MAUI prompt for biometric/Pin authentication when leaving the app and then going back to it

Question

I'm using the nuget package Plugin.Fingerprint in my MAUI app to enable the use of the device authentication. I have the code working on one of my forms. But now Im trying to apply it so when I resume the use of the app it will prompt for a security check (if enabled).

In my MauiProgram.cs I Have

builder.ConfigureLifecycleEvents(AppLifecycle => {
#if ANDROID
     AppLifecycle.AddAndroid(android => android
        .OnRestart((activity) =>
        
            LocalDeviceAuthPrompt()               
        ));
#endif
    });

and a private method

private static bool LocalDeviceAuthPrompt()
{
    var isAvailable = CrossFingerprint.Current.IsAvailableAsync(true).Result;

    if (isAvailable)
    {
        var request = new AuthenticationRequestConfiguration
        ("Login using biometrics", "Confirm login with your biometrics");
        request.AllowAlternativeAuthentication = true;
        var result = CrossFingerprint.Current.AuthenticateAsync(request).Result;

        if (result.Authenticated)
        {
            return true;
        }
        
        return false;
    }

    return true;
}

I know theres plenty wrong with it, for a start async is needed but the AppLifecycle implementation doesnt support it. It also doesnt work. the event fires but I never get a security prompt. Does anyone have any advice/recommendations

UPDATE1

So I removed the above code and added it to the app.xaml.cs file as follows

protected override async void OnResume()
    {
        var isAvailable = await CrossFingerprint.Current.IsAvailableAsync(true);

        if (isAvailable)
        {
            var request = new AuthenticationRequestConfiguration
            ("Login using biometrics", "Confirm login with your biometrics");
            request.AllowAlternativeAuthentication = true;
            var result = await CrossFingerprint.Current.AuthenticateAsync(request);

            Console.Write(result);

        }
    }

I do get to decorate the method with async but it has the exact same issue. It doesn't go any further than line "CrossFingerprint.Current.AuthenticateAsync(request)" . No error it just hangs

Answer 1

I have created a new .net 6.0 maui project to test your code and it worked when I put the code in the MainActivity's OnResume method.

Add permission in the AndroidManifest.xml:

<uses-permission android:name="android.permission.USE_FINGERPRINT" />
<uses-permission android:name="android.permission.USE_BIOMETRIC" /> 

And my MainActivity:

public class MainActivity : MauiAppCompatActivity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        CrossFingerprint.SetCurrentActivityResolver(() => this);
      //bool a = ActivityCompat.CheckSelfPermission(this, Manifest.Permission.UseBiometric) == Permission.Granted;
      // check the permission at runtime
    }
    protected override async void OnResume()
    {
        base.OnResume();
        var isAvailable = await CrossFingerprint.Current.IsAvailableAsync(true);
        if (isAvailable)
        {
            var request = new AuthenticationRequestConfiguration
            ("Login using biometrics", "Confirm login with your biometrics");
            request.AllowAlternativeAuthentication = true;
            var result = await CrossFingerprint.Current.AuthenticateAsync(request);
            Console.Write(result);
        }
    }
}

And the result image: