[controls] fix memory leak in CollectionView

Fixes: #10578
Context: https://github.com/Vroomer/MAUI-navigation-memory-leak.git

After testing the above sample, I found that adding a `CollectionView`
to a `Page`, makes it and the entire page live forever.

This is WIP, as it is still failing on iOS/Catalyst. This fixes Android
& Windows so far.

src/Controls/src/Core/Handlers/Items/Android/MauiRecyclerView.cs

@@ -42,6 +42,10 @@ public class MauiRecyclerView<TItemsView, TAdapter, TItemsViewSource> : Recycler
 
  ItemTouchHelper _itemTouchHelper;
  SimpleItemTouchHelperCallback _itemTouchHelperCallback;
+ WeakNotifyPropertyChangedProxy _layoutPropertyChangedProxy;
+ PropertyChangedEventHandler _layoutPropertyChanged;
+
+ ~MauiRecyclerView() => _layoutPropertyChangedProxy?.Unsubscribe();
 
  public MauiRecyclerView(Context context, Func<IItemsLayout> getItemsLayout, Func<TAdapter> getAdapter) : base(context)
  {
@@ -58,9 +62,10 @@ public MauiRecyclerView(Context context, Func<IItemsLayout> getItemsLayout, Func
  public virtual void TearDownOldElement(TItemsView oldElement)
  {
  // Stop listening for layout property changes
- if (ItemsLayout != null)
+ if (_layoutPropertyChangedProxy is not null)
  {
- ItemsLayout.PropertyChanged -= LayoutPropertyChanged;
+ _layoutPropertyChangedProxy.Unsubscribe();
+ _layoutPropertyChanged = null;
  }
 
  // Stop listening for ScrollTo requests
@@ -283,14 +288,16 @@ public virtual void UpdateCanReorderItems()
 
  public virtual void UpdateLayoutManager()
  {
- if (ItemsLayout != null)
- ItemsLayout.PropertyChanged -= LayoutPropertyChanged;
+ _layoutPropertyChangedProxy?.Unsubscribe();
 
  ItemsLayout = _getItemsLayout();
 
  // Keep track of the ItemsLayout's property changes
  if (ItemsLayout != null)
- ItemsLayout.PropertyChanged += LayoutPropertyChanged;
+ {
+ _layoutPropertyChanged ??= LayoutPropertyChanged;
+ _layoutPropertyChangedProxy = new WeakNotifyPropertyChangedProxy(ItemsLayout, _layoutPropertyChanged);
+ }
 
  SetLayoutManager(SelectLayoutManager(ItemsLayout));
 

src/Controls/src/Core/Handlers/Items/StructuredItemsViewHandler.Windows.cs

@@ -16,6 +16,10 @@ public partial class StructuredItemsViewHandler<TItemsView> : ItemsViewHandler<T
  {
  View _currentHeader;
  View _currentFooter;
+ WeakNotifyPropertyChangedProxy _layoutPropertyChangedProxy;
+ PropertyChangedEventHandler _layoutPropertyChanged;
+
+ ~StructuredItemsViewHandler() => _layoutPropertyChangedProxy?.Unsubscribe();
 
  protected override IItemsLayout Layout { get => ItemsView?.ItemsLayout; }
 
@@ -24,15 +28,26 @@ protected override void ConnectHandler(ListViewBase platformView)
  base.ConnectHandler(platformView);
 
  if (Layout is not null)
- Layout.PropertyChanged += LayoutPropertyChanged;
+ {
+ _layoutPropertyChanged ??= LayoutPropertyChanged;
+ _layoutPropertyChangedProxy = new WeakNotifyPropertyChangedProxy(Layout, _layoutPropertyChanged);
+ }
+ else if (_layoutPropertyChangedProxy is not null)
+ {
+ _layoutPropertyChangedProxy.Unsubscribe();
+ _layoutPropertyChangedProxy = null;
+ }
  }
 
  protected override void DisconnectHandler(ListViewBase platformView)
  {
  base.DisconnectHandler(platformView);
 
