WPF中自定义GridLengthAnimation_实用技巧_

 public class GridLengthAnimation : AnimationTimeline { /// 
 /// Returns the type of object to animate /// 
 public override Type TargetPropertyType => typeof(GridLength); /// 
 /// Creates an instance of the animation object /// 
 /// Returns the instance of the GridLengthAnimation protected override System.Windows.Freezable CreateInstanceCore() { return new GridLengthAnimation(); } /// 
 /// Dependency property for the From property /// 
 public static readonly DependencyProperty FromProperty = DependencyProperty.Register("From", typeof(GridLength), typeof(GridLengthAnimation)); /// 
 /// CLR Wrapper for the From depenendency property /// 
 public GridLength From { get { return (GridLength)GetValue(GridLengthAnimation.FromProperty); } set { SetValue(GridLengthAnimation.FromProperty, value); } } /// 
 /// Dependency property for the To property /// 
 public static readonly DependencyProperty ToProperty = DependencyProperty.Register("To", typeof(GridLength), typeof(GridLengthAnimation)); /// 
 /// CLR Wrapper for the To property /// 
 public GridLength To { get { return (GridLength)GetValue(GridLengthAnimation.ToProperty); } set { SetValue(GridLengthAnimation.ToProperty, value); } } /// 
 /// Animates the grid let set /// 
 /// The original value to animate /// The final value /// The animation clock (timer) /// Returns the new grid length to set 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); } 

 /// 
 /// The  dependency property's name. /// 
 public const string EasingFunctionPropertyName = "EasingFunction"; /// 
 /// Gets or sets the value of the  /// property. This is a dependency property. /// 
 public IEasingFunction EasingFunction { get { return (IEasingFunction)GetValue(EasingFunctionProperty); } set { SetValue(EasingFunctionProperty, value); } } /// 
 /// Identifies the  dependency property. /// 
 public static readonly DependencyProperty EasingFunctionProperty = DependencyProperty.Register( EasingFunctionPropertyName, typeof(IEasingFunction), typeof(GridLengthAnimation), new UIPropertyMetadata(null)); 

 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); }