c# - 在 ScrollView 中滚动到选定的 Treeviewitem

Question

我有一个包含 TreeView 的滚动查看器。

我以编程方式填充 TreeView (未绑定(bind))，并将 TreeView 展开为预定的 TreeView 项。一切正常。

我的问题是，当树展开时，我希望作为 treeview 父级的 scrollview 滚动到我刚刚展开的 treeviewitem。有任何想法吗？ - 请记住， TreeView 每次展开时可能都不具有相同的结构，因此排除了仅存储当前滚动位置并重置为该位置的可能性...

Answer 1

我遇到了同样的问题，TreeView 没有滚动到所选项目。

我所做的是，在将树扩展到选定的 TreeViewItem 之后，我调用了一个 Dispatcher Helper 方法来允许 UI 更新，然后在选定的项目上使用 TransformToAncestor 来找到它在 ScrollViewer 中的位置。这是代码:

    // Allow UI Rendering to Refresh
    DispatcherHelper.WaitForPriority();

    // Scroll to selected Item
    TreeViewItem tvi = myTreeView.SelectedItem as TreeViewItem;
    Point offset = tvi.TransformToAncestor(myScroll).Transform(new Point(0, 0));
    myScroll.ScrollToVerticalOffset(offset.Y);

这是 DispatcherHelper 代码:

public class DispatcherHelper
{
    private static readonly DispatcherOperationCallback exitFrameCallback = ExitFrame;

    /// <summary>
    /// Processes all UI messages currently in the message queue.
    /// </summary>
    public static void WaitForPriority()
    {
        // Create new nested message pump.
        DispatcherFrame nestedFrame = new DispatcherFrame();

        // Dispatch a callback to the current message queue, when getting called,
        // this callback will end the nested message loop.
        // The priority of this callback should be lower than that of event message you want to process.
        DispatcherOperation exitOperation = Dispatcher.CurrentDispatcher.BeginInvoke(
            DispatcherPriority.ApplicationIdle, exitFrameCallback, nestedFrame);

        // pump the nested message loop, the nested message loop will immediately
        // process the messages left inside the message queue.
        Dispatcher.PushFrame(nestedFrame);

        // If the "exitFrame" callback is not finished, abort it.
        if (exitOperation.Status != DispatcherOperationStatus.Completed)
        {
            exitOperation.Abort();
        }
    }

    private static Object ExitFrame(Object state)
    {
        DispatcherFrame frame = state as DispatcherFrame;

        // Exit the nested message loop.
        frame.Continue = false;
        return null;
    }
}