如何在 .cs 代码中设置按钮的背景显示画笔？

Question

目前我知道如何使用一些系统画笔，例如

xxx.Background = (SolidColorBrush)Application.Current.Resources["SystemControlForegroundAccentBrush"];

但是如何使用显示画笔呢？ 我也是这样用的，

xxx.Background = (SolidColorBrush)Application.Current.Resources["SystemControlBackgroundBaseLowRevealBackgroundBrush"];

它会抛出错误。

System.InvalidCastException:“Unable to cast object of type 
    'Microsoft.UI.Xaml.Media.RevealBackgroundBrush' to type 
    'Windows.UI.Xaml.Media.SolidColorBrush'.”

Answer 1

我们不能像一般BackgroundBrush那样设置显示刷。 RevealBackgroundBrush 是动态效果，不独立存在。换句话说，RevealBackgroundBrush 取决于状态。要在自定义控件或重新模板化的控件上启用 Reveal，您需要修改控件的控件模板。大多数控件模板在根部都有一个网格；更新该根网格的VisualState 以使用 Reveal。例如，如果您想为按钮添加RevealBackgroundBrush。

<Style TargetType="Button" x:Key="ButtonStyle1">
    <Setter Property="Background" Value="{ThemeResource ButtonRevealBackground}" />
    <Setter Property="Foreground" Value="{ThemeResource ButtonForeground}" />
    <Setter Property="BorderBrush" Value="{ThemeResource ButtonRevealBorderBrush}" />
    <Setter Property="BorderThickness" Value="2" />
    <Setter Property="Padding" Value="8,4,8,4" />
    <Setter Property="HorizontalAlignment" Value="Left" />
    <Setter Property="VerticalAlignment" Value="Center" />
    <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
    <Setter Property="FontWeight" Value="Normal" />
    <Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}" />
    <Setter Property="UseSystemFocusVisuals" Value="True" />
    <Setter Property="FocusVisualMargin" Value="-3" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="Button">
                <Grid x:Name="RootGrid" Background="{TemplateBinding Background}">

                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Normal">

                                <Storyboard>
                                    <PointerUpThemeAnimation Storyboard.TargetName="RootGrid" />
                                </Storyboard>
                            </VisualState>

                            <VisualState x:Name="PointerOver">
                                <VisualState.Setters>
                                    <Setter Target="RootGrid.(RevealBrush.State)" Value="PointerOver" />
                                    <Setter Target="RootGrid.Background" Value="{ThemeResource ButtonRevealBackgroundPointerOver}" />
                                    <Setter Target="ContentPresenter.BorderBrush" Value="Transparent"/>
                                    <Setter Target="ContentPresenter.Foreground" Value="{ThemeResource ButtonForegroundPointerOver}" />
                                </VisualState.Setters>

                                <Storyboard>
                                    <PointerUpThemeAnimation Storyboard.TargetName="RootGrid" />
                                </Storyboard>
                            </VisualState>

                            <VisualState x:Name="Pressed">
                                <VisualState.Setters>
                                    <Setter Target="RootGrid.(RevealBrush.State)" Value="Pressed" />
                                    <Setter Target="RootGrid.Background" Value="{ThemeResource ButtonRevealBackgroundPressed}" />
                                    <Setter Target="ContentPresenter.BorderBrush" Value="{ThemeResource ButtonRevealBackgroundPressed}" />
                                    <Setter Target="ContentPresenter.Foreground" Value="{ThemeResource ButtonForegroundPressed}" />
                                </VisualState.Setters>

                                <Storyboard>
                                    <PointerDownThemeAnimation Storyboard.TargetName="RootGrid" />
                                </Storyboard>
                            </VisualState>

                            <VisualState x:Name="Disabled">
                                <VisualState.Setters>
                                    <Setter Target="RootGrid.Background" Value="{ThemeResource ButtonRevealBackgroundDisabled}" />
                                    <Setter Target="ContentPresenter.BorderBrush" Value="{ThemeResource ButtonRevealBorderBrushDisabled}" />
                                    <Setter Target="ContentPresenter.Foreground" Value="{ThemeResource ButtonForegroundDisabled}" />
                                </VisualState.Setters>
                            </VisualState>
                        </VisualStateGroup>

                    </VisualStateManager.VisualStateGroups>
                    <ContentPresenter x:Name="ContentPresenter"
        BorderBrush="{TemplateBinding BorderBrush}"
        BorderThickness="{TemplateBinding BorderThickness}"
        Content="{TemplateBinding Content}"
        ContentTransitions="{TemplateBinding ContentTransitions}"
        ContentTemplate="{TemplateBinding ContentTemplate}"
        Padding="{TemplateBinding Padding}"
        HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
        VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
        AutomationProperties.AccessibilityView="Raw" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style >

用法

Btn.Style = (Style)App.Current.Resources["ButtonStyle1"];