如何顯示WPF中所有子節點的treeviewItem擴展器箭頭顯示？

Question

我附上了我的問題屏幕截圖。 因此，請參考它，我只需要在樹狀視圖中展開箭頭圖標，即可在首次加載時對所有節點可見。

問題是樹視圖項目沒有子意味着箭頭不可見。 但初始時間負載我需要該箭頭可見。 用戶擴展后，它將隱藏。

根有子節點。 但是其他人沒有。 因此，只有我可以加載擴展時間。

Answer 1

此行為放在TreeViewItem的ControlTemplate中。 僅有一種更改方法-更改TreeViewItem的控件模板。

我使用了默認模板和ToggleButton和TreeViewItem的樣式。

您應該只在TreeViewItem的ControlTemplate中注釋一個觸發器：

<Trigger Property="HasItems" Value="False">
    <Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>

結果視圖： 結果視圖

在下面粘貼所有樣式和模板。

ToggleButton的樣式：

<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的樣式：

<Style TargetType="TreeViewItem">
    <EventSetter Event="Expanded" Handler="TreeViewItem_Expanded"/>
    <Setter Property="Template" Value="{DynamicResource ItemTemplate}"/>
</Style>

窗口：

<Grid>
    <TreeView>
        <TreeViewItem Header="Root" IsExpanded="True">
            <TreeViewItem Header="Inner 1"/>
            <TreeViewItem Header="Inner 2"/>
        </TreeViewItem>
    </TreeView>
</Grid>