c# - 控制模板资源中 Storyboard 的 Hooking Completed 事件的问题

Question

我正在创建一个名为 ImageFader 的自定义控件。样式模板如下所示:

<ControlTemplate TargetType="{x:Type controls:ImageFader}">
    <Grid>
        <Image HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
                Stretch="{TemplateBinding Stretch}"
                x:Name="PART_SourceImage" Opacity="1" />

        <Image HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
                Stretch="{TemplateBinding Stretch}"
                x:Name="PART_TargetImage" Opacity="0" />

    </Grid>
    <ControlTemplate.Resources>
        <Storyboard x:Key="FadeImageStoryboard">
            <!-- fade in the new image -->
            <DoubleAnimation From="0" To="1"
                                Duration="{TemplateBinding FadeTime}"
                                Storyboard.TargetName="PART_TargetImage"
                                Storyboard.TargetProperty="Opacity" />

            <!-- fade out the previous image -->
            <DoubleAnimation From="1" To="0"
                                Duration="{TemplateBinding FadeTime}"
                                Storyboard.TargetName="PART_SourceImage"
                                Storyboard.TargetProperty="Opacity" />

        </Storyboard>
    </ControlTemplate.Resources>
</ControlTemplate>

在代码中，我有这个:

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    SourceImage = Template.FindName("PART_SourceImage", this) as Image;
    TargetImage = Template.FindName("PART_TargetImage", this) as Image;
    FadeImageStoryboard = Template.Resources["FadeImageStoryboard"] as Storyboard;

    FadeImageStoryboard.Completed += new EventHandler(FadeImageStoryboard_Completed);
}

在完成的处理程序中，我尝试交换图像并重置它们的不透明度:

private void FadeImageStoryboard_Completed(object sender, EventArgs e)
{
    SourceImage.Source = TargetImage.Source;
    SourceImage.Opacity = 1;
    TargetImage.Opacity = 0;
}

我使用这个在 DispatchTimer 中启动动画:

FadeImageStoryboard.Begin(this, this.Template, true);

一切正常，直到我将两个或多个 ImageFader 控件放在同一个窗口上。当我这样做时(使用 DispatchTimer 以不同的时间间隔启动动画) Storyboard完成事件为两个 ImageFaders 运行。

我相信我的控件正在从模板资源中获取 Storyboard作为静态引用。

如何避免这种情况？

Answer 1

一个解决方案可能是从代码创建 Storyboard，它不会变得太丑:)

只需为此更改您的代码:

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    SourceImage = Template.FindName("PART_SourceImage", this) as Image;
    TargetImage = Template.FindName("PART_TargetImage", this) as Image;
    FadeImageStoryboard = GetFadeImageStoryboard();

    FadeImageStoryboard.Completed += new EventHandler(FadeImageStoryboard_Completed);
}

private Storyboard GetFadeImageStoryboard()
{
    DoubleAnimation fadeNewImage = new DoubleAnimation { From = 0, To = 1, Duration = FadeTime };
    Storyboard.SetTarget(fadeNewImage, SourceImage);
    Storyboard.SetTargetProperty(fadeNewImage, new PropertyPath("Opacity"));

    DoubleAnimation fadePreviousImage = new DoubleAnimation { From = 0, To = 1, Duration = FadeTime };
    Storyboard.SetTarget(fadePreviousImage, TargetImage);
    Storyboard.SetTargetProperty(fadePreviousImage, new PropertyPath("Opacity"));

    Storyboard fadeImageStoryboard = new Storyboard();
    fadeImageStoryboard.Children.Add(fadeNewImage);
    fadeImageStoryboard.Children.Add(fadePreviousImage);

    return fadeImageStoryboard;
}

而且每个控件都会有自己的 Storyboard。我不认为将这些 Storyboard 作为模板的一部分是个好主意，因为它们是此控件正确行为的重要组成部分，而且它们也没有太多需要更改的地方(所以几乎所有代码必须重复的模板)。