在显示ContextMenu之前,右键单击选择TreeView节点

Question

我想在显示ContextMenu之前右键单击选择一个WPF TreeView节点.

对于WinForms,我可以使用这样的代码在上下文菜单下点击查找节点,WPF的替代方案是什么？

Answer 1

根据树的填充方式,发送方和e.Source值可能会有所不同.

其中一个可能的解决方案是使用e.OriginalSource并使用VisualTreeHelper查找TreeViewItem:

private void OnPreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    TreeViewItem treeViewItem = VisualUpwardSearch(e.OriginalSource as DependencyObject);

    if (treeViewItem != null)
    {
        treeViewItem.Focus();
        e.Handled = true;
    }
}

static TreeViewItem VisualUpwardSearch(DependencyObject source)
{
    while (source != null && !(source is TreeViewItem))
        source = VisualTreeHelper.GetParent(source);

    return source as TreeViewItem;
}

Answer 2

如果您想要一个仅限XAML的解决方案,您可以使用Blend Interactivity.

假设TreeView数据绑定到具有Boolean属性IsSelected和String属性的视图模型的分层集合Name以及命名的子项集合Children.

<TreeView ItemsSource="{Binding Items}">
  <TreeView.ItemContainerStyle>
    <Style TargetType="TreeViewItem">
      <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
    </Style>
  </TreeView.ItemContainerStyle>
  <TreeView.ItemTemplate>
    <HierarchicalDataTemplate ItemsSource="{Binding Children}">
      <TextBlock Text="{Binding Name}">
        <i:Interaction.Triggers>
          <i:EventTrigger EventName="PreviewMouseRightButtonDown">
            <ei:ChangePropertyAction PropertyName="IsSelected" Value="true" TargetObject="{Binding}"/>
          </i:EventTrigger>
        </i:Interaction.Triggers>
      </TextBlock>
    </HierarchicalDataTemplate>
  </TreeView.ItemTemplate>
</TreeView>

有两个有趣的部分:

1. 该TreeViewItem.IsSelected属性IsSelected与视图模型上的属性绑定.将IsSelectedview-model上的属性设置为true将选择树中的相应节点.

2. 当PreviewMouseRightButtonDown触发节点的可视部分时(在此示例a中TextBlock)IsSelected,视图模型上的属性设置为true.回到1.您可以看到在树中单击的相应节点成为选定节点.

在项目中获得Blend Interactivity的一种方法是使用NuGet包Unofficial.Blend.Interactivity.

Answer 3

使用"item.Focus();" 似乎没有100%工作,使用"item.IsSelected = true;" 确实.

Answer 4

使用alex2k8的原创想法,正确处理来自Wieser Software Ltd的非可视化,来自Stefan的XAML,来自Erlend的IsSelected,以及我对真正制作静态方法Generic的贡献:

XAML:

<TreeView.ItemContainerStyle> 
    <Style TargetType="{x:Type TreeViewItem}"> 
        <!-- We have to select the item which is right-clicked on --> 
        <EventSetter Event="TreeViewItem.PreviewMouseRightButtonDown"
                     Handler="TreeViewItem_PreviewMouseRightButtonDown"/> 
    </Style> 
</TreeView.ItemContainerStyle>

C#代码背后:

void TreeViewItem_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    TreeViewItem treeViewItem = 
              VisualUpwardSearch<TreeViewItem>(e.OriginalSource as DependencyObject);

    if(treeViewItem != null)
    {
        treeViewItem.IsSelected = true;
        e.Handled = true;
    }
}

static T VisualUpwardSearch<T>(DependencyObject source) where T : DependencyObject
{
    DependencyObject returnVal = source;

    while(returnVal != null && !(returnVal is T))
    {
        DependencyObject tempReturnVal = null;
        if(returnVal is Visual || returnVal is Visual3D)
        {
            tempReturnVal = VisualTreeHelper.GetParent(returnVal);
        }
        if(tempReturnVal == null)
        {
            returnVal = LogicalTreeHelper.GetParent(returnVal);
        }
        else returnVal = tempReturnVal;
    }

    return returnVal as T;
}

编辑:以前的代码总是适用于这种情况,但在另一种情况下,当LogicalTreeHelper返回一个值时,VisualTreeHelper.GetParent返回null,因此修复了该问题.

Answer 5

在XAML中,在XAML中添加PreviewMouseRightButtonDown处理程序:

    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <!-- We have to select the item which is right-clicked on -->
            <EventSetter Event="TreeViewItem.PreviewMouseRightButtonDown" Handler="TreeViewItem_PreviewMouseRightButtonDown"/>
        </Style>
    </TreeView.ItemContainerStyle>

然后像这样处理事件:

    private void TreeViewItem_PreviewMouseRightButtonDown( object sender, MouseEventArgs e )
    {
        TreeViewItem item = sender as TreeViewItem;
        if ( item != null )
        {
            item.Focus( );
            e.Handled = true;
        }
    }

Answer 6

几乎是正确的,但你需要注意树中的非视觉效果(例如Run,像a ).

static DependencyObject VisualUpwardSearch<T>(DependencyObject source) 
{
    while (source != null && source.GetType() != typeof(T))
    {
        if (source is Visual || source is Visual3D)
        {
            source = VisualTreeHelper.GetParent(source);
        }
        else
        {
            source = LogicalTreeHelper.GetParent(source);
        }
    }
    return source; 
}

Answer 7

我认为注册一个类处理程序应该可以解决问题.只需在app.xaml.cs代码文件中的TreeViewItem的PreviewMouseRightButtonDownEvent上注册一个路由事件处理程序,如下所示:

/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        EventManager.RegisterClassHandler(typeof(TreeViewItem), TreeViewItem.PreviewMouseRightButtonDownEvent, new RoutedEventHandler(TreeViewItem_PreviewMouseRightButtonDownEvent));

        base.OnStartup(e);
    }

    private void TreeViewItem_PreviewMouseRightButtonDownEvent(object sender, RoutedEventArgs e)
    {
        (sender as TreeViewItem).IsSelected = true;
    }
}