Platform specific dependency in .net MAUI

I've tried to implement platform specific dependency for hide keyboard.

Platforms/Android/KeyboardHelper.cs

namespace MobileApp.Platforms.Android
{
    public static partial class KeyboardHelper
    {
        public static void HideKeyboard()
        {
            var context = Platform.AppContext;
            var inputMethodManager = context.GetSystemService(Context.InputMethodService) as InputMethodManager;
            if (inputMethodManager != null)
            {
                var activity = Platform.CurrentActivity;
                var token = activity.CurrentFocus?.WindowToken;
                inputMethodManager.HideSoftInputFromWindow(token, HideSoftInputFlags.None);
                activity.Window.DecorView.ClearFocus();
            }
        }
    }
}

Platforms/iOS/KeyboardHelper.cs

namespace MobileApp.Platforms.iOS
{
    public static partial class KeyboardHelper
    {
        public static void HideKeyboard()
        {
            UIApplication.SharedApplication.Delegate.GetWindow().EndEditing(true);
        }
    }
}

I've resolved through dependency injection.
Register in app.xaml.cs
DependencyService.Register<IKeyboardHelper, MobileApp.Platforms.KeyboardHelper>();

and use it in when i need:

DependencyService.Get<IKeyboardHelper>().HideKeyboard();

You created two different classes:

• MobileApp.Platforms.Android.KeyboardHelper
• MobileApp.Platforms.iOS.KeyboardHelper

If you wanted platform-specific implementations of the same class, they would have to be in the same namespace.

Platforms/Android/KeyboardHelper.cs

namespace MobileApp
{
    public static partial class KeyboardHelper
    {
        public static void HideKeyboard()
        {
            // ... the Android implementation ...
        }
    }
}

Platforms/iOS/KeyboardHelper.cs

namespace MobileApp
{
    public static partial class KeyboardHelper
    {
        public static void HideKeyboard()
        {
            // ... the iOS implementation ...
        }
    }
}

With the above approach, you will need an implementation defined for every target you are compiling for, or you will need a default no-op implementationed defined somewhere.

Alternatively, you could create a single file for all implementations, leveraging conditional compilation directives:

KeyboardHelper.cs

namespace MobileApp
{
    public static class KeyboardHelper
    {
        public static void HideKeyboard()
        {
#if IOS
            // ... the iOS implementation ...
#elif ANDROID
            // ... the Android implementation ...
#else
            // ... the default implementation (if there is one) ...
#endif
        }
    }
}

Note: If you want the iOS implementation to also apply to Mac Catalyst, you could use either #if __IOS__ or you can use #if IOS || MACCATALYST. They do the same thing.

When invoking the code, you do not need to do a runtime check for platform. Just call KeyboardHelper.HideKeyboard().

See also: https://learn.microsoft.com/dotnet/maui/platform-integration/invoke-platform-code