fix(NavigationBar): Ensure proper iOS back button behavior (#548)

samples/Uno.Toolkit.Samples/Uno.Toolkit.Samples.Shared/Shell.xaml

@@ -11,15 +11,13 @@
 			 mc:Ignorable="wasm xamarin">
 
 	<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
-
 		<Grid.RowDefinitions>
 			<RowDefinition x:Name="TopPaddingRow"
 						   Height="0" />
 			<RowDefinition Height="Auto" />
 			<RowDefinition Height="*" />
 		</Grid.RowDefinitions>
 
-
 		<!-- We set CompactModeThresholdWidth to a very high value so that it never happens. We don't want to use the compact mode. -->
 		<muxc:NavigationView Grid.Row="2"
 							 x:Name="NavigationViewControl"

src/Uno.Toolkit.RuntimeTests/Tests/NavigationBarTests.cs

@@ -215,27 +215,16 @@ public async Task Can_Set_MainCommand_Label_Or_Content()
 			await UnitTestsUIContentHelper.WaitForIdle();
 
 			// FirstPage
-			var firstNavBar = await LoadNavigationBarFrom<FirstPage>();
-			Assert.IsNull(firstNavBar?.BackItem);
+			var firstNavBar = await frame.NavigateAndGetNavBar<FirstPage>();
+			Assert.IsNull(firstNavBar?.GetNativeNavBar()?.BackItem);
 
 			// LabelTitlePage
-			var labelTitleNavBar = await LoadNavigationBarFrom<LabelTitlePage>();
-			Assert.AreEqual("Label Title", labelTitleNavBar?.BackItem?.BackButtonTitle);
+			var labelTitleNavBar = await frame.NavigateAndGetNavBar<LabelTitlePage>();
+			Assert.AreEqual("Label Title", labelTitleNavBar?.GetNativeNavBar()?.BackItem?.BackButtonTitle);
 
 			// ContentTitlePage 
-			var contentTitleNavBar = await LoadNavigationBarFrom<ContentTitlePage>();
-			Assert.AreEqual("Content Title", contentTitleNavBar?.BackItem?.BackButtonTitle);
-
-			async Task<UINavigationBar?> LoadNavigationBarFrom<TPage>() where TPage : Page
-			{
-				frame.Navigate(typeof(TPage));
-				await UnitTestsUIContentHelper.WaitForIdle();
-
-				var page = frame.Content as TPage;
-				await UnitTestsUIContentHelper.WaitForLoaded(page!);
-				var navBar = page?.FindChild<NavigationBar>();
-				return navBar?.GetRenderer<NavigationBar, NavigationBarRenderer>(null)?.Native;
-			}	
+			var contentTitleNavBar = await frame.NavigateAndGetNavBar<ContentTitlePage>();
+			Assert.AreEqual("Content Title", contentTitleNavBar?.GetNativeNavBar()?.BackItem?.BackButtonTitle);	
 		}
 
 		[TestMethod]
@@ -266,7 +255,7 @@ public async Task MainCommand_Use_LeftBarButtonItem_When_No_BackStack()
 				var firstPage = frame.Content as NavBarFirstPage;
 				firstPageNavBar = firstPage?.FindChild<NavigationBar>();
 
-				var renderedNativeNavItem = firstPageNavBar?.GetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>(null)?.Native;
+				var renderedNativeNavItem = firstPageNavBar.GetNativeNavItem();
 
 				Assert.IsNotNull(renderedNativeNavItem?.LeftBarButtonItem);
 
@@ -277,7 +266,7 @@ public async Task MainCommand_Use_LeftBarButtonItem_When_No_BackStack()
 				var secondPage = frame.Content as NavBarSecondPage;
 				secondPageNavBar = secondPage?.FindChild<NavigationBar>();
 
-				renderedNativeNavItem = secondPageNavBar?.GetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>(null)?.Native;
+				renderedNativeNavItem = secondPageNavBar.GetNativeNavItem();
 
 				Assert.IsNull(renderedNativeNavItem?.LeftBarButtonItem);
 			}
@@ -313,14 +302,30 @@ public async Task NavigationBar_Does_Render_Within_AutoLayout()
 			AssertNavigationBar(frame);
 		}
 
