WPF中自定义GridLengthAnimation

技术  /  管理员 发布于 7年前   332

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，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 name="defaultOriginValue">The original value to animate</param>    /// <param name="defaultDestinationValue">The final value</param>    /// <param name="animationClock">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"/>

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