WPF中的PathAnimation(路径动画)
周银辉
在WPF中我们可以指定元素按照某一路径运动而形成动画,这称之为路径动画,在SDK中你会发现以[Type]AnimationUsingPath这种形式命名的类,它们就是用来创建路径动画的,其中[Type]表示一系列类型比如double,point等,这与DoubleAnimation等的命名方式一致。
为对路径动画有一个大体上的认识,你可以粘贴下面的代码到XamlPad:
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Name="Window"
Title="Window1"
Width="640" Height="480">
<Window.Resources>
<Storyboard x:Key="Timeline1" RepeatBehavior = "Forever" AutoReverse="True">
<DoubleAnimationUsingPath BeginTime="00:00:00" Duration="00:00:02" Storyboard.TargetName="button" Storyboard.TargetProperty="(UIElement.RenderTransform).(TransformGroup.Children)[3].(TranslateTransform.X)" Source="X">
<DoubleAnimationUsingPath.PathGeometry>
<PathGeometry Figures="M-68,149.00022 C-39.695816,109.3744 -17.383496,83.397528 39,74.000287 C73.433618,68.261356 91.198465,71.210009 125,89.000273 C157.86626,106.29829 181.01028,123.79991 204,155.00021 C213.7418,168.22121 224.03351,180.96708 234,194.00017 C246.07551,209.79121 257.36571,220.41957 275,231.00014 C285.57406,237.34456 295.83653,242.84775 307,248.00012 C317.8183,252.99318 324.46505,252.89547 337,252.00012 C362.92461,250.14836 384.46844,240.41978 404,225.00014"/>
</DoubleAnimationUsingPath.PathGeometry>
</DoubleAnimationUsingPath>
<DoubleAnimationUsingPath BeginTime="00:00:00" Duration="00:00:02" Storyboard.TargetName="button" Storyboard.TargetProperty="(UIElement.RenderTransform).(TransformGroup.Children)[3].(TranslateTransform.Y)" Source="Y">
<DoubleAnimationUsingPath.PathGeometry>
<PathGeometry Figures="M-68,149.00022 C-39.695816,109.3744 -17.383496,83.397528 39,74.000287 C73.433618,68.261356 91.198465,71.210009 125,89.000273 C157.86626,106.29829 181.01028,123.79991 204,155.00021 C213.7418,168.22121 224.03351,180.96708 234,194.00017 C246.07551,209.79121 257.36571,220.41957 275,231.00014 C285.57406,237.34456 295.83653,242.84775 307,248.00012 C317.8183,252.99318 324.46505,252.89547 337,252.00012 C362.92461,250.14836 384.46844,240.41978 404,225.00014"/>
</DoubleAnimationUsingPath.PathGeometry>
</DoubleAnimationUsingPath>
</Storyboard>
</Window.Resources>
<Window.Triggers>
<EventTrigger RoutedEvent="FrameworkElement.Loaded">
<BeginStoryboard Storyboard="{StaticResource Timeline1}"/>
</EventTrigger>
</Window.Triggers>
<Grid x:Name="LayoutRoot">
<Path Fill="#FFFFFFFF" Stretch="Fill" Stroke="#FF000000" Margin="63.5,128.847,87.5,133.025" Data="M64,207 C92.304184,167.37414 114.6165,141.39725 171,132 205.43362,126.26106 223.19847,129.20972 257,147 289.86626,164.29803 313.01028,181.79967 336,213 345.7418,226.22101 356.03351,238.96689 366,252 378.07551,267.79105 389.36571,278.41942 407,289 417.57406,295.34443 427.83653,300.84763 439,306 449.8183,310.99306 456.46505,310.89535 469,310 494.92461,308.14824 516.46844,298.41966
536,283"/>
<Button RenderTransformOrigin="0.5,0.5" HorizontalAlignment="Left" Margin="82,30,0,0" x:Name="button" VerticalAlignment="Top" Width="100" Height="56" Content="Button">
<Button.RenderTransform>
<TransformGroup>
<ScaleTransform ScaleX="1" ScaleY="1"/>
<SkewTransform AngleX="0" AngleY="0"/>
<RotateTransform Angle="0"/>
<TranslateTransform X="0" Y="0"/>
</TransformGroup>
</Button.RenderTransform>
</Button>
</Grid>
</Window>
你可以得到如图所示的一个窗体:
窗体上的按钮沿着曲线来回的运动(按钮的中心始终与曲线相切)。
1,使用Microsoft Expression Blend工具为我们自动生成路径动画
打造路径动画的最简单的方式是使用 Microsoft Expression Blend工具来自动生成,当然这自然会失去灵活性。
第一步:创建动画对象(比如上图中的那个Button)
第二步:创建动画路径(比如一条曲线,一个圆)
记得将路径的逻辑树层次上调整得比刚才那个按钮低
第三步:将路径转化为MotionPath
选中逻辑树上的[Path]对象,单击菜单栏的Object,选择Path子项,在选择Convert To MotionPath,则会弹出如下窗口:
其要求你选择MotionPath的目标,也就是路径动画的目标,我们这里选择我们的button按钮
单击OK,其会自动为你生成Timeline(此后的操作就与打造普通Timeline 的操作一样了,其实此时该路径动画已经生成,你可以单击Timeline录制旁边的“播放”按钮来观看效果了,或直接F5)
2,使用代码来打造更灵活的路径动画
我更喜欢使用手写代码的方式来做更多的事情,这让事情变得更容易控制,同时也更具有灵活性。
以DoubleAnimationUsingPath为例,我们逐步讲解一下如何使用代码来打造上面的示例。
为了让对象沿着曲线运动,我们通过改变一个TranslateTransform的X与Y值来做到,并将该TranslateTransform指定给按钮的RenderTransform。
