How do I handle runtime Bluetooth permissions in an MvvmCross app

1. Declare Permissions in AndroidManifest.xml**

First, you need to declare the necessary permissions in your `AndroidManifest.xml` file. For Android versions older than Android 12 (API 31), you need the following permissions:

xml

For Android 12 and later, you need to add these additional runtime permissions:

xml

2. Request Runtime Permissions**

To request runtime permissions, you can use a similar approach as in native Android apps. You will need to check if the permissions are granted and request them if necessary.

Here's an example of how you might implement this in your MvvmCross Android project:

csharp
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
using MvvmCross.Platforms.Android.Views;

public class MainActivity : MvxActivity
{
    private const int RequestCode = 10023;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        // Other initialization code
    }

    private async Task CheckAndRequestBluetoothPermissions()
    {
        if (Build.VERSION.SdkInt >= BuildVersionCodes.S)
        {
            var bluetoothScanStatus = await CheckPermission(Manifest.Permission.BluetoothScan);
            var bluetoothConnectStatus = await CheckPermission(Manifest.Permission.BluetoothConnect);

            if (bluetoothScanStatus != PermissionStatus.Granted || bluetoothConnectStatus != PermissionStatus.Granted)
            {
                await RequestBluetoothPermissions();
            }
        }
        else
        {
            var locationStatus = await CheckPermission(Manifest.Permission.AccessFineLocation);
            if (locationStatus != PermissionStatus.Granted)
            {
                await RequestLocationPermission();
            }
        }
    }

    private async Task CheckPermission(string permission)
    {
        return await Permissions.RequestAsync(permission);
    }

    private async Task RequestBluetoothPermissions()
    {
        var permissions = new[] { Manifest.Permission.BluetoothScan, Manifest.Permission.BluetoothConnect };
        await RequestPermissionsAsync(permissions, RequestCode);
    }

    private async Task RequestLocationPermission()
    {
        var permissions = new[] { Manifest.Permission.AccessFineLocation };
        await RequestPermissionsAsync(permissions, RequestCode);
    }

    public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
    {
        base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == RequestCode)
        {
            foreach (var result in grantResults)
            {
                if (result == Permission.Denied)
                {
                    // Handle denied permission
                }
            }
        }
    }
}

3. Handle Permission Results**

After requesting permissions, you need to handle the results in the `OnRequestPermissionsResult` method. This method is called after the user has responded to the permission request dialog.

4. Use Dependency Injection for Cross-Platform Handling**

For a more cross-platform approach, you can use dependency injection to abstract the permission handling logic. This involves creating an interface that defines methods for checking and requesting permissions, and then implementing this interface on each platform.

Here's a simplified example:

csharp
public interface IBluetoothService
{
    Task CheckPermission(string permission);
    Task RequestPermission(string permission);
}

// Android implementation
public class BluetoothService : IBluetoothService
{
    public async Task CheckPermission(string permission)
    {
        return await CheckPermission(permission);
    }

    public async Task RequestPermission(string permission)
    {
        await RequestPermissionsAsync(new[] { permission }, RequestCode);
    }
}

// iOS implementation would be similar but with iOS-specific code

By using this approach, you can easily manage Bluetooth permissions across different platforms in your MvvmCross app.