Strange scrollbar behaviour with VirtualizationStrategyDefinition

[Igor]

I have a RadDataBoundLisbox defined as below

<telerikPrimitives:RadDataBoundListBox ItemsSource="{Binding TitleItems}" ItemTemplateSelector="{StaticResource TitleItemTemplateSelector}" SelectedItem="{Binding SelectedTitleItem, Mode=TwoWay}">
    <telerikPrimitives:RadDataBoundListBox.VirtualizationStrategyDefinition>
        <telerikPrimitives:WrapVirtualizationStrategyDefinition Orientation="Horizontal"/>
     </telerikPrimitives:RadDataBoundListBox.VirtualizationStrategyDefinition>
</telerikPrimitives:RadDataBoundListBox>

All the items in this listbox are approximately 220px wide so there are always 2 items on one line show. When I scroll the listbox, the scrollbar is not fluid, it jumps, looking like it is skipping every second item. Like scrolling by 2 lines insted of one.

[Ves]

Hi Igor,

Indeed, we are aware of a problem with the scrollbar "jumping" in such scenario. However, this does not result in skipping items. If you experience this (skipping items) can you please open a support ticket and send us a small project, reproducing the problem, so that we can investigate it? Thank you.

Best regards,
Ves
Telerik

 

 

[Igor]

No skipping items, just the scrollbar jumping. I had to use the standard listbox instead.

[Rosy Topchiyska]

Hello Igor,

The scroll bar of the RadDataBoundListBox uses logical units. This means that it could take discrete positions that correspond to the position of the current item in the source. When you have small amount of items and their total height is big enough, you can see the jumping of the scroll bar as it takes its discrete values.

Regards,
Rosy Topchiyska
Telerik

 

 

[Igor]

Any way to fix this? The standard ListBox does not have this problem.

[Ves]

Hi Igor,

We are working on it, but I am afraid, there is no fix that you could apply at the moment. Please, accept our apologies for the inconvenience.

Best regards,
Ves
Telerik

 

 

[Michael]

Dear community

I have the same issue with my RadDataBoundListBox. I have a ObservableCollection with an ImageModel with the path to my local image (IsolatedStorage). When I load the images, the ListBox "jumps" (like described above) everytime i update a Property (with 'notify property changed').

Everything works great except the "jumping" of the list. It jumps to the top position of the current top visible element.

Exists a workaround now for this problem/bug? I am working with UI for WindowsPhone 8 (2014.3 1201)

Thank you

[Rosy Topchiyska]

Hello Michael,

Thank you for contacting us.

This "jumping" happens only if the property change makes the item's visual element change its size. Unfortunately, we can not suggest a proper workaround at this time.

Regards,
Rosy Topchiyska
Telerik

 

 

[Igor]

Still no workaround for the jumping?

[Rosy Topchiyska]

Hello Igor,

There is no workaround for this issue at this moment.

We are interested in your future plans for using Windows Phone 8.0, especially why do you continue to develop applications for Windows Phone 8.0, since there are newer platforms - Windows Universal and Universal Windows Platform.

We have rich control suites for these platforms and if you miss something from the UI for Windows Phone suite, please share it with us. You can take a look our RadListView control that has been created to replace the legacy control RadDataBoundListBox, which is also available.

I look forward to your reply.

Regards,
Rosy Topchiyska
Telerik by Progress

[Igor]

I continue developing (or better say maintaining) a Windows Phone 8 app because the client will not pay for rewriting it to a newer SDK (which would take months a costs much money).

[Tsvyatko]

Hi Igor,

Thank you for clarifying your scenario. 

We have identified that addressing this issue require a major refactoring in the DataBoundListBox. Unfortunately, I cannot provide a time frame of addressing it.

I have logged public issue in our feedback portal so you can track its progress.

Regards,
Tsvyatko
Telerik by Progress

[Igor]

Could you also log the second problem reported by Michael? It is more important for me, the problem that the whole list "jumps" when something changes in a DataTemplate.

[Tsvyatko]

Hi Igor,

would it be possible to specify the exact issue/thread that you are referring to.

Thank you in advance

Regards,
Tsvyatko
Telerik by Progress

[Igor]

Just look a few posts up as I mentioned. When I make a change in the DateTemplate using binding that changes some UI (hides or displays an control) that whole list "jumps" meaning it scrolls a bit up or down.

[Tsvyatko]

Hello Igor,

I have added this issue in the feedback portal as well. You can track its progress. Also, you can log issues there directly through your account.

Regards,
Tsvyatko
Telerik by Progress