRenderer.cs

@@ -47,12 +47,12 @@ void SetImage(ImageCell cell, CellTableViewCell target)
 
 			source.LoadImage(cell.FindMauiContext(), (result) =>
 			{
-				var uiimage = result.Value;
-				if (uiimage != null)
+				var uiimage = result?.Value;
+				if (uiimage is not null)
 				{
 					NSRunLoop.Main.BeginInvokeOnMainThread(() =>
 					{
-						if (target.Cell != null)
+						if (target.Cell is not null)
 						{
 							target.ImageView.Image = uiimage;
 							target.SetNeedsLayout();

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/SwitchCellRenderer.cs

@@ -28,7 +28,7 @@ public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell,
 			else
 			{
 				uiSwitch = tvc.AccessoryView as UISwitch;
-				tvc.PropertyChanged -= HandlePropertyChanged;
+				tvc.InternalPropertyChanged -= HandlePropertyChanged;
 			}
 
 			SetRealCell(item, tvc);
@@ -45,7 +45,7 @@ public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell,
 			_defaultOnColor = UISwitch.Appearance.OnTintColor;
 
 			tvc.Cell = item;
-			tvc.PropertyChanged += HandlePropertyChanged;
+			tvc.InternalPropertyChanged += HandlePropertyChanged;
 			tvc.AccessoryView = uiSwitch;
 #pragma warning disable CA1416, CA1422 // TODO: 'UITableViewCell.TextLabel' is unsupported on: 'ios' 14.0 and later
 			tvc.TextLabel.Text = boolCell.Text;

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/TextCellRenderer.cs

@@ -24,12 +24,12 @@ public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell,
 			if (!(reusableCell is CellTableViewCell tvc))
 				tvc = new CellTableViewCell(UITableViewCellStyle.Subtitle, item.GetType().FullName);
 			else
-				tvc.PropertyChanged -= HandleCellPropertyChanged;
+				tvc.InternalPropertyChanged -= HandleCellPropertyChanged;
 
 			SetRealCell(item, tvc);
 
 			tvc.Cell = textCell;
-			tvc.PropertyChanged = HandleCellPropertyChanged;
+			tvc.InternalPropertyChanged += HandleCellPropertyChanged;
 
 #pragma warning disable CA1416, CA1422 // TODO: 'UITableViewCell.TextLabel', DetailTextLabel is unsupported on: 'ios' 14.0 and later
 			tvc.TextLabel.Text = textCell.Text;

src/Controls/src/Core/Compatibility/Handlers/ListView/iOS/ViewCellRenderer.cs

@@ -43,9 +43,9 @@ public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell,
 
 		internal sealed class ViewTableCell : UITableViewCell, INativeElementView
 		{
-			IMauiContext MauiContext => _viewCell.FindMauiContext();
+			IMauiContext MauiContext => ViewCell?.FindMauiContext();
 			WeakReference<IPlatformViewHandler> _rendererRef;
-			ViewCell _viewCell;
+			WeakReference<ViewCell> _viewCell;
 
 			Element INativeElementView.Element => ViewCell;
 			internal bool SupressSeparator { get; set; }
@@ -57,13 +57,15 @@ public ViewTableCell(string key) : base(UITableViewCellStyle.Default, key)
 
 			public ViewCell ViewCell
 			{
-				get { return _viewCell; }
+				get => _viewCell?.GetTargetOrDefault();
 				set
 				{
-					if (_viewCell == value)
-						return;
-
-					_viewCell?.Handler?.DisconnectHandler();
+					if (_viewCell is not null)
+					{
+						if (_viewCell.TryGetTarget(out var viewCell) && viewCell == value)
+							return;
+						viewCell?.Handler?.DisconnectHandler();
+					}
 					UpdateCell(value);
 				}
 			}
@@ -82,7 +84,7 @@ void ViewCellPropertyChanged(object sender, PropertyChangedEventArgs e)
 				var realCell = (ViewTableCell)GetRealCell(viewCell);
 
 				if (e.PropertyName == Cell.IsEnabledProperty.PropertyName)
-					UpdateIsEnabled(_viewCell.IsEnabled);
+					UpdateIsEnabled(viewCell.IsEnabled);
 			}
 
 			public override void LayoutSubviews()
@@ -149,11 +151,11 @@ protected override void Dispose(bool disposing)
 						_rendererRef = null;
 					}
 
