Grouped CollectionView visible

[Rodrigo]

Hi!

I migrated from Listview to Collectionview and I have 2 problems.
Can you help me?
1- Is it possible to hide the group indicator?
2- This blank space appears at the end of the layout. In the Listview everything is ok, but in the CollectionView I couldn't identify it. Do you know what it could be?

[Yana]

Hi Rodrigo,

Both issues can be resolved by creating a GroupViewStyle for the CollectionView:

1 - the group indicator is added into the GroupView ControlTemplate, so you'd need to override it to remove it.

2 - this is the padding set inside the GroupViewStyle.

Here is a sample GroupViewStyle you can use:

<ControlTemplate x:Key="RadCollectionViewGroupItem_ControlTemplate">
        <Grid ColumnDefinitions="*"
                Padding="{TemplateBinding ActualPadding}">
        <ContentPresenter />
    </Grid>
</ControlTemplate>

<Style x:Key="GroupHeaderStyle" TargetType="telerik:RadCollectionViewGroupView">
    <Setter Property="ControlTemplate" Value="{StaticResource RadCollectionViewGroupItem_ControlTemplate}" />
    <Setter Property="Padding" Value="0" />
</Style>

 

Just apply the GroupHeaderStyle resource to the CollectionView's GroupViewStyle:

<telerik:RadCollectionView ItemsSource="{Binding Locations}"
                        DisplayMemberPath="City"
                        GroupViewStyle="{StaticResource GroupHeaderStyle}">
    <telerik:RadCollectionView.BindingContext>
        <local:ViewModel />
    </telerik:RadCollectionView.BindingContext>
    <telerik:RadCollectionView.GroupDescriptors>
        <telerik:PropertyGroupDescriptor PropertyName="Country" />
    </telerik:RadCollectionView.GroupDescriptors>
</telerik:RadCollectionView>

Give it a try and let me know if you have any additional questions on this.

Regards,
Yana
Progress Telerik

[Rodrigo]

Perfect! Thanks.
If I want it to always be expanded when someone clicks on the grouping, what should I do?

Regards,

Rodrigo.

[Lance | Senior Manager Technical Support]

Hi Rodrigo,

If I understand you correctly, you don't want a specific group to be collapsed if it is expanded and the user taps it?  There isn't a setting right now where you can define an exact group to not be collapsible.

However I have an idea that you can try that achieves the same end result.

When a group is tapped, it will trigger the GroupTapped event. Inside this event you can get a reference to the group's context;  see if the IsExpanded=false and the group's name. If all conditions match, then programmatically re-expand it.

Here's an example to explain better:

private async void RadCollectionView_OnGroupTapped(object sender, RadTappedEventArgs<GroupContext> e)
{
    // Get the references we need
    var collectionView = sender as RadCollectionView;
    var dataView = collectionView.GetDataView();

    // If the group is currently expanded and the group's title is "Belgium"
    if (!e.Data.IsExpanded && e.Data.Key.ToString() == "Belgium")
    {
        // Find the matching IDataGroup
        var matchingGroup = dataView.GetGroups().FirstOrDefault(g => g.Key == e.Data.Key);

        // You need a very short delay to allow the previous change's animation
        await Task.Delay(20);

        // Re-expand it
        dataView.ExpandGroup(matchingGroup);
    }
}

While this does have a very quick collapse/expand animation, it will force that group to stay open and achieves the ultimate goal.

Outside of this, we would need to build in an GroupTapping pre-trigger event that allows you to call some sort of e.Cancel() method to cancel the operation. I will mention this desire to the dev team to consider for future planning.

[Edit] Fixed misspelling and grammar to better clarify the suggestion.

[Rodrigo]

Hi Lance!

Thanks for help!

Regards,

Rodrigo.

[Lance | Senior Manager Technical Support]

Hi Rodrigo, I spoke with the devs and indeed my recommendation is the only suitable path right now. I did open this Feature Request on your behalf for them to consider adding something more official in time => [CollectionView] Add Cancellation support for group expand/collapse.