public override void OnMapRendered(Carto.Graphics.Bitmap bitmap)
 {
     if (ScreenCaptured != null)
     {
         ScreenshotEventArgs args = new ScreenshotEventArgs { Bitmap = bitmap };
         ScreenCaptured(this, args);
     }
 }
        void OnScreenCaptured(object sender, ScreenshotEventArgs e)
        {
            this.bitmap = e.Bitmap;

            if (((int)Build.VERSION.SdkInt) >= Marshmallow)
            {
                RequestPermissions(
                    new string[] { Android.Manifest.Permission.WriteExternalStorage, Android.Manifest.Permission.ReadExternalStorage },
                    RequestCode
                );
            }
            else {
                OnPermissionGranted();
            }
        }