Detect when pages are popped from clicking on tab (#9086)

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue9006.cs

@@ -0,0 +1,83 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 9006, "[Bug] Unable to open a new Page for the second time in Xamarin.Forms Shell Tabbar",
+		PlatformAffected.iOS)]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.Shell)]
+#endif
+	public class Issue9006 : TestShell
+	{
+		protected override void Init()
+		{
+			Routing.RegisterRoute("Issue9006_ContentPage", typeof(ContentPage));
+			Routing.RegisterRoute("Issue9006_FinalPage", typeof(ContentPage));
+
+			var contentPage = AddBottomTab("Tab 1");
+			Items[0].CurrentItem.AutomationId = "Tab1AutomationId";
+			AddBottomTab("Ignore Me");
+
+			Label label = new Label()
+			{
+				Text = "Clicking on the first tab should pop you back to the root",
+				AutomationId = "FinalLabel"
+			};
+
+			Button button = null;
+			bool navigated = false;
+			button = new Button()
+			{
+				Text = "Click Me",
+				AutomationId = "Click Me",
+				Command = new Command(async () =>
+				{
+					await GoToAsync("Issue9006_ContentPage");
+					await GoToAsync("Issue9006_FinalPage");
+					
+					button.Text = "Click me again. If pages get pushed again then test has passed.";
+					DisplayedPage.Content = new StackLayout()
+					{
+						Children =
+						{
+							label
+						}
+					};
+					if (navigated)
+						label.Text = "Success";
+
+					navigated = true;
+				})
+			};
+
+			contentPage.Content = new StackLayout()
+			{
+				Children =
+				{
+					button
+				}
+			};
+		}
+
+
+#if UITEST && __IOS__
+		[Test]
+		public void ClickingOnTabToPopToRootDoesntBreakNavigation()
+		{
+			RunningApp.Tap("Click Me");
+			RunningApp.WaitForElement("FinalLabel");
+			RunningApp.Tap("Tab1AutomationId");
+			RunningApp.Tap("Click Me");
+			RunningApp.Tap("Success");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/TestPages/TestPages.cs

@@ -602,6 +602,14 @@ namespace Xamarin.Forms.Controls
 #endif
 		}
 
+		protected ContentPage DisplayedPage
+		{
+			get
+			{
+				return (ContentPage)(CurrentItem.CurrentItem as IShellSectionController).PresentedPage;
+			}
+		}
+
 		public ContentPage AddTopTab(string title)
 		{
 			var page = new ContentPage();
@@ -633,8 +641,15 @@ namespace Xamarin.Forms.Controls
 
 		public ContentPage AddBottomTab(string title)
 		{
-
 			ContentPage page = new ContentPage();
+			if (Items.Count == 0)
+			{
+				var item = AddContentPage(page);
+				item.Items[0].Items[0].Title = title ?? page.Title;
+				item.Items[0].Title = title ?? page.Title;
+				return page;
+			}
+
 			Items[0].Items.Add(new ShellSection()
 			{
 				Title = title,

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -11,6 +11,7 @@
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)CollectionViewGroupTypeIssue.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8262.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue9006.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8207.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue6362.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7505.cs" />
@@ -1684,4 +1685,4 @@
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
-</Project>
+</Project>

Xamarin.Forms.Core/Shell/IShellSectionController.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Threading.Tasks;
 using Xamarin.Forms.Internals;
 
@@ -21,8 +22,19 @@ namespace Xamarin.Forms
 
 		void SendInsetChanged(Thickness inset, double tabThickness);
 
+		void SendPopping(Task poppingCompleted);
+		void SendPoppingToRoot(Task finishedPopping);
+
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
 		void SendPopped();
+
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
 		void SendPopping(Page page);
+
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
 		void SendPopped(Page page);
 	}
 }

Xamarin.Forms.Core/Shell/ShellSection.cs

@@ -118,6 +118,45 @@ namespace Xamarin.Forms
 			_lastTabThickness = tabThickness;
 		}
 
+		async void IShellSectionController.SendPopping(Task poppingCompleted)
+		{
+			if (_navStack.Count <= 1)
+				throw new Exception("Nav Stack consistency error");
+
+			var page = _navStack[_navStack.Count - 1];
+
+			_navStack.Remove(page);
+			UpdateDisplayedPage();
+
+			await poppingCompleted;
+
+			RemovePage(page);
+			SendUpdateCurrentState(ShellNavigationSource.Pop);
+		}
+
+		async void IShellSectionController.SendPoppingToRoot(Task finishedPopping)
+		{
+			if (_navStack.Count <= 1)
+				throw new Exception("Nav Stack consistency error");
+
+			var oldStack = _navStack;
+			_navStack = new List<Page> { null };
+
+			for (int i = 1; i < oldStack.Count; i++)
+				oldStack[i].SendDisappearing();
+
+			UpdateDisplayedPage();
+			await finishedPopping;
+
+			for (int i = 1; i < oldStack.Count; i++)
+				RemovePage(oldStack[i]);
+
+			SendUpdateCurrentState(ShellNavigationSource.PopToRoot);
+		}
+
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
+
 		void IShellSectionController.SendPopped()
 		{
 			if (_navStack.Count <= 1)
@@ -131,6 +170,8 @@ namespace Xamarin.Forms
 			SendUpdateCurrentState(ShellNavigationSource.Pop);
 		}
 
