Set Window Parent before initialize the child ContentPage (#8653)

* Set Window Parent before initialize the child ContentPage

* - fire appearing after parent is set on window

* Update Application.Impl.cs

* - fix up tests

* - fix application stub

* - wire up test app to test window

* - fix additional windows

Co-authored-by: Shane Neuville <[email protected]>

src/Controls/src/Core/HandlerImpl/Application/Application.Impl.cs

@@ -139,6 +139,15 @@ void AddWindow(Window window)
 
 			if (window is NavigableElement ne)
 				ne.NavigationProxy.Inner = NavigationProxy;
+
+			// Once the window has been attached to the application. 
+			// The window will finish propagating events like `Appearing`.
+			//
+			// I could fire this from 'OnParentSet` inside Window but
+			// I'd rather wait until Application is done wiring itself
+			// up to the window before triggering any down stream life cycle
+			// events.
+			window.FinishedAddingWindowToApplication(this);
 		}
 	}
-}
+}

src/Controls/src/Core/HandlerImpl/Window/Window.Impl.cs

@@ -264,15 +264,21 @@ void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
 				{
 					_visualChildren.Add(item);
 					OnChildAdded(item);
-					// TODO once we have better life cycle events on pages 
-					if (item is Page)
+
+					if (Parent != null && item is Page)
 					{
 						SendWindowAppearing();
 					}
 				}
 			}
 		}
 
+		internal void FinishedAddingWindowToApplication(Application application)
+		{
+			if (Parent != null)
+				SendWindowAppearing();
+		}
+
 		void SendWindowAppearing()
 		{
 			Page?.SendAppearing();

src/Controls/src/Core/Page.cs

@@ -463,8 +463,10 @@ public void SendAppearing()
 		{
 			// Only fire appearing if the page has been added to the windows
 			// Visual Hierarchy
+			// The window/application will take care of re-firing this appearing 
+			// if it needs to
 			var window = this.FindParentOfType<Window>();
-			if (window == null)
+			if (window?.Parent == null)
 			{
 				return;
 			}

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

@@ -402,7 +402,7 @@ public void ThrowsExceptionWhenAddingAlreadyParentedFlyout()
 		}
 
 		[Test]
-		public void FlyoutPageAppearingAnDisappearingPropagatesToFlyout()
+		public void FlyoutPageAppearingAndDisappearingPropagatesToFlyout()
 		{
 			int disappearing = 0;
 			int appearing = 0;
@@ -414,7 +414,7 @@ public void FlyoutPageAppearingAnDisappearingPropagatesToFlyout()
 				Detail = new ContentPage() { Title = "detail" }
 			};
 
-			_ = new Window(flyoutPage);
+			_ = new TestWindow(flyoutPage);
 			flyout.Appearing += (_, __) => appearing++;
 			flyout.Disappearing += (_, __) => disappearing++;
 
@@ -433,7 +433,7 @@ public void FlyoutPageAppearingAnDisappearingPropagatesToFlyout()
 		}
 
 		[Test]
-		public void FlyoutPageAppearingAnDisappearingPropagatesToDetail()
+		public void FlyoutPageAppearingAndDisappearingPropagatesToDetail()
 		{
 			int disappearing = 0;
 			int appearing = 0;
@@ -445,7 +445,7 @@ public void FlyoutPageAppearingAnDisappearingPropagatesToDetail()
 				Detail = detail
 			};
 
-			_ = new Window(flyoutPage);
+			_ = new TestWindow(flyoutPage);
 
 			detail.Appearing += (_, __) => appearing++;
 			detail.Disappearing += (_, __) => disappearing++;

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

@@ -22,7 +22,7 @@ public async Task AppearingFiresForInitialPage(bool useMaui)
 			NavigationPage nav = new TestNavigationPage(useMaui, contentPage);
 
 			Assert.IsNull(resultPage);
-			_ = new Window(nav);
+			_ = new TestWindow(nav);
 			Assert.AreEqual(resultPage, contentPage);
 		}
 
@@ -44,7 +44,7 @@ public async Task PushLifeCycle(bool useMaui)
 				=> pageAppearing = (ContentPage)sender;
 
 			NavigationPage nav = new TestNavigationPage(useMaui, initialPage);
-			_ = new Window(nav);
+			_ = new TestWindow(nav);
 			nav.SendAppearing();
 
 			await nav.PushAsync(pushedPage);
@@ -64,7 +64,7 @@ public async Task PopLifeCycle(bool useMaui)
 			ContentPage pageDisappeared = null;
 
 			NavigationPage nav = new TestNavigationPage(useMaui, initialPage);
-			_ = new Window(nav);
+			_ = new TestWindow(nav);
 			nav.SendAppearing();
 
 			initialPage.Appearing += (sender, _)
@@ -94,7 +94,7 @@ public async Task RemoveLastPage(bool useMaui)
 			ContentPage pageDisappeared = null;
 
