怎么用Shape做动画

这篇文章将为大家详细讲解有关怎么用Shape做动画，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。

1. 使用PointAnimation

使用PointAnimation可以让Shape变形，但实际上没看到多少人会这么用，毕竟WPF做的软件多数不需要这么花俏。

1.1 在XAML上使用PointAnimation

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在这个例子里最头痛的地方是Property-path 语法，如果不能熟记的话最好依赖Blend生成。

1.2 在代码中使用PointAnimation

如果Point数量很多，例如图表，通常会在C#代码中使用PointAnimation：

_storyboard = new Storyboard();Random random = new Random();for (int i = 0; i < _pathFigure.Segments.Count; i++){var animation = new PointAnimation { Duration = TimeSpan.FromSeconds(3) };    Storyboard.SetTarget(animation, _pathFigure.Segments[i]);    Storyboard.SetTargetProperty(animation, "(LineSegment.Point)");    animation.EnableDependentAnimation = true;    animation.EasingFunction = new QuarticEase { EasingMode = EasingMode.EaseOut };    animation.To = new Point((_pathFigure.Segments[i] as LineSegment).Point.X, (i % 2 == 0 ? 1 : -1) * i * 1.2 + 60);    _storyboard.Children.Add(animation);}_storyboard.Begin();

因为可以直接SetTarget，所以Property-path语法就可以很简单。

2. 扩展PointAnimation

上面两个例子的动画都还算简单，如果更复杂些，XAML或C#代码都需要写到很复杂。我参考了这个网页 想做出类似的动画，但发现需要写很多XAML所以放弃用PointAnimation实现。这个页面的动画核心是这段HTML：

只需一组Point的集合就可以控制所有Point的动画，确实比PointAnimation高效很多。 在WPF中可以通过继承Timeline实现一个PointCollectionAnimamtion，具体可以参考这个项目。可惜的是虽然UWP的Timeline类并不封闭，但完全不知道如何继承并派生一个自定义的Animation。

这时候需要稍微变通一下思维。可以将DoubleAnimation理解成这样：Storyboard将TimeSpan传递给DoubleAnimation，DoubleAnimation通过这个TimeSpan（有时还需要结合EasingFunction）计算出目标属性的当前值最后传递给目标属性，如下图所示：

既然这样，也可以接收到这个计算出来的Double，再通过Converter计算出目标的PointCollection值：

假设告诉这个Converter当传入的Double值（命名为Progress）为0的时候，PointCollection是{0,0 1,1 …}，Progress为100时PointCollection是{1,1 2,2 …}，当Progress处于其中任何值时的计算方法则是：

private PointCollection GetCurrentPoints(PointCollection fromPoints, PointCollection toPoints, double percentage){var result = new PointCollection();for (var i = 0;        i < Math.Min(fromPoints.Count, toPoints.Count);        i++)    {        var x = (1 - percentage / 100d) * fromPoints[i].X + percentage / 100d * toPoints[i].X;        var y = (1 - percentage / 100d) * fromPoints[i].Y + percentage / 100d * toPoints[i].Y;        result.Add(new Point(x, y));    }return result;}

这样就完成了从TimeSpan到PointCollection的转换过程。然后就是定义在XAML上的使用方式。参考上面PointCollectionAnimation，虽然多了个Converter，但XAML也应该足够简洁：

97.3,0 127.4,60.9 194.6,70.7 145.9,118.1 157.4,185.1 97.3,153.5 37.2,185.1 48.6,118.1 0,70.7 67.2,60.9110,58.2 147.3,0 192.1,29 141.7,105.1 118.7,139.8 88.8,185.1 46.1,156.5 0,125 23.5,86.6 71.1,116.7…

最终我选择了将这个Converter命名为ProgressToPointCollectionBridge。可以看出Polygon 将Points绑定到ProgressToPointCollectionBridge，DoubleAnimation 改变ProgressToPointCollectionBridge.Progress，从而改变Points。XAML的简洁程度还算令人满意，如果需要操作多个点的话相对于PointAnimation的优势就很大。

运行结果如下：

完整的XAML：

97.3,0 127.4,60.9 194.6,70.7 145.9,118.1 157.4,185.1 97.3,153.5 37.2,185.1 48.6,118.1 0,70.7 67.2,60.9110,58.2 147.3,0 192.1,29 141.7,105.1 118.7,139.8 88.8,185.1 46.1,156.5 0,125 23.5,86.6 71.1,116.7

ProgressToPointCollectionBridge:

[ContentProperty(Name = nameof(Children))]public class ProgressToPointCollectionBridge : DependencyObject{public ProgressToPointCollectionBridge()    {        Children = new ObservableCollection();    }/// 
///     获取或设置Points的值/// 
public PointCollection Points    {get { return (PointCollection) GetValue(PointsProperty); }set { SetValue(PointsProperty, value); }    }/// 
///     获取或设置Progress的值/// 
public double Progress    {get { return (double) GetValue(ProgressProperty); }set { SetValue(ProgressProperty, value); }    }/// 
///     获取或设置Children的值/// 
public Collection Children    {get { return (Collection) GetValue(ChildrenProperty); }set { SetValue(ChildrenProperty, value); }    }protected virtual void OnProgressChanged(double oldValue, double newValue)    {UpdatePoints();    }protected virtual void OnChildrenChanged(Collection oldValue, Collection newValue)    {var oldCollection = oldValue as INotifyCollectionChanged;if (oldCollection != null)            oldCollection.CollectionChanged -= OnChildrenCollectionChanged;var newCollection = newValue as INotifyCollectionChanged;if (newCollection != null)            newCollection.CollectionChanged += OnChildrenCollectionChanged;UpdatePoints();    }private void OnChildrenCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)    {UpdatePoints();    }private void UpdatePoints()    {if (Children == null || Children.Any() == false)        {            Points = null;        }else if (Children.Count == 1)        {var fromPoints = new PointCollection();for (var i = 0; i < Children[0].Count; i++)                fromPoints.Add(new Point(0, 0));var toPoints = Children[0];            Points = GetCurrentPoints(fromPoints, toPoints, Progress);        }else{var rangePerSection = 100d / (Children.Count - 1);var fromIndex = Math.Min(Children.Count - 2, Convert.ToInt32(Math.Floor(Progress / rangePerSection)));            fromIndex = Math.Max(fromIndex, 0);var toIndex = fromIndex + 1;            PointCollection fromPoints;if (fromIndex == toIndex)            {                fromPoints = new PointCollection();for (var i = 0; i < Children[0].Count; i++)                    fromPoints.Add(new Point(0, 0));            }else{                fromPoints = Children.ElementAt(fromIndex);            }var toPoints = Children.ElementAt(toIndex);            var percentage = (Progress / rangePerSection - fromIndex) * 100;            Points = GetCurrentPoints(fromPoints, toPoints, percentage);        }    }private PointCollection GetCurrentPoints(PointCollection fromPoints, PointCollection toPoints, double percentage)    {var result = new PointCollection();for (var i = 0;            i < Math.Min(fromPoints.Count, toPoints.Count);            i++)        {            var x = (1 - percentage / 100d) * fromPoints[i].X + percentage / 100d * toPoints[i].X;            var y = (1 - percentage / 100d) * fromPoints[i].Y + percentage / 100d * toPoints[i].Y;            result.Add(new Point(x, y));        }return result;    }#region DependencyProperties#endregion}

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