+		[TestMethod]
+		public async Task NavigationBar_Renders_BackItem_Within_AutoLayout()
+		{
+			var frame = new Frame { Width = 600, Height = 200 };;
+			await UnitTestUIContentHelperEx.SetContentAndWait(frame);
+
+			var firstNavBar = await frame.NavigateAndGetNavBar<NavBarAutoLayoutPage>();
+
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			frame.Navigate(typeof(NavBarAutoLayoutPage2));
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			await UnitTestUIContentHelperEx.WaitFor(() => firstNavBar?.GetNativeNavItem()?.BackButtonTitle == "Hello");
+		}
+
 		private static void AssertNavigationBar(Frame frame)
 		{
 			var page = frame.Content as Page;
 			var presenter = frame.FindChild<NativeFramePresenter>();
 			var navBar = page?.FindChild<NavigationBar>();
 
-			var renderedNativeNavItem = navBar?.GetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>(null)?.Native;
-			var renderedNativeNavBar = navBar?.GetRenderer<NavigationBar, NavigationBarRenderer>(null)?.Native;
+			var renderedNativeNavItem = navBar.GetNativeNavItem();
+			var renderedNativeNavBar = navBar.GetNativeNavBar();
 
 			Assert.IsNotNull(presenter);
 			Assert.IsFalse(presenter!.NavigationController.NavigationBarHidden);
@@ -329,6 +334,8 @@ private static void AssertNavigationBar(Frame frame)
 			Assert.AreSame(renderedNativeNavBar, presenter.NavigationController.NavigationBar);
 		}
 
+
+
 		private sealed partial class FirstPage : Page
 		{
 			public FirstPage()
@@ -383,5 +390,28 @@ public NavBarTestPage()
 		}
 #endif
 	}
+
+#if __IOS__
+	public static class NavigationBarTestHelper
+	{
+		public static UINavigationBar? GetNativeNavBar(this NavigationBar? navBar) => navBar
+			?.TryGetRenderer<NavigationBar, NavigationBarRenderer>()
+			?.Native;
+
+		public static UINavigationItem? GetNativeNavItem(this NavigationBar? navBar) => navBar
+			?.TryGetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>()
+			?.Native;
+
+		public static async Task<NavigationBar?> NavigateAndGetNavBar<TPage>(this Frame frame) where TPage : Page
+		{
+			frame.Navigate(typeof(TPage));
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			var page = frame.Content as TPage;
+			await UnitTestsUIContentHelper.WaitForLoaded(page!);
+			return page?.FindChild<NavigationBar>();
+		}	
+	}
+#endif
 }
 

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarAutoLayoutPage2.xaml

@@ -0,0 +1,18 @@
+<Page x:Class="Uno.Toolkit.RuntimeTests.Tests.TestPages.NavBarAutoLayoutPage2"
+	  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	  xmlns:local="using:Uno.Toolkit.RuntimeTests.Tests.TestPages"
+	  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	  xmlns:utu="using:Uno.Toolkit.UI"
+	  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	  mc:Ignorable="d"
+	  Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+	<utu:AutoLayout>
+		<utu:NavigationBar Content="Testing 2">
+			<utu:NavigationBar.MainCommand>
+				<AppBarButton Label="Hello" />
+			</utu:NavigationBar.MainCommand>
+		</utu:NavigationBar>
+	</utu:AutoLayout>
+</Page>

src/Uno.Toolkit.RuntimeTests/Tests/TestPages/NavBarAutoLayoutPage2.xaml.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Uno.Toolkit.UI;
+
+#if IS_WINUI
+using Microsoft.UI;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.UI.Xaml.Data;
+using Microsoft.UI.Xaml.Input;
+using Microsoft.UI.Xaml.Media;
+using Microsoft.UI.Xaml.Navigation;
+#else
+using Windows.UI;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+#endif
+
+namespace Uno.Toolkit.RuntimeTests.Tests.TestPages
+{
+	public sealed partial class NavBarAutoLayoutPage2 : Page
+	{
+		public NavBarAutoLayoutPage2()
+		{
+			this.InitializeComponent();
+		}
+	}
+}

src/Uno.Toolkit.UI/Controls/NavigationBar/AppBarButtonRenderer.Android.cs

@@ -44,9 +44,18 @@ internal class AppBarButtonRenderer : Renderer<AppBarButton, IMenuItem>
 		private bool _isInOverflow;
 		private DependencyObject? _elementParent;
 
