【Win10】让 AppBarButton 支持更复杂的 Icon 内容

2023-08-23 09:14:10

最近有一个需求，需要制作这么一个 AppBarButton：

这个 AppBarButton 的 Icon 是一个评论框图标里面再显示评论数（大于 99 条则显示 99+）。其中评论数是通过数据绑定得来的。

要单独显示这个评论框图标或者单独显示评论数都不是难题，然而要同时显示这两者就成了一个大问题了，因为 AppBarButton 的 Icon 属性只能设置一个。再看看 Icon 属性的类型，是 IconElement 这个类。但是，这个类的构造函数是内部的，我们也没法继承它。那么，从 Icon 属性上入手是不可能了。

但是，要注意到，绝大部分的控件都是有模板的，然后可以修改的。对于 AppBarButton，是不是也这样呢？答案是肯定的。

在 MSDN 上，我们可以查阅到 AppBarButton 的默认样式和模板：https://msdn.microsoft.com/zh-cn/library/windows/apps/mt299105.aspx

<!-- Default style for Windows.UI.Xaml.Controls.AppBarButton -->

<Style TargetType="AppBarButton">

  <Setter Property="Background" Value="Transparent"/>

  <Setter Property="Foreground" Value="{ThemeResource SystemControlForegroundBaseHighBrush}"/>

  <Setter Property="HorizontalAlignment" Value="Left"/>

  <Setter Property="VerticalAlignment" Value="Top"/>

  <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}"/>

  <Setter Property="FontWeight" Value="Normal"/>

  <Setter Property="Width" Value="68"/>

  <Setter Property="UseSystemFocusVisuals" Value="True" />

  <Setter Property="Template">

    <Setter.Value>

      <ControlTemplate TargetType="AppBarButton">

        <Grid

            x:Name="Root"

            MinWidth="{TemplateBinding MinWidth}"

            MaxWidth="{TemplateBinding MaxWidth}"

            Background="{TemplateBinding Background}">

          <VisualStateManager.VisualStateGroups>

            <VisualStateGroup x:Name="ApplicationViewStates">

              <VisualState x:Name="FullSize"/>

              <VisualState x:Name="Compact">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="TextLabel" Storyboard.TargetProperty="Visibility">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="Collapsed"/>

                  </ObjectAnimationUsingKeyFrames>

                </Storyboard>

              </VisualState>

              <VisualState x:Name="Overflow">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentRoot" Storyboard.TargetProperty="Visibility">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="Collapsed"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Visibility">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>

                  </ObjectAnimationUsingKeyFrames>

                </Storyboard>

              </VisualState>

              <VisualState x:Name="OverflowWithToggleButtons">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentRoot" Storyboard.TargetProperty="Visibility">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="Collapsed"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Visibility">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Margin">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="38,11,0,13"/>

                  </ObjectAnimationUsingKeyFrames>

                </Storyboard>

              </VisualState>

            </VisualStateGroup>

            <VisualStateGroup x:Name="CommonStates">

              <VisualState x:Name="Normal">

                <Storyboard>

                  <PointerUpThemeAnimation Storyboard.TargetName="OverflowTextLabel" />

                </Storyboard>

              </VisualState>

              <VisualState x:Name="PointerOver">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Root" Storyboard.TargetProperty="Background">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightListLowBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Content" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="TextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <PointerUpThemeAnimation Storyboard.TargetName="OverflowTextLabel" />

                </Storyboard>

              </VisualState>

              <VisualState x:Name="Pressed">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Root" Storyboard.TargetProperty="Background">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightListMediumBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Content" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="TextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltBaseHighBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <PointerDownThemeAnimation Storyboard.TargetName="OverflowTextLabel" />

                </Storyboard>

              </VisualState>

              <VisualState x:Name="Disabled">

                <Storyboard>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Content" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledBaseLowBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="TextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledBaseLowBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                  <ObjectAnimationUsingKeyFrames Storyboard.TargetName="OverflowTextLabel" Storyboard.TargetProperty="Foreground">

                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledBaseLowBrush}"/>

                  </ObjectAnimationUsingKeyFrames>

                </Storyboard>

              </VisualState>

            </VisualStateGroup>

          </VisualStateManager.VisualStateGroups>

          <StackPanel x:Name="ContentRoot" MinHeight="{ThemeResource AppBarThemeCompactHeight}">

            <ContentPresenter

                x:Name="Content"

                Height="20"

                Margin="0,14,0,4"

                Content="{TemplateBinding Icon}"

                Foreground="{TemplateBinding Foreground}"

                HorizontalAlignment="Stretch"

                AutomationProperties.AccessibilityView="Raw"/>

            <TextBlock

                x:Name="TextLabel"

                Text="{TemplateBinding Label}"

                Foreground="{TemplateBinding Foreground}"

                FontSize="12"

                FontFamily="{TemplateBinding FontFamily}"

                TextAlignment="Center"

                TextWrapping="Wrap"

                Margin="0,0,0,6"/>

          </StackPanel>

          <TextBlock

              x:Name="OverflowTextLabel"

              Text="{TemplateBinding Label}"

              Foreground="{TemplateBinding Foreground}"

              FontSize="15"

              FontFamily="{TemplateBinding FontFamily}"

              TextAlignment="Left"

              TextTrimming="Clip"

              TextWrapping="NoWrap"

              HorizontalAlignment="Stretch"

              VerticalAlignment="Center"

              Margin="12,11,0,13"

              Visibility="Collapsed"/>

        </Grid>

      </ControlTemplate>

    </Setter.Value>

  </Setter>

</Style>

仔细看一下这个模板，我们可以发现这么一句：

Content="{TemplateBinding Icon}"

我们尝试一下将 Icon 修改为 Content。（Content 属性是 AppBarButton 从 Button 类继承得来的，但是 AppBarButton 它自身并没有使用到这个属性。）

然后编写 XAML 测试下：

<CommandBar>

    <AppBarButton Style="{StaticResource MyAppBarButtonStyle}"

                             Label="评论">

        <AppBarButton.Content>

            <Grid>

                <FontIcon Glyph=""

                                 FontFamily="Segoe MDL2 Assets"

                                 HorizontalAlignment="Center"

                                 VerticalAlignment="Center" />

                <TextBlock Text="99+"

                                   HorizontalAlignment="Center"

                                   VerticalAlignment="Center"

                                   FontSize="9"

                                   RenderTransformOrigin="0.5,0.5">

                    <TextBlock.RenderTransform>

                        <TranslateTransform Y="-2.5" />

                    </TextBlock.RenderTransform>

                </TextBlock>

            </Grid>

        </AppBarButton.Content>

    </AppBarButton>

</CommandBar>

运行后，你应该可以看到文章开头的效果了。

最后，当然是稍微封装下了，因为 AppBarButton 是能够继承的。由于没啥技术含量-_-|||，这里就大家自己弄了。

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