 			NavigationPage nav = new TestNavigationPage(useMaui, initialPage);
-			_ = new Window(nav);
+			_ = new TestWindow(nav);
 			nav.SendAppearing();
 
 			initialPage.Appearing += (sender, _)

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

@@ -694,7 +694,7 @@ public void TabBarSetsOnWindowForSingleNavigationPage()
 		{
 			var contentPage1 = new ContentPage();
 			var navigationPage = new TestNavigationPage(true, contentPage1);
-			var window = new Window(navigationPage);
+			var window = new TestWindow(navigationPage);
 
 			Assert.IsNotNull(window.Toolbar);
 			Assert.IsNull(contentPage1.Toolbar);
@@ -713,7 +713,7 @@ public void TabBarSetsOnFlyoutPage()
 				Flyout = new ContentPage() { Title = "Flyout" }
 			};
 
-			var window = new Window(flyoutPage);
+			var window = new TestWindow(flyoutPage);
 
 			Assert.IsNull(window.Toolbar);
 			Assert.IsNull(contentPage1.Toolbar);
@@ -740,7 +740,7 @@ public void TabBarSetsOnWindowWithFlyoutPageNestedInTabbedPage()
 				}
 			};
 
-			var window = new Window(tabbedPage);
+			var window = new TestWindow(tabbedPage);
 
 			Assert.IsNotNull(window.Toolbar);
 			Assert.IsNull(contentPage1.Toolbar);
@@ -752,7 +752,7 @@ public void TabBarSetsOnWindowWithFlyoutPageNestedInTabbedPage()
 		[Test]
 		public async Task TabBarSetsOnModalPageWhenWindowAlsoHasNavigationPage()
 		{
-			var window = new Window(new TestNavigationPage(true, new ContentPage()));
+			var window = new TestWindow(new TestNavigationPage(true, new ContentPage()));
 			var contentPage1 = new ContentPage();
 			var navigationPage = new TestNavigationPage(true, contentPage1);
 			await window.Navigation.PushModalAsync(navigationPage);
@@ -765,7 +765,7 @@ public async Task TabBarSetsOnModalPageWhenWindowAlsoHasNavigationPage()
 		[Test]
 		public async Task TabBarSetsOnModalPageForSingleNavigationPage()
 		{
-			var window = new Window(new ContentPage());
+			var window = new TestWindow(new ContentPage());
 			var contentPage1 = new ContentPage();
 			var navigationPage = new TestNavigationPage(true, contentPage1);
 			await window.Navigation.PushModalAsync(navigationPage);
@@ -778,7 +778,7 @@ public async Task TabBarSetsOnModalPageForSingleNavigationPage()
 		[Test]
 		public async Task TabBarSetsOnFlyoutPageInsideModalPage()
 		{
-			var window = new Window(new ContentPage());
+			var window = new TestWindow(new ContentPage());
 			var contentPage1 = new ContentPage();
 			var navigationPage = new TestNavigationPage(true, contentPage1);
 			var flyoutPage = new FlyoutPage()
@@ -799,7 +799,7 @@ public async Task TabBarSetsOnFlyoutPageInsideModalPage()
 		public async Task TabBarSetsOnModalPageWithFlyoutPageNestedInTabbedPage()
 		{
 			// ModalPage => TabbedPage => FlyoutPage => NavigationPage
-			var window = new Window(new ContentPage());
+			var window = new TestWindow(new ContentPage());
 			var contentPage1 = new ContentPage();
 			var navigationPage = new TestNavigationPage(true, contentPage1);
 			var flyoutPage = new FlyoutPage()

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

@@ -123,7 +123,7 @@ public async Task PushModalPage()
 		{
 			var previousPage = new LCPage();
 			var lcPage = new LCPage();
-			var window = new Window(previousPage);
+			var window = new TestWindow(previousPage);
 
 			await window.Navigation.PushModalAsync(lcPage);
 
@@ -141,7 +141,7 @@ public async Task PopModalPage()
 			var firstPage = new LCPage();
 			var poppedPage = new LCPage();
 
-			var window = new Window(firstPage);
+			var window = new TestWindow(firstPage);
 			await window.Navigation.PushModalAsync(poppedPage);
 			await window.Navigation.PopModalAsync();
 
@@ -161,7 +161,7 @@ public async Task PopToAModalPage()
 			var firstModalPage = new LCPage();
 			var secondModalPage = new LCPage();
 
-			var window = new Window(firstPage);
+			var window = new TestWindow(firstPage);
 			await window.Navigation.PushModalAsync(firstModalPage);
 			await window.Navigation.PushModalAsync(secondModalPage);
 
@@ -188,7 +188,7 @@ public async Task PushSecondModalPage()
 			var firstModalPage = new LCPage();
 			var secondModalPage = new LCPage();
 
