有没有人知道为什么焦点枢轴项目的蓝色下划线不可见？ xaml（在一个新创建的具有.NET核心2.0，VS 2017 15.3.2的空UWP应用程序中）很简单：
<Pivot>
<PivotItem Header="Testt 1">Test 1</PivotItem>
<PivotItem Header="Testt 2">Test 2</PivotItem>
<PivotItem Header="Testt 3">Test 3</PivotItem>
</Pivot>
和MS说“默认情况下，对数据库标题的键盘焦点用下划线表示。” （https://docs.microsoft.com/en-us/windows/uwp/controls-and-patterns/tabs-pivot）
启动后很少次，它出现在第一个枢轴项目上，但在点击另一个枢轴项目后消失了。
答案 0 :(得分：3)
在PivotHeaderItem的样式中，有一个Rectangle名为FocusPipe，它是您在键盘导航期间看到的焦点视觉效果。默认情况下，只有在Focused状态时才会显示。
如果您想让它可见，只需在Visibility，Visible和Selected州中将其SelectedPressed设置为SelectedPointerOver。
<Application.Resources>
<Style TargetType="PivotHeaderItem">
<Setter Property="FontSize"
Value="{ThemeResource PivotHeaderItemFontSize}" />
<Setter Property="FontFamily"
Value="{ThemeResource PivotHeaderItemFontFamily}" />
<Setter Property="FontWeight"
Value="{ThemeResource PivotHeaderItemThemeFontWeight}" />
<Setter Property="CharacterSpacing"
Value="{ThemeResource PivotHeaderItemCharacterSpacing}" />
<Setter Property="Background"
Value="{ThemeResource PivotHeaderItemBackgroundUnselected}" />
<Setter Property="Foreground"
Value="{ThemeResource PivotHeaderItemForegroundUnselected}" />
<Setter Property="Padding"
Value="{ThemeResource PivotHeaderItemMargin}" />
<Setter Property="Height"
Value="48" />
<Setter Property="VerticalContentAlignment"
Value="Center" />
<Setter Property="IsTabStop"
Value="False" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="PivotHeaderItem">
<Grid x:Name="Grid"
Background="{TemplateBinding Background}"
Padding="{TemplateBinding Padding}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="SelectionStates">
<VisualStateGroup.Transitions>
<VisualTransition From="Unselected"
To="UnselectedLocked"
GeneratedDuration="0:0:0.33" />
<VisualTransition From="UnselectedLocked"
To="Unselected"
GeneratedDuration="0:0:0.33" />
</VisualStateGroup.Transitions>
<VisualState x:Name="Disabled">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundDisabled}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundDisabled}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unselected" />
<VisualState x:Name="UnselectedLocked">
<Storyboard>
<DoubleAnimation Storyboard.TargetName="ContentPresenterTranslateTransform"
Storyboard.TargetProperty="X"
Duration="0"
To="{ThemeResource PivotHeaderItemLockedTranslation}" />
<DoubleAnimation Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="(UIElement.Opacity)"
Duration="0"
To="0" />
</Storyboard>
</VisualState>
<VisualState x:Name="Selected">
<VisualState.Setters>
<Setter Target="FocusPipe.Visibility"
Value="Visible" />
</VisualState.Setters>
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundSelected}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundSelected}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="UnselectedPointerOver">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundUnselectedPointerOver}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundUnselectedPointerOver}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="SelectedPointerOver">
<VisualState.Setters>
<Setter Target="FocusPipe.Visibility"
Value="Visible" />
</VisualState.Setters>
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundSelectedPointerOver}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundSelectedPointerOver}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="UnselectedPressed">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundUnselectedPressed}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundUnselectedPressed}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="SelectedPressed">
<VisualState.Setters>
<Setter Target="FocusPipe.Visibility"
Value="Visible" />
</VisualState.Setters>
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
Storyboard.TargetProperty="Foreground">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemForegroundSelectedPressed}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Grid"
Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0"
Value="{ThemeResource PivotHeaderItemBackgroundSelectedPressed}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<VisualState.Setters>
<Setter Target="FocusPipe.Visibility"
Value="Visible" />
</VisualState.Setters>
</VisualState>
<VisualState x:Name="Unfocused" />
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid.RenderTransform>
<TranslateTransform x:Name="ContentPresenterTranslateTransform" />
</Grid.RenderTransform>
<ContentPresenter x:Name="ContentPresenter"
Content="{TemplateBinding Content}"
ContentTemplate="{TemplateBinding ContentTemplate}"
FontSize="{TemplateBinding FontSize}"
FontFamily="{TemplateBinding FontFamily}"
FontWeight="{TemplateBinding FontWeight}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
OpticalMarginAlignment="TrimSideBearings" />
<Rectangle x:Name="FocusPipe"
Fill="{ThemeResource PivotHeaderItemFocusPipeFill}"
Height="2"
VerticalAlignment="Bottom"
HorizontalAlignment="Stretch"
Visibility="Collapsed" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Application.Resources>
答案 1 :(得分：0)
一个简单的答案是：
<SolidColorBrush x:Key="PivotHeaderItemSelectedPipeFill" Color="Yellow"/>
黄色下划线。