Android – How to add permission popup?

How to add a popup asking for permission access?

Xamarin

        public void RequestPermissions()
        {
            if (Build.VERSION.SdkInt >= BuildVersionCodes.M)
            {
                if (ContextCompat.CheckSelfPermission(MainActivity.AppInstance, Manifest.Permission.Camera) != Permission.Granted || ContextCompat.CheckSelfPermission(MainActivity.AppInstance, Manifest.Permission.RecordAudio) != Permission.Granted)
                {
                    List<string> req = new List<string>();

                    if (ContextCompat.CheckSelfPermission(MainActivity.AppInstance, Manifest.Permission.Camera) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.Camera);
                    }

                    if (ContextCompat.CheckSelfPermission(MainActivity.AppInstance, Manifest.Permission.RecordAudio) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.RecordAudio);
                    }

                    ActivityCompat.RequestPermissions(MainActivity.AppInstance, req.ToArray(), PERMISSIONS_REQUEST_CAPTURE);
                }
            }
        }

How to catch event when permission is turned on/off?

Xamarin

// MainActivity.cs

namespace VAST.Demo.Droid
{

...

        private const int PERMISSIONS_REQUEST_CAPTURE = 1;
        private const int PERMISSIONS_REQUEST_MEDIA_PROJECTION = 2;
        public static MediaProjectionManager mediaProjectionManager = null;
        public static Result mediaProjectionResultCode = 0;
        public static Intent mediaProjectionResultData = null;

        protected override void OnCreate(Bundle savedInstanceState)
        {
...
        }

        protected override void OnResume()
        {
            base.OnResume();

            if (Build.VERSION.SdkInt >= BuildVersionCodes.M)
            {
                if (CheckSelfPermission(Manifest.Permission.Camera) != Permission.Granted ||
                    CheckSelfPermission(Manifest.Permission.RecordAudio) != Permission.Granted)
                {
                    List<string> req = new List<string>();
                    if (CheckSelfPermission(Manifest.Permission.Camera) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.Camera);
                    }
                    if (CheckSelfPermission(Manifest.Permission.RecordAudio) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.RecordAudio);
                    }
                    if (CheckSelfPermission(Manifest.Permission.ReadExternalStorage) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.ReadExternalStorage);
                    }
                    if (CheckSelfPermission(Manifest.Permission.WriteExternalStorage) != Permission.Granted)
                    {
                        req.Add(Manifest.Permission.WriteExternalStorage);
                    }
                    RequestPermissions(req.ToArray(), PERMISSIONS_REQUEST_CAPTURE);
                }

                if (Build.VERSION.SdkInt >= BuildVersionCodes.Lollipop)
                {
                    mediaProjectionManager = (MediaProjectionManager)GetSystemService(Context.MediaProjectionService);
                    if (mediaProjectionResultCode != Result.Ok || mediaProjectionResultData == null)
                    {
                        StartActivityForResult(mediaProjectionManager.CreateScreenCaptureIntent(), PERMISSIONS_REQUEST_MEDIA_PROJECTION);
                    }
                }
            }
        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            if (requestCode == PERMISSIONS_REQUEST_MEDIA_PROJECTION)
            {
                if (resultCode != Result.Ok)
                {
                    return;
                }

                mediaProjectionResultCode = resultCode;
                mediaProjectionResultData = data;
                
                // DO SOMETHING, START AN ANDROID SERVICE
...
            }

            base.OnActivityResult(requestCode, resultCode, data);
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] global::Android.Content.PM.Permission[] grantResults)
        {

            switch (requestCode)
            {

                case PERMISSIONS_REQUEST_CAPTURE:
                    {
                        bool allGranted = true;
                        foreach (Permission res in grantResults)
                        {
                            if (res != Permission.Granted)
                            {
                                allGranted = false;
                                break;
                            }
                        }
                        if (allGranted)
                        {
                        }
                        break;
                    }

                default:
                    Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
                    base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
                    break;

            }
        }
    }
}


How to navigate to permission setting screen?

Xamarin

        public void CheckOverlayPermission()
        {
            if (Build.VERSION.SdkInt >= BuildVersionCodes.M)
            {
                if (!Android.Provider.Settings.CanDrawOverlays(MainActivity.AppInstance))
                {
                    Intent intent = new Intent(Android.Provider.Settings.ActionManageOverlayPermission);
                    intent.AddFlags(ActivityFlags.NewTask);
                    Application.Context.StartActivity(intent);
                }
            }
        }