CODEWITHSUNDEEP
c#uwpuwp-xaml
Saravana Kumar
Saravana Kumar

Reputation: 379

UWP custom virtualized listview

I'm trying to recreate a listview with virtualization to get deeper understanding of how listview works. For this I'm creating a custom panel. When the listview items are arranged vertically I need to know the panel height. Suppose if the items are of same height then I can find the height of panel as ItemsSource.Count * itemHeight. If the items are of varying height how can i set the height of panel without computing the height of all the individual items.

Also when all items are of same height then I can scroll to an item based on the item's index in ItemsSource (ie) index * itemheight will give the position of the item in the panel. In case of varying height how can I find this position. Please guide. Thanks

Upvotes: 1

Views: 94

Answers (1)

Junjie Zhu - MSFT
Junjie Zhu - MSFT

Reputation: 3024

OK, I understand. It is recommended to use VirtualizingStackPanel in ItemsPanelTemplate. After using VirtualizingStackPanel, it changes from Physical scrolling to Logical scrolling. This will eliminate the effect of height differences.

<ListView.ItemsPanel>
      <ItemsPanelTemplate>
             <VirtualizingStackPanel Loaded="ItemsStackPanel_Loaded"/>
       </ItemsPanelTemplate>
</ListView.ItemsPanel>

private void ItemsStackPanel_Loaded(object sender, RoutedEventArgs e)
{
    var scrollViewer = YourListView.GetScrollViewer();
    scrollViewer.VerticalSnapPointsType = SnapPointsType.OptionalSingle;
    scrollViewer.ViewChanged += ScrollViewer_ViewChanged; ;
}

private void ScrollViewer_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
{
    var elemnt = (sender as ScrollViewer);
    if (elemnt != null)
    {
        Debug.WriteLine($"Scrollable Height : {elemnt.ScrollableHeight} Scrolled Height {elemnt.VerticalOffset}");
    }
}

//a sample which scroll into 8 logically
private void Button_Click(object sender, RoutedEventArgs e)
{
    var scrollViewer = AuthorGroupsListView.GetScrollViewer();

    scrollViewer.ChangeView(null, 8, null, true);

}

Upvotes: 1

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