通过覆盖或样式使 ScrollViewer 的 ScrollBar 始终可见

Question

我正在尝试使 ScrollViewer 的 ScrollBar 始终可见，因此它不仅在我尝试滚动文本视图时出现，而且用户知道还有更多内容要查看。 刚开始不知什么原因，我以为我只需要更改需要覆盖画笔的颜色，但实际上，滚动条正在淡入淡出，因此需要更改 ScrollViewer 或 ScrollBar 的模板。

我找到了刚刚放在 App.Resources 部分中的 ScrollViewer 模板，但我不知道如何编辑它，因此 ScrollBar 始终可见：

<Style TargetType="ScrollViewer">
    <Setter Property="HorizontalScrollMode" Value="Enabled" />
    <Setter Property="VerticalScrollMode" Value="Enabled" />
    <Setter Property="IsHorizontalRailEnabled" Value="True" />
    <Setter Property="IsVerticalRailEnabled" Value="True" />
    <Setter Property="IsTabStop" Value="False" />
    <Setter Property="ZoomMode" Value="Enabled" />
    <Setter Property="HorizontalContentAlignment" Value="Left"/>
    <Setter Property="VerticalContentAlignment" Value="Top"/>
    <Setter Property="VerticalScrollBarVisibility" Value="Visible"/>
    <Setter Property="Padding" Value="0"/>
    <Setter Property="BorderThickness" Value="0"/>
    <Setter Property="BorderBrush" Value="Transparent"/>
    <Setter Property="Background" Value="Transparent"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ScrollViewer">
                <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="ScrollingIndicatorStates">
                            <VisualStateGroup.Transitions>
                                <VisualTransition From="MouseIndicator" To="NoIndicator">
                                    <Storyboard>
                                        <FadeOutThemeAnimation TargetName="ScrollBarSeparator" BeginTime="0:0:3" />
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="VerticalScrollBar"
                                                                   Storyboard.TargetProperty="IndicatorMode">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:3">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <ScrollingIndicatorMode>None</ScrollingIndicatorMode>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HorizontalScrollBar"
                                                                   Storyboard.TargetProperty="IndicatorMode">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:3">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <ScrollingIndicatorMode>None</ScrollingIndicatorMode>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualTransition>
                                <VisualTransition From="TouchIndicator" To="NoIndicator">
                                    <Storyboard>
                                        <FadeOutThemeAnimation TargetName="ScrollBarSeparator" />
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="VerticalScrollBar"
                                                                   Storyboard.TargetProperty="IndicatorMode">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0.5">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <ScrollingIndicatorMode>None</ScrollingIndicatorMode>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HorizontalScrollBar"
                                                                   Storyboard.TargetProperty="IndicatorMode">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0.5">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <ScrollingIndicatorMode>None</ScrollingIndicatorMode>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualTransition>
                            </VisualStateGroup.Transitions>

                            <VisualState x:Name="NoIndicator">
                                <Storyboard>
                                    <FadeOutThemeAnimation TargetName="ScrollBarSeparator" />
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="TouchIndicator">
                                <Storyboard>
                                                                            <FadeInThemeAnimation TargetName="ScrollBarSeparator" />

