[Windows] Fix titlebar not persisting when page is swapped

src/Controls/src/Core/TitleBar/TitleBar.cs

@@ -256,6 +256,16 @@ public TitleBar()
 			}
 		}
 
+		internal void Cleanup()
+		{
+			PropertyChanged -= TitleBar_PropertyChanged;
+			if (Window is not null)
+			{
+				Window.Activated -= Window_Activated;
+				Window.Deactivated -= Window_Deactivated;
+			}
+		}
+
 		private void TitleBar_PropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{
 			if (e.PropertyName == nameof(Window) && Window is not null)

src/Controls/src/Core/Window/Window.cs

@@ -392,6 +392,7 @@ static void TitleBarChanged(BindableObject bindable, object oldValue, object new
 			{
 				if (oldValue is TitleBar prevTitleBar)
 				{
+					prevTitleBar.Cleanup();
 					self.RemoveLogicalChild(prevTitleBar);
 				}
 

src/Controls/tests/Core.UnitTests/TitleBarTests.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.Maui.Controls.Core.UnitTests
+{
+
+	public class TitleBarTests : BaseTestFixture
+	{
+		[Fact, Category(TestCategory.Memory)]
+		public async Task TitleBarDoesNotLeak()
+		{
+			var application = new Application();
+
+			WeakReference CreateReference()
+			{
+				var window = new Window { Page = new ContentPage() };
+				var firstTitleBar = new TitleBar();
+				var secondTitleBar = new TitleBar();
+				var reference = new WeakReference(firstTitleBar);
+
+				window.TitleBar = firstTitleBar;
+
+				application.OpenWindow(window);
+
+				window.TitleBar = secondTitleBar;
+
+				((IWindow)window).Destroying();
+				return reference;
+			}
+
+			var reference = CreateReference();
+
+			// GC
+			await TestHelpers.Collect();
+
+			Assert.False(reference.IsAlive, "TitleBar should not be alive!");
+
+			GC.KeepAlive(application);
+		}
+	}
+}

src/Controls/tests/DeviceTests/Elements/Window/WindowTests.Windows.cs

@@ -12,6 +12,7 @@
 using Xunit;
 using WPanel = Microsoft.UI.Xaml.Controls.Panel;
 using static Microsoft.Maui.DeviceTests.AssertHelpers;
+using Windows.UI;
 
 namespace Microsoft.Maui.DeviceTests
 {
@@ -239,6 +240,45 @@ await CreateHandlerAndAddToWindow<WindowHandlerStub>(window, async (handler) =>
 			});
 		}
 
+		[Theory]
+		[ClassData(typeof(WindowPageSwapTestCases))]
+		public async Task TitlebarWorksWhenSwitchingPage(WindowPageSwapTestCase swapOrder)
+		{
+			SetupBuilder();
+
+			var firstRootPage = swapOrder.GetNextPageType();
+			var window = new Window(firstRootPage)
+			{
+				TitleBar = new TitleBar()
+				{
+					Title = "Hello World",
+					BackgroundColor = Colors.CornflowerBlue
+				}
+			};
+
+			await CreateHandlerAndAddToWindow<WindowHandlerStub>(window, async (handler) =>
+			{
+				await OnLoadedAsync(swapOrder.Page);
+				while (!swapOrder.IsFinished())
+				{
+					var nextRootPage = swapOrder.GetNextPageType();
+					window.Page = nextRootPage;
+
+					try
+					{
+						await OnLoadedAsync(swapOrder.Page);
+
+						var navView = GetWindowRootView(handler);
+						Assert.NotNull(navView.TitleBar);
+					}
+					catch (Exception exc)
+					{
+						throw new Exception($"Failed to swap to {nextRootPage}", exc);
+					}
+				}
+			});
+		}
+
 		[Collection(ControlsHandlerTestBase.RunInNewWindowCollection)]
 		[Category(TestCategory.Lifecycle)]
 		public class WindowTestsRunInNewWindowCollection : ControlsHandlerTestBase

src/Controls/tests/DeviceTests/Elements/Window/WindowTests.cs

@@ -53,6 +53,8 @@ void SetupBuilder()
 					handlers.AddHandler(typeof(FlyoutPage), typeof(PhoneFlyoutPageRenderer));
 #endif
 
+					handlers.AddHandler<IContentView, ContentViewHandler>();
+
 					handlers.AddHandler<Button, ButtonHandler>();
 					handlers.AddHandler<Entry, EntryHandler>();
 					handlers.AddHandler<Editor, EditorHandler>();

src/Core/src/Handlers/Window/WindowHandler.Windows.cs

@@ -52,6 +52,7 @@ protected override void DisconnectHandler(UI.Xaml.Window platformView)
 			if (windowRootContentManager is not null)
 			{
 				windowRootContentManager.OnApplyTemplateFinished -= WindowRootContentManagerOnApplyTemplateFinished;
+				windowRootContentManager.SetTitleBar(null, null);
 				windowRootContentManager.Disconnect();
 			}
 
@@ -78,18 +79,7 @@ public static void MapContent(IWindowHandler handler, IWindow window)
 			_ = handler.MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
 			var windowManager = handler.MauiContext.GetNavigationRootManager();
-			var previousRootView = windowManager.RootView;
-
-			windowManager.Disconnect();
-			windowManager.Connect(handler.VirtualView.Content?.ToPlatform(handler.MauiContext));
-
-			if (handler.PlatformView.Content is WindowRootViewContainer container)
-			{
-				if (previousRootView != null && previousRootView != windowManager.RootView)
-					container.RemovePage(previousRootView);
-
-				container.AddPage(windowManager.RootView);
-			}
+			windowManager.Connect(handler);
 
 			window.VisualDiagnosticsOverlay?.Initialize();
 		}

src/Core/src/Platform/Windows/NavigationRootManager.cs

@@ -82,6 +82,32 @@ void OnBackRequested(NavigationView sender, NavigationViewBackRequestedEventArgs
 		internal MauiToolbar? Toolbar => _rootView.Toolbar;
 		public FrameworkElement RootView => _rootView;
 
+		internal void Connect(IWindowHandler handler)
+		{
+			_ = handler.MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
+
+			var platformWindow = _platformWindow.GetTargetOrDefault();
+			if (platformWindow is null)
+			{
+				return;
+			}
+
+			var previousRootView = RootView;
+
+			Disconnect();
+			Connect(handler.VirtualView.Content?.ToPlatform(handler.MauiContext));
+
+			if (platformWindow.Content is WindowRootViewContainer container)
+			{
+				if (previousRootView is not null && previousRootView != RootView)
+				{
+					container.RemovePage(previousRootView);
+				}
+
+				container.AddPage(RootView);
+			}
+		}
+
 		public virtual void Connect(UIElement? platformView)
 		{
 			if (_rootView.Content != null)
@@ -120,7 +146,6 @@ public virtual void Disconnect()
 			}
 
 			SetToolbar(null);
-			SetTitleBar(null, null);
 
 			if (_rootView.Content is RootNavigationView navView)
 				navView.Content = null;

src/Core/src/Platform/Windows/WindowRootView.cs

@@ -80,6 +80,8 @@ internal MenuBar? MenuBar
 			}
 		}
 
+		internal ITitleBar? TitleBar => _titleBar;
+
 		public DataTemplate? AppTitleBarTemplate
 		{
 			get => (DataTemplate?)GetValue(AppTitleBarTemplateProperty);