.NET MAUI Documentation

Platform-Specific Features on iOS

This tutorial guides you through implementing and utilizing platform-specific features in your .NET MAUI application for iOS. .NET MAUI allows you to access native APIs and UI elements that are unique to each platform, providing a truly native experience.

Understanding Platform-Specific Code

There are several ways to handle platform-specific code in .NET MAUI:

• Conditional Compilation: Using preprocessor directives like #if IOS to include or exclude code blocks based on the target platform.
• Dependency Injection: Registering platform-specific implementations of interfaces and injecting them into your shared code.
• Platform-Specific Views: Creating custom renderers or handlers for controls that require significant platform-specific UI.

Accessing Native iOS APIs

You can directly call into the native iOS SDK from your .NET MAUI application. For example, to access the device's accelerometer:

#if IOS
using UIKit;
using CoreMotion;

public static class AccelerometerHelper
{
    private static CMMotionManager motionManager = new CMMotionManager();

    public static void StartAccelerometerUpdates()
    {
        if (motionManager.AccelerometerAvailable)
        {
            motionManager.AccelerometerUpdateInterval = 0.1; // Update every 0.1 seconds
            motionManager.StartAccelerometerUpdatesOfSubtype(CMMotionActivitySubtype.Other, null, (data, error) =>
            {
                if (data != null)
                {
                    Console.WriteLine($"X: {data.Acceleration.X}, Y: {data.Acceleration.Y}, Z: {data.Acceleration.Z}");
                    // You can then update your UI or perform actions based on this data
                }
            });
        }
    }

    public static void StopAccelerometerUpdates()
    {
        motionManager.StopAccelerometerUpdates();
    }
}
#endif
            

Customizing Native Controls

For more advanced customization, you can leverage .NET MAUI's handler architecture. Handlers allow you to customize native controls without diverging from the .NET MAUI API. Here's a conceptual example of customizing an iOS `UIButton`:

1. Define a Custom Control in Shared Code:

public class CustomButton : Button
{
    public static readonly BindableProperty CustomBackgroundColorProperty =
        BindableProperty.Create(nameof(CustomBackgroundColor), typeof(Color), typeof(CustomButton), Colors.Blue);

    public Color CustomBackgroundColor
    {
        get { return (Color)GetValue(CustomBackgroundColorProperty); }
        set { SetValue(CustomBackgroundColorProperty, value); }
    }
}
            

2. Create a Custom iOS Handler:

This typically involves creating a new project or folder for iOS-specific code and implementing a handler that targets the native iOS control.

#if IOS
using Microsoft.Maui.Handlers;
using UIKit;
using CoreGraphics;

public class CustomButtonHandler : ButtonHandler
{
    protected override void ConnectHandler(object nativeView)
    {
        base.ConnectHandler(nativeView);
        if (nativeView is UIButton uiButton)
        {
            // Access the custom property from the shared MAUI control
            var mauiButton = (CustomButton)Element;
            UpdateBackgroundColor(uiButton, mauiButton);
        }
    }

    protected override void DisconnectHandler(object nativeView)
    {
        base.DisconnectHandler(nativeView);
        // Clean up any event handlers or resources
    }

    private void UpdateBackgroundColor(UIButton uiButton, CustomButton mauiButton)
    {
        if (mauiButton.CustomBackgroundColor != null)
        {
            uiButton.BackgroundColor = UIColor.FromRGB(
                (nfloat)mauiButton.CustomBackgroundColor.Red,
                (nfloat)mauiButton.CustomBackgroundColor.Green,
                (nfloat)mauiButton.CustomBackgroundColor.Blue
            );
        }
    }

    // You would also override UpdateProperty to handle changes to CustomBackgroundColor
}
#endif
            

3. Register the Handler in your iOS AppDelegate:

#if IOS
// ... other using statements
using Microsoft.Maui.Hosting;
using UIKit;

// Inside your AppDelegate class
public class AppDelegate : MauiUIApplicationDelegate
{
    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();

    public override void FinishedLaunching(UIApplication application, NSDictionary launchOptions)
    {
        // Register the custom handler
        Microsoft.Maui.MauiApp.CreateBuilder()
            .ConfigureMauiHandlers(handlers =>
            {
                handlers.AddHandler(typeof(CustomButton), typeof(CustomButtonHandler));
            })
            .Build();
        base.FinishedLaunching(application, launchOptions);
    }
}
#endif
            

Platform-Specific UI Elements

Sometimes you might need to use UI elements that are unique to iOS. You can embed native iOS views directly into your .NET MAUI layout.

Example: Using a Native `UIPickerView`

This involves creating a shared control, then providing a platform-specific implementation for iOS that wraps the native `UIPickerView` and maps its events and data to your shared model.

Best Practices

• Keep Shared Code Clean: Minimize platform-specific code in your main shared project. Use dependency injection or abstract interfaces.
• Test Thoroughly: Always test your platform-specific implementations on actual iOS devices.
• Use Abstractions: Define interfaces in your shared code and implement them for each platform. This promotes loose coupling and easier testing.
• Leverage .NET MAUI Features: Explore the extensibility points of .NET MAUI, such as handlers and the app lifecycle, before resorting to very low-level native calls.

By understanding and utilizing these techniques, you can create rich, platform-specific experiences for your users on iOS while maintaining a single codebase.