[Android] CollectionView Crashes when ItemSource Changed

[minaairsupport]

Description

App Crash when ItemSource Changed for CollectionView

Steps to Reproduce

1. Create ContentPage contain CollectionView
2. init item source for CollectionView with an empty list
3. Load data from web service and make any delay then fill this ItemSource

Expected Behavior

ItemSource Changed

Actual Behavior

App Crashes with this error

JniEnvironment+InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args)
Java.Lang.IllegalStateException: Observer md51558244f76c53b6aeda52c8a337f2c37.DataChangeObserver@e23f401 was not registered.

Basic Information

• Version with issue: 4.0.0.94569-pre3
• Last known good version:
• IDE: Visual Studio Mac 2017 , 2019
• Platform Target Frameworks:
  • Android: 7.0
• Nuget Packages:4.0.0.94569-pre3
• Affected Devices:Nexsus 4 , Android 7.0 api 24

[kingces95]

Can you please attach a reproduction? I'm guessing how and where the delay is injected will affect whether this reproduces.

[rubenglam]

Same error 👍 . I have a searchView that filters the items and when there are 0 items, just after modify the query to that it contains items the app crash with the same error.

[davidbritch]

@kingces95 I've been able to repro this in 4.0-pre5. Setting the ItemsSource property after a 2 second delay causes a crash:

        protected override async void OnAppearing()
        {
            base.OnAppearing();

            await Task.Delay(2000);
            collectionView.ItemsSource = (BindingContext as MonkeysViewModel).Monkeys;
        }

I tried all kinds of threading options, and marshalling to the UI thread (when appropriate) and it always happens.

Repro steps

1. Run the attached sample (either iOS or Android).
2. Browse to the EmptyViewLoadSimulationPage.
3. Wait 2 seconds.

Actual result

Sample crashes.

Expected result.

Sample updates the CollectionView from an ObservableCollection.

Repro link

CollectionViewDemos.zip

iOS Crash

MonoTouchException:

Android crash

IllegalStateException:

[davidbritch]

@hartez I've retried this on 3.6 and 4.0-pre6 and the results are identical for both. On iOS a MonoTouchException occurs, as per the screenshot above. On Android it works fine.

[hartez]

This crash is fixed for Android in 4.0.0-pre6 and for iOS in 4.0.0-pre8.