假设我们动画中的路径(也就是示例中的那条曲线)为path1,动画的对象为border1,如果你有过编写WPF动画代码的经验,那么你可以很轻松地编写出以下代码:
animationX.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationX.Source = PathAnimationSource.X;
animationX.Duration = new Duration(TimeSpan.FromSeconds(2));
DoubleAnimationUsingPath animationY = new DoubleAnimationUsingPath();
animationY.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationY.Source = PathAnimationSource.Y;
animationY.Duration = animationX.Duration;
将代码补充完整后如下:
this.border1.RenderTransform = translate;
NameScope.SetNameScope(this, new NameScope());
this.RegisterName("translate", translate);
DoubleAnimationUsingPath animationX = new DoubleAnimationUsingPath();
animationX.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationX.Source = PathAnimationSource.X;
animationX.Duration = new Duration(TimeSpan.FromSeconds(2));
DoubleAnimationUsingPath animationY = new DoubleAnimationUsingPath();
animationY.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationY.Source = PathAnimationSource.Y;
animationY.Duration = animationX.Duration;
Storyboard story = new Storyboard();
story.RepeatBehavior = RepeatBehavior.Forever;
story.AutoReverse = true;
story.Children.Add(animationX);
story.Children.Add(animationY);
Storyboard.SetTargetName(animationX, "translate");
Storyboard.SetTargetName(animationY, "translate");
Storyboard.SetTargetProperty(animationX, new PropertyPath(TranslateTransform.XProperty));
Storyboard.SetTargetProperty(animationY, new PropertyPath(TranslateTransform.YProperty));
story.Begin(this);
但不难发现,图中方块运动的路径与曲线并为完全重合,而是存在X与Y方向上的平移。这是一个很让人头疼的问题,但是我发现,只要在动画播放之前,将方块的中心位置设置为与动画所在容器的(0,0)位置向重合,那么该问题就可以被避免。
修改后的代码:
Canvas.SetLeft(this.border1, -this.border1.ActualWidth / 2);
TranslateTransform translate = new TranslateTransform();
this.border1.RenderTransform = translate;
NameScope.SetNameScope(this, new NameScope());
this.RegisterName("translate", translate);
DoubleAnimationUsingPath animationX = new DoubleAnimationUsingPath();
animationX.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationX.Source = PathAnimationSource.X;
animationX.Duration = new Duration(TimeSpan.FromSeconds(2));
DoubleAnimationUsingPath animationY = new DoubleAnimationUsingPath();
animationY.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationY.Source = PathAnimationSource.Y;
animationY.Duration = animationX.Duration;
Storyboard story = new Storyboard();
story.RepeatBehavior = RepeatBehavior.Forever;
story.AutoReverse = true;
story.Children.Add(animationX);
story.Children.Add(animationY);
Storyboard.SetTargetName(animationX, "translate");
Storyboard.SetTargetName(animationY, "translate");
Storyboard.SetTargetProperty(animationX, new PropertyPath(TranslateTransform.XProperty));
Storyboard.SetTargetProperty(animationY, new PropertyPath(TranslateTransform.YProperty));
story.Begin(this);
刚才已经提到,PathAnimationSource枚举拥有第三个值Angle,它是用来使我们的动画对象沿着路径旋转的,旋转对象与移动类似,但需要注意的是:
(1)旋转时对象的中心点始终与路径相切,那么你需要注意旋转时对象的中心在哪,比如上面的方块的中心点在其长宽的50%处,那么我们设置其RenderTransformOrigin为(0.5,0.5)
RotateTransform rotate = new RotateTransform();
TransformGroup group = new TransformGroup();
group.Children.Add(rotate);//先旋转
group.Children.Add(translate);//再平移
this.border1.RenderTransform = group;
Canvas.SetLeft(this.border1, -this.border1.ActualWidth / 2);
this.border1.RenderTransformOrigin = new Point(0.5, 0.5);
TranslateTransform translate = new TranslateTransform();
RotateTransform rotate = new RotateTransform();
TransformGroup group = new TransformGroup();
group.Children.Add(rotate);//先旋转
group.Children.Add(translate);//再平移
this.border1.RenderTransform = group;
NameScope.SetNameScope(this, new NameScope());
this.RegisterName("translate", translate);
this.RegisterName("rotate", rotate);
DoubleAnimationUsingPath animationX = new DoubleAnimationUsingPath();
animationX.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationