Infinite Scrolling in a ListView - windows-phone-8.1

Question

I'm trying to implemented infinite scrolling in my listview.
The approach is to get the scroll bar within the listview and hook an event handler to it's scroll event.
<CollectionViewSource x:Key="PaginatedData"
IsSourceGrouped="True"
ItemsPath="CommentaryList"
Source="{Binding paginatedCommentary}"/>
<ListView x:Name="commentaryListView"
Loaded="commentaryListView_Loaded"
ItemTemplate="{StaticResource CommentaryListTemplate}"
ItemsSource="{Binding Source={StaticResource PaginatedData}}"/>
private void commentaryListView_Loaded(object sender, RoutedEventArgs e)
{
var scrollViewer = commentaryListView.GetFirstDescendantOfType<ScrollViewer>();
var scrollbars = new List<ScrollBar>(scrollViewer.GetDescendantsOfType<ScrollBar>());
var verticalBar = scrollbars.FirstOrDefault(x => x.Orientation == Orientation.Vertical);
if (verticalBar != null)
verticalBar.Scroll += BarScroll;
}
private void BarScroll(object sender, ScrollEventArgs e)
{
if (e.ScrollEventType != ScrollEventType.EndScroll) return;
var bar = sender as ScrollBar;
if (bar == null) return;
if (e.NewValue >= bar.Maximum)
{
datacontext.pageCommentaryItems();
}
}
Can't seem to figure out what I'm doing here, but it's never hitting the BarScroll event handler.
Appreciate your help. Thank you :)

Answer 1

I recommend you use the ListView's ViewChanged event directly:
private void OnListViewLoaded(object sender, RoutedEventArgs e)
{
var listview = sender as ListViewBase;
if (listview != null)
{
// Attach to the view changed event
_scrollViewer = listview.GetFirstDescendantOfType<ScrollViewer>();
if (_scrollViewer != null)
{
_scrollViewer.ViewChanged += OnViewChanged;
}
}
}
private void OnViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
{
// If scrollviewer is scrolled down at least 90%
if (_scrollViewer.VerticalOffset > Math.Max(_scrollViewer.ScrollableHeight * 0.9, _scrollViewer.ScrollableHeight - 150))
{
// Execute whatever you want
}
}

Answer 2

A much simpler solution would be to create an observable collection that implements the ISupportIncrementalLoading interface and bind it to your ListView. This will make the ListView do incremental scrolling without any need to implement it yourself. See https://marcominerva.wordpress.com/2013/05/22/implementing-the-isupportincrementalloading-interface-in-a-window-store-app/