public static void ScrollItem(ListViewBase control, int indexDelta)
{
if (control == null || control.Items == null)
{
return;
}
var scrollViewer = VisualTreeUtilities.GetVisualChild <ScrollViewer>(control);
var p = new Point(Window.Current.Bounds.Width / 2, 10);
var transform = control.TransformToVisual(Window.Current.Content);
var checkPoint = transform.TransformPoint(p);
var q = from lvi in VisualTreeHelper.FindElementsInHostCoordinates(checkPoint, scrollViewer).OfType <ListViewItem>()
where lvi.Content != null
select lvi.Content;
var item = q.FirstOrDefault();
if (item == null)
{
return;
}
var index = control.Items.IndexOf(item);
var nextItemIndex = index + indexDelta;
if (index != -1 && nextItemIndex >= 0 && nextItemIndex < control.Items.Count)
{
var nextItem = control.Items[nextItemIndex];
control.ScrollIntoView(nextItem, ScrollIntoViewAlignment.Leading);
}
}
void _element_LayoutUpdated(object sender, object e)
{
if (!_loaded)
{
return;
}
if (_scrollViewer == null)
{
_scrollViewer = VisualTreeUtilities.GetVisualChild <ScrollViewer>(_element);
if (_scrollViewer == null)
{
return;
}
}
var canSetHorizontalOffset = _scrollViewer.ScrollableWidth > 0D &&
_scrollableWidth > 0D &&
Math.Abs(1D - (_scrollViewer.ScrollableWidth / _scrollableWidth)) < Tolerance;
if (canSetHorizontalOffset && !_horizontalSet)
{
_scrollViewer.ChangeView(_horizontalOffset, null, null, true);
_horizontalSet = true;
}
var canSetVerticalOffset = _scrollViewer.ScrollableHeight > 0D &&
_scrollableHeight > 0D &&
Math.Abs(1D - (_scrollViewer.ScrollableHeight / _scrollableHeight)) < Tolerance;
if (canSetVerticalOffset && !_verticalSet)
{
_scrollViewer.ChangeView(null, _verticalOffset, null, true);
_verticalSet = true;
}
if (_verticalSet && _horizontalSet)
{
_element.LayoutUpdated -= _element_LayoutUpdated;
}
}
public void Save([NotNull] Dictionary <string, object> pageState, string keyPrefix)
{
if (pageState == null)
{
throw new ArgumentNullException("pageState");
}
if (_scrollViewer == null)
{
_scrollViewer = VisualTreeUtilities.GetVisualChild <ScrollViewer>(_element);
if (_scrollViewer == null)
{
return;
}
}
pageState[keyPrefix + "ScrollableWidth"] = _scrollViewer.ScrollableWidth;
pageState[keyPrefix + "ScrollableHeight"] = _scrollViewer.ScrollableHeight;
pageState[keyPrefix + "HorizontalOffset"] = _scrollViewer.HorizontalOffset;
pageState[keyPrefix + "VerticalOffset"] = _scrollViewer.VerticalOffset;
}
