private void CustomVirtualizingStackPanel_MouseWheelDownEvent(object sender, RoutedEventArgs e)
{
CustomVirtualizingStackPanel panel = sender as CustomVirtualizingStackPanel;
if (panel != null)
{
ScrollViewer scrollViewer = GetParent <ScrollViewer>(panel);
if (scrollViewer != null)
{
double dVer = scrollViewer.VerticalOffset;
double dViewport = scrollViewer.ViewportHeight;
double dExtent = scrollViewer.ExtentHeight;
//滚动至最底部
if (dVer + dViewport >= dExtent)
{
ResultPage page = scrollViewer.Tag as ResultPage;
if (page != null)
{
page.Start();
}
}
}
}
}
/// <summary>
/// 查找TreeView中TreeViewItem
/// <para>警告:该方法只能用于TreeView.ItemsHost、TreeView.ItemContainerStyle中ItemsPanel的对象为 CustomVirtualizingStackPanel 方为有效,否则会发生异常</para>
/// </summary>
/// <param name="container"></param>
/// <param name="item"></param>
/// <returns></returns>
public static TreeViewItem GetTreeViewItem(this ItemsControl container, object item)
{
if (container != null)
{
if (container.DataContext == item)
{
return(container as TreeViewItem);
}
if (container.Items.Count == 0)
{
return(null);
}
if (container is TreeViewItem && !((TreeViewItem)container).IsExpanded)
{
container.SetValue(TreeViewItem.IsExpandedProperty, true);
}
container.ApplyTemplate();
ItemsPresenter itemsPresenter = (ItemsPresenter)container.Template.FindName("ItemsHost", container);
if (itemsPresenter != null)
{
itemsPresenter.ApplyTemplate();
}
else
{
itemsPresenter = FindVisualChild <ItemsPresenter>(container);
if (itemsPresenter == null)
{
container.UpdateLayout();
itemsPresenter = FindVisualChild <ItemsPresenter>(container);
}
}
Panel itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);
CustomVirtualizingStackPanel virtualizingPanel = itemsHostPanel as CustomVirtualizingStackPanel;
for (int i = 0, count = container.Items.Count; i < count; i++)
{
TreeViewItem subContainer;
if (virtualizingPanel != null)
{
virtualizingPanel.BringIntoView(i);
subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
}
else
{
subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
subContainer.BringIntoView();
}
if (subContainer != null)
{
TreeViewItem resultContainer = GetTreeViewItem(subContainer, item);
if (resultContainer != null)
{
return(resultContainer);
}
else
{
subContainer.IsExpanded = false;
}
}
}
}
return(null);
}
