Creating Cross-Platform Apps with Xamarin: A Complete Guide for Modern Mobile Development

📘 Chapter 4: Working with Platform-Specific Features and Native APIs

🧭 What You’ll Learn

In this chapter, you will explore:

• Accessing device hardware and native features in Xamarin
• Using Xamarin.Essentials for common cross-platform features
• Implementing platform-specific behavior using DependencyService
• Writing and consuming custom renderers
• Accessing platform APIs with native bindings
• Sharing native capabilities without breaking UI abstraction
• Debugging and maintaining cross-platform feature parity

By the end of this chapter, you’ll be able to unlock native power across Android and iOS without leaving your shared Xamarin.Forms project.

🧩 The Challenge of Platform-Specific Features

Xamarin.Forms is designed for maximum code reuse, but not every mobile platform behaves identically. You may encounter scenarios like:

• Using the camera or GPS
• Reading from the accelerometer
• Handling native alerts, toasts, or notifications
• Accessing OS-specific APIs like Face ID, Android Intents, etc.

Xamarin offers several tools to handle this without breaking cross-platform harmony.

🔧 Option 1: Xamarin.Essentials

Xamarin.Essentials is a library by Microsoft that wraps native APIs behind simple cross-platform APIs.

✅ Installation

bash

Install-Package Xamarin.Essentials

Or in .csproj:

xml

<PackageReference Include="Xamarin.Essentials" Version="1.8.0" />

✅ Initialization

• Android: Add Xamarin.Essentials.Platform.Init(...) in MainActivity.cs
• iOS: Add Xamarin.Essentials.Platform.Init() in AppDelegate.cs

🔑 Key APIs in Xamarin.Essentials

🔍 Sample: Get Device Location

csharp

using Xamarin.Essentials;

var location = await Geolocation.GetLastKnownLocationAsync();

if (location != null)

{

    Console.WriteLine($"Lat: {location.Latitude}, Long: {location.Longitude}");

}

🧩 Option 2: DependencyService for Platform-Specific Code

When Xamarin.Essentials doesn't cover your use case, use DependencyService to inject platform-specific implementations.

✅ Step-by-Step Example

Goal: Use native vibration on Android only.

1️⃣ Define Interface in Shared Project

csharp

public interface IDeviceVibrator

{

    void VibrateDevice();

}

2️⃣ Implement in Android Project

MainActivity.cs or separate service class:

csharp

[assembly: Dependency(typeof(DeviceVibrator))]

namespace MyApp.Droid

{

    public class DeviceVibrator : IDeviceVibrator

    {

        public void VibrateDevice()

        {

            var vibrator = (Vibrator)Android.App.Application.Context.GetSystemService(Context.VibratorService);

            vibrator?.Vibrate(VibrationEffect.CreateOneShot(500, VibrationEffect.DefaultAmplitude));

        }

    }

}

3️⃣ Call It in Shared Code

csharp

DependencyService.Get<IDeviceVibrator>()?.VibrateDevice();

🧬 Option 3: Custom Renderers

Custom renderers allow you to override the rendering behavior of Xamarin.Forms controls with platform-native views.

✅ When to Use:

• Customize how a control looks or behaves on Android/iOS
• Add native effects, animations, or accessibility options
• Integrate with native SDKs

🔍 Example: Custom Button Renderer

1️⃣ In Shared Project

csharp

public class CustomButton : Button

{

    // You can add custom properties here if needed

}

2️⃣ Android Renderer

csharp

[assembly: ExportRenderer(typeof(CustomButton), typeof(CustomButtonRenderer))]

namespace MyApp.Droid.Renderers

{

    public class CustomButtonRenderer : ButtonRenderer

    {

        public CustomButtonRenderer(Context context) : base(context) { }

        protected override void OnElementChanged(ElementChangedEventArgs<Button> e)

        {

            base.OnElementChanged(e);

            if (Control != null)

            {

                Control.SetBackgroundColor(Android.Graphics.Color.Red);

                Control.SetAllCaps(false);

            }

        }

    }

}

3️⃣ iOS Renderer

csharp

[assembly: ExportRenderer(typeof(CustomButton), typeof(CustomButtonRenderer))]

namespace MyApp.iOS.Renderers

{

    public class CustomButtonRenderer : ButtonRenderer

    {

        protected override void OnElementChanged(ElementChangedEventArgs<Button> e)

        {

            base.OnElementChanged(e);

            if (Control != null)

            {

                Control.BackgroundColor = UIColor.Red;

            }

        }

    }

}

🔍 Platform Checks in Shared Code

You can conditionally run code based on platform using:

✅ Device.RuntimePlatform

csharp

if (Device.RuntimePlatform == Device.Android)

{

    // Android-specific behavior

}

✅ OnPlatform XAML Markup

xml

<Label Text="Welcome!"

       FontSize="{OnPlatform Android=18, iOS=20}" />

🔗 Using Native Bindings

You can create bindings to existing native libraries (e.g., Objective-C .framework, or Java .aar/.jar files) to use third-party native SDKs in your Xamarin app.

This process involves creating Binding Library projects in Visual Studio.

📱 Table: Summary of Native Feature Access Methods

✅ Best Practices

• Keep platform code isolated in DependencyService or Renderer files
• Use Xamarin.Essentials where possible to reduce code complexity
• Ensure you test each platform separately, especially with sensors or permissions
• Use permissions APIs to check runtime access on Android 6.0+ and iOS
• Don't over-customize—prefer shared UI unless a native experience is necessary

🧠 Example Use Cases and Matching Solutions