[英]InvalidOperationException when trying to animate background color of a styled button in WPF
我正在尝试以编程方式触发按钮上的彩色动画,但是当我这样做时却遇到了System.InvalidOperationException
。 似乎无法解析TargetProperty
因为我已经使用模板/内容演示者设置了按钮的样式。
我使用<Button>
样式的原因是强制样式保持一致(并避免使用默认的蓝色悬停效果)。 我也有一个DataTrigger,可以在显示该按钮时将其背景颜色设置为动画(即使其可见)。 这是完整的<Style>
定义:
<Style x:Key="PopUnder" TargetType="Button">
<Setter Property="Foreground" Value="Black" />
<Setter Property="FontSize" Value="34" />
<Setter Property="FontWeight" Value="SemiBold" />
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Border Name="Border" Background="White" BorderBrush="Red" BorderThickness="0,1,0,1">
<TextBlock TextWrapping="Wrap" TextAlignment="Center" VerticalAlignment="Center" LineStackingStrategy="BlockLineHeight" LineHeight="40" Text="{TemplateBinding Content}" />
</Border>
<ControlTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Visibility}" Value="Visible">
<DataTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetName="Border" Storyboard.TargetProperty="(Background).(SolidColorBrush.Color)" RepeatBehavior="Forever">
<LinearColorKeyFrame Value="White" KeyTime="0:0:0" />
<LinearColorKeyFrame Value="LightCoral" KeyTime="0:0:1" />
<LinearColorKeyFrame Value="White" KeyTime="0:0:2" />
</ColorAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
</DataTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
但我也希望能够通过代码在同一按钮上触发不同的动画。 因此,我在其他地方(在样式定义之外)定义了一个单独的<Storyboard>
,我可以使用TryFindResource()
... Begin()
触发该TryFindResource()
。 但是,由于该按钮使用的是模板,因此我无法在我的XAML中正确获取Background color属性(如下所示)。
<Storyboard x:Key="StatusGood" Completed="AnimationStatusGood_Completed">
<ColorAnimationUsingKeyFrames Storyboard.TargetName="PopUnderMessage" Storyboard.TargetProperty="(Border).(Background).(SolidColorBrush.Color)">
<LinearColorKeyFrame Value="LightGreen" KeyTime="0:0:0" />
<LinearColorKeyFrame Value="White" KeyTime="0:0:1" />
</ColorAnimationUsingKeyFrames>
</Storyboard>
我在这里为Storyboard.TargetProperty
属性尝试了几个不同的值:
但是它们都在相同的异常上产生不同的变化。 我承认由于缺乏对XAML模板和属性路径的了解,我有点盲目地将飞镖扔在板上。 我该如何工作?
尝试执行此操作,完全省略Storyboard.TargetName
,并从Storyboard.TargetProperty
省略Border
:
<Storyboard x:Key="StatusGood" Completed="AnimationStatusGood_Completed">
<ColorAnimationUsingKeyFrames
Storyboard.TargetProperty="(Background).(SolidColorBrush.Color)">
<LinearColorKeyFrame Value="LightGreen" KeyTime="0:0:0" />
<LinearColorKeyFrame Value="White" KeyTime="0:0:1" />
</ColorAnimationUsingKeyFrames>
</Storyboard>
为样式按钮命名:
<Button
x:Name="button"
Content="Hello, world!"
Style="{StaticResource PopUnder}" Click="ButtonBase_OnClick" />
要激活情节提要:
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
{
Storyboard storyboard = (Storyboard)this.TryFindResource("StatusGood");
Border border = FindVisualChild<Border>(button, "Border");
storyboard.Begin(border);
}
作为参考, FindVisualChild
帮助函数:
private static T FindVisualChild<T>(
DependencyObject parent,
string name = null)
where T : DependencyObject
{
if (parent != null)
{
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);
T candidate = child as T;
if (candidate != null)
{
if (name == null)
{
return candidate;
}
FrameworkElement element = candidate as FrameworkElement;
if (name == element?.Name)
{
return candidate;
}
}
T childOfChild = FindVisualChild<T>(child, name);
if (childOfChild != null)
{
return childOfChild;
}
}
}
return default(T);
}
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