                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="VerticalScrollBar"
                                                               Storyboard.TargetProperty="IndicatorMode"
                                                               Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <ScrollingIndicatorMode>TouchIndicator</ScrollingIndicatorMode>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HorizontalScrollBar"
                                                               Storyboard.TargetProperty="IndicatorMode"
                                                               Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <ScrollingIndicatorMode>TouchIndicator</ScrollingIndicatorMode>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="MouseIndicator">
                                <Storyboard>
                                    <FadeInThemeAnimation TargetName="ScrollBarSeparator" />
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="VerticalScrollBar"
                                                               Storyboard.TargetProperty="IndicatorMode"
                                                               Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <ScrollingIndicatorMode>MouseIndicator</ScrollingIndicatorMode>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HorizontalScrollBar"
                                                               Storyboard.TargetProperty="IndicatorMode"
                                                               Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <ScrollingIndicatorMode>MouseIndicator</ScrollingIndicatorMode>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <Grid Background="{TemplateBinding Background}">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition Width="Auto"/>
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="*"/>
                            <RowDefinition Height="Auto"/>
                        </Grid.RowDefinitions>
                        <ScrollContentPresenter x:Name="ScrollContentPresenter"
                                            Grid.RowSpan="2"
                                            Grid.ColumnSpan="2"
                                            ContentTemplate="{TemplateBinding ContentTemplate}"
                                            Margin="{TemplateBinding Padding}" />
                        <ScrollBar x:Name="VerticalScrollBar"
                               Grid.Column="1"
                               IsTabStop="False"
                               Maximum="{TemplateBinding ScrollableHeight}"
                               Orientation="Vertical"
                               Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}"
                               Value="{TemplateBinding VerticalOffset}"
                               ViewportSize="{TemplateBinding ViewportHeight}"
                               HorizontalAlignment="Right"/>
                        <ScrollBar x:Name="HorizontalScrollBar"
                               IsTabStop="False"
                               Maximum="{TemplateBinding ScrollableWidth}"
                               Orientation="Horizontal"
                               Grid.Row="1"
                               Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}"
                               Value="{TemplateBinding HorizontalOffset}"
                               ViewportSize="{TemplateBinding ViewportWidth}" />
                        <!-- Change the opacity below, to zero. otherwise, the right and bottom border end up showing up as a single pixel lit on the screen even if the scroll is disabled. -->
                        <Border x:Name="ScrollBarSeparator"
                            Grid.Row="1"
                            Grid.Column="1"
                            Opacity="0"
                            BorderThickness="0,0,1,1"
                            Background="{StaticResource ScrollBarTrackBackgroundThemeBrush}"
                            BorderBrush="{StaticResource ScrollBarTrackBorderThemeBrush}" />
                    </Grid>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

我尝试删除代码的各个部分，但结果是 ScrollBar 完全消失了。

Answer 1

您为什么不直接将ScrollViewer 实例的VerticalScrollBarVisibility 和/或HorizontalScrollBarVisibility 设置为Visible，而不是从样式中移除褪色行为？

<ScrollViewer VerticalScrollBarVisibility="Visible">
     <!-- ScrollViewer Content -->
</ScrollViewer>

评论后编辑：

我想我想出了一个“解决方案”。我不确定这是否是实现这一目标的最佳方式，但它似乎可以提供您想要的结果。

为ScrollViewer 创建一个自定义样式，然后为垂直/水平ScrollBar 本身创建一个样式（使用Blend，这是我之前假设您所做的）。 获得默认样式的副本后，编辑以下行：

<VisualState x:Name="NoIndicator">
    <Storyboard>
        <FadeOutThemeAnimation BeginTime="0" TargetName="HorizontalPanningRoot"/>
        <FadeOutThemeAnimation BeginTime="0" TargetName="VerticalPanningRoot"/>
        <Fade**In**ThemeAnimation BeginTime="0" TargetName="HorizontalRoot"/>
        <Fade**In**ThemeAnimation BeginTime="0" TargetName="VerticalRoot"/>
    </Storyboard>
</VisualState>

我的猜测是，这实际上会导致ScrollBar 在未与之交互时淡入，这意味着它始终可见。

这是相关的 ScrollViewer XAML（我无法在答案中包含全部内容）。请注意，ScrollViewer 设置为使用我的自定义样式ScrollViewerStyle1，然后在该样式中将VerticalScrollBar 设置为我的ScrollBar 自定义样式ScrollBarCustomStyle1，其中修改了NoIndicator VisualState。如果需要，您可以对水平滚动条执行相同操作。

