用户选择子项后 TreeView 自动选择父项

Question

在我的窗口中，我有一个 TreeView 和 TextBox。假设 TextBox 用于编写自定义脚本，而 TreeView 是一种选择要插入的函数的方法；想想 Crystal Report 脚本编辑器。

我的目标是让用户单击 TreeView 的其中一个子项并将该子项插入到 TextBox 中。子节点是一个函数签名，位于父节点下。然后用户可以导航到文本框，选择一个函数参数并将其替换为另一个函数签名。为此，我处理了 TreeView 的 SelectedItemChanged 事件，设置了 TextBox 的 SelectedText，然后尝试在更改后突出显示文本。

TextBox 的 SelectedText 已正确交换。但是，文本没有被突出显示，滚动条也没有滚动到选定的文本。

这是我为重现行为而编写的测试项目中的 XAML：

  <Window x:Class="SelectedTextWeirdness.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:System="clr-namespace:System;assembly=mscorlib"
          xmlns:SelectedTextWeirdness="clr-namespace:SelectedTextWeirdness" Title="MainWindow" Width="600" Height="600"
          x:Name="Me">
     <Grid>
        <Grid.RowDefinitions>
           <RowDefinition Height="Auto" />
           <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <TreeView Grid.Row="0" x:Name="treeView" ItemsSource="{Binding ElementName=Me, Path=TreeViewItems, Mode=TwoWay}" 
                  SelectedItemChanged="treeView_SelectedItemChanged" Margin="10">
           <TreeView.Resources>
              <HierarchicalDataTemplate DataType="{x:Type SelectedTextWeirdness:Parent}" ItemsSource="{Binding Children}">
                 <TextBlock Text="{Binding Name}" />
              </HierarchicalDataTemplate>
              <DataTemplate DataType="{x:Type SelectedTextWeirdness:Child}">
                 <TextBlock Text="{Binding Name}" />
              </DataTemplate>
           </TreeView.Resources>
        </TreeView>
        <TextBox Grid.Row="1" x:Name="scriptTextBox" Margin="10" Height="200" Width="Auto" FontFamily="Consolas, Courier New" 
                 HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Auto"
                 MaxLines="9999" AcceptsReturn="True" AcceptsTab="True" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" 
                 Text="{Binding Path=Script, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                 />
     </Grid>
  </Window>

下面是代码隐藏：

  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Windows;
  using System.Windows.Controls;
  using System.Windows.Data;
  using System.Windows.Documents;
  using System.Windows.Input;
  using System.Windows.Media;
  using System.Windows.Media.Imaging;
  using System.Windows.Navigation;
  using System.Windows.Shapes;

  namespace SelectedTextWeirdness
  {
     public class Child
     {
        public string Name
        {
           get;
           set;
        }
     }

     public class Parent
     {
        public string Name
        {
           get;
           set;
        }

        public List<Child> Children
        {
           get;
           set;
        }   
     }

     /// <summary>
     /// Interaction logic for MainWindow.xaml
     /// </summary>
     public partial class MainWindow : Window
     {
        public List<Parent> TreeViewItems
        {
           get;
           set;
        }

        public MainWindow()
        {
           BuildTreeViewItems();

           InitializeComponent();
        }

        private void BuildTreeViewItems()
        {
           TreeViewItems = new List<Parent>()
                              {
                                 new Parent()
                                    {
                                       Name = "Parent1",
                                       Children =
                                          new List<Child>()
                                             {
                                                new Child() {Name = "ReallyLongFunctionNameNumber1(ReallyLongLeft1, ReallyLongRight1)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber2(ReallyLongLeft2, ReallyLongRight2)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber3(ReallyLongLeft3, ReallyLongRight3)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber4(ReallyLongLeft4, ReallyLongRight4)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber5(ReallyLongLeft5, ReallyLongRight5)"}
                                             }
                                    },
                                 new Parent()
                                    {
                                       Name = "Parent2",
                                       Children =
                                          new List<Child>()
                                             {
                                                new Child() {Name = "ReallyLongFunctionNameNumber1(ReallyLongLeft1, ReallyLongRight1)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber2(ReallyLongLeft2, ReallyLongRight2)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber3(ReallyLongLeft3, ReallyLongRight3)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber4(ReallyLongLeft4, ReallyLongRight4)"},
                                                new Child() {Name = "ReallyLongFunctionNameNumber5(ReallyLongLeft5, ReallyLongRight5)"}
                                             }
                                    }
                              };
        }

        private void treeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
           var tree = (TreeView)sender;
           var selectedItem = tree.SelectedItem as Child;
           if (selectedItem != null)
           {
              int selectionStart = scriptTextBox.SelectionStart;
              string selectedText = selectedItem.Name;
              scriptTextBox.SelectedText = selectedText;
              scriptTextBox.Focus();            
              scriptTextBox.Select(selectionStart, selectedText.Length);
           }
        }
     }
  }

我已尝试设置 SelectedItemChanged e.Handled = true。那没有用。我已经尝试处理 TextBox 的 LostFocus 并设置 e.Handled = true 并且没有奏效。这似乎只在我使用 HierarchicalDateTemplate 时发生。如果我将数据更改为仅一级，则此设置可以正常工作。

有什么想法吗？

Answer 1

核心问题是在事件处理程序中更改Focus()。通过在 BeginInvoke 中调用焦点来推迟焦点。

类似：

delegate void voidDelegate();

private void treeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
    var tree = (TreeView)sender;
    var selectedItem = tree.SelectedItem as Child;
    if (selectedItem != null)
    {
        int selectionStart = scriptTextBox.SelectionStart;
        string selectedText = selectedItem.Name;
        voidDelegate giveFocusDelegate = new  voidDelegate(giveFocus);  
        Dispatcher.BeginInvoke(giveFocusDelegate, new object[] { });
        scriptTextBox.SelectedText = selectedText;         
    }
}

private void giveFocus()
{
    scriptTextBox.Focus();
}    

应该让你离目标更近。

编辑：我们怎么知道这会起作用？

正如the documentation for Dispatcher.BeginInvoke 所说：

操作被添加到 Dispatcher 的事件队列中 指定 DispatcherPriority。

因此，无论您调用 beginInvoke 的任务的优先级如何，调用可能发生的最近时间是在当前操作的执行结束之后：beginInvoked 操作被“推送”到调度程序队列的某个位置，这是有效的在一个线程上。