[XAMARIN FORMS] Background task for 'closed' applications

Background task for 'closed' applications

Handling a background task in Xamarin Forms, even when the application is closed, can be challenging due to the mobile operating systems' restrictions on background activities. Here's a detailed solution using a combination of Dependency Service, Background Services, and Platform-Specific Implementations.

Step 1: Create an Interface

First, create an interface in your shared Xamarin Forms project that defines the method for starting the background task.

public interface IBackgroundTask
{
    void StartBackgroundTask();
}

Step 2: Implement Platform-Specific Services

Android Implementation:

In your Android project, create a service that implements the IBackgroundTask interface.

1. Create a Service:

[Service]
public class MyBackgroundService : Service
{
    public override IBinder OnBind(Intent intent) => null;

    public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
    {
        // Your background task logic here
        // For example: Start a long-running task
        return StartCommandResult.Sticky;
    }
}

1. Implement the Interface:

[assembly: Dependency(typeof(BackgroundTask_Android))]
public class BackgroundTask_Android : IBackgroundTask
{
    public void StartBackgroundTask()
    {
        var intent = new Intent(Android.App.Application.Context, typeof(MyBackgroundService));
        Android.App.Application.Context.StartService(intent);
    }
}

iOS Implementation:

For iOS, due to stricter background task policies, you typically need to use Background Fetch or Background Processing tasks.

1. Use Background Fetch: In the AppDelegate, register the background fetch.

public override void PerformFetch(UIApplication application, Action<UIBackgroundFetchResult> completionHandler)
{
    // Your background task logic here
    completionHandler(UIBackgroundFetchResult.NewData);
}

1. Implement the Interface:

[assembly: Dependency(typeof(BackgroundTask_iOS))]
public class BackgroundTask_iOS : IBackgroundTask
{
    public void StartBackgroundTask()
    {
        UIApplication.SharedApplication.SetMinimumBackgroundFetchInterval(UIApplication.BackgroundFetchIntervalMinimum);
    }
}

Step 3: Use the Dependency Service in Xamarin Forms

In your Xamarin Forms project, you can now start the background task by calling the StartBackgroundTask method from the dependency service.

public class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();
        DependencyService.Get<IBackgroundTask>().StartBackgroundTask();
    }
}

Be careful

• Android: You may need to request additional permissions like WAKE_LOCK and ensure your app is configured to run in the background.

• iOS: Background tasks are limited to specific activities like background fetch or location updates. Apple has strict guidelines on what can be done in the background.

• Cross-Platform Alternatives: You can use plugins like Xamarin.Essentials for simple tasks or third-party libraries like Shiny for more complex background processing.