需求
我們想在編輯一個列表中某一個條目時，將編輯的詳情內容也放置當前面，比如右側。
可以通過將一個Grid,分成兩個Cloumn,動態調整兩個Cloumn的Width，就可以實現這個需求。
我們知道，Clomun的Width是個，而默認的動畫沒有這樣子的。我們就需要自己實現這樣一人動畫。
設計
我們從Animation的類圖上看到
我們可以從需求
我們想在編輯一個列表中某一個條目時，將編輯的詳情內容也放置當前面，比如右側。
可以通過將一個Grid,分成兩個Cloumn,動態調整兩個Cloumn的Width，就可以實現這個需求。
我們知道，Clomun的Width是個GridLength，而默認的動畫沒有這樣子的。我們就需要自己實現這樣一人動畫。
設計
我們從Animation的類圖上看到AnimationTimeline繼承，重寫其GetCurrentValue
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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，我們仿著默認動畫實現了From,To,同時將其屬性定義為GridLength,當動畫執行時，我們重寫了GetCurrentValue,使其根據From/To屬性相關聯。
優化
通過以上代碼，我們實現了在GridLength變化時，實現動畫。但是，試用后我們發現，動畫，有點太線性。這個時候，怎么辦？
可以通過引入EasingFunction來實現。我們知道EasingFunction其實就是一個與時間t有關的時間函數f(t).通過時間函數的處理，我們使動畫過渡不要那么線性。
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/// <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)); |
對應的，還要重寫GetCurrentValue函數。
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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
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<anim:GridLengthAnimation Storyboard.TargetProperty="Width" From="0" To="*" Duration="0:0:0.5"/> |
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