如何：自定义滚动条上的滚动块大小

本主题说明如何将 ScrollBar 的 Thumb 设置为固定大小，以及如何为 ScrollBar 的 Thumb 指定最小大小。

创建具有固定滚动块大小的滚动条

以下示例创建一个具有固定大小的 Thumb 的 ScrollBar。 该示例将 Thumb 的 ViewportSize 属性设置为 NaN 并设置 Thumb 的高度。 若要创建具有固定宽度的 Thumb 的水平 ScrollBar，请设置 Thumb 的宽度。

<Style TargetType="ScrollBar">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="ScrollBar">
        <Grid Name="Bg"
              Background="{TemplateBinding Background}"
              SnapsToDevicePixels="true">
          <Grid.RowDefinitions>
            <RowDefinition MaxHeight="{DynamicResource 
            {x:Static SystemParameters.VerticalScrollBarButtonHeightKey}}"/>
            <RowDefinition Height="0.00001*"/>
            <RowDefinition MaxHeight="{DynamicResource 
            {x:Static SystemParameters.VerticalScrollBarButtonHeightKey}}"/>
          </Grid.RowDefinitions>
          <RepeatButton Style="{StaticResource ScrollBarButton}"
                        IsEnabled="{TemplateBinding IsMouseOver}"
                        Height="18"
                      
                        Command="ScrollBar.LineUpCommand"
                        Content="M 0 4 L 8 4 L 4 0 Z" />
          <!-- Set the ViewporSize to NaN to disable autosizing of the Thumb. -->
          <Track Name="PART_Track" 
                 ViewportSize="NaN"
                 IsDirectionReversed="true"
                 Grid.Row="1"
                 Grid.ZIndex="-1">
            <Track.DecreaseRepeatButton>
              <RepeatButton Style="{StaticResource VerticalScrollBarPageButton}"
                            Command="ScrollBar.PageUpCommand"/>
            </Track.DecreaseRepeatButton>
            <Track.IncreaseRepeatButton>
              <RepeatButton Style="{StaticResource VerticalScrollBarPageButton}"
                            Command="ScrollBar.PageDownCommand"/>
            </Track.IncreaseRepeatButton>
            <Track.Thumb>
              <!-- Set the height of the Thumb.-->
              <Thumb Height="30"/>
            </Track.Thumb>
          </Track>
          <RepeatButton 
            Grid.Row="2" 
            Style="{StaticResource ScrollBarButton}"
            Height="18"
            Command="ScrollBar.LineDownCommand"
            Content="M 0 0 L 4 4 L 8 0 Z"/>

        </Grid>
        <ControlTemplate.Triggers>
          <Trigger SourceName="PART_Track" Property="IsEnabled" Value="false">
            <Setter TargetName="PART_Track" Property="Visibility" Value="Hidden"/>
          </Trigger>
        </ControlTemplate.Triggers>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

创建具有固定滚动块大小的滚动条

以下示例创建一个具有最小大小的 Thumb 的 ScrollBar。 此示例设置 VerticalScrollBarButtonHeightKey 的值。 若要创建具有最小宽度的 Thumb 的水平 ScrollBar，请设置 HorizontalScrollBarButtonWidthKey。

<Style TargetType="ScrollBar">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="ScrollBar">
        <Grid Name="Bg"
              Background="{TemplateBinding Background}"
              SnapsToDevicePixels="true">
          <Grid.RowDefinitions>
            <RowDefinition MaxHeight="{DynamicResource 
            {x:Static SystemParameters.VerticalScrollBarButtonHeightKey}}"/>
            <RowDefinition Height="0.00001*"/>
            <RowDefinition MaxHeight="{DynamicResource 
            {x:Static SystemParameters.VerticalScrollBarButtonHeightKey}}"/>
          </Grid.RowDefinitions>
          <RepeatButton Style="{StaticResource ScrollBarButton}"
                        IsEnabled="{TemplateBinding IsMouseOver}"
                        Height="18"
                        Command="ScrollBar.LineUpCommand"
                        Content="M 0 4 L 8 4 L 4 0 Z" />
          <Track Name="PART_Track" 
               IsDirectionReversed="true"
               Grid.Row="1"
               Grid.ZIndex="-1">
            <Track.Resources>
              <!-- Set the Thumb's minimum height to 50.
            The Thumb's minimum height is half the
            value of VerticalScrollBarButtonHeightKey. -->
              <sys:Double 
                x:Key="{x:Static SystemParameters.VerticalScrollBarButtonHeightKey}">
                100
              </sys:Double>
            </Track.Resources>
            <Track.DecreaseRepeatButton>
              <RepeatButton Style="{StaticResource VerticalScrollBarPageButton}"
                            Command="ScrollBar.PageUpCommand"/>
            </Track.DecreaseRepeatButton>
            <Track.IncreaseRepeatButton>
              <RepeatButton Style="{StaticResource VerticalScrollBarPageButton}"
                            Command="ScrollBar.PageDownCommand"/>
            </Track.IncreaseRepeatButton>
            <Track.Thumb>
              <Thumb/>
            </Track.Thumb>
          </Track>
          <RepeatButton 
            Grid.Row="2" 
            Style="{StaticResource ScrollBarButton}"
            Height="18"
            Command="ScrollBar.LineDownCommand"
            Content="M 0 0 L 4 4 L 8 0 Z"/>
        </Grid>
        <ControlTemplate.Triggers>
          <Trigger SourceName="PART_Track" 
                   Property="IsEnabled" Value="false">
            <Setter TargetName="PART_Track" 
                    Property="Visibility" Value="Hidden"/>
          </Trigger>
        </ControlTemplate.Triggers>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

另请参阅

• ScrollBar 样式和模板