Fixed Net 8: Page and control Unloaded events firing on iOS when navigating to another page (#25852)

* Fix included and UI test case added

* Snapshot added for windows platform.

* Test case modified and committed

* Comments added for my fix.

* comments modified

* - fix up test and extension a bit

---------

Co-authored-by: Karthik Raja <karthikraja.kalaimani@syncfusion.com>
Co-authored-by: Shane Neuville <shneuvil@microsoft.com>

Author: 3 people

src/Controls/tests/TestCases.HostApp/Issues/Issue21916.cs

@@ -0,0 +1,72 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 21916, "Page and control Unloaded events firing on iOS when navigating to another page", PlatformAffected.iOS)]
+	public class Issue21916 : Shell
+	{
+		public Issue21916()
+		{
+			CurrentItem = new Issue21916_MainPage();
+		}
+
+		public class Issue21916_MainPage : ContentPage
+		{
+			int mainPageLoadedCount = 0;
+			int mainPageUnloadedCount = 0;
+			Label label;
+			bool isNavigated;
+			public Issue21916_MainPage()
+			{
+				var stack = new StackLayout();
+				label = new Label();
+				var Button = new Button();
+				Button.Text = "Click to navigate new page";
+				Button.AutomationId = "Button";
+				Button.Clicked += Clicked;
+				stack.Children.Add(Button);
+				stack.Children.Add(label);
+				this.Content = stack;
+				this.Loaded += MainPage_Loaded;
+				this.Unloaded += MainPage_UnLoaded;
+			}
+
+			private async void Clicked(object sender, EventArgs e)
+			{
+				isNavigated = true;
+				await Navigation.PushAsync(new Issue21916_NewPage());
+			}
+
+			private void MainPage_UnLoaded(object sender, EventArgs e)
+			{
+				mainPageUnloadedCount++;
+			}
+
+			private void MainPage_Loaded(object sender, EventArgs e)
+			{
+				if (isNavigated)
+				{
+					mainPageLoadedCount++;
+					label.Text = $"Unloaded event triggered {mainPageUnloadedCount} times\nLoaded event triggered {mainPageLoadedCount} times";
+				}
+			}
+		}
+
+		public class Issue21916_NewPage : ContentPage
+		{
+			public Issue21916_NewPage()
+			{
+				var stack = new StackLayout();
+				var Button = new Button();
+				Button.Text = "Click to navigate main page";
+				Button.AutomationId = "Button";
+				Button.Clicked += Clicked;
+				stack.Children.Add(Button);
+				this.Content = stack;
+			}
+
+			private void Clicked(object sender, EventArgs e)
+			{
+				Shell.Current.GoToAsync("..");
+			}
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue21916.cs

@@ -0,0 +1,28 @@
+#if !ANDROID && !MACCATALYST
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue21916 : _IssuesUITest
+	{
+		public Issue21916(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "Page and control Unloaded events firing on iOS when navigating to another page"; 
+		
+		[Test]
+		[Category(UITestCategories.Shell)]
+		public void Shell_Issue21916()
+		{
+			App.WaitForElement("Button");
+			App.Click("Button");
+			App.WaitForElement("Button");
+			App.Click("Button");
+			VerifyScreenshot();
+		}
+	}
+}
+#endif

src/Controls/tests/TestCases.WinUI.Tests/snapshots/windows/Shell_Issue21916.png

@@ -648,7 +648,9 @@ internal static IDisposable OnLoaded(this UIView uiView, Action action)
 
 				void OnLifeCycleEventsMovedToWindow(object? sender, EventArgs e)
 				{
-					OnLoadedCheck(null);
+					//The MovedToWindow fires multiple times during navigation animations, causing repeated OnLoadedCheck calls. 
+					//BeginInvokeOnMainThread ensures OnLoadedCheck executes after all window transitions are complete.
+					uiView.BeginInvokeOnMainThread(() => OnLoadedCheck(null));
 				}
 			}
 			else
@@ -728,7 +730,9 @@ internal static IDisposable OnUnloaded(this UIView uiView, Action action)
 
 				void OnLifeCycleEventsMovedToWindow(object? sender, EventArgs e)
 				{
-					UnLoadedCheck();
+					//The MovedToWindow fires multiple times during navigation animations, causing repeated UnLoadedCheck calls. 
+					//BeginInvokeOnMainThread ensures UnLoadedCheck executes after all window transitions are complete.
+					uiView.BeginInvokeOnMainThread(UnLoadedCheck);
 				}
 			}