Fix memory leak on snackbar (#3034)

* Use `WeakReference` under the hood

* add extension method for WeakReference

* Update src/CommunityToolkit.Maui/Alerts/Snackbar/Snackbar.shared.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Pedro Jesus <pedrojesus@Pedros-MacBook-Pro.local>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

src/CommunityToolkit.Maui/Alerts/Snackbar/Snackbar.shared.cs

@@ -8,6 +8,7 @@ public partial class Snackbar : ISnackbar
 	static readonly WeakEventManager weakEventManager = new();
 
 	bool isDisposed;
+	WeakReference<IView>? weakView;
 
 	/// <summary>
 	/// Initializes a new instance of <see cref="Snackbar"/>
@@ -57,7 +58,20 @@ public string ActionButtonText
 	public Action? Action { get; init; }
 
 	/// <inheritdoc/>
-	public IView? Anchor { get; init; }
+	public IView? Anchor
+	{
+		get => weakView?.GetTargetOrDefault();
+		init
+		{
+			if (value is null)
+			{
+				weakView = null;
+				return;
+			}
+
+			weakView = new(value);
+		}
+	}
 
 	/// <summary>
 	/// Occurs when <see cref="IsShown"/> changes.

src/CommunityToolkit.Maui/Extensions/WeakReferenceExtensions.cs

@@ -0,0 +1,17 @@
+namespace CommunityToolkit.Maui.Extensions;
+
+static class WeakReferenceExtensions
+{
+	public static T? GetTargetOrDefault<T>(this WeakReference<T> self)
+		where T : class
+	{
+		ArgumentNullException.ThrowIfNull(self);
+
+		if (self.TryGetTarget(out var target))
+		{
+			return target;
+		}
+
+		return default;
+	}
+}