在DataTemplate中显示和聚焦TextBox

Question

我已经搜索了很多地方，但是我无法解决这个问题。我正在构建一个具有可编辑项的ListBox。我为ListBox.ItemTemplate准备了一个DataTemplate，其中包含（除其他内容之外）TextBlock和TextBox。TextBlock始终可见，只有在用户双击TextBlock后，TextBox才可见。当用户单击列表中的另一项时，TextBox会再次隐藏以显示TextBlock。所有这些都很好用。请查看我的代码：

XAML

<Window.Resources>
   <local:GoalCollection x:Key="goals"/>
   <DataTemplate x:Key="GoalItemTemplate" DataType="local:Goal">
      <Grid>
         <TextBlock Text="{Binding Title}"
                    MouseLeftButtonDown="TextBlock_MouseLeftButtonDown"
                    VerticalAlignment="Center"/>
         <TextBox Name="EntryBox"
                  Text="{Binding Title}"
                  Visibility="Hidden"
                  BorderBrush="{x:Null}"
                  Padding="-2,0,0,0"
                  Panel.ZIndex="1"
                  Margin="-2,0,0,0"/>
      </Grid>
   </DataTemplate>
</Window.Resources>
<Grid>
   <Grid.ColumnDefinitions>
      <ColumnDefinition />
      <ColumnDefinition Width="2*" />
   </Grid.ColumnDefinitions>
   <ListBox Name="GoalsList"
      ItemsSource="{Binding Source={StaticResource goals}}"
      HorizontalContentAlignment="Stretch"
      ItemTemplate="{StaticResource GoalItemTemplate}"
      SelectionChanged="GoalsList_SelectionChanged" />
</Grid>

C#

public partial class MainWindow : Window
{
    GoalCollection goals;
    public MainWindow()
    {
       InitializeComponent();
    }

    private childItem FindVisualChild<childItem>(DependencyObject obj)
    where childItem : DependencyObject { ... }

    protected override void OnInitialized(EventArgs e)
    {
       base.OnInitialized(e);
       goals = (GoalCollection)Resources["goals"];
    }

    private void TextBlock_MouseLeftButtonDown(object sender, 
                                               MouseButtonEventArgs e)
    {
       if (e.ClickCount == 2)
       {
          TextBlock tblk = sender as TextBlock;
          if (tblk == null) 
             return;
          TextBox tbx = ((Grid)tblk.Parent).FindName("EntryBox") as TextBox;
          if (tbx == null) 
             return;
          tbx.Visibility = Visibility.Visible;
          Keyboard.Focus(tbx);
       }
    }

    private void GoalsList_SelectionChanged(object sender, 
                                            SelectionChangedEventArgs e)
    {
       ListBoxItem lbi;
       ContentPresenter cp;
       DataTemplate dt;
       TextBox tbx;

       foreach (Goal item in e.RemovedItems)
       {
          lbi = (ListBoxItem)GoalsList.ItemContainerGenerator.
                                       ContainerFromItem(item);
          cp = FindVisualChild<ContentPresenter>(lbi);
          dt = cp.ContentTemplate;
          tbx = (TextBox)dt.FindName("EntryBox", cp);
          if (tbx == null) 
             continue;
          tbx.Visibility = Visibility.Hidden;
       }
    }
 }

我遇到的问题是，双击后TextBox立即将焦点返回到主机ListBoxItem。需要额外的(第三次)点击才能将焦点聚焦在TextBox上。

通过跟踪代码，我发现TextBox确实接收到了焦点，但随后立即失去了焦点(尝试为`TextBox.LostKeyboardFocus'事件添加处理程序，并逐步执行'TextBlock_MouseLeftButtonDown()'方法)。有什么建议吗？

谢谢。

- gregsdennis

Answer 1

我猜测点击事件正在向上传递到ListBox，并且它通过选择该项来处理它。

尝试在单击事件处理程序中添加以下内容（在Keyboard.Focus(tbx);之后）

e.Handled = true;

- Adam Barney

---

您，先生，真是个天才！我总是忘记了那个。 - gregsdennis

Answer 2

如果你想让一个子元素获得焦点，可以尝试使用FocusManager。

<DataTemplate x:Key="MyDataTemplate" DataType="ListBoxItem">
   <Grid>
      <WrapPanel Orientation="Horizontal" 
                 FocusManager.FocusedElement="{Binding ElementName=tbText}">
         <CheckBox IsChecked="{Binding Path=Completed}" Margin="5" />
         <Button Style="{StaticResource ResourceKey=DeleteButtonTemplate}" 
                 Margin="5" Click="btnDeleteItem_Click" />
         <TextBox Name="tbText" 
                  Text="{Binding Path=Text}" 
                  Width="200" 
                  TextWrapping="Wrap" 
                  AcceptsReturn="True" 
                  Margin="5" 
                  Focusable="True"/>
         <DatePicker Text="{Binding Path=Date}" Margin="5"/>
      </WrapPanel>
   </Grid>
</DataTemplate>

- Jesse Seger