Virtual list is causing problem

In my app I have a tabsheet component with two different components for each tab. One of the component is a virtuallist. The Virtualist is always updated dynamiclly when I insert data via a form. By switiching from one tab to another and back to the tab with the virtuallist and adding new data to the list I get these kind of error (picture) from the browser.

Does anyone know where this error is coming from ?

Can yo please show the code where you create the template?

this is how i initialize the virtuallist

private void initializeVirtualList(){

    Long userId = this.getSecurityService().getUserId();

    List<GroupRequest> requests = this.getGroupUiService().getTraininGroupRequestByTrainer(userId);


    this.groupRequestInMemoryDataProvider = new ListDataProvider<>(this.getGroupRequestsBuffer());

    this.groupRequests = new VirtualList<>();


if you mean this by the template

And this is how i intialize the renderer

So it works initially, correct?
Does it break only when you switch tabs in a tabsheet, or does it also break by adding new items?

When I switch tabs in a tabsheet. The first switch the virtuallist works. But switching back to another tab where I can insert data to the virtuallist leads to a probleam

I asked our components team to see if anyone has thoughts on what might be causing it. It seems like that exception is coming from the internals of virtuallist

so what does this actually mean ?

There is probably an internal error in the component by using it within tabs :wink:

Ohh okay. Yeah it might be. I switched the virtual list component with a grid and it works just fine

Hi, I tried the provided code snippets but couldn’t reproduce the issue. The VirtualList rendered fine inside the TabSheet and changing between the tabs worked ok as well. Tried with V23.3 and V24.

Please submit an issue at and attach a minimal repro that can be run as is.