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
 		void IShellSectionController.SendPopping(Page page)
 		{
 			if (_navStack.Count <= 1)
@@ -140,9 +181,11 @@ namespace Xamarin.Forms
 			SendAppearanceChanged();
 		}
 
+		[Obsolete]
+		[EditorBrowsable(EditorBrowsableState.Never)]
 		void IShellSectionController.SendPopped(Page page)
 		{
-			if(_navStack.Contains(page))
+			if (_navStack.Contains(page))
 				_navStack.Remove(page);
 
 			RemovePage(page);
@@ -313,6 +356,7 @@ namespace Xamarin.Forms
 
 			if (previousPage != DisplayedPage)
 			{
+				previousPage?.SendDisappearing();
 				PresentedPageAppearing();
 				SendAppearanceChanged();
 			}

Xamarin.Forms.Platform.iOS/Renderers/ShellSectionRenderer.cs

@@ -63,6 +63,7 @@ namespace Xamarin.Forms.Platform.iOS
 		TaskCompletionSource<bool> _popCompletionTask;
 		IShellSectionRootRenderer _renderer;
 		ShellSection _shellSection;
+		bool _ignorePopCall;
 
 		public ShellSectionRenderer(IShellContext context)
 		{
@@ -265,16 +266,48 @@ namespace Xamarin.Forms.Platform.iOS
 			DisposePage(page);
 		}
 
-		protected virtual async void OnPopToRootRequested(NavigationRequestedEventArgs e)
+		public override UIViewController[] PopToRootViewController(bool animated)
 		{
-			var animated = e.Animated;
+			if (!_ignorePopCall && ViewControllers.Length > 1)
+			{
+				ProcessPopToRoot();
+			}
 
+			return base.PopToRootViewController(animated);
+		}
+
+		async void ProcessPopToRoot()
+		{
 			var task = new TaskCompletionSource<bool>();
 			var pages = _shellSection.Stack.ToList();
 			_completionTasks[_renderer.ViewController] = task;
-			e.Task = task.Task;
+			((IShellSectionController)ShellSection).SendPoppingToRoot(task.Task);
+			await task.Task;
 
-			PopToRootViewController(animated);
+			for (int i = pages.Count - 1; i >= 1; i--)
+			{
+				var page = pages[i];
+				DisposePage(page);
+			}
+		}
+
+		protected virtual async void OnPopToRootRequested(NavigationRequestedEventArgs e)
+		{
+			var animated = e.Animated;
+			var task = new TaskCompletionSource<bool>();
+			var pages = _shellSection.Stack.ToList();
+
+			try
+			{
+				_ignorePopCall = true;
+				_completionTasks[_renderer.ViewController] = task;
+				e.Task = task.Task;
+				PopToRootViewController(animated);
+			}
+			finally
+			{
+				_ignorePopCall = false;
+			}
 
 			await e.Task;
 
@@ -328,6 +361,7 @@ namespace Xamarin.Forms.Platform.iOS
 			_ = _context.ApplyNativeImageAsync(ShellSection, ShellSection.IconProperty, icon =>
 			{
 				TabBarItem = new UITabBarItem(ShellSection.Title, icon, null);
+				TabBarItem.AccessibilityIdentifier = ShellSection.AutomationId ?? ShellSection.Title;
 			});
 		}
 
@@ -399,11 +433,10 @@ namespace Xamarin.Forms.Platform.iOS
 			var poppedPage = _shellSection.Stack[_shellSection.Stack.Count - 1];
 
 			// this is used to setup appearance changes based on the incoming page
-			((IShellSectionController)_shellSection).SendPopping(poppedPage);
+			((IShellSectionController)_shellSection).SendPopping(popTask);
 
 			await popTask;
 
-			((IShellSectionController)_shellSection).SendPopped(poppedPage);
 			DisposePage(poppedPage);
 		}
 
@@ -491,17 +524,22 @@ namespace Xamarin.Forms.Platform.iOS
 				navigationController.SetNavigationBarHidden(!navBarVisible, true);
 
 				var coordinator = viewController.GetTransitionCoordinator();
-				if (coordinator != null)
+				if (coordinator != null && coordinator.IsInteractive)
 				{
 					// handle swipe to dismiss gesture 
-					coordinator.NotifyWhenInteractionEndsUsingBlock((context) =>
-					{
-						if (!context.IsCancelled)
-						{
-							_self._popCompletionTask = new TaskCompletionSource<bool>();
-							_self.SendPoppedOnCompletion(_self._popCompletionTask.Task);
-						}
-					});
+					if (Forms.IsiOS10OrNewer)
+						coordinator.NotifyWhenInteractionChanges(OnInteractionChanged);
+					else
+						coordinator.NotifyWhenInteractionEndsUsingBlock(OnInteractionChanged);
+				}
+			}
+
+			void OnInteractionChanged(IUIViewControllerTransitionCoordinatorContext context)
+			{
+				if (!context.IsCancelled)
+				{
+					_self._popCompletionTask = new TaskCompletionSource<bool>();
+					_self.SendPoppedOnCompletion(_self._popCompletionTask.Task);
 				}
 			}
 		}