如何为 DropShadowEffect 的不透明度设置动画？

Question

我有一个使用以下样式的带有边框的 WPF 项目。计划是让发光效果在鼠标移过边框时淡入，在离开时淡出。

<Style x:Key="BorderGlow" TargetType="Border">
    <Style.Resources>
        <Storyboard x:Key="GlowOn">
            <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetProperty="(DropShadowEffect.Opacity)">
                <SplineDoubleKeyFrame KeyTime="0:0:0.3" Value="1"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
        <Storyboard x:Key="GlowOff">
            <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetProperty="(DropShadowEffect.Opacity)">
                <SplineDoubleKeyFrame KeyTime="0:0:0.3" Value="0"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
    </Style.Resources>

    <Setter Property="CornerRadius" Value="6,1,6,1" />
    <Setter Property="BorderBrush" Value="{StaticResource SelectedBorder}" />
    <Setter Property="BorderThickness" Value="1" />
    <Setter Property="Background" Value="{StaticResource DeselectedBackground}" />
    <Setter Property="RenderTransformOrigin" Value="0.5,0.5" />
    <Setter Property="TextBlock.Foreground" Value="{StaticResource SelectedForeground}" />

    <Setter Property="RenderTransform">
        <Setter.Value>
            <RotateTransform Angle="90"/>
        </Setter.Value>
    </Setter>

    <Setter Property="Effect">
        <Setter.Value>
            <DropShadowEffect ShadowDepth="0" BlurRadius="8" Color="#FFB0E9EF"/>
        </Setter.Value>
    </Setter>

    <Style.Triggers>
        <Trigger Property="IsMouseOver" Value="True">

            <Trigger.EnterActions>
                <BeginStoryboard Storyboard="{StaticResource GlowOn}"/>
            </Trigger.EnterActions>

            <Trigger.ExitActions>
                <BeginStoryboard Storyboard="{StaticResource GlowOff}"/>
            </Trigger.ExitActions>

        </Trigger>
    </Style.Triggers>
</Style>

问题是，什么都没有发生！如果我在 Storyboard TargetProperty 中将“DropShadowEffect”更改为“UIElement”，则动画会起作用，但这会使整个控件褪色。

如何仅淡化 DropShadowEffect？

Answer 1

这是西蒙回答的后续，我有一个ListView，其中ListViewItem 的Template 项目在Grid 上有一个DropShadow。长话短说，因为一个覆盖ListViewItem，选定的项目和悬停不再起作用。为了让它们工作，我必须修改Opacity，并且有两种方法可以访问Effect，具体取决于其中一种方法；我在下面展示...这里是两个 sn-ps 的 完整 示例：

在选择期间设置

<ListView.ItemContainerStyle>
    <Style TargetType="ListViewItem">
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Cursor" Value="Hand"/>
            </Trigger>

            <MultiTrigger>
                <MultiTrigger.Conditions>
                    <Condition Property="IsSelected" Value="true" />
                    <Condition Property="Selector.IsSelectionActive" Value="true" />
                </MultiTrigger.Conditions>
                <Setter Property="FontWeight" Value="Bold" />
                <Setter Property="Effect">
                    <Setter.Value>
                        <DropShadowEffect Opacity="1"/>
                    </Setter.Value>
                </Setter>
            </MultiTrigger>
        </Style.Triggers>

设置为Grid.Triggers

<Grid Background="GhostWhite">
    <Grid.Effect>
        <DropShadowEffect Opacity="0" />
    </Grid.Effect>
    <GridViewRowPresenter Content="{TemplateBinding Content}"
                      HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                      VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                      SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />

    <Grid.Triggers>
        <EventTrigger RoutedEvent="MouseEnter">
            <BeginStoryboard>
                    <Storyboard>
                        <DoubleAnimationUsingKeyFrames 
                                        BeginTime="00:00:00"
                                        Storyboard.TargetProperty="(Effect).Opacity">
                            <SplineDoubleKeyFrame KeyTime="0:0:0.1" Value=".2"/>
                            <SplineDoubleKeyFrame KeyTime="0:0:0.4" Value=".6"/>
                            <SplineDoubleKeyFrame KeyTime="0:0:0.6" Value="1"/>
                        </DoubleAnimationUsingKeyFrames>
                    </Storyboard>
            </BeginStoryboard>
        </EventTrigger>

Answer 2

需要注意的几点

1) 您需要针对 Border 的实际属性 - 您实际上是在尝试针对 Effect 属性的值 (DropShadowEffect)，而不是属性本身。

2) 需要对PropertyPath的语法进行排序。

将您的 Storyboard.Target 属性更改为以下内容，您应该没问题：

Storyboard.TargetProperty="(Effect).Opacity"

编辑注释中注明的工作代码：

<Border BorderThickness="10" Height="100" Width="100">
    <Border.BorderBrush>
        <SolidColorBrush Color="Red"></SolidColorBrush>
    </Border.BorderBrush>
    <Border.Style>
        <Style TargetType="Border">
            <Style.Resources>
                <Storyboard x:Key="GlowOn">
                    <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" 
                          Storyboard.TargetProperty="(Effect).Opacity">
                        <SplineDoubleKeyFrame KeyTime="0:0:0.3" Value="1"/>
                    </DoubleAnimationUsingKeyFrames>
                </Storyboard>
                <Storyboard x:Key="GlowOff">
                    <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" 
                          Storyboard.TargetProperty="(Effect).Opacity">
                        <SplineDoubleKeyFrame KeyTime="0:0:0.3" Value="0"/>
                    </DoubleAnimationUsingKeyFrames>
                </Storyboard>
            </Style.Resources>

            <Setter Property="CornerRadius" Value="6,1,6,1" />
        <!--<Setter Property="BorderBrush"
                    Value="{StaticResource SelectedBorder}" />-->
            <Setter Property="BorderThickness" Value="1" />
        <!--<Setter Property="Background"
                    Value="{StaticResource DeselectedBackground}" />-->
            <Setter Property="RenderTransformOrigin" Value="0.5,0.5" />
        <!--<Setter Property="TextBlock.Foreground"
                    Value="{StaticResource SelectedForeground}" />-->

            <Setter Property="RenderTransform">
                <Setter.Value>
                    <RotateTransform Angle="90"/>
                </Setter.Value>
            </Setter>

            <Setter Property="Effect">
                <Setter.Value>
                    <DropShadowEffect ShadowDepth="20"
                                      BlurRadius="8"
                                      Color="#FFB0E9EF"/>
                </Setter.Value>
            </Setter>

            <Style.Triggers>
                <Trigger Property="IsMouseOver" Value="True">

                    <Trigger.EnterActions>
                        <BeginStoryboard
                              Storyboard="{StaticResource GlowOn}"/>
                    </Trigger.EnterActions>

                    <Trigger.ExitActions>
                        <BeginStoryboard
                              Storyboard="{StaticResource GlowOff}"/>
                    </Trigger.ExitActions>

                </Trigger>
            </Style.Triggers>

        </Style>
    </Border.Style>
</Border>