可以通过将一个Grid,分成两个Cloumn,动态调整两个Cloumn的Width，就可以实现这个需求。
我们知道，Clomun的Width是个，而默认的动画没有这样子的。我们就需要自己实现这样一人动画。
设计
我们从Animation的类图上看到
我们可以从需求
我们想在编辑一个列表中某一个条目时，将编辑的详情内容也放置当前面，比如右侧。
可以通过将一个Grid,分成两个Cloumn,动态调整两个Cloumn的Width，就可以实现这个需求。
我们知道，Clomun的Width是个GridLength，而默认的动画没有这样子的。我们就需要自己实现这样一人动画。
设计
我们从Animation的类图上看到AnimationTimeline继承，重写其GetCurrentValue
public class GridLengthAnimation : AnimationTimeline { /// <summary> /// Returns the type of object to animate /// </summary> public override Type TargetPropertyType => typeof(GridLength); /// <summary> /// Creates an instance of the animation object /// </summary> /// <returns>Returns the instance of the GridLengthAnimation</returns> protected override System.Windows.Freezable CreateInstanceCore() { return new GridLengthAnimation(); } /// <summary> /// Dependency property for the From property /// </summary> public static readonly DependencyProperty FromProperty = DependencyProperty.Register("From", typeof(GridLength), typeof(GridLengthAnimation)); /// <summary> /// CLR Wrapper for the From depenendency property /// </summary> public GridLength From { get { return (GridLength)GetValue(GridLengthAnimation.FromProperty); } set { SetValue(GridLengthAnimation.FromProperty, value); } } /// <summary> /// Dependency property for the To property /// </summary> public static readonly DependencyProperty ToProperty = DependencyProperty.Register("To", typeof(GridLength), typeof(GridLengthAnimation)); /// <summary> /// CLR Wrapper for the To property /// </summary> public GridLength To { get { return (GridLength)GetValue(GridLengthAnimation.ToProperty); } set { SetValue(GridLengthAnimation.ToProperty, value); } } /// <summary> /// Animates the grid let set /// </summary> /// <param>The original value to animate</param> /// <param>The final value</param> /// <param>The animation clock (timer)</param> /// <returns>Returns the new grid length to set</returns> public override object GetCurrentValue(object defaultOriginValue, object defaultDestinationValue, AnimationClock animationClock) { double fromVal = ((GridLength)GetValue(GridLengthAnimation.FromProperty)).Value; double toVal = ((GridLength)GetValue(GridLengthAnimation.ToProperty)).Value; if (fromVal > toVal) return new GridLength((1 - animationClock.CurrentProgress.Value) * (fromVal - toVal) + toVal, GridUnitType.Star); else return new GridLength(animationClock.CurrentProgress.Value * (toVal - fromVal) + fromVal, GridUnitType.Star); }
如上所示，我们仿着默认动画实现了From,To,同时将其属性定义为GridLength,当动画执行时，我们重写了GetCurrentValue,使其根据From/To属性相关联。
优化
通过以上代码，我们实现了在GridLength变化时，实现动画。但是，试用后我们发现，动画，有点太线性。这个时候，怎么办？
可以通过引入EasingFunction来实现。我们知道EasingFunction其实就是一个与时间t有关的时间函数f(t).通过时间函数的处理，我们使动画过渡不要那么线性。
/// <summary> /// The <see cref="EasingFunction" /> dependency property's name. /// </summary> public const string EasingFunctionPropertyName = "EasingFunction"; /// <summary> /// Gets or sets the value of the <see cref="EasingFunction" /> /// property. This is a dependency property. /// </summary> public IEasingFunction EasingFunction { get { return (IEasingFunction)GetValue(EasingFunctionProperty); } set { SetValue(EasingFunctionProperty, value); } } /// <summary> /// Identifies the <see cref="EasingFunction" /> dependency property. /// </summary> public static readonly DependencyProperty EasingFunctionProperty = DependencyProperty.Register( EasingFunctionPropertyName, typeof(IEasingFunction), typeof(GridLengthAnimation), new UIPropertyMetadata(null));
对应的，还要重写GetCurrentValue函数。
public override object GetCurrentValue(object defaultOriginValue, object defaultDestinationValue, AnimationClock animationClock) { double fromVal = ((GridLength)GetValue(FromProperty)).Value; double toVal = ((GridLength)GetValue(ToProperty)).Value; //check that from was set from the caller //if (fromVal == 1) // //set the from as the actual value // fromVal = ((GridLength)defaultDestinationValue).Value; double progress = animationClock.CurrentProgress.Value; IEasingFunction easingFunction = EasingFunction; if (easingFunction != null) { progress = easingFunction.Ease(progress); } if (fromVal > toVal) return new GridLength((1 - progress) * (fromVal - toVal) + toVal, GridUnitType.Star); return new GridLength(progress * (toVal - fromVal) + fromVal, GridUnitType.Star); }
使用
<anim:GridLengthAnimation Storyboard.TargetProperty="Width" From="0" To="*" Duration="0:0:0.5"/>