-		public AppBarButtonRenderer(AppBarButton element, bool isInOverflow = false) : base(element)
+		public bool IsInOverflow
+		{
+			get => _isInOverflow;
+			set
+			{
+				_isInOverflow = value;
+				Invalidate();
+			}
+		}
+
+		public AppBarButtonRenderer(AppBarButton element) : base(element)
 		{
-			_isInOverflow = isInOverflow;
 			element.ViewAttachedToWindow += OnElementAttachedToWindow;
 		}
 

src/Uno.Toolkit.UI/Controls/NavigationBar/AppBarButtonRenderer.iOS.cs

@@ -124,7 +124,6 @@ protected override void Render()
 			native.Image = null;
 			native.ClearCustomView();
 			native.Title = element.Content is string content ? content : element.Label;
-
 			if (element.Icon != null)
 			{
 				switch (element.Icon)

src/Uno.Toolkit.UI/Controls/NavigationBar/NativeFramePresenter.iOS.cs

@@ -861,8 +861,7 @@ public FrameNavigationController() : base(typeof(UnoNavigationBar), typeof(UIToo
 			public override UIViewController PopViewController(bool animated)
 			{
 				var lowerNavigationBar = LowerController?.GetNavigationBar();
-				var renderer = lowerNavigationBar?.GetRenderer(() => (NavigationBarRenderer?)null);
-				if (renderer != null)
+				if (lowerNavigationBar?.TryGetRenderer<NavigationBar, NavigationBarRenderer>() is { } renderer)
 				{
 					// Set navigation bar properties for page about to become visible. This gives a nice animation and works around bug on 
 					// iOS 11.2 where TitleTextAttributes aren't updated properly (https://openradar.appspot.com/37567828)
@@ -878,10 +877,11 @@ public override void PushViewController(UIViewController viewController, bool an
 
 				if (viewController is PageViewController pvc)
 				{
-					var pushedNavBar = pvc.GetNavigationBar();
-
-					var renderer = pushedNavBar?.GetRenderer(() => (NavigationBarNavigationItemRenderer?)null);
-					renderer?.SetBackItem(LowerController?.NavigationItem);
+					var pushedNavBar = pvc.View?.FindTopNavigationBar();
+					if (pushedNavBar?.TryGetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>() is { } renderer)
+					{
+						renderer.BackItem = LowerController?.NavigationItem;
+					}
 				}
 			}
 		}

src/Uno.Toolkit.UI/Controls/NavigationBar/NativeNavigationBarPresenter.Android.cs

@@ -51,7 +51,7 @@ private void OnLoaded(object sender, RoutedEventArgs e)
 			var navBar = TemplatedParent as NavigationBar;
 			if (navBar is { })
 			{
-				Content = navBar.GetRenderer(() => new NavigationBarRenderer(navBar)).Native;
+				Content = navBar.GetOrAddDefaultRenderer().Native;
 				navBar.MainCommand.Click += OnMainCommandClicked;
 				_mainCommandClickHandler.Disposable = null;
 				_mainCommandClickHandler.Disposable = Disposable.Create(() => navBar.MainCommand.Click -= OnMainCommandClicked);

src/Uno.Toolkit.UI/Controls/NavigationBar/NativeNavigationBarPresenter.iOS.cs

@@ -71,15 +71,10 @@ private void OnLoaded(object sender, RoutedEventArgs e)
 			{
 				navBar = TemplatedParent as NavigationBar;
 				_navBarRef = new WeakReference<NavigationBar?>(navBar);
-
-				_navigationBar = navBar?.GetRenderer(RendererFactory).Native;
-
-			}
-			else
-			{
-				_navigationBar = navBar?.ResetRenderer(RendererFactory).Native;
 			}
 
+			_navigationBar = navBar?.GetOrAddDefaultRenderer().Native;
+
 			if (navBar is { })
 			{
 				navBar.MainCommand.Click += OnMainCommandClick;
@@ -133,15 +128,6 @@ private void OnMainCommandClick(object sender, RoutedEventArgs e)
 			}
 		}
 
-		NavigationBarRenderer RendererFactory()
-		{
-			NavigationBar? navBar = null;
-
-			_navBarRef?.TryGetTarget(out navBar);
-
-			return new NavigationBarRenderer(navBar!);
-		}
-
 		protected override Size MeasureOverride(Size size)
 		{
 			var measuredSize = base.MeasureOverride(size);

src/Uno.Toolkit.UI/Controls/NavigationBar/NavigationAppBarButtonRenderer.Android.cs

