c# - WPF 改变方向 DoubleAnimation

Question

我在画布内有如下图像：

<Canvas x:Name="cnvMain"  ClipToBounds="True" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"  SnapsToDevicePixels="True">
    <Image x:Name="Image1"   Stretch="None" Canvas.Bottom="0"  Source="ImageGallery/Desert.jpg" ></Image>
</Canvas>

对于上下移动图像，我使用了 DoubleAnimation，如下所示：

 DoubleAnimation _Animation;
    private Storyboard _StoryBoard;

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        Canvas.SetZIndex(Image1, 1);

        _Animation = new DoubleAnimation();
        _Animation.From = -Image1.ActualHeight;
        _Animation.To = cnvMain.ActualHeight;
        _Animation.RepeatBehavior = RepeatBehavior.Forever;
        _Animation.Duration = new Duration(TimeSpan.Parse("0:0:10"));
        _Animation.FillBehavior = FillBehavior.Stop;
        Storyboard.SetTarget(_Animation, Image1);
        Storyboard.SetTargetProperty(_Animation, new PropertyPath(Canvas.BottomProperty));
        _StoryBoard = new Storyboard();
        _StoryBoard.Children.Add(_Animation);
        _StoryBoard.Begin();
        _StoryBoard.Pause();
    }
    public void Pause()
    {
        _StoryBoard.Pause();
    }
    public void Up()
    {
        _Animation.From = cnvMain.ActualHeight;
        _Animation.To = -Image1.ActualHeight;
        _StoryBoard.Resume();

    }
    public void Down()
    {
        _Animation.From = Image1.ActualHeight;
        _Animation.To = -cnvMain.ActualHeight;
        _StoryBoard.Resume();

    }

使用 From 和 To 在 UserControl_Loaded 中初始化动画。我的问题是这个属性在 Down 和 Top 方法调用中没有改变（方法有效，但图像向上移动）

Answer 1

我将其更改为喜欢以下，并且有效。

DoubleAnimation _Animation;
    private Storyboard _StoryBoard;

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        LoadAnimaiton(false);
        _StoryBoard.Pause();
    }

    private void LoadAnimaiton(bool up)
    {
        _StoryBoard = new Storyboard();
        _Animation = new DoubleAnimation(100.0, new Duration(TimeSpan.Parse("0:0:10")));
        _Animation.From = cnvMain.ActualHeight;
        _Animation.To = -Image1.ActualHeight;
        _Animation.RepeatBehavior = RepeatBehavior.Forever;
        _Animation.FillBehavior = FillBehavior.Stop;
        Storyboard.SetTarget(_Animation, Image1);
        Storyboard.SetTargetProperty(_Animation, new PropertyPath(Canvas.BottomProperty));

        if (up)
        {
            _Animation.From = cnvMain.ActualHeight;
            _Animation.To = -cnvMain.ActualHeight;
        }
        else
        {
            _Animation.From = -cnvMain.ActualHeight;
            _Animation.To = cnvMain.ActualHeight;
        }

        _StoryBoard.Children.Add(_Animation);

        _StoryBoard.Begin();
    }
    public void Pause()
    {
        _StoryBoard.Pause();
    }
    public void Down()
    {
        LoadAnimaiton(true);
    }

    public void Up()
    {
        LoadAnimaiton(false);
    }