Silverlight 中的动画边距变化

Question

我正在 Silverlight 中对边框大小进行动画调整，但是我还需要逐渐删除其周围的边距（当前为 50）。 Blend 似乎不会为边距变化生成补间 - 它只是一次性从 50 跳到 0。有办法实现这一点吗？

Answer 1

问题是边距实际上是“System.Windows.Thickness”类型，它不是依赖项对象，因此 Left、Top、Right 和 Bottom 不是依赖项属性，因此无法使用 DoubleAnimation 进行动画处理（允许补间） 。

用于对边距进行动画处理的是不补间的 ObjectAnimation。这就是为什么您会看到边距从原始位置跳到新位置的原因。作为另一个常见的示例，当您尝试在 Visible 和 Collapsed 之间设置 Visibility 属性的动画时，会发生同样的情况。

您要么需要执行基于计时器的动画才能为边距设置动画，要么为厚度对象实现您自己的动画类型。

Answer 2

Ben Lemmon 给出了一个优雅的解决方案： http ://blogs.msdn.com/blemmon/archive/2009/03/18/animating-margins-in-silverlight.aspx

Answer 3

这是一个更新版本，它允许您从 XAML 中制作动画

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace NiceCards.Animations
{
    public class ThicknessAnimationX
    {
        public static readonly DependencyProperty ElementProperty = DependencyProperty.RegisterAttached("Element", typeof(DependencyObject), typeof(DoubleAnimation), new PropertyMetadata(new PropertyChangedCallback(OnElementPropertyChanged)));

        // The time along the animation from 0-1
        public static DependencyProperty TimeProperty = DependencyProperty.RegisterAttached("Time", typeof(double), typeof(DoubleAnimation), new PropertyMetadata(OnTimeChanged));

        // The object being animated
        public static DependencyProperty TargetProperty = DependencyProperty.RegisterAttached("Target", typeof(DependencyObject), typeof(ThicknessAnimationX), null);
        public static DependencyProperty TargetPropertyProperty = DependencyProperty.RegisterAttached("TargetProperty", typeof(DependencyProperty), typeof(DependencyObject), null);

        public static readonly DependencyProperty FromProperty = DependencyProperty.RegisterAttached("From", typeof(Thickness), typeof(DoubleAnimation), null);
        public static readonly DependencyProperty ToProperty = DependencyProperty.RegisterAttached("To", typeof(Thickness), typeof(DoubleAnimation), null);

        public static void SetElement(DependencyObject o, DependencyObject value)
        {
            o.SetValue(ElementProperty, value);
        }

        public static DependencyObject GetElement(DependencyObject o)
        {
            return (DependencyObject)o.GetValue(ElementProperty);
        }

        private static void OnElementPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (e.NewValue != null)
            {
                DoubleAnimation doubleAnimation = (DoubleAnimation)d;

                doubleAnimation.SetValue(TargetProperty, e.NewValue);
                doubleAnimation.From = 0;
                doubleAnimation.To = 1;
                doubleAnimation.SetValue(TargetPropertyProperty, FrameworkElement.MarginProperty);
                Storyboard.SetTargetProperty(doubleAnimation, new PropertyPath("(ThicknessAnimationX.Time)"));
                Storyboard.SetTarget(doubleAnimation, doubleAnimation);
            }
        }


        private static void OnTimeChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            DoubleAnimation animation = (DoubleAnimation)sender;
            double time = GetTime(animation);
            Thickness from = (Thickness)sender.GetValue(FromProperty);
            Thickness to = (Thickness)sender.GetValue(ToProperty);
            DependencyProperty targetProperty = (DependencyProperty)sender.GetValue(TargetPropertyProperty);
            DependencyObject target = (DependencyObject)sender.GetValue(TargetProperty);
            target.SetValue(targetProperty, new Thickness((to.Left - from.Left) * time + from.Left,
                                                          (to.Top - from.Top) * time + from.Top,
                                                          (to.Right - from.Right) * time + from.Right,
                                                          (to.Bottom - from.Bottom) * time + from.Bottom));
        }

        public static double GetTime(DoubleAnimation animation)
        {
            return (double)animation.GetValue(TimeProperty);
        }

        public static void SetTime(DoubleAnimation animation, double value)
        {
            animation.SetValue(TimeProperty, value);
        }

        public static Thickness GetFrom(DoubleAnimation animation)
        {
            return (Thickness)animation.GetValue(FromProperty);
        }

        public static void SetFrom(DoubleAnimation animation, Thickness value)
        {
            animation.SetValue(FromProperty, value);
        }

        public static Thickness GetTo(DoubleAnimation animation)
        {
            return (Thickness)animation.GetValue(ToProperty);
        }

        public static void SetTo(DoubleAnimation animation, Thickness value)
        {
            animation.SetValue(ToProperty, value);
        }
    }   
}

然后您可以在 XAML 中执行此操作

<VisualStateManager.VisualStateGroups>
    <VisualStateGroup x:Name="Positions">
        <VisualStateGroup.Transitions>
            <VisualTransition GeneratedDuration="0:0:0.2"/>
        </VisualStateGroup.Transitions>
        <VisualState x:Name="Left">                    
            <Storyboard>
                <DoubleAnimation Duration="0:0:0.3" NiceCards:ThicknessAnimationX.To="0,0,0,0" NiceCards:ThicknessAnimationX.Element="{Binding ElementName=rectangle1}" Storyboard.TargetName="rectangle1" Storyboard.TargetProperty="Opacity"/>
            </Storyboard>                       
        </VisualState>
        <VisualState x:Name="Right">                    
            <Storyboard>
                <DoubleAnimation Duration="0:0:0.3" NiceCards:ThicknessAnimationX.To="0,200,0,0" NiceCards:ThicknessAnimationX.Element="{Binding ElementName=rectangle1}" Storyboard.TargetName="rectangle1" Storyboard.TargetProperty="Opacity"/>
            </Storyboard>                    
        </VisualState>
    </VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle Height="100" HorizontalAlignment="Left" Margin="23,25,0,0" x:Name="rectangle1" Stroke="Black" StrokeThickness="1" VerticalAlignment="Top" Width="200" Fill="#FF1BAA00"/>

请注意，如果您未在 XAML 中将 Target 属性设置为 DoubleAnimation，则将无法在 Blend 中显示控件/页面。要解决此问题，只需添加一个假目标属性（在上面的代码中我添加了不透明度属性，它是一个双精度值），并且无论如何它都会在运行时被覆盖