-			var window = new Window(firstPage);
+			var window = new TestWindow(firstPage);
 			await window.Navigation.PushModalAsync(firstModalPage);
 
 			firstModalPage.ClearNavigationArgs();

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

@@ -335,7 +335,7 @@ public void BusySentWhenBusyPageAppears()
 
 			Assert.That(sent, Is.False, "Busy message sent while not visible");
 
-			_ = new Window(page);
+			_ = new TestWindow(page);
 
 			Assert.That(sent, Is.True, "Busy message not sent when visible");
 		}
@@ -344,7 +344,7 @@ public void BusySentWhenBusyPageAppears()
 		public void BusySentWhenBusyPageDisappears()
 		{
 			var page = new ContentPage { IsBusy = true };
-			_ = new Window(page);
+			_ = new TestWindow(page);
 			((IPageController)page).SendAppearing();
 
 			var sent = false;
@@ -366,7 +366,7 @@ public void BusySentWhenVisiblePageSetToBusy()
 			MessagingCenter.Subscribe<Page, bool>(this, Page.BusySetSignalName, (p, b) => sent = true);
 
 			var page = new ContentPage();
-			_ = new Window(page);
+			_ = new TestWindow(page);
 			((IPageController)page).SendAppearing();
 
 			Assert.That(sent, Is.False, "Busy message sent appearing while not busy");
@@ -465,7 +465,7 @@ public void SendAppearing()
 			bool sent = false;
 			page.Appearing += (sender, args) => sent = true;
 
-			_ = new Window(page);
+			_ = new TestWindow(page);
 
 			Assert.True(sent);
 		}
@@ -474,7 +474,7 @@ public void SendAppearing()
 		public void SendDisappearing()
 		{
 			var page = new ContentPage();
-			_ = new Window(page);
+			_ = new TestWindow(page);
 
 			((IPageController)page).SendAppearing();
 
@@ -494,7 +494,7 @@ public void SendAppearingDoesntGetCalledMultipleTimes()
 			int countAppearing = 0;
 			page.Appearing += (sender, args) => countAppearing++;
 
-			_ = new Window(page);
+			_ = new TestWindow(page);
 			((IPageController)page).SendAppearing();
 
 			Assert.That(countAppearing, Is.EqualTo(1));
@@ -524,7 +524,7 @@ public void SendAppearingToChildrenAfter()
 			};
 			navPage.Appearing += (sender, e) => sentNav = true;
 
-			_ = new Window(navPage);
+			_ = new TestWindow(navPage);
 
 			Assert.True(sentNav);
 			Assert.True(sent);
@@ -537,7 +537,7 @@ public void SendDisappearingToChildrenPageFirst()
 			var page = new ContentPage();
 
 			var navPage = new NavigationPage(page);
-			_ = new Window(navPage);
+			_ = new TestWindow(navPage);
 			((IPageController)navPage).SendAppearing();
 
 			bool sentNav = false;

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

@@ -324,7 +324,7 @@ public List<List<Element>> GenerateTestFlyoutItems()
 
 			public TestShell()
 			{
-				_ = new Window() { Page = this };
+				_ = new TestWindow() { Page = this };
 				Routing.RegisterRoute(nameof(TestPage1), typeof(TestPage1));
 				Routing.RegisterRoute(nameof(TestPage2), typeof(TestPage2));
 				Routing.RegisterRoute(nameof(TestPage3), typeof(TestPage3));

src/Controls/tests/Core.UnitTests/TestClasses/TestApp.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.Maui.Controls.Core.UnitTests
+{
+	public class TestApp : Application
+	{
+		ContentPage _withPage;
+		TestWindow _window;
+
+		public TestApp() : base(false)
+		{
+
+		}
+
+		public TestApp(TestWindow window) : base(false)
+		{
+			_window = window;
+		}
+
+		public TestWindow CreateWindow() =>
+			(TestWindow)(this as IApplication).CreateWindow(null);
+
+		protected override Window CreateWindow(IActivationState activationState)
+		{
+			return _window ?? new TestWindow(_withPage ?? new ContentPage());
+		}
+
+		public TestWindow CreateWindow(ContentPage withPage)
+		{
+			_withPage = withPage;
+			return (TestWindow)(this as IApplication).CreateWindow(null);
+		}
+	}
+}

src/Controls/tests/Core.UnitTests/TestClasses/TestWindow.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.Maui.Controls.Core.UnitTests
+{
+	public class TestWindow : Window
+	{
+		public TestWindow()
+		{
+
+		}
+
+		public TestWindow(Page page) : base(page)
+		{
+		}
+
+		protected override void OnPropertyChanged([CallerMemberName] string propertyName = null)
+		{
+			base.OnPropertyChanged(propertyName);
+			if (propertyName == PageProperty.PropertyName &&
+				Parent == null)
+			{
+				var app = new TestApp(this);
+				_ = (app as IApplication).CreateWindow(null);
+			}
+		}
+	}
+}