ScrollViewer 样式：

<ScrollContentPresenter x:Name="ScrollContentPresenter" Grid.ColumnSpan="2" ContentTemplate="{TemplateBinding ContentTemplate}" Margin="{TemplateBinding Padding}" Grid.RowSpan="2"/>
<ScrollBar x:Name="VerticalScrollBar" Grid.Column="1" HorizontalAlignment="Right" IsTabStop="False" Maximum="{TemplateBinding ScrollableHeight}" Orientation="Vertical" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" Value="{TemplateBinding VerticalOffset}" ViewportSize="{TemplateBinding ViewportHeight}" Style="{StaticResource ScrollBarStyle1}"/>
<ScrollBar x:Name="HorizontalScrollBar" IsTabStop="False" Maximum="{TemplateBinding ScrollableWidth}" Orientation="Horizontal" Grid.Row="1" Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" Value="{TemplateBinding HorizontalOffset}" ViewportSize="{TemplateBinding ViewportWidth}"/>
<Border x:Name="ScrollBarSeparator" BorderBrush="{ThemeResource ScrollBarTrackBorderThemeBrush}" BorderThickness="0,0,1,1" Background="{ThemeResource ScrollBarTrackBackgroundThemeBrush}" Grid.Column="1" Grid.Row="1"/>

Answer 2

为了达到预期的效果，你需要改变滚动条的样式，因为滚动查看器是由滚动条组成的。

工作滚动条

 <x:Double x:Key="ScrollBarMinThemeWidth">7</x:Double>
    <x:Double x:Key="ScrollBarMinThemeHeight">7</x:Double>
    <x:Double x:Key="ScrollBarPanningThumbThemeHeight">2.4</x:Double>
    <x:Double x:Key="ScrollBarPanningThumbThemeWidth">2.4</x:Double>
    <Style  TargetType="ScrollBar">
        <Setter Property="MinWidth" Value="{ThemeResource ScrollBarMinThemeWidth}"/>
        <Setter Property="MinHeight" Value="{ThemeResource ScrollBarMinThemeHeight}"/>
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="Foreground" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="IsTabStop" Value="False"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ScrollBar">
                    <Grid x:Name="Root" Background="Red">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="PointerOver"/>
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <DoubleAnimation Duration="0" To="0.5" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="ScrollingIndicatorStates">
                                <VisualState x:Name="TouchIndicator">
                                    <!--<Storyboard>
                                        <FadeInThemeAnimation Storyboard.TargetName="HorizontalPanningRoot"/>
                                        <FadeInThemeAnimation Storyboard.TargetName="VerticalPanningRoot"/>
                                    </Storyboard>-->
                                </VisualState>
                                <VisualState x:Name="MouseIndicator"/>
                                <VisualState x:Name="NoIndicator">
                                    <!--<Storyboard>
                                        <FadeOutThemeAnimation BeginTime="0" Storyboard.TargetName="HorizontalPanningRoot"/>
                                        <FadeOutThemeAnimation BeginTime="0" Storyboard.TargetName="VerticalPanningRoot"/>
                                    </Storyboard>-->
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Grid x:Name="HorizontalPanningRoot" MinWidth="53">
                            <Rectangle x:Name="HorizontalPanningThumb" AutomationProperties.AccessibilityView="Raw" Fill="{ThemeResource ScrollBarPanningBackgroundThemeBrush}" HorizontalAlignment="Left" Height="{ThemeResource ScrollBarPanningThumbThemeHeight}" MinWidth="{ThemeResource ScrollBarMinThemeWidth}"/>
                        </Grid>
                        <Grid x:Name="VerticalPanningRoot" MinHeight="53">
                            <Rectangle x:Name="VerticalPanningThumb" AutomationProperties.AccessibilityView="Raw" Fill="{ThemeResource ScrollBarPanningBackgroundThemeBrush}" MinHeight="{ThemeResource ScrollBarMinThemeHeight}" VerticalAlignment="Top" Width="{ThemeResource ScrollBarPanningThumbThemeWidth}"/>
                        </Grid>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

<ScrollViewer Height="300" Margin="30" ScrollViewer.VerticalScrollMode="Enabled"  ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Visible">
    <TextBlock FontSize="20" TextWrapping="Wrap" Text="Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum quinta decima. Eodem modo typi, qui nunc nobis videntur parum clari, fiant sollemnes in futurum."/>      
</ScrollViewer>

结果