Dialog Fragment Service

.NET 9.0 introduced a breaking change in how modal pages work in Android - they now use a DialogFragment. This breaking change resulted in broken functionality within the .NET MAUI Community Toolkit. The DialogFragmentService provides a mechanism to fix the breaking changes,

IDialogFragmentService is an interface that allows developers to customize the behavior and appearence of Modal pages in .NET MAUI for Android. The .NET MAUI Community Toolkit provides a default implementation to make sure its features, like StatusBarColor will work with the new Modal implementation.

Usage

By default the .NET MAUI Community Toolkit registers the DialogFragmentService, but you can control that as follows

public static class MauiProgram
{

 public static MauiApp CreateMauiApp()
 {
  var builder = MauiApp.CreateBuilder()
        .UseMauiCommunityToolkit(static options =>
        {
            options.SetShouldUseStatusBarBehaviorOnAndroidModalPage(false);
        });
        return builder.Build();
    }
}

There will be cases where you want to fix and customize the DialogFragment to match your apps needs, in these scenarios you can create your own implementation of the IDialogFragmentService interface and use in combination with other implementations.

Create you own service

The following example shows how to present the modals in immersive mode. In order to achieve this we need to have access to the DialogFragment and configure its Window to behave in the required way.

For that, first we will need to create a class that implements the IDialogFragmentService interface and customize the method that we need. And make sure this class will only compile for android, otherwise it will fail to build other targets.

sealed class MyDialogFragmentService : IDialogFragmentService
{
    // Ommiting other methods
    
    public void OnFragmentStarted(AndroidX.Fragment.App.FragmentManager fm, AndroidX.Fragment.App.Fragment f)
    {
        if (f is not DialogFragment dialogFragment)
        {
            return;
        }

        if (dialogFragment is not { Dialog.Window: { } window })
        {
            return;
        }
        
        if (OperatingSystem.IsAndroidVersionAtLeast(30))
        {
           window.SetDecorFitsSystemWindows(false);
           window.InsetsController?.Hide(WindowInsets.Type.SystemBars());
           if (window.InsetsController is not null)
           {
                window.InsetsController.SystemBarsBehavior = (int)WindowInsetsControllerBehavior.ShowTransientBarsBySwipe;
           }
        }
        else
        {
           SystemUiFlags systemUiVisibility = (SystemUiFlags)window.DecorView.SystemUiVisibility;
           systemUiVisibility |= SystemUiFlags.HideNavigation;
           systemUiVisibility |= SystemUiFlags.Immersive;
           window.DecorView.SystemUiVisibility = (StatusBarVisibility)systemUiVisibility;
        }
    }
}

After implementing what is needed it's time to register it into the fragment lifecycle callback, the place to do it is inside the MauiApp builder. Here's the code snippet:

public static class MauiProgram
{

 public static MauiApp CreateMauiApp()
 {
    var builder = MauiApp.CreateBuilder()
    builder.ConfigureLifecycleEvents(static lifecycleBuilder =>
    {
        lifecycleBuilder.AddAndroid(static androidBuilder =>
        {
            androidBuilder.OnCreate(static (activity, _) =>
            {
                if (activity is not AndroidX.AppCompat.App.AppCompatActivity componentActivity)
                {
                    return;
                }

                if (componentActivity.GetFragmentManager() is not AndroidX.Fragment.App.FragmentManager fragmentManager)
                {
                    return;
                }

                fragmentManager.RegisterFragmentLifecycleCallbacks(new FragmentLifecycleManager(new MyDialogFragmentService()), false);
            });
        });
    });
        return builder.Build();
    }
}

And now, all modals will be showed in full-screen mode.

API

You can find the source code for IDialogFragmentService over on the .NET MAUI Community Toolkit GitHub repository and about the FragmentLifecycleManager over on the .NET MAUI Community Toolkit GitHub repository.