How to disable expanding/collapsing of tree items in WPF TreeView on double-click

问题

How can I disable tree items collapsing/expanding when I double-click on tree item? I still would like to do this by clicking on toggle button, but not when I double-click on item.

This is XAML I have:

<TreeView Grid.Column="0" Grid.Row="0" ItemsSource="{Binding Categories}" helpers:TreeViewHelper.SelectedItem="{Binding SelectedCategory, Mode=TwoWay}" >
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True"/>
        </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate DataType="{x:Type core:Category}" ItemsSource="{Binding SubCategories}">
            <Label Content="{Binding Name}">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="MouseDoubleClick">
                        <i:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=DataContext.CreateGroupsFromCategoryCommand , Mode=OneWay}" CommandParameter="{Binding}" />
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </Label>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

I would like to do this only in XAML.

Thank you for your help.

回答1:

You should suppress the double click event on treeviewitem:

<TreeView Grid.Column="0" Grid.Row="0" ItemsSource="{Binding Categories}" helpers:TreeViewHelper.SelectedItem="{Binding SelectedCategory, Mode=TwoWay}" TreeViewItem.PreviewMouseDoubleClick="TreeViewItem_PreviewMouseDoubleClick" >
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True"/>
        </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate DataType="{x:Type core:Category}" ItemsSource="{Binding SubCategories}">
            <Label Content="{Binding Name}">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="MouseDoubleClick">
                        <i:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=DataContext.CreateGroupsFromCategoryCommand , Mode=OneWay}" CommandParameter="{Binding}" />
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </Label>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

Code Behind:

private void TreeViewItem_PreviewMouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    //this will suppress the event that is causing the nodes to expand/contract 
    e.Handled = true;
}

回答2:

You could implement a custom EventTrigger in your views code behind, as suggested here: https://stackoverflow.com/a/7688249/1206431

public class HandlingEventTrigger : System.Windows.Interactivity.EventTrigger
{
    protected override void OnEvent(System.EventArgs eventArgs)
    {
        var routedEventArgs = eventArgs as RoutedEventArgs;
        if (routedEventArgs != null)
            routedEventArgs.Handled = true;

        base.OnEvent(eventArgs);
    }
}

Add the namespace to your view like this xmlns:views="clr-namespace:YourNamespace.Views"

And then replace <i:EventTrigger EventName="MouseDoubleClick"> with <local:HandlingEventTrigger EventName="PreviewMouseDoubleClick">.

The HandlingEventTrigger will stop the event from being passed further up the visual tree and therefore not expanding/collapsing your tree, and using PreviewMouseDoubleClick instead of MouseDoubleClick will allow you to still fire your own command.

来源：https://stackoverflow.com/questions/53466305/how-to-disable-expanding-collapsing-of-tree-items-in-wpf-treeview-on-double-clic

标签

wpf

xaml

mvvm

treeview

expand