WPF 中的 ListBoxItem ControlTemplate 设计存在问题？

Question

这是我的 XAML：

<ListBox 
  Name="PlaylistListBox" 
  ScrollViewer.CanContentScroll="False" 
  HorizontalContentAlignment="Stretch" 
  ItemsSource="{Binding Source={StaticResource ResourceKey=MyListBoxView}}" 
  ItemTemplateSelector="{Binding Source={StaticResource ResourceKey=MySelector}}" 
  MouseDoubleClick="PlaylistListBox_MouseDoubleClick" >
  <ListBox.ItemContainerStyle> 
    <Style TargetType="ListBoxItem">
      <Setter Property="SnapsToDevicePixels" Value="true"/>
      <Setter Property="OverridesDefaultStyle" Value="true"/>
      <Setter Property="Template"> 
        <Setter.Value>
          <ControlTemplate TargetType="ListBoxItem"> 
            <Border 
              Name="Border" 
              CornerRadius="4" 
              SnapsToDevicePixels="true">
              <ContentPresenter />
            </Border>
            <ControlTemplate.Triggers>
              <Trigger Property="IsSelected" Value="true">
                <Setter TargetName="Border" Property="Background" Value="Black" />

                <!-- The following setter for opacity is giving me headaches -->
                <Setter TargetName="Border" Property="Opacity" Value="0.5" />

              </Trigger>
            </ControlTemplate.Triggers>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
      <EventSetter 
        Event="Loaded" 
        Handler="PlaylistListBoxItem_Loaded" />
    </Style>
  </ListBox.ItemContainerStyle>
</ListBox>

两个问题：

1. 由于 Opacity setter，整个项目透明 50%。我想要的只是 ListBoxItem ControlTemplate 中定义的边框为透明，其内容 以保持完全不透明度。
2. 当 ListBox 不存在时，如何制作 Setter/Trigger 以使相同的边框变为红色 焦点集中？它应该类似于 InFocus="False" 和 IsSelected="True"。

感谢您的澄清。

Answer 1

1. 您应该在内容下方放置另一个边框，并使其半透明，保持主要内容完全可见。您可以通过使用 Grid 并首先在其中放置“背景”边框，然后再放置内容来实现此目的。这样，您将仅在背景边框上设置不透明度，而不是在内容上设置不透明度；

2. 您可以为此使用 MultiTrigger。

这是修改后的样式，显示了我的意思：

<ListBox 
  Name="PlaylistListBox" 
  ScrollViewer.CanContentScroll="False" 
  HorizontalContentAlignment="Stretch" 
  ItemsSource="{Binding Source={StaticResource ResourceKey=MyListBoxView}}" 
  ItemTemplateSelector="{Binding Source={StaticResource ResourceKey=MySelector}}" 
  MouseDoubleClick="PlaylistListBox_MouseDoubleClick" >
  <ListBox.ItemContainerStyle> 
    <Style TargetType="ListBoxItem">
      <Setter Property="SnapsToDevicePixels" Value="true"/>
      <Setter Property="OverridesDefaultStyle" Value="true"/>
      <Setter Property="Template"> 
        <Setter.Value>
          <ControlTemplate TargetType="ListBoxItem"> 
            <Grid>
              <Border 
                 Name="BackgroundBorder" 
                 CornerRadius="4" 
                 SnapsToDevicePixels="true">                 
              </Border>
              <Border Name="Border">
                 <ContentPresenter />
              </Border>
            </Grid>
            <ControlTemplate.Triggers>
              <Trigger Property="IsSelected" Value="true">
                <Setter TargetName="BackgroundBorder" Property="Background" Value="Black" />

                <!-- The following setter for opacity is giving me headaches -->
                <Setter TargetName="BackgroundBorder" Property="Opacity" Value="0.5" />

              </Trigger>
              <MultiTrigger>
                 <MultiTrigger.Conditions>
                      <Condition Property="IsSelected" Value="True"/>
                      <Condition Property="IsFocused" Value="False"/>
                 </MultiTrigger.Conditions>
                 <Setter TargetName="BackgroundBorder" Property="Background" Value="Red" />
              </MultiTrigger>
            </ControlTemplate.Triggers>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
      <EventSetter 
        Event="Loaded" 
        Handler="PlaylistListBoxItem_Loaded" />
    </Style>
  </ListBox.ItemContainerStyle>
</ListBox>