WPF 的选项卡项 : Specified element is already the logical child of another element. 先断开连接

Question

我有一个带有 CloseableTabItems 的 CloseableTabControl 我正在尝试动态添加:

public class CloseableTabControl : TabControl
{
    protected override DependencyObject GetContainerForItemOverride()
    {
        return new CloseableTabItem();
    }
}  


public class CloseableTabItem : TabItem
{
    public static readonly RoutedEvent CloseTabEvent =
        EventManager.RegisterRoutedEvent("CloseTab", RoutingStrategy.Bubble,
        typeof(RoutedEventHandler), typeof(CloseableTabItem));

    public event RoutedEventHandler CloseTab
    {
        add { AddHandler(CloseTabEvent, value); }
        remove { RemoveHandler(CloseTabEvent, value); }
    }

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        var closeButton = Template.FindName("closeButton", this) as Button;
        if (closeButton != null)
        closeButton.Click += CloseButtonClick;
    }

    void CloseButtonClick(object sender, RoutedEventArgs e)
    {
        RaiseEvent(new RoutedEventArgs(CloseTabEvent, this));
    }
}

XAML 如下:

    <local:CloseableTabControl Grid.Column="2" Grid.Row="1" SelectedIndex="{Binding SelectedTabIndex}" ItemsSource="{Binding TabItems}">
    <local:CloseableTabControl.Resources>
        <DataTemplate DataType="{x:Type TestEditor:TestEditorViewModel}">
             <TestEditor:TestEditorView/>
        </DataTemplate>
        <DataTemplate DataType="{x:Type TestParameterEditor:TestParameterEditorViewModel}">
             <TestParameterEditor:TestParameterEditorView/>
        </DataTemplate>
    </local:CloseableTabControl.Resources>
    <local:CloseableTabControl.ItemContainerStyle>
        <Style TargetType="local:CloseableTabItem">
            <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TabItem}">
                    <Grid>
                        <Border Name="Border" Background="{DynamicResource Brush2}" BorderBrush="{DynamicResource Brush5}" BorderThickness="1,1,1,1" CornerRadius="6,6,0,0" >
                            <DockPanel>
                                <ContentPresenter x:Name="ContentSite"
                                     VerticalAlignment="Center"
                                     HorizontalAlignment="Center"
                                     ContentSource="Header"
                                     Margin="12,2,12,2"/>
                                <Button Name="closeButton" 
                                     HorizontalAlignment="Center" 
                                     Margin="3,0,3,0" 
                                     VerticalAlignment="Center" 
                                     Width="16" 
                                     Height="16" 
                                     DockPanel.Dock="Right" 
                                     Style="{DynamicResource CloseableTabItemButtonStyle}" 
                                     ToolTip="Close Tab">
                                     <Path Stretch="Fill" StrokeThickness="0.5" Stroke="#FF333333" Fill="#FF969696" Data="F1 M 2.28484e-007,1.33331L 1.33333,0L 4.00001,2.66669L 6.66667,6.10352e-005L 8,1.33331L 5.33334,4L 8,6.66669L 6.66667,8L 4,5.33331L 1.33333,8L 1.086e-007,6.66669L 2.66667,4L 2.28484e-007,1.33331 Z " HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
                                </Button>
                            </DockPanel>
                         </Border>
                      </Grid>
                      <ControlTemplate.Triggers>
                          <Trigger Property="IsSelected" Value="True">
                              <Setter TargetName="Border" Property="Background" Value="{DynamicResource lightBrush}" />
                          </Trigger>
                          <Trigger Property="IsSelected" Value="False">
                              <Setter TargetName="Border" Property="Background" Value="{DynamicResource Brush1}" />
                          </Trigger>
                      </ControlTemplate.Triggers>
                  </ControlTemplate>
               </Setter.Value>
            </Setter>
            <Setter Property="Header">
                <Setter.Value>
                    <StackPanel Orientation="Horizontal" ToolTip="{Binding Caption}">
                         <Image Height="18" Source="{Binding ImageName}"/>
                         <TextBlock Text="{Binding Title}" Margin="2,0,0,0"/>
                    </StackPanel>
                </Setter.Value>
            </Setter>
         </Style>
      </local:CloseableTabControl.ItemContainerStyle>
  </local:CloseableTabControl>  

当我在此窗口的 View 模型的构造函数中仅添加一个选项卡时，一切都很好:

TabItems.Add(TestEditorViewModel);

但是当我添加多个时，我得到了提到的异常。
我已尝试按照说明进行操作 here并将 XAML 分离到 ItemTemplate 和 ContentTemplate 但这导致了 StackOverFlowException(由 ContentPresenter 部分引起模板，我不知道为什么)。
我应该如何处理这个问题？
谢谢

Answer 1

问题出在 Header 属性的 Setter 上。当第一个 TabItem 应用了 Style 时，将创建一个新的 StackPanel。当创建第二个 TabItem 并应用 Style 时，same StackPanel 将分配给它的 header 属性。在 WPF 中，视觉对象只能有 1 个父对象，因此您会收到上述异常。相反，您应该定义一个包含 StackPanel 的 HeaderTemplate，以便每次将 Style 应用于 TabItem 时new StackPanel 是在 WPF 扩展 HeaderTemplate 时生成的。

请参阅此相关帖子:

WTF WPF TabControl?

干杯!