Can you provide an example of handling push notifications in an MvvmCross ViewModel

1. Setting Up Push Notifications

First, you need to set up your application to receive push notifications. This typically involves registering your app with a notification service like Firebase Cloud Messaging (FCM) for Android or Apple Push Notification Service (APNs) for iOS. You will need to integrate the necessary SDKs into your platform-specific projects.

2. Customizing AppStart for Notifications

In MvvmCross, you can customize the `AppStart` to handle notifications. This is useful for navigating to a specific ViewModel when the app is launched from a notification.

csharp
public class App : MvxApplication
{
    public override void Initialize()
    {
        // Register services and other initialization
        RegisterAppStart();
    }

    public override TParameter Startup(TParameter parameter)
    {
        // Handle the parameter passed from the notification
        if (parameter != null)
        {
            // Navigate to a specific ViewModel based on the parameter
            var navigationService = Mvx.IoCProvider.Resolve();
            if (navigationService.CanNavigate())
            {
                navigationService.Navigate(parameter);
            }
        }
        return parameter;
    }
}

3. Handling Notifications in the ViewModel

To handle notifications in a ViewModel, you can use the `Init` method if your ViewModel implements `IMvxViewModel`. This method is called when the ViewModel is initialized with parameters.

csharp
public class NotificationViewModel : MvxViewModel
{
    public override async Task Init(TParameter parameter)
    {
        // Handle the notification data here
        await base.Init(parameter);
        // Perform any necessary actions based on the parameter
    }
}

4. Navigation with Parameters

To navigate to a ViewModel with parameters, you can use the `ShowViewModel` method provided by MvvmCross's navigation service.

csharp
public class MainViewModel : MvxViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public MainViewModel(IMvxNavigationService navigationService)
    {
        _navigationService = navigationService;
    }

    public IMvxAsyncCommand ShowNotificationCommand
    {
        get
        {
            return new MvxAsyncCommand(async () =>
            {
                var parameter = new NotificationParameter(); // Example parameter
                await _navigationService.Navigate(parameter);
            });
        }
    }
}

5. Using MvxNotifyTask for Async Operations

If your notification handling involves asynchronous operations, you can use `MvxNotifyTask` to manage these tasks and handle exceptions gracefully.

csharp
public class NotificationViewModel : MvxViewModel
{
    private MvxNotifyTask _notificationTask;

    public MvxNotifyTask NotificationTask
    {
        get => _notificationTask;
        private set => SetProperty(ref _notificationTask, value);
    }

    public override async Task Init(TParameter parameter)
    {
        await base.Init(parameter);
        NotificationTask = MvxNotifyTask.Create(async () =>
        {
            try
            {
                // Perform async operation here
                await HandleNotificationAsync(parameter);
            }
            catch (Exception ex)
            {
                // Handle exception
                OnException(ex);
            }
        });
    }

    private async Task HandleNotificationAsync(TParameter parameter)
    {
        // Handle notification data asynchronously
    }

    private void OnException(Exception exception)
    {
        // Log or handle the exception
    }
}

6. Platform-Specific Handling

On Android, you need to handle the `OnNewIntent` method in your Activity to capture notifications when the app is already running. On iOS, you handle notifications in the `AppDelegate` class.

For Android:

csharp
[Activity(Label = "MyActivity")]
public class MyActivity : MvxActivity
{
    protected override void OnNewIntent(Intent intent)
    {
        base.OnNewIntent(intent);
        // Handle notification intent here
    }
}

For iOS:

csharp
[Register("AppDelegate")]
public class AppDelegate : MvxApplicationDelegate
{
    public override bool OpenUrl(UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
    {
        // Handle notification URL here
        return true;
    }
}

By following these steps, you can effectively handle push notifications in an MvvmCross application, navigating to specific ViewModels and handling notification data as needed.