CODEWITHSUNDEEP
c#multithreadingwindows-phone-8xamarin.iosxamarin
JKennedy
JKennedy

Reputation: 18799

Cross Thread Exception when trying to display Images from Camera Roll on Windows Phone

I am building a Windows phone app using Xamarin in a portable class Library. I have got the Images from the Windows Phone Camera Roll and I am passing the List back to the PCL and assigning the Image to an ImageSource in my view.

Windows Phone Get Images:

foreach (var image in CameraRollPictures)
{
    Image img = new Image();
    img.Source = ImageSource.FromStream(() => image.GetImage());
    images.Add(img);
}           
return images;

PCL method:

    private RelayCommand _importPhoto;
    public RelayCommand ImportPhoto
    {
        get
        {
            return _importPhoto
                ?? (_importPhoto = new RelayCommand(
                                      () =>
                                      {
                                          IOperations op = DependencyService.Get<IOperations>();                                            
                                          Task<List<Image>> t = new Task<List<Image>>(() =>
                                          {
                                              return op.ImportPhoto();

                                          });
                                          t.ContinueWith((sender) =>
                                              {
                                                  PageOp.Navigate(new TaggingPage());
                                                  if (sender.Result.Count != 0)
                                                  {
                                                      try
                                                      {
                                                          App.Locator.TaggingPageVM.ImageSrc = sender.Result[0].Source;
                                                      }
                                                      catch (Exception ex)
                                                      {

                                                      }
                                                  }
                                              }, TaskScheduler.FromCurrentSynchronizationContext());
                                          t.Start();
                                      }));

View:

<Image Source="{Binding ImageSrc}"/>

The Exception:

{System.UnauthorizedAccessException: Invalid cross-thread access.
at MS.Internal.XcpImports.CheckThread() at System.Windows.DependencyObject..ctor(UInt32 nativeTypeIndex, IntPtr constructDO) at System.Windows.Media.Imaging.BitmapImage..ctor()
at Xamarin.Forms.Platform.WinPhone.StreamImagesourceHandler.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() at Xamarin.Forms.Platform.WinPhone.ImageRenderer.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.AsyncMethodBuilderCore.b__3(Object state)}

UPDATE

If I load a picture from a resource then it works fine.

App.Locator.TaggingPageVM.ImageSrc = ImageSource.FromFile("50175950-tulips-microsofts.jpg");

It must be an error to do with the images created on the windows phone and passing those images back to my PCL

Upvotes: 1

Views: 794

Answers (1)

JKennedy
JKennedy

Reputation: 18799

I'm using Xamarin so:

Device.BeginInvokeOnMainThread(() => { App.Locator.TaggingPageVM.ImageSrc = sender.Result[0].Source; });

Fixed the Cross-Thread error

Upvotes: 1

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