- if (Layout is not null)
- Layout.PropertyChanged -= LayoutPropertyChanged;
+ if (_layoutPropertyChangedProxy is not null)
+ {
+ _layoutPropertyChangedProxy.Unsubscribe();
+ _layoutPropertyChangedProxy = null;
+ }
  }
 
  void LayoutPropertyChanged(object sender, PropertyChangedEventArgs e)

src/Controls/src/Core/PublicAPI/net-android/PublicAPI.Unshipped.txt

@@ -3,6 +3,7 @@
 Microsoft.Maui.Controls.Border.~Border() -> void
 Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.FrameRenderer(Android.Content.Context! context, Microsoft.Maui.IPropertyMapper! mapper) -> void
 Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.FrameRenderer(Android.Content.Context! context, Microsoft.Maui.IPropertyMapper! mapper, Microsoft.Maui.CommandMapper! commandMapper) -> void
+Microsoft.Maui.Controls.Handlers.Items.MauiRecyclerView<TItemsView, TAdapter, TItemsViewSource>.~MauiRecyclerView() -> void
 Microsoft.Maui.Controls.LayoutOptions.Equals(Microsoft.Maui.Controls.LayoutOptions other) -> bool
 Microsoft.Maui.Controls.Region.Equals(Microsoft.Maui.Controls.Region other) -> bool
 Microsoft.Maui.Controls.Shapes.Matrix.Equals(Microsoft.Maui.Controls.Shapes.Matrix other) -> bool

src/Controls/src/Core/PublicAPI/net-windows/PublicAPI.Unshipped.txt

@@ -1,6 +1,7 @@
 #nullable enable
 *REMOVED*override Microsoft.Maui.Controls.RefreshView.MeasureOverride(double widthConstraint, double heightConstraint) -> Microsoft.Maui.Graphics.Size
 Microsoft.Maui.Controls.Border.~Border() -> void
+Microsoft.Maui.Controls.Handlers.Items.StructuredItemsViewHandler<TItemsView>.~StructuredItemsViewHandler() -> void
 override Microsoft.Maui.Controls.Handlers.BoxViewHandler.NeedsContainer.get -> bool
 Microsoft.Maui.Controls.Handlers.BoxViewHandler
 Microsoft.Maui.Controls.Handlers.BoxViewHandler.BoxViewHandler() -> void

src/Controls/tests/DeviceTests/Elements/NavigationPage/NavigationPageTests.cs

@@ -5,6 +5,7 @@
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Controls.Handlers.Compatibility;
+using Microsoft.Maui.Controls.Handlers.Items;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Handlers;
 using Microsoft.Maui.Hosting;
@@ -34,6 +35,7 @@ void SetupBuilder()
  handlers.AddHandler<Window, WindowHandlerStub>();
  handlers.AddHandler<Frame, FrameRenderer>();
  handlers.AddHandler<Label, LabelHandler>();
+ handlers.AddHandler<CollectionView, CollectionViewHandler>();
  });
  });
  }
@@ -298,7 +300,7 @@ public async Task DoesNotLeak()
 
  await CreateHandlerAndAddToWindow<WindowHandlerStub>(new Window(navPage), async (handler) =>
  {
- var page = new ContentPage { Title = "Page 2", Content = new VerticalStackLayout { new Label() } };
+ var page = new ContentPage { Title = "Page 2", Content = new VerticalStackLayout { new Label(), new CollectionView() } };
  pageReference = new WeakReference(page);
  await navPage.Navigation.PushAsync(page);
  await navPage.Navigation.PopAsync();

src/Controls/tests/DeviceTests/Elements/Shell/ShellTests.cs

@@ -8,6 +8,7 @@
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Controls.Handlers;
 using Microsoft.Maui.Controls.Handlers.Compatibility;
+using Microsoft.Maui.Controls.Handlers.Items;
 using Microsoft.Maui.Devices;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Handlers;
@@ -34,6 +35,7 @@ void SetupBuilder()
  SetupShellHandlers(handlers);
  handlers.AddHandler(typeof(NavigationPage), typeof(NavigationViewHandler));
  handlers.AddHandler(typeof(Button), typeof(ButtonHandler));
+ handlers.AddHandler(typeof(CollectionView), typeof(CollectionViewHandler));
  });
  });
  }
@@ -968,7 +970,7 @@ await CreateHandlerAndAddToWindow<ShellHandler>(shell, async (handler) =>
  {
  await OnLoadedAsync(shell.CurrentPage);
 
- var page = new ContentPage { Title = "Page 2", Content = new VerticalStackLayout { new Label() } };
+ var page = new ContentPage { Title = "Page 2", Content = new VerticalStackLayout { new Label(), new CollectionView() } };
  pageReference = new WeakReference(page);
 
  await shell.Navigation.PushAsync(page);