[ios/android] fix memory leak in ImageButton (#18602)

* [ios] fix memory leak in `ImageButton`

Context: #18365

Adding a parameter to the test:

    [Theory("Handler Does Not Leak")]
    [InlineData(typeof(ImageButton))]
    public async Task HandlerDoesNotLeak(Type type)

Shows a memory leak in `ImageButton`, caused by the cycle

* `ImageButtonHandler` ->
* `UIButton` events like `TouchUpInside` ->
* `ImageButtonHandler`

I could solve this problem by creating a `ImageButtonProxy` class -- the
same pattern I've used in other PRs to avoid cycles. This makes an
intermediate type to handle the events and breaks the cycle.

Still thinking if the analyzer could have caught this, issue filed at:

jonathanpeppers/memory-analyzers#12

* [android] fix memory leak in `ImageButton`

Context: a270ebd
Context: 1bbe79d
Context: material-components/material-components-android#2063

Reviewing a GC dump of the device tests, I noticed a `System.Action`
keeping the `ImageButton` alive:

    Microsoft.Maui.Controls.ImageButton
        System.Action
            Java.Lang.Thread.RunnableImplementor

So next, I looked for `System.Action` and found the path on the
`ReferencedTypes` tab:

    System.Action
        Microsoft.Maui.Platform.ImageButtonExtensions.[]c__DisplayClass4_0
            Google.Android.Material.ImageView.ShapeableImageView
            Microsoft.Maui.Controls.ImageButton

Which led me to the code:

    public static async void UpdatePadding(this ShapeableImageView platformButton, IImageButton imageButton)
    {
        platformButton.SetContentPadding(imageButton);
        platformButton.Post(() =>
        {
            platformButton.SetContentPadding(imageButton);
        });
        platformButton.SetContentPadding(imageButton);
    }

?!? Why is this code calling `SetContentPadding` three times?

Reviewing the commit history:

* a270ebd
* 1bbe79d
* material-components/material-components-android#2063

I could comment out the code and the leak is solved, but I found I could
also change the code to use `await Task.Yield()` for the same result.

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

@@ -37,6 +37,7 @@ void SetupBuilder()
 				handlers.AddHandler<Polyline, PolylineHandler>();
 				handlers.AddHandler<IContentView, ContentViewHandler>();
 				handlers.AddHandler<Image, ImageHandler>();
+				handlers.AddHandler<ImageButton, ImageButtonHandler>();
 				handlers.AddHandler<IndicatorView, IndicatorViewHandler>();
 				handlers.AddHandler<RefreshView, RefreshViewHandler>();
 				handlers.AddHandler<IScrollView, ScrollViewHandler>();
@@ -60,6 +61,7 @@ void SetupBuilder()
 	[InlineData(typeof(Editor))]
 	[InlineData(typeof(GraphicsView))]
 	[InlineData(typeof(Image))]
+	[InlineData(typeof(ImageButton))]
 	[InlineData(typeof(IndicatorView))]
 	[InlineData(typeof(Label))]
 	[InlineData(typeof(Picker))]

src/Core/src/Handlers/ImageButton/ImageButtonHandler.iOS.cs

@@ -5,6 +5,8 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class ImageButtonHandler : ViewHandler<IImageButton, UIButton>
 	{
+		readonly ImageButtonProxy _proxy = new();
+
 		protected override UIButton CreatePlatformView()
 		{
 			var platformView = new UIButton(UIButtonType.System)
@@ -17,18 +19,14 @@ protected override UIButton CreatePlatformView()
 
 		protected override void ConnectHandler(UIButton platformView)
 		{
-			platformView.TouchUpInside += OnButtonTouchUpInside;
-			platformView.TouchUpOutside += OnButtonTouchUpOutside;
-			platformView.TouchDown += OnButtonTouchDown;
+			_proxy.Connect(VirtualView, platformView);
 
 			base.ConnectHandler(platformView);
 		}
 
 		protected override void DisconnectHandler(UIButton platformView)
 		{
-			platformView.TouchUpInside -= OnButtonTouchUpInside;
-			platformView.TouchUpOutside -= OnButtonTouchUpOutside;
-			platformView.TouchDown -= OnButtonTouchDown;
+			_proxy.Disconnect(platformView);
 
 			base.DisconnectHandler(platformView);
 
@@ -55,22 +53,6 @@ public static void MapPadding(IImageButtonHandler handler, IImageButton imageBut
 			(handler.PlatformView as UIButton)?.UpdatePadding(imageButton);
 		}
 
-		void OnButtonTouchUpInside(object? sender, EventArgs e)
-		{
-			VirtualView?.Released();
-			VirtualView?.Clicked();
-		}
-
-		void OnButtonTouchUpOutside(object? sender, EventArgs e)
-		{
-			VirtualView?.Released();
-		}
-
-		void OnButtonTouchDown(object? sender, EventArgs e)
-		{
-			VirtualView?.Pressed();
-		}
-
 		partial class ImageButtonImageSourcePartSetter
 		{
 			public override void SetImageSource(UIImage? platformImage)
@@ -85,5 +67,47 @@ public override void SetImageSource(UIImage? platformImage)
 				button.VerticalAlignment = UIControlContentVerticalAlignment.Fill;
 			}
 		}
+
+		class ImageButtonProxy
+		{
+			WeakReference<IImageButton>? _virtualView;
+
+			IImageButton? VirtualView => _virtualView is not null && _virtualView.TryGetTarget(out var v) ? v : null;
+
+			public void Connect(IImageButton virtualView, UIButton platformView)
+			{
+				_virtualView = new(virtualView);
+
+				platformView.TouchUpInside += OnButtonTouchUpInside;
+				platformView.TouchUpOutside += OnButtonTouchUpOutside;
+				platformView.TouchDown += OnButtonTouchDown;
+			}
+
+			public void Disconnect(UIButton platformView)
+			{
+				platformView.TouchUpInside -= OnButtonTouchUpInside;
+				platformView.TouchUpOutside -= OnButtonTouchUpOutside;
+				platformView.TouchDown -= OnButtonTouchDown;
+			}
+
+			void OnButtonTouchUpInside(object? sender, EventArgs e)
+			{
+				if (VirtualView is IImageButton imageButton)
+				{
+					imageButton.Released();
+					imageButton.Clicked();
+				}
+			}
+
+			void OnButtonTouchUpOutside(object? sender, EventArgs e)
+			{
+				VirtualView?.Released();
+			}
+
+			void OnButtonTouchDown(object? sender, EventArgs e)
+			{
+				VirtualView?.Pressed();
+			}
+		}
 	}
 }

src/Core/src/Platform/Android/ImageButtonExtensions.cs

@@ -1,4 +1,5 @@
-using Android.Graphics.Drawables;
+using System.Threading.Tasks;
+using Android.Graphics.Drawables;
 using Android.Widget;
 using Google.Android.Material.ImageView;
 using Google.Android.Material.Shape;
@@ -41,13 +42,12 @@ public static void UpdateCornerRadius(this ShapeableImageView platformButton, IB
 				.Build();
 		}
 
-		public static void UpdatePadding(this ShapeableImageView platformButton, IImageButton imageButton)
+		public static async void UpdatePadding(this ShapeableImageView platformButton, IImageButton imageButton)
 		{
 			platformButton.SetContentPadding(imageButton);
-			platformButton.Post(() =>
-			{
-				platformButton.SetContentPadding(imageButton);
-			});
+
+			// see: https://github.com/material-components/material-components-android/issues/2063
+			await Task.Yield();
 			platformButton.SetContentPadding(imageButton);
 		}