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[Android] Fix app hang when PopModalAsync called immediately after PushModalAsync #32853

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[Android] Fix app hang when PopModalAsync called immediately after PushModalAsync #32853

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Copilot Nov 25, 2025
3a47dee
Fix app hang when PopModalAsync called after PushModalAsync with Task…
Copilot Nov 25, 2025
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55 changes: 45 additions & 10 deletions src/Controls/src/Core/Platform/ModalNavigationManager/ModalNavigationManager.Android.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand All @@ -185,19 +183,33 @@ async Task PresentModal(Page modal, bool animated)

if (animated)
{
dialogFragment!.AnimationEnded += OnAnimationEnded;
TaskCompletionSource<bool> animationCompletionSource = new();

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
// when PopModalAsync is called immediately after PushModalAsync (e.g., with Task.Yield())
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;
}
}

Expand All @@ -208,8 +220,10 @@ internal class ModalFragment : DialogFragment
NavigationRootManager? _navigationRootManager;
static readonly ColorDrawable TransparentColorDrawable = new(AColor.Transparent);
bool _pendingAnimation = true;
bool _presentationCompleted = false;

public event EventHandler? AnimationEnded;
internal event EventHandler? AnimationEnded;
internal event EventHandler? PresentationCompleted;


public bool IsAnimated { get; internal set; }
Expand Down Expand Up @@ -356,11 +370,18 @@ 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);

// Signal that the modal is fully presented and ready
FirePresentationCompleted();
}

public override void OnDismiss(IDialogInterface dialog)
Expand All @@ -385,6 +406,9 @@ public override void OnDestroy()
{
base.OnDestroy();
FireAnimationEnded();

// SAFETY: If destroyed before OnStart completed, fire PresentationCompleted to prevent deadlock
FirePresentationCompleted();
}

void FireAnimationEnded()
Expand All @@ -398,6 +422,17 @@ void FireAnimationEnded()
AnimationEnded?.Invoke(this, EventArgs.Empty);
}

void FirePresentationCompleted()
{
if (_presentationCompleted)
{
return;
}

_presentationCompleted = true;
PresentationCompleted?.Invoke(this, EventArgs.Empty);
}


sealed class CustomComponentDialog : ComponentDialog
{
Expand Down
42 changes: 42 additions & 0 deletions src/Controls/tests/TestCases.HostApp/Issues/Issue32310.cs
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Original file line number Diff line number Diff line change
@@ -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;
}
}
26 changes: 26 additions & 0 deletions src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32310.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
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");

// If the fix works, the modal should push and pop quickly,
// and we should be back to the same page with the button visible
App.WaitForElement("NavigateButton", timeout: TimeSpan.FromSeconds(10));
}
}