此行为位于 TreeViewItem 的 ControlTemplate 中。只有一种方法可以更改它 - 更改 TreeViewItem 的控件模板。
我使用了 ToggleButton 和 TreeViewItem 的默认模板和样式。
你应该只在 TreeViewItem 的 ControlTemplate 中评论一个触发器:
<Trigger Property="HasItems" Value="False">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
此结果视图:结果视图
下面我粘贴所有样式和模板。
ToggleButton 的样式:
<Style TargetType="{x:Type ToggleButton}" x:Key="TreeViewItemToggleButtonStyle">
<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" Width="16">
<Path x:Name="ExpandPath" Data="M0,0 L0,6 L6,0 z" Fill="White" Stroke="#FF818181">
<Path.RenderTransform>
<RotateTransform Angle="135" CenterY="3" CenterX="3"/>
</Path.RenderTransform>
</Path>
</Border>
<ControlTemplate.Triggers>
<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>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Stroke" TargetName="ExpandPath" Value="#FF27C7F7"/>
<Setter Property="Fill" TargetName="ExpandPath" Value="#FFCCEEFB"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
<Condition Property="IsChecked" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Stroke" TargetName="ExpandPath" Value="#FF1CC4F7"/>
<Setter Property="Fill" TargetName="ExpandPath" Value="#FF82DFFB"/>
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
TreeViewItem 的 ControlTemplate:
<ControlTemplate TargetType="{x:Type TreeViewItem}" x:Key="ItemTemplate">
<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" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{DynamicResource TreeViewItemToggleButtonStyle}"/>
<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" ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}" ContentStringFormat="{TemplateBinding HeaderStringFormat}" 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>
<!-- Commented 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.InactiveSelectionHighlightBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
TreeViewItem 的样式:
<Style TargetType="TreeViewItem">
<EventSetter Event="Expanded" Handler="TreeViewItem_Expanded"/>
<Setter Property="Template" Value="{DynamicResource ItemTemplate}"/>
</Style>
窗户:
<Grid>
<TreeView>
<TreeViewItem Header="Root" IsExpanded="True">
<TreeViewItem Header="Inner 1"/>
<TreeViewItem Header="Inner 2"/>
</TreeViewItem>
</TreeView>
</Grid>
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