Fix memory leak in CollectionViewHandler2.SubscribeToItemsLayoutPropertyChanged

Co-authored-by: PureWeen <5375137+PureWeen@users.noreply.github.com>

Author: 2 people

src/Controls/src/Core/Handlers/Items2/CollectionViewHandler2.iOS.cs

@@ -1,6 +1,7 @@
 #nullable disable
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Text;
 using Foundation;
 using Microsoft.Maui.Handlers;
@@ -63,10 +64,19 @@ public CollectionViewHandler2(PropertyMapper mapper = null) : base(mapper ?? Map
 
 	public partial class CollectionViewHandler2 : ItemsViewHandler2<ReorderableItemsView>
 	{
+		IItemsLayout _currentItemsLayout;
+		PropertyChangedEventHandler _itemsLayoutPropertyChangedHandler;
+
 		// Reorderable
 		protected override ItemsViewController2<ReorderableItemsView> CreateController(ReorderableItemsView itemsView, UICollectionViewLayout layout)
 			 => new ReorderableItemsViewController2<ReorderableItemsView>(itemsView, layout);
 
+		protected override void DisconnectHandler(UIView platformView)
+		{
+			UnsubscribeFromItemsLayoutPropertyChanged();
+			base.DisconnectHandler(platformView);
+		}
+
 		public static void MapCanReorderItems(CollectionViewHandler2 handler, ReorderableItemsView itemsView)
 		{
 			(handler.Controller as ReorderableItemsViewController2<ReorderableItemsView>)?.UpdateCanReorderItems();
@@ -202,21 +212,41 @@ public static void MapItemSizingStrategy(CollectionViewHandler2 handler, Structu
 
 		void SubscribeToItemsLayoutPropertyChanged(IItemsLayout itemsLayout)
 		{
+			// Unsubscribe from the previous ItemsLayout if it exists
+			UnsubscribeFromItemsLayoutPropertyChanged();
+
 			if (itemsLayout is not null)
 			{
-				itemsLayout.PropertyChanged += (sender, args) =>
+				// Create the handler if it doesn't exist
+				if (_itemsLayoutPropertyChangedHandler == null)
 				{
-					if (args.PropertyName == nameof(ItemsLayout.SnapPointsAlignment) ||
-						args.PropertyName == nameof(ItemsLayout.SnapPointsType) ||
-						args.PropertyName == nameof(GridItemsLayout.VerticalItemSpacing) ||
-						args.PropertyName == nameof(GridItemsLayout.HorizontalItemSpacing) ||
-						args.PropertyName == nameof(GridItemsLayout.Span) ||
-						args.PropertyName == nameof(LinearItemsLayout.ItemSpacing))
-
+					_itemsLayoutPropertyChangedHandler = (sender, args) =>
 					{
-						UpdateLayout();
-					}
-				};
+						if (args.PropertyName == nameof(ItemsLayout.SnapPointsAlignment) ||
+							args.PropertyName == nameof(ItemsLayout.SnapPointsType) ||
+							args.PropertyName == nameof(GridItemsLayout.VerticalItemSpacing) ||
+							args.PropertyName == nameof(GridItemsLayout.HorizontalItemSpacing) ||
+							args.PropertyName == nameof(GridItemsLayout.Span) ||
+							args.PropertyName == nameof(LinearItemsLayout.ItemSpacing))
+
+						{
+							UpdateLayout();
+						}
+					};
+				}
+
+				// Subscribe to the new ItemsLayout
+				itemsLayout.PropertyChanged += _itemsLayoutPropertyChangedHandler;
+				_currentItemsLayout = itemsLayout;
+			}
+		}
+
+		void UnsubscribeFromItemsLayoutPropertyChanged()
+		{
+			if (_currentItemsLayout is not null && _itemsLayoutPropertyChangedHandler is not null)
+			{
+				_currentItemsLayout.PropertyChanged -= _itemsLayoutPropertyChangedHandler;
+				_currentItemsLayout = null;
 			}
 		}
 	}

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

@@ -251,6 +251,40 @@ public void IndexPathValidTest()
 			Assert.False(source.IsIndexPathValid(invalidSection));
 		}
 
+		[Fact(DisplayName = "CollectionView Unsubscribes From ItemsLayout PropertyChanged")]
+		public async Task CollectionViewUnsubscribesFromItemsLayoutPropertyChanged()
+		{
+			SetupBuilder();
+
+			var collectionView = new CollectionView
+			{
+				ItemsSource = new List<string> { "Item 1", "Item 2", "Item 3" },
+				ItemTemplate = new DataTemplate(() => new Label()),
+				ItemsLayout = new LinearItemsLayout(ItemsLayoutOrientation.Vertical)
+			};
+
+			await CreateHandlerAndAddToWindow<CollectionViewHandler2>(collectionView, async handler =>
+			{
+				// Verify handler is created
+				Assert.NotNull(handler);
+				
+				// Change the ItemsLayout to trigger a new subscription
+				var newLayout = new LinearItemsLayout(ItemsLayoutOrientation.Horizontal);
+				collectionView.ItemsLayout = newLayout;
+				
+				// Give the handler time to process the change
+				await Task.Delay(100);
+				
+				// Disconnect the handler - this should unsubscribe from the ItemsLayout
+				((IElementHandler)handler).DisconnectHandler();
+				
+				// Verify that changing the ItemsLayout properties doesn't cause issues after disconnect
+				// If the handler is not properly unsubscribed, this could cause a crash or memory leak
+				newLayout.SnapPointsAlignment = SnapPointsAlignment.End;
+				newLayout.SnapPointsType = SnapPointsType.Mandatory;
+			});
+		}
+
 		/// <summary>
 		/// Simulates what a developer might do with a Page/View
 		/// </summary>