DialogFragment service docs (#511)

* docs

* fix author name

* Text review

Co-authored-by: Shaun Lawrence <shaunrlawrence@gmail.com>

---------

Co-authored-by: Shaun Lawrence <shaunrlawrence@gmail.com>

Author: pictos

docs/maui/platform-specific/DialogFragment-customization.md

@@ -0,0 +1,117 @@
+---
+title: Dialog Fragment Service - .NET MAUI Community Toolkit
+author: pictos
+description: The DialogFragmentService provides an easy way to control the behavior of Modal pages in Android.
+ms.date: 02/01/2025
+---
+
+# Dialog Fragment Service
+
+.NET 9.0 introduced a breaking change in how modal pages work in Android - they now use a [`DialogFragment`](https://developer.android.com/reference/android/app/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
+
+```csharp
+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.
+
+```csharp
+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:
+
+```csharp
+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](https://github.com/CommunityToolkit/Maui/blob/main/src/CommunityToolkit.Maui.Core/Interfaces/IDialogFragmentService.android.cs) and about the `FragmentLifecycleManager` over on the [.NET MAUI Community Toolkit GitHub repository](https://github.com/CommunityToolkit/Maui/blob/main/src/CommunityToolkit.Maui.Core/Services/FragmentLifecycleManager.android.cs).