[ios/catalyst] fix memory leak in CollectionView cells

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewController.cs

@@ -377,7 +377,7 @@ protected object GetItemAtIndex(NSIndexPath index)
 			return ItemsSource[index];
 		}
 
-		[UnconditionalSuppressMessage("Memory", "MEM0003", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MEM0003", Justification = "Proven safe in test: CollectionViewTests.ItemsSourceDoesNotLeak")]
 		void CellContentSizeChanged(object sender, EventArgs e)
 		{
 			if (_disposed)
@@ -400,7 +400,7 @@ void CellContentSizeChanged(object sender, EventArgs e)
 			}
 		}
 
-		[UnconditionalSuppressMessage("Memory", "MEM0003", Justification = "Proven safe in test: MemoryTests.HandlerDoesNotLeak")]
+		[UnconditionalSuppressMessage("Memory", "MEM0003", Justification = "Proven safe in test: CollectionViewTests.ItemsSourceDoesNotLeak")]
 		void CellLayoutAttributesChanged(object sender, LayoutAttributesChangedEventArgs args)
 		{
 			CacheCellAttributes(args.NewAttributes.IndexPath, args.NewAttributes.Size);

src/Controls/src/Core/Handlers/Items/iOS/TemplatedCell.cs

@@ -11,8 +11,19 @@ namespace Microsoft.Maui.Controls.Handlers.Items
 {
 	public abstract class TemplatedCell : ItemsViewCell
 	{
-		public event EventHandler<EventArgs> ContentSizeChanged;
-		public event EventHandler<LayoutAttributesChangedEventArgs> LayoutAttributesChanged;
+		readonly WeakEventManager _weakEventManager = new();
+
+		public event EventHandler<EventArgs> ContentSizeChanged
+		{
+			add => _weakEventManager.AddEventHandler(value);
+			remove => _weakEventManager.RemoveEventHandler(value);
+		}
+
+		public event EventHandler<LayoutAttributesChangedEventArgs> LayoutAttributesChanged
+		{
+			add => _weakEventManager.AddEventHandler(value);
+			remove => _weakEventManager.RemoveEventHandler(value);
+		}
 
 		protected CGSize ConstrainedSize;
 
@@ -287,12 +298,12 @@ void MeasureInvalidated(object sender, EventArgs args)
 
 		protected void OnContentSizeChanged()
 		{
-			ContentSizeChanged?.Invoke(this, EventArgs.Empty);
+			_weakEventManager.HandleEvent(this, EventArgs.Empty, nameof(ContentSizeChanged));
 		}
 
 		protected void OnLayoutAttributesChanged(UICollectionViewLayoutAttributes newAttributes)
 		{
-			LayoutAttributesChanged?.Invoke(this, new LayoutAttributesChangedEventArgs(newAttributes));
+			_weakEventManager.HandleEvent(this, new LayoutAttributesChangedEventArgs(newAttributes), nameof(LayoutAttributesChanged));
 		}
 
 		protected abstract bool AttributesConsistentWithConstrainedDimension(UICollectionViewLayoutAttributes attributes);

src/Controls/tests/DeviceTests/Elements/CollectionView/CollectionViewTests.cs

@@ -6,6 +6,7 @@
 using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Handlers.Compatibility;
 using Microsoft.Maui.Controls.Handlers.Items;
 using Microsoft.Maui.Controls.Platform;
 using Microsoft.Maui.DeviceTests.Stubs;
@@ -41,7 +42,11 @@ void SetupBuilder()
 					handlers.AddHandler<Button, ButtonHandler>();
 					handlers.AddHandler<SwipeView, SwipeViewHandler>();
 					handlers.AddHandler<SwipeItem, SwipeItemMenuItemHandler>();
-
+#if IOS || MACCATALYST
+					handlers.AddHandler(typeof(NavigationPage), typeof(NavigationRenderer));
+#else
+					handlers.AddHandler(typeof(NavigationPage), typeof(NavigationViewHandler));
+#endif
 #if IOS && !MACCATALYST
 					handlers.AddHandler<CacheTestCollectionView, CacheTestCollectionViewHandler>();
 #endif
@@ -102,40 +107,64 @@ public async Task ItemsSourceDoesNotLeak()
 		{
 			SetupBuilder();
 
-			IList logicalChildren = null;
-			WeakReference weakReference = null;
-			var collectionView = new CollectionView
-			{
-				Header = new Label { Text = "Header" },
-				Footer = new Label { Text = "Footer" },
-				ItemTemplate = new DataTemplate(() => new Label())
-			};
+			var weakReferences = new List<WeakReference>();
 
-			await CreateHandlerAndAddToWindow<CollectionViewHandler>(collectionView, async handler =>
 			{
-				var data = new ObservableCollection<string>()
+				var labels = new List<Label>();
+				IList logicalChildren = null;
+				var collectionView = new CollectionView
 				{
-					"Item 1",
-					"Item 2",
-					"Item 3"
+					Header = new Label { Text = "Header" },
+					Footer = new Label { Text = "Footer" },
+					ItemTemplate = new DataTemplate(() => 
+					{
+						var label = new Label();
+						labels.Add(label);
+						return label;
+					}),
 				};
-				weakReference = new WeakReference(data);
-				collectionView.ItemsSource = data;
-				await Task.Delay(100);
 
-				// Get ItemsView._logicalChildren
-				var flags = BindingFlags.NonPublic | BindingFlags.Instance;
-				logicalChildren = typeof(Element).GetField("_internalChildren", flags).GetValue(collectionView) as IList;
-				Assert.NotNull(logicalChildren);
+				var navPage = new NavigationPage(new ContentPage { Title = "Page 1" });
 
-				// Replace with cloned collection
-				collectionView.ItemsSource = new ObservableCollection<string>(data);
-				await Task.Delay(100);
-			});
+				await CreateHandlerAndAddToWindow<WindowHandlerStub>(new Window(navPage), async handler =>
+				{
+					await navPage.PushAsync(new ContentPage { Content = collectionView });
+
+					var data = new ObservableCollection<string>()
+					{
+						"Item 1",
+						"Item 2",
+						"Item 3"
+					};
+					weakReferences.Add(new(data));
+					collectionView.ItemsSource = data;
+					await Task.Delay(100);
+
+					Assert.NotEmpty(labels);
+					foreach (var label in labels)
+					{
+						weakReferences.Add(new(label));
+						weakReferences.Add(new(label.Handler));
+						weakReferences.Add(new(label.Handler.PlatformView));
+					}
+
+					// Get ItemsView._logicalChildren
+					var flags = BindingFlags.NonPublic | BindingFlags.Instance;
+					logicalChildren = typeof(Element).GetField("_internalChildren", flags).GetValue(collectionView) as IList;
+					Assert.NotNull(logicalChildren);
+
+					// Replace with cloned collection
+					collectionView.ItemsSource = new ObservableCollection<string>(data);
+					await Task.Delay(100);
+					await navPage.PopAsync();
+				});
+
+
+				Assert.NotNull(logicalChildren);
+				Assert.True(logicalChildren.Count <= 5, "_logicalChildren should not grow in size!");
+			}
 
-			await AssertionExtensions.WaitForGC(weakReference);
-			Assert.NotNull(logicalChildren);
-			Assert.True(logicalChildren.Count <= 5, "_logicalChildren should not grow in size!");
+			await AssertionExtensions.WaitForGC([.. weakReferences]);
 		}
 
 		[Theory]