-					if (_viewCell != null)
+					if (ViewCell is ViewCell viewCell)
 					{
-						_viewCell.PropertyChanged -= ViewCellPropertyChanged;
-						_viewCell.View.MeasureInvalidated -= OnMeasureInvalidated;
-						SetRealCell(_viewCell, null);
+						viewCell.PropertyChanged -= ViewCellPropertyChanged;
+						viewCell.View.MeasureInvalidated -= OnMeasureInvalidated;
+						SetRealCell(viewCell, null);
 					}
 					_viewCell = null;
 				}
@@ -165,10 +167,10 @@ protected override void Dispose(bool disposing)
 
 			IPlatformViewHandler GetNewRenderer()
 			{
-				if (_viewCell.View == null)
-					throw new InvalidOperationException($"ViewCell must have a {nameof(_viewCell.View)}");
+				if (ViewCell is not ViewCell viewCell || viewCell.View == null)
+					throw new InvalidOperationException($"ViewCell must have a {nameof(viewCell.View)}");
 
-				var newRenderer = _viewCell.View.ToHandler(_viewCell.View.FindMauiContext());
+				var newRenderer = viewCell.View.ToHandler(viewCell.View.FindMauiContext());
 				_rendererRef = new WeakReference<IPlatformViewHandler>(newRenderer);
 				ContentView.ClearSubviews();
 				ContentView.AddSubview(newRenderer.VirtualView.ToPlatform());
@@ -179,37 +181,37 @@ void UpdateCell(ViewCell cell)
 			{
 				Performance.Start(out string reference);
 
-				var oldCell = _viewCell;
-				if (oldCell != null)
+				if (ViewCell is ViewCell oldCell)
 				{
 					BeginInvokeOnMainThread(oldCell.SendDisappearing);
 					oldCell.PropertyChanged -= ViewCellPropertyChanged;
 					oldCell.View.MeasureInvalidated -= OnMeasureInvalidated;
 				}
 
-				_viewCell = cell;
-
 				if (cell is null)
 				{
+					_viewCell = null;
 					_rendererRef = null;
 					ContentView.ClearSubviews();
 					return;
 				}
 
-				_viewCell.PropertyChanged += ViewCellPropertyChanged;
-				BeginInvokeOnMainThread(_viewCell.SendAppearing);
+				_viewCell = new(cell);
+
+				cell.PropertyChanged += ViewCellPropertyChanged;
+				BeginInvokeOnMainThread(cell.SendAppearing);
 
 				IPlatformViewHandler renderer;
 				if (_rendererRef == null || !_rendererRef.TryGetTarget(out renderer))
 					renderer = GetNewRenderer();
 				else
 				{
-					var viewHandlerType = MauiContext.Handlers.GetHandlerType(_viewCell.View.GetType());
+					var viewHandlerType = MauiContext.Handlers.GetHandlerType(cell.View.GetType());
 					var reflectableType = renderer as System.Reflection.IReflectableType;
 					var rendererType = reflectableType != null ? reflectableType.GetTypeInfo().AsType() : (renderer != null ? renderer.GetType() : typeof(System.Object));
 
 					if (rendererType == viewHandlerType/* || (renderer is Platform.DefaultRenderer && type == null)*/)
-						renderer.SetVirtualView(this._viewCell.View);
+						renderer.SetVirtualView(cell.View);
 					else
 					{
 						//when cells are getting reused the element could be already set to another cell
@@ -219,8 +221,8 @@ void UpdateCell(ViewCell cell)
 					}
 				}
 
