如何为WPF Treeview挂钩BeforeNodeExpand和AfterNodeExpand？

Question

意图:在填充节点子节点的持续时间内显示busy/Wait光标.

似乎隐藏在WPF中.我记得在Winforms Tree Control中有一些你可以订阅的事件 - 实现这一点.

目前我有一个TreeView,它有许多与其SelectedItem相关的列表视图.所有控件都是数据绑定,并使用DataTemplates显示项目.代码是有用的.但是,当我扩展一个有很多孩子的树节点时,UI变得迟钝..看起来点击没有注册..而我是一个不耐烦的用户去点击节点点击.

那我该怎么做？我想在AfterExpand中将Cursor设置为Wait并在AfterExpand中重置.

代码乱涂乱画:

<HierarchicalDataTemplate DataType="{x:Type local:LinqToSqlNodeClass}" ItemsSource="{Binding Path=Children}">
  // visual representation
</HierarchicalDataTemplate>
// more typed data templates 

<TreeView ItemsSource="{Binding Path=Nodes}" />

Answer 1

ItemContainerGenerator将在Expanded事件之后开始生成,因此您可以使用它来设置Cursor,并在ItemContainerGenerator.StatusChanged触发时将其设置回来,以指示您的子项已被填充.

由于TreeViewItem.Expanded是一个路由事件,您可以在某个父级别订阅:

myTreeView.AddHandler(TreeViewItem.ExpandedEvent, new RoutedEventHandler(TreeViewItemExpanded));

TreeViewItemExpanded在其他地方定义的地方,如下所示:

private void TreeViewItemExpanded(object sender, RoutedEventArgs e)
{
    // we will only go through with this if our children haven't been populated
    TreeViewItem sourceItem = e.OriginalSource as TreeViewItem;
    if ((sourceItem != null)
        && (sourceItem.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated))
    {
        // create a handler that will check our children and reset the cursor when the ItemContainerGenerator has finished
        EventHandler itemsGenerated = null;
        DateTime before = DateTime.Now;
        itemsGenerated = delegate(object o, EventArgs args)
        {
            // if the children are done being generated...
            if ((o as ItemContainerGenerator).Status == GeneratorStatus.ContainersGenerated)
            {
                (o as ItemContainerGenerator).StatusChanged -= itemsGenerated;  // we're done, so remove the handler
                sourceItem.Dispatcher.BeginInvoke(DispatcherPriority.DataBind, (ThreadStart)delegate    // asynchronous reset of cursor
                {
                    myWindow.Cursor = Cursors.Arrow;    // reset cursor
                    Debug.WriteLine("Expanded in " + (DateTime.Now - before));
                });
            }
        };
        sourceItem.ItemContainerGenerator.StatusChanged += itemsGenerated;  // add the handler
        myWindow.Cursor = Cursors.Wait;     // wait cursor
    }
    e.Handled = true;
}