xamarin形成ios相机崩溃问题

Question

我有一个xamarin表单跨平台应用程序。在该应用程序中，我使用xamarin表单依赖服务从本机平台上的iOS和Android设备拍照。 Android相机工作正常但iOS相机突然出现错误和应用程序崩溃。我记录并跟踪iOS相机的问题如下。

**由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'应用程序尝试以模态方式呈现活动控制器。'

以下是用于拍照的我的iOS原生代码，它返回照片流作为结果。我使用依赖服务从我的共享xamarin表单项目中调用此方法或服务。

public Task<CameraResult> TakePictureAsync(bool cameraFlag)   {    var tcs = new TaskCompletionSource<CameraResult>();


Camera.TakePicture(UIApplication.SharedApplication.KeyWindow.RootViewController, (imagePickerResult) =>
   {
    if (imagePickerResult == null)
    {
     tcs.TrySetResult(null);
     return;
    }
    var photo = imagePickerResult.ValueForKey(new NSString("UIImagePickerControllerOriginalImage")) as UIImage;
    // You can get photo meta data with using the following
    // var meta = obj.ValueForKey(new NSString("UIImagePickerControllerMediaMetadata")) as NSDictionary;
    var documentsDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
    string imageName = Settings.AppuserUserId + "_" + Guid.NewGuid();
    string jpgFilename = Path.Combine(documentsDirectory, imageName + ".jpg");
    NSData imgData = photo.AsJPEG();
    NSError err = null;

    if (imgData.Save(jpgFilename, false, out err))
    {
     CameraRes
ult result = new CameraResult();
     result.Picture = ImageSource.FromStream(imgData.AsStream);
     result.FilePath = jpgFilename;
     tcs.TrySetResult(result);
    }
    else
    {
     tcs.TrySetException(new Exception(err.LocalizedDescription));
    }    });

   return tcs.Task;   }


void OnImagePickerFinishedPickingMedia(object sender, UIImagePickerMediaPickedEventArgs args)
        {
            UIImage image = args.EditedImage ?? args.OriginalImage;
            if (image != null)
            {
                // Convert UIImage to .NET Stream object
                CameraResult result = new CameraResult();
                NSData data = image.AsJPEG();
                result.Picture = ImageSource.FromStream(data.AsStream);
                taskCompletionSource.SetResult(result);
            }
            else
            {
                taskCompletionSource.SetResult(null);
            }
            imagePicker.DismissModalViewController(true);
        }

        void OnImagePickerCancelled(object sender, EventArgs args)
        {
            taskCompletionSource.SetResult(null);
            imagePicker.DismissModalViewController(true);
        }
    }

请分享此问题和错误的任何解决方案。