-				UpdateIsEnabled(_viewCell.IsEnabled);
-				_viewCell.View.MeasureInvalidated += OnMeasureInvalidated;
+				UpdateIsEnabled(cell.IsEnabled);
+				cell.View.MeasureInvalidated += OnMeasureInvalidated;
 				Performance.Stop(reference);
 			}
 

src/Controls/tests/DeviceTests/Memory/MemoryTests.cs

@@ -30,6 +30,7 @@ void SetupBuilder()
 				handlers.AddHandler<CheckBox, CheckBoxHandler>();
 				handlers.AddHandler<DatePicker, DatePickerHandler>();
 				handlers.AddHandler<Entry, EntryHandler>();
+				handlers.AddHandler<EntryCell, EntryCellRenderer>();
 				handlers.AddHandler<Editor, EditorHandler>();
 				handlers.AddHandler<Frame, FrameRenderer>();
 				handlers.AddHandler<GraphicsView, GraphicsViewHandler>();
@@ -41,6 +42,7 @@ void SetupBuilder()
 				handlers.AddHandler<IContentView, ContentViewHandler>();
 				handlers.AddHandler<Image, ImageHandler>();
 				handlers.AddHandler<ImageButton, ImageButtonHandler>();
+				handlers.AddHandler<ImageCell, ImageCellRenderer>();
 				handlers.AddHandler<IndicatorView, IndicatorViewHandler>();
 				handlers.AddHandler<RefreshView, RefreshViewHandler>();
 				handlers.AddHandler<IScrollView, ScrollViewHandler>();
@@ -49,11 +51,13 @@ void SetupBuilder()
 				handlers.AddHandler<Stepper, StepperHandler>();
 				handlers.AddHandler<SwipeView, SwipeViewHandler>();
 				handlers.AddHandler<Switch, SwitchHandler>();
+				handlers.AddHandler<SwitchCell, SwitchCellRenderer>();
 				handlers.AddHandler<TableView, TableViewRenderer>();
 				handlers.AddHandler<TextCell, TextCellRenderer>();
 				handlers.AddHandler<TimePicker, TimePickerHandler>();
 				handlers.AddHandler<Toolbar, ToolbarHandler>();
 				handlers.AddHandler<WebView, WebViewHandler>();
+				handlers.AddHandler<ViewCell, ViewCellRenderer>();
 #if IOS || MACCATALYST
 				handlers.AddHandler<NavigationPage, NavigationRenderer>();
 #else
@@ -242,6 +246,49 @@ public async Task GestureDoesNotLeak(Type type)
 		await AssertionExtensions.WaitForGC(viewReference, handlerReference);
 	}
 
+	[Theory("Cells Do Not Leak")]
+	[InlineData(typeof(TextCell))]
+	[InlineData(typeof(EntryCell))]
+	[InlineData(typeof(ImageCell))]
+	[InlineData(typeof(SwitchCell))]
+	[InlineData(typeof(ViewCell))]
+	public async Task CellsDoNotLeak(Type type)
+	{
+		SetupBuilder();
+
+		WeakReference viewReference = null;
+		WeakReference handlerReference = null;
+
+		var observable = new ObservableCollection<int> { 1 };
+		var navPage = new NavigationPage(new ContentPage { Title = "Page 1" });
+
+		await CreateHandlerAndAddToWindow(new Window(navPage), async () =>
+		{
+			await navPage.Navigation.PushAsync(new ContentPage
+			{
+				Content = new ListView
+				{
+					ItemTemplate = new DataTemplate(() =>
+					{
+						var cell = (Cell)Activator.CreateInstance(type);
+						if (cell is ViewCell viewCell)
+						{
+							viewCell.View = new Label();
+						}
+						viewReference = new WeakReference(cell);
+						handlerReference = new WeakReference(cell.Handler);
+						return cell;
+					}),
+					ItemsSource = observable
+				}
+			});
+
+			await navPage.Navigation.PopAsync();
+		});
+
+		await AssertionExtensions.WaitForGC(viewReference, handlerReference);
+	}
+
 #if IOS
 	[Fact]
 	public async Task ResignFirstResponderTouchGestureRecognizer()