UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread.

[jocontacter]

Platform (please complete the following information):

• OS: iOS
• Device: iPhone6
• Sdk vervion: iOS 11
• Xamarin.Forms: [3.5.0.169047]

UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread.

To Reproduce
Occurs when back button pressed on await Navigation.PopAsync()

Exceptions (if applicable)

UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread. (UIKit.UIKitThreadAccessException)
  at UIKit.UIApplication.EnsureUIThread () [0x00020] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.2.1.15/src/Xamarin.iOS/UIKit/UIApplication.cs:89 
  at UIKit.UIView.RemoveFromSuperview () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.2.1.15/src/Xamarin.iOS/UIKit/UIView.g.cs:1443 
  at Xamarin.Forms.Platform.iOS.ViewRenderer`2[TView,TNativeView].Dispose (System.Boolean disposing) [0x00025] in <9d4a50eabbf24c359a14266d8712c429>:0 
  at FFImageLoading.Forms.Platform.CachedImageRenderer.Dispose (System.Boolean disposing) [0x00015] in C:\projects\ffimageloading\source\FFImageLoading.Forms.Touch\CachedImageRenderer.cs:86 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.2.1.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in <9d4a50eabbf24c359a14266d8712c429>:0 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.2.1.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Sharpnado.Presentation.Forms.iOS.Renderers.HorizontalList.UIViewCellHolderQueue.Clear () [0x00027] in D:\Dev\Sharpnado\src\Xamarin-Forms-Practices\Sharpnado.Presentation.Forms\Sharpnado.Presentation.Forms.iOS\Renderers\HorizontalList\UIViewCellHolderQueue.cs:38 
  at Sharpnado.Presentation.Forms.iOS.Renderers.HorizontalList.iOSViewSource.Dispose (System.Boolean disposing) [0x00000] in D:\Dev\Sharpna
do\src\Xamarin-Forms-Practices\Sharpnado.Presentation.Forms\Sharpnado.Presentation.Forms.iOS\Renderers\HorizontalList\iOSViewSource.cs:215 
  at Foundation.NSObject.Finalize () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.2.1.15/src/Xamarin.iOS/Foundation/NSObject2.cs:143 

[roubachof]

Well I don't really se where I can go from here since it's dependent from the code you wrote (FFImageLoading.Forms.Platform.CachedImageRenderer)

[jocontacter]

Well I don't really se where I can go from here since it's dependent from the code you wrote (FFImageLoading.Forms.Platform.CachedImageRenderer)

_viewCellHolderCellHolderQueue?.Clear(); in Dispose() method in class Sharpnado.Presentation.Forms.iOS\Renderers\HorizontalList\iOSViewSource.cs ->
foreach (var view in _views) { view.CellContent.Dispose(); } and in this line you are not in ui thread but if cellcontent is ffImageLoading - it must be in UI thread. Can you advice some workaround to fix my exceptions?

[jocontacter]

May be we can solve it this way?
`
{
if(disposing)
{
_viewCellHolderCellHolderQueue?.Clear();
}

foreach (var weakCreatedCell in _createdCells.Values)
{
	if (weakCreatedCell.TryGetTarget(out var createdCell))
	{
		createdCell.Reset();
	}
}

if(disposing)
{
	_createdCells.Clear();
}

base.Dispose(disposing);

}
`

[roubachof]

I surely fucked up the dispose pattern here. It should be

protected override void Dispose(bool disposing)
{
    if (disposing)
    {
        _viewCellHolderCellHolderQueue?.Clear();

        foreach (var weakCreatedCell in _createdCells.Values)
        {
            if (weakCreatedCell.TryGetTarget(out var createdCell))
            {
                createdCell.Reset();
            }
        }

        _createdCells.Clear();
    }
    
    base.Dispose(disposing);
}

Could you test this code and see if it solves the issue ?

[jocontacter]

Could you test this code and see if it solves the issue ?

I made big refactor of my code so it doesn't disposing while running now. And i have hard deadline on my current project so i can't. But if i will catch any simillar exceptions i will clone your code and try it. Thank you for so good component and links in your wiki! It is helped me a lot!(sorry for poor english skills)

[roubachof]

anyway I fixed the dispose pattern on ios view source. We'll release it next week