@@ -39,13 +39,19 @@ namespace Uno.Toolkit.UI
 {
 	internal class NavigationAppBarButtonRenderer : Renderer<AppBarButton, Toolbar>
 	{
-		private readonly MainCommandMode _mode;
-
-		public NavigationAppBarButtonRenderer(AppBarButton element, MainCommandMode mode) : base(element) 
+		private MainCommandMode _mode;
+		public MainCommandMode Mode
 		{
-			_mode = mode;
+			get => _mode;
+			set
+			{
+				_mode = value;
+				Invalidate();
+			}
 		}
 
+		public NavigationAppBarButtonRenderer(AppBarButton element) : base(element) { }
+
 		protected override Toolbar CreateNativeInstance() => throw new NotSupportedException("The Native instance must be provided.");
 
 		protected override IEnumerable<IDisposable> Initialize()

src/Uno.Toolkit.UI/Controls/NavigationBar/NavigationBarHelper.iOS.cs

@@ -2,6 +2,8 @@
 using System;
 using System.Linq;
 using UIKit;
+using SpriteKit;
+using Microsoft.UI.Xaml.Automation.Peers;
 
 #if IS_WINUI
 using Microsoft.UI.Xaml;
@@ -15,14 +17,18 @@ namespace Uno.Toolkit.UI
 {
 	internal static class NavigationBarHelper
 	{
-		internal static void SetNavigationBar(NavigationBar NavigationBar, UIKit.UINavigationBar? navigationBar)
+		internal static void SetNavigationBar(NavigationBar navigationBar, UIKit.UINavigationBar? uiNavigationBar)
 		{
-			NavigationBar.GetRenderer(() => new NavigationBarRenderer(NavigationBar)).Native = navigationBar;
+			navigationBar.AddOrUpdateRenderer(
+				onCreate: navBar => new NavigationBarRenderer(navBar) { Native = uiNavigationBar },
+				onUpdate: (navBar, renderer) => renderer.Native = uiNavigationBar);
 		}
 
-		internal static void SetNavigationItem(NavigationBar NavigationBar, UIKit.UINavigationItem? navigationItem)
+		internal static void SetNavigationItem(NavigationBar navigationBar, UIKit.UINavigationItem? navigationItem)
 		{
-			NavigationBar.GetRenderer(() => new NavigationBarNavigationItemRenderer(NavigationBar)).Native = navigationItem;
+			navigationBar.AddOrUpdateRenderer(
+				onCreate: navBar => new NavigationBarNavigationItemRenderer(navBar) { Native = navigationItem },
+				onUpdate: (navBar, renderer) => renderer.Native = navigationItem);
 		}
 
 		/// <summary>
@@ -139,11 +145,25 @@ private static void EnsureNavigationItem(NavigationBar topNavigationBar, UIViewC
 		{
 			// The Native view from the renderer may have been set to a dummy NavigationItem if we were not able to find
 			// a NavigationBar in the PageCreated method. If that is the case, set it to the pageController's NavigationItem
-			var nativeItem = topNavigationBar.GetRenderer(() => (NavigationBarNavigationItemRenderer?)null)?.Native;
-			if (!ReferenceEquals(nativeItem, pageController.NavigationItem))
+			var renderer = topNavigationBar.TryGetRenderer<NavigationBar, NavigationBarNavigationItemRenderer>();
+
+			if (!ReferenceEquals(renderer?.Native, pageController.NavigationItem))
 			{
 				SetNavigationItem(topNavigationBar, pageController.NavigationItem);
 			}
+
+			// We should also ensure that the renderer's BackItem is set to the previous page's NavigationItem
+			// in order to ensure that the back button icon and label are properly rendered.
+			var vcs = pageController.NavigationController?.ViewControllers;
+			var lowerVc = vcs?.Length > 1 ? vcs[vcs.Length - 2] : null;
+
+			if (lowerVc != null && renderer is { })
+			{
+				if (!ReferenceEquals(renderer.BackItem, lowerVc.NavigationItem))
+				{
+					renderer.BackItem = lowerVc.NavigationItem;
+				}
+			}
 		}
 
 		/// <summary>