BACK BUTTON VS NET 10

Question

Platform: Android

With NET MAUI 9.0, pressing the 'hardware' Back Button generates the following events:

When the current page is MainPage:

OnSleep
Android – OnStop
Android – OnDestroy
shut down the app

When the current page is any other page: Go back to the previous page in the navigation stack

With NET MAUI 10, running the Emulator for API 35, the behavior is:

When the current page is MainPage: similar to above, but during shut down of the app, throws an unhandled exception ‘Android.Runtime.JavaProxyThrowable’ with InnerEception: “Cannot access a disposed object”

When the current page is any other page: Go back to the previous page in the navigation stack (same as NET 9)

With NET MAUI 10, running in a real cellular with API 36: the exception is thrown also when the current page in not MainPage.

I tried to add:

    protected override bool OnBackButtonPressed()
    {
        Debug.WriteLine("Back button pressed in ChildPage");
        return true;
    }

and also:

    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
#if ANDROID
            .ConfigureLifecycleEvents(events =>
            {
                events.AddAndroid(android => android.OnBackPressed((activity) =>
                {
                    Debug.WriteLine("Android - OnBackPressed");
                    return true;
                }));
            })
#endif
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            });
#if DEBUG
		builder.Logging.AddDebug();
#endif
        return builder.Build();
    }

It happens that these events are detected when running in the Emulator, but they are completely ignored when running in the cellular phone.

Is this a bug in NET 10? Will it be fixed?

Answer 1

Hello @Giorgio Sfiligoi ,

Since the MAUI IServiceProvider (the .NET host) is already disposed when an Android fragment (ShellFragmentContainer.OnDestroy) attempts to resolve services.

I have tested your provided project, and my assumption is that the most likely trigger is an early shutdown call (for example App.Current.Quit() in ChildPage.OnQuitClicked) or a lifecycle ordering change/bug in MAUI 10 where the host is disposed before fragments finish their OnDestroy work on some devices / API levels. The IServiceProvider can be found in output log following:

While this behavior not affecting your application, you can ignore it. If this concerns you, you can raise the github issue so that the MAUI team can look into it.

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I hope this clarifies!