WPF TreeView：隐藏所有叶节点的展开符号

Question

如何在 WPF TreeView 中隐藏叶节点的展开/折叠符号？

也就是说：如何让叶子节点自动展开？

有什么方法可以使用 XAML 实现这一目标？

谢谢，

Answer 1

我不知道纯 XAML 解决方案，但您可以绑定 TreeviewItem 的 IsExpanded 属性，并将叶节点上的此属性默认设置为 true（您不必具有此属性在其他节点上完全没有。

<Style TargetType="controls:TreeViewItem">
   <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"></Setter>
</Style>

Answer 2

将 TreeViewItems 绑定到 ObservableCollection 并将 ObservableCollection 留空。这样，展开/折叠符号不会显示，因为 UI 知道没有什么可以展开的。这是我的一些代码中的相关部分：

XAML：

<TreeView x:Name="TreeView"
    ItemsSource="{Binding TopLevelNodes}" 
    VirtualizingStackPanel.IsVirtualizing="True"
    VirtualizingStackPanel.VirtualizationMode="Recycling">

    <TreeView.Resources>
        <HierarchicalDataTemplate
            DataType="{x:Type local:ViewModel}" ItemsSource="{Binding Children}">

视图模型：

ObservableCollection<ObjectBaseViewModel> _children;

public ObservableCollection<ObjectBaseViewModel> Children
{
    get
    {
        if (_children == null)
            _children = new ObservableCollection<ViewModel>();

        return _children;
    }
}

Answer 3

与其他答案类似，展开您可以使用的所有节点

<TreeView >
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True" />
        </Style>
    </TreeView.ItemContainerStyle>

这将使所有 TreeViewItems 自动展开。但是，您仍然会看到展开/折叠切换按钮。要摆脱那个，你必须像这样重新模板 TreeViewItem

<TreeView ...
          ItemContainerStyle="{StaticResource TreeViewItemExpandedStyle}">

还有样式（几乎是 Xaml）

<Style x:Key="TreeViewItemExpandedStyle" TargetType="{x:Type TreeViewItem}">
    <Setter Property="Background" Value="Transparent"/>
    <Setter Property="IsExpanded" Value="True"/>
    <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
    <Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
    <Setter Property="Padding" Value="1,0,0,0"/>
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
    <Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TreeViewItem}">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition MinWidth="19" Width="Auto"/>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition/>
                    </Grid.RowDefinitions>
                    <ToggleButton x:Name="Expander" IsEnabled="False" Visibility="Hidden" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ExpandCollapseToggleStyle}"/>
                    <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                        <ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                    </Border>
                    <ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"/>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsExpanded" Value="false">
                        <Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
                    </Trigger>
                    <Trigger Property="HasItems" Value="false">
                        <Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
                    </Trigger>
                    <Trigger Property="IsSelected" Value="true">
                        <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                    </Trigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="IsSelected" Value="true"/>
                            <Condition Property="IsSelectionActive" Value="false"/>
                        </MultiTrigger.Conditions>
                        <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
                    </MultiTrigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <Trigger Property="VirtualizingStackPanel.IsVirtualizing" Value="true">
            <Setter Property="ItemsPanel">
                <Setter.Value>
                    <ItemsPanelTemplate>
                        <VirtualizingStackPanel/>
                    </ItemsPanelTemplate>
                </Setter.Value>
            </Setter>
        </Trigger>
    </Style.Triggers>
</Style>

<Style x:Key="TreeViewItemFocusVisual">
    <Setter Property="Control.Template">
        <Setter.Value>
            <ControlTemplate>
                <Rectangle/>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>
<PathGeometry x:Key="TreeArrow" Figures="M0,0 L0,6 L6,0 z"/>
<Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type ToggleButton}">
    <Setter Property="Focusable" Value="False"/>
    <Setter Property="Width" Value="16"/>
    <Setter Property="Height" Value="16"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ToggleButton}">
                <Border Background="Transparent" Height="16" Padding="5,5,5,5" Width="16">
                    <Path x:Name="ExpandPath" Data="{StaticResource TreeArrow}" Fill="Transparent" Stroke="#FF989898">
                        <Path.RenderTransform>
                            <RotateTransform Angle="135" CenterY="3" CenterX="3"/>
                        </Path.RenderTransform>
                    </Path>
                </Border>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsMouseOver" Value="True">
                        <Setter Property="Stroke" TargetName="ExpandPath" Value="#FF1BBBFA"/>
                        <Setter Property="Fill" TargetName="ExpandPath" Value="Transparent"/>
                    </Trigger>
                    <Trigger Property="IsChecked" Value="True">
                        <Setter Property="RenderTransform" TargetName="ExpandPath">
                            <Setter.Value>
                                <RotateTransform Angle="180" CenterY="3" CenterX="3"/>
                            </Setter.Value>
                        </Setter>
                        <Setter Property="Fill" TargetName="ExpandPath" Value="#FF595959"/>
                        <Setter Property="Stroke" TargetName="ExpandPath" Value="#FF262626"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Answer 4

首先将 IsExpanded 设置为 true

   <Style x:Key="{x:Type TreeViewItem}"
TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded"
    Value="True" />

然后隐藏扩展器

<Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type TreeViewItem}">
 <ControlTemplate.Triggers>
     <Trigger Property="HasItems"
         Value="false">
         <Setter TargetName="Expander"
            Property="Visibility"
            Value="Hidden" />
     </Trigger>
     <Trigger Property="HasItems"
              Value="true">
         <Setter TargetName="Expander"
             Property="Visibility"
             Value="Hidden" />
     </Trigger>
                   </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

使用树视图而不是带有行详细信息的数据网格的一个很好的理由是向上和向下箭头键可以无缝地从扩展详细信息遍历到标题详细信息。