Alternate color for listview item UWP

Question

I have a class to color alternate the background of item, but if I delete a item, the background color does not update. Is there a way to refresh the background color after deleting an item?

The code for alterante color. class listview:

public class AlternatingRowListView : ListView
{
    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {
        base.PrepareContainerForItemOverride(element, item);
        var listViewItem = element as ListViewItem;
        if (listViewItem != null)
        {
            var index = IndexFromContainer(element);

            if (index % 2 == 0)
            {
                listViewItem.Background = new SolidColorBrush(Colors.LightBlue);
            }
            else
            {
                listViewItem.Background = new SolidColorBrush(Colors.Transparent);
            }
        }

    }
}

code xaml:

<local:AlternatingRowListView x:Name="listview">
        <ListViewItem>item 1</ListViewItem>
        <ListViewItem>item 2</ListViewItem>
        <ListViewItem>item 3</ListViewItem>
        <ListViewItem>item 4</ListViewItem>
        <local:AlternatingRowListView.ItemTemplate>
            <DataTemplate>

            </DataTemplate>
        </local:AlternatingRowListView.ItemTemplate>
</local:AlternatingRowListView>

Thanks in advance.

Answer 1

You just need to extend your already extended AlternatingRowListView control a bit to achieve what you need.

You can monitor whenever an item gets removed from the list by subscribing to the VectorChanged event of the Items, and then you just loop through all the already realized items below(visually) the removed item and change their background colors accordingly.

Something like this would do -

public AlternatingRowListView()
{
    DefaultStyleKey = typeof(ListView);

    Items.VectorChanged += OnItemsVectorChanged;
}

private void OnItemsVectorChanged(IObservableVector<object> sender, IVectorChangedEventArgs args)
{
    // When an item is removed from the list...
    if (args.CollectionChange == CollectionChange.ItemRemoved)
    {
        var removedItemIndex = (int)args.Index;

        // We don't really care about the items that are above the deleted one, so the starting index
        // is the removed item's index.
        for (var i = removedItemIndex; i < Items.Count; i++)
        {
            if (ContainerFromIndex(i) is ListViewItem listViewItem)
            {
                listViewItem.Background = i % 2 == 0 ? 
                    new SolidColorBrush(Colors.LightBlue) : new SolidColorBrush(Colors.Transparent);
            }
            // If it's null, it means virtualization is on and starting from this index the container
            // is not yet realized, so we can safely break the loop.
            else
            {
                break;
            }
        }
    }
}