[Android] Fix for App Hang When PopModalAsync Is Called Immediately After PushModalAsync with Task.Yield()

src/Controls/src/Core/Platform/ModalNavigationManager/ModalNavigationManager.Android.cs

@@ -107,7 +107,7 @@ Task<Page> PopModalPlatformAsync(bool animated)
 				return Task.FromResult(modal);
 			}
 
-			var source = new TaskCompletionSource<Page>();
+			var source = new TaskCompletionSource<Page>(TaskCreationOptions.RunContinuationsAsynchronously);
 
 			if (animated && dialogFragment.View is not null)
 			{
@@ -168,8 +168,6 @@ async Task PushModalPlatformAsync(Page modal, bool animated)
 
 		async Task PresentModal(Page modal, bool animated)
 		{
-			TaskCompletionSource<bool> animationCompletionSource = new();
-
 			var parentView = GetModalParentView();
 
 			var dialogFragment = new ModalFragment(WindowMauiContext, modal)
@@ -185,19 +183,32 @@ async Task PresentModal(Page modal, bool animated)
 
 			if (animated)
 			{
-				dialogFragment!.AnimationEnded += OnAnimationEnded;
+				TaskCompletionSource<bool> animationCompletionSource = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+				dialogFragment.AnimationEnded += OnAnimationEnded;
+
+				void OnAnimationEnded(object? sender, EventArgs e)
+				{
+					dialogFragment.AnimationEnded -= OnAnimationEnded;
+					animationCompletionSource.SetResult(true);
+				}
 
 				await animationCompletionSource.Task;
 			}
 			else
 			{
-				animationCompletionSource.TrySetResult(true);
-			}
+				// Non-animated modals need to wait for presentation completion to prevent race conditions
+				TaskCompletionSource<bool> presentationCompletionSource = new();
 
-			void OnAnimationEnded(object? sender, EventArgs e)
-			{
-				dialogFragment!.AnimationEnded -= OnAnimationEnded;
-				animationCompletionSource.SetResult(true);
+				dialogFragment.PresentationCompleted += OnPresentationCompleted;
+
+				void OnPresentationCompleted(object? sender, EventArgs e)
+				{
+					dialogFragment.PresentationCompleted -= OnPresentationCompleted;
+					presentationCompletionSource.SetResult(true);
+				}
+
+				await presentationCompletionSource.Task;
 			}
 		}
 
@@ -208,9 +219,10 @@ internal class ModalFragment : DialogFragment
 			NavigationRootManager? _navigationRootManager;
 			static readonly ColorDrawable TransparentColorDrawable = new(AColor.Transparent);
 			bool _pendingAnimation = true;
+			bool _pendingNavigation = true;
 
-			public event EventHandler? AnimationEnded;
-
+			internal event EventHandler? AnimationEnded;
+			internal event EventHandler? PresentationCompleted;
 
 			public bool IsAnimated { get; internal set; }
 
@@ -356,13 +368,25 @@ public override void OnStart()
 				var dialog = Dialog;
 
 				if (dialog is null || dialog.Window is null || View is null)
+				{
+					// SAFETY: Fire event even on early return to prevent deadlock
+					FirePresentationCompleted();
 					return;
+				}
 
 				int width = ViewGroup.LayoutParams.MatchParent;
 				int height = ViewGroup.LayoutParams.MatchParent;
 				dialog.Window.SetLayout(width, height);
 			}
 
+			public override void OnResume()
+			{
+				base.OnResume();
+
+				// Signal that the modal is fully presented and ready
+				FirePresentationCompleted();
+			}
+
 			public override void OnDismiss(IDialogInterface dialog)
 			{
 				_modal.PropertyChanged -= OnModalPagePropertyChanged;
@@ -385,6 +409,9 @@ public override void OnDestroy()
 			{
 				base.OnDestroy();
 				FireAnimationEnded();
+
+				// SAFETY: If destroyed before OnStart completed, fire PresentationCompleted to prevent deadlock
+				FirePresentationCompleted();
 			}
 
 			void FireAnimationEnded()
@@ -398,6 +425,15 @@ void FireAnimationEnded()
 				AnimationEnded?.Invoke(this, EventArgs.Empty);
 			}
 
+			void FirePresentationCompleted()
+			{
+				if (!_pendingNavigation)
+					return;
+
+				_pendingNavigation = false;
+				PresentationCompleted?.Invoke(this, EventArgs.Empty);
+			}
+
 
 			sealed class CustomComponentDialog : ComponentDialog
 			{

src/Controls/tests/TestCases.HostApp/Issues/Issue32310.cs

@@ -0,0 +1,42 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 32310, "App hangs if PopModalAsync is called after PushModalAsync with single await Task.Yield()", PlatformAffected.Android)]
+public class Issue32310 : ContentPage
+{
+	public Issue32310()
+	{
+		var navigateButton = new Button
+		{
+			Text = "Perform Modal Navigation",
+			AutomationId = "NavigateButton",
+			VerticalOptions = LayoutOptions.Center,
+			HorizontalOptions = LayoutOptions.Center
+		};
+
+		navigateButton.Clicked += (s, e) =>
+		{
+			Dispatcher.DispatchAsync(async () =>
+			{
+				await Navigation.PushModalAsync(new ContentPage() { Content = new Label() { Text = "Hello!" } }, false);
+
+				await Task.Yield();
+
+				await Navigation.PopModalAsync();
+			});
+		};
+
+		var layout = new VerticalStackLayout
+		{
+			Padding = new Thickness(30, 0),
+			Spacing = 25,
+			VerticalOptions = LayoutOptions.Center,
+			HorizontalOptions = LayoutOptions.Center,
+			Children =
+			{
+				navigateButton
+			}
+		};
+
+		Content = layout;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32310.cs

@@ -0,0 +1,24 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue32310 : _IssuesUITest
+{
+	public Issue32310(TestDevice device) : base(device)
+	{
+	}
+
+	public override string Issue => "App hangs if PopModalAsync is called after PushModalAsync with single await Task.Yield()";
+
+	[Test]
+	[Category(UITestCategories.Navigation)]
+	public void ModalNavigationShouldNotHang()
+	{
+		App.WaitForElement("NavigateButton");
+		App.Tap("NavigateButton");
+		App.WaitForElement("NavigateButton");
+		VerifyScreenshot();
+	}
+}