WPF - 顺序动画简单示例

Question

我正在学习 WPF 动画，但对如何按顺序应用动画感到困惑。作为一个简单的例子，我在一个统一的网格中有四个矩形，并且想依次更改每个矩形的颜色。这是我目前所拥有的：

public partial class Window1 : Window
{
    Rectangle blueRect;
    Rectangle redRect;
    Rectangle greenRect;
    Rectangle yellowRect;

    public Window1()
    {
        InitializeComponent();
        blueRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Blue, Name="Blue"};
        redRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Red, Name="Yellow"};
        greenRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Green, Name="Green" };
        yellowRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Yellow, Name="Yellow" };

        UniformGrid1.Children.Add(blueRect);
        UniformGrid1.Children.Add(redRect);
        UniformGrid1.Children.Add(greenRect);
        UniformGrid1.Children.Add(yellowRect);

    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        animateCell(blueRect, Colors.Blue);
        animateCell(redRect, Colors.Red);
    }

    private void animateCell(Rectangle rectangle, Color fromColor)
    {
        Color toColor = Colors.White;
        ColorAnimation ani = new ColorAnimation(toColor, new Duration(TimeSpan.FromMilliseconds(300)));
        ani.AutoReverse = true;

        SolidColorBrush newBrush = new SolidColorBrush(fromColor);
        ani.BeginTime = TimeSpan.FromSeconds(2);
        rectangle.Fill = newBrush;
        newBrush.BeginAnimation(SolidColorBrush.ColorProperty, ani);
        //NameScope.GetNameScope(this).RegisterName(rectangle.Name, rectangle);
        //Storyboard board = new Storyboard();
        //board.Children.Add(ani);
        //Storyboard.SetTargetName(rectangle, rectangle.Name);
        //Storyboard.SetTargetProperty(ani, new PropertyPath(SolidColorBrush.ColorProperty));
        //board.Begin();

    }

实现此目的最简单的方法是什么？ cmets 中的代码是我的第一个猜测，但它无法正常工作。

Answer 1

应该有一个事件ani.Completed - 处理该事件并开始动画的下一个阶段，然后开始运行第一个阶段，每个阶段都会触发下一个阶段。

ColorAnimation ani = // whatever...

ani.Completed += (s, e) => 
   {
       ColorAnimation ani2 = // another one...

       // and so on
   };

newBrush.BeginAnimation(SolidColorBrush.ColorProperty, ani);

更新：

public partial class Window1 : Window
{
    Rectangle blueRect;
    Rectangle redRect;
    Rectangle greenRect;
    Rectangle yellowRect;

    public Window1()
    {
        InitializeComponent();
        blueRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Blue, Name = "Blue" };
        redRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Red, Name = "Yellow" };
        greenRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Green, Name = "Green" };
        yellowRect = new Rectangle() { Fill = System.Windows.Media.Brushes.Yellow, Name = "Yellow" };

        UniformGrid1.Children.Add(blueRect);
        UniformGrid1.Children.Add(redRect);
        UniformGrid1.Children.Add(greenRect);
        UniformGrid1.Children.Add(yellowRect);
    }

    IEnumerable<Action<Action>> AnimationSequence()
    {
        for (; ; )
        {
            yield return AnimateCell(blueRect, Colors.Blue);
            yield return AnimateCell(redRect, Colors.Red);
            yield return AnimateCell(greenRect, Colors.Green);
            yield return AnimateCell(yellowRect, Colors.Yellow);
        }
    }

    private IEnumerator<Action<Action>> _actions;

    private void RunNextAction()
    {
        if (_actions.MoveNext())
            _actions.Current(RunNextAction);
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        _actions = AnimationSequence().GetEnumerator();
        RunNextAction();
    }

    private Action<Action> AnimateCell(Rectangle rectangle, Color fromColor)
    {
        return completed =>
        {
            Color toColor = Colors.White;
            ColorAnimation ani = new ColorAnimation(toColor, 
                                    new Duration(TimeSpan.FromMilliseconds(300)));
            ani.AutoReverse = true;
            ani.Completed += (s, e) => completed();

            SolidColorBrush newBrush = new SolidColorBrush(fromColor);
            ani.BeginTime = TimeSpan.FromSeconds(2);
            rectangle.Fill = newBrush;
            newBrush.BeginAnimation(SolidColorBrush.ColorProperty, ani);
        };
    }
}

尝试将以上内容粘贴到您的程序中。它可以满足您的需求，但在其他情况下可能对您有用。它仍然是事件驱动的，但它使用“迭代器方法”（带有 yield return）来营造一种印象，即它是在动画进行时阻塞的顺序编码。

这样做的好处是您可以以非常直观的方式使用 AnimationSequence 方法 - 您可以在一系列语句中写出动画的时间线，或使用循环，或任何您想要的。

Answer 2

我尝试过的解决方案是使用这样的队列。这将允许您动态添加到动画链中。我不确定是否需要锁，但为了安全起见，我把它留在了里面。

Queue<Object[]> animationQueue = new Queue<Object[]>();

void sequentialAnimation(DoubleAnimation da, Animatable a, DependencyProperty dp)
{
    da.Completed += new EventHandler(da_Completed);

    lock (animationQueue)
    {
        if (animationQueue.Count == 0) // no animation pending
        {
            animationQueue.Enqueue(new Object[] { da, a, dp });
            a.BeginAnimation(dp, da);
        }
        else
        {
            animationQueue.Enqueue(new Object[] { da, a, dp });
        }
    }
}

void da_Completed(object sender, EventArgs e)
{
    lock (animationQueue)
    {
        Object[] completed = animationQueue.Dequeue();
        if (animationQueue.Count > 0)
        {
            Object[] next = animationQueue.Peek();
            DoubleAnimation da = (DoubleAnimation)next[0];
            Animatable a = (Animatable)next[1];
            DependencyProperty dp = (DependencyProperty)next[2];

            a.BeginAnimation(dp, da);
        }
    }
}

Answer 3

这可以通过使用具有矛盾名称ParallelTimeline 的类并仔细调整BeginTime 属性来完成。请注意，在下面的示例中，第二个 DoubleAnimation 的 BeginTime 属性如何设置为第一个的持续时间。

<ParallelTimeline>
      <DoubleAnimation
           Storyboard.TargetName="FlashRectangle" 
           Storyboard.TargetProperty="Opacity"
           From="0.0" To="1.0" Duration="0:0:1"/>
      <DoubleAnimation BeginTime="0:0:0.05"
           Storyboard.TargetName="FlashRectangle" 
           Storyboard.TargetProperty="Opacity"
           From="1.0" To="0.0" Duration="0:0:2"/>
 </ParallelTimeline>