带有子菜单的Checkable MenuItem [英] Checkable MenuItem With Sub Menus

问题描述

您可以在WPF中将顶层菜单设置为可检查状态吗?我似乎无法使它正常工作.

Can you have submenus with the top level set to checkable in WPF? I can't seem to get this to work.

<Window.ContextMenu>
    <ContextMenu>
        <MenuItem Header="Top Level 1" IsCheckable="True" IsChecked="True">
            <MenuItem Header="Sub Level" />
            <MenuItem Header="Sub Level" />
        </MenuItem>
        <MenuItem Header="Top Level 2">
            <MenuItem Header="Sub Level" />
            <MenuItem Header="Sub Level" />
        </MenuItem>
    </ContextMenu>
</Window.ContextMenu>

最高级别1是可检查的，但子级别不会出现.有什么想法吗?

Top Level 1 is checkable, but the sub levels don't appear. Any thoughts?

推荐答案

如果您深入研究MenuItem的ControlTemplate，您会发现它根据其Role属性使用不同的模板.

If you dig into MenuItem's ControlTemplate, you will see that it uses different templates depending on it's Role property.

菜单样式和模板

<Style x:Key="{x:Type MenuItem}"
       TargetType="{x:Type MenuItem}">
  <Setter Property="OverridesDefaultStyle"
          Value="True" />
  <Style.Triggers>
    <Trigger Property="Role"
             Value="TopLevelHeader">
      <Setter Property="Template"
              Value="{StaticResource {x:Static MenuItem.TopLevelHeaderTemplateKey}}" />
      <Setter Property="Grid.IsSharedSizeScope"
              Value="true" />
    </Trigger>
    <Trigger Property="Role"
             Value="TopLevelItem">
      <Setter Property="Template"
              Value="{StaticResource {x:Static MenuItem.TopLevelItemTemplateKey}}" />
    </Trigger>
    <Trigger Property="Role"
             Value="SubmenuHeader">
      <Setter Property="Template"
              Value="{StaticResource {x:Static MenuItem.SubmenuHeaderTemplateKey}}" />
    </Trigger>
    <Trigger Property="Role"
             Value="SubmenuItem">
      <Setter Property="Template"
              Value="{StaticResource {x:Static MenuItem.SubmenuItemTemplateKey}}" />
    </Trigger>
  </Style.Triggers>
</Style>

似乎默认情况下它可以允许检查或子项目.

Seems like it can either allow checking or subitems by default.

要解决此问题，请使用以下代码:

To workaround that, use following code:

XAML:

<ContextMenu>
    <MenuItem Header="Top Level 1" 
              Mouse.PreviewMouseUp="MenuItem_MouseLeftButtonUp">
        <MenuItem Header="Sub Level" />
        <MenuItem Header="Sub Level" />
    </MenuItem>
    <MenuItem Header="Top Level 2">
        <MenuItem Header="Sub Level" />
        <MenuItem Header="Sub Level" />
    </MenuItem>
</ContextMenu>

后面的代码:

private void MenuItem_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    (sender as MenuItem).IsChecked = !(sender as MenuItem).IsChecked;
}

我强烈建议将此功能转换/封装为Attached Property或Behavior.

I strongly recommend converting/encapsulating this piece of functionality into an Attached Property or a Behavior.

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