Hi Didi,

Just a quick update regarding the issue I previously reported.

Setting animation: false in the ScrollItemIntoView method helped significantly to reduce the problem. However, during field testing, I encountered the issue once again. It is now very rare and hard to reproduce, but it still results in the same exception:

EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
   at Telerik.Maui.Controls.RadCollectionView.<OnScrollViewScrolled>b__159_0()

This indicates the issue is not fully resolved, although it happens much less frequently now.

I understand this may be difficult to track down due to its intermittent nature. You may need to treat this as a separate issue from this ticket and open a separate one.

Best regards,
Rodrigo

Hi Didi!

After further testing, I was able to consistently prevent the issue by disabling the animation in the ScrollItemIntoView method. Once I set animation: false, the exception stopped occurring during navigation back.

listView.ScrollItemIntoView(itemData.SelectedItem, false);

It seems the problem was related to the ongoing scroll animation when navigating back, which caused the crash. Disabling the animation resolved the issue in my case.

Regards,

Rodrigo

Hello Didi,

Thanks for the clarification.

In my production app, even after collecting all items and waiting on the page for a while before navigating back, the issue still occasionally occurs — although it's much rarer.

What I shared earlier was a forced test scenario, just to help reproduce the issue more easily. In the actual app, I'm not triggering navigation during ongoing operations — but it seems the error can still happen under specific timing conditions.

Additionally, in my app I also make sure to prevent ScrollItemIntoView from being called on page disappear. For example:

protected override void OnDisappearing()
{
    if (_isEventAttached && listView != null)
    {
        listView.SelectionChanged -= listView_SelectionChanged;
        _isEventAttached = false;
    }

    base.OnDisappearing();
}

Even with this precaution, the issue I mentioned still happens occasionally.

Let me know if there's anything else I can try or monitor on my side.

Regards,
Rodrigo

Hello Didi,

After further investigation and testing in my application (especially in debug mode), I was able to consistently reproduce the issue.

The key detail is that my app is using modal navigation.

To reproduce the issue in the sample I previously shared, simply update the navigation line as follows:

private void OnButtonClicked(object sender, EventArgs e)
{
    //Navigation.PushAsync(new CollectionPage());
    Navigation.PushModalAsync(new CollectionPage());
}

After switching from PushAsync to PushModalAsync, the issue starts occurring when navigating back.

To trigger the problem:

1. Tap on "Collect" to start the collection process.

2. While it’s collecting, tap on another item from a different group.

3. Then navigate back to the previous screen.

This sequence consistently reproduces the exception.

I hope this helps to reproduce and diagnose the issue.

Regards,

Rodrigo.

Hi Didi,

I was able to generate an app that reproduces the issue, but it only happens in release mode.

To trigger it:
- Open the app and navigate to the CollectionPage screen.
- Tap the "Collect" button and perform several collects.
- Then go back to the previous screen.
- Repeat this process a few times.

Sometimes after entering the CollectionPage a second time, the app will close, or crash — but it's not consistent. It can happen after a few repetitions.

Hope you're able to reproduce it.

Hi Didi,

Unfortunately, I wasn't able to reproduce the issue consistently in my app, and as I mentioned, it's hard to pinpoint exactly when it happens.

To help diagnose it, I made the following change in my application to capture it in the log:

public partial class App : Application
{
    public App()
    {
        InitializeComponent();

        // Catch unhandled exceptions on the main thread
        AppDomain.CurrentDomain.UnhandledException += OnUnhandledException;

        // Catch unobserved task exceptions
        TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;
    }

    private void OnUnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        if (e.ExceptionObject is Exception ex)
        {
            App.loggingService.Error(ex, "UnhandledException");
        }
        else
        {
            App.loggingService.Error($"ExceptionObject (non-Exception): {e.ExceptionObject?.ToString()}\n");
        }
    }

    private void OnUnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
    {
        App.loggingService.Error("UnobservedTaskException", e.Exception);
        e.SetObserved(); // Prevents the app from crashing
    }
}

This is what I captured in the logs:

ERROR: UnhandledException
EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
   at Telerik.Maui.Controls.RadCollectionView.<OnScrollViewScrolled>b__159_0()
   at Microsoft.Maui.Dispatching.Dispatcher.<>c__DisplayClass3_0.<DispatchImplementation>b__0()
   at Java.Lang.Thread.RunnableImplementor.Run()
   at Java.Lang.IRunnableInvoker.n_Run(IntPtr jnienv, IntPtr native__this)
   at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PP_V(_JniMarshal_PP_V callback, IntPtr jnienv, IntPtr klazz)

My current setup is:

• .NET 9 (Android)

• Telerik UI for .NET MAUI version 10.1.0

• Microsoft.Maui.Controls - Version: 9.0.50

• Microsoft.Maui.Controls.Compatibility - Version: 9.0.50

• Android 13

If I'm able to create a sample app that reproduces the issue, I will share it with you.

Thanks!

Hi!

I am facing the same issue with RadCollectionView in .NET MAUI.
The application crashes unexpectedly, and in the Android log, I was only able to identify this:

I am using .NET 9(Android) and tested with Telerik UI for .NET MAUI versions 10.0.0 and 10.1.0.

• Microsoft.Maui.Controls - Version: 9.0.50

• Microsoft.Maui.Controls.Compatibility - Version: 9.0.50
  

Unfortunately, I haven’t been able to determine a specific action or moment when the crash consistently occurs.
However, it tends to happen after navigating through items in the RadCollectionView, and repeatedly leaving and entering the page.

Please let me know if there is a fix or workaround for this issue.

 FATAL EXCEPTION: main

 android.runtime.JavaProxyThrowable: [System.NullReferenceException]: Object reference not set to an instance of an object
at Telerik.Maui.Controls.RadCollectionView.<OnScrollViewScrolled>b__159_0 + 0x23(Unknown Source)
at Microsoft.Maui.Dispatching.Dispatcher+<>c__DisplayClass3_0.<DispatchImplementation>b__0 + 0x0(Unknown Source)
at Java.Lang.Thread+RunnableImplementor.Run + 0x8(Unknown Source)
at Java.Lang.IRunnableInvoker.n_Run + 0x8(Unknown Source)
at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PP_V + 0x5(Unknown Source)
at mono.java.lang.RunnableImplementor.n_run(Native Method)
at mono.java.lang.RunnableImplementor.run(RunnableImplementor.java:29)
at android.os.Handler.handleCallback(Handler.java:942)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:226)
at android.os.Looper.loop(Looper.java:313)
at android.app.ActivityThread.main(ActivityThread.java:8762)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:604)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1067)
 Shared library 'liblog' not loaded, p/invoke '__android_log_print' may fail
 UNHANDLED EXCEPTION:
 Android.Runtime.JavaProxyThrowable: Exception_WasThrown, Android.Runtime.JavaProxyThrowable

@Didi - see comments below... this wasn't happening in 9.0.0 version of the library.

Our crash analytics are reporting it as an unobserved task exception thrown on the dispatcher thread pool - so we can't trace exactly which of our many collection views are throwing it.
So

- 10.0.0 only

- iOS only (we don't see any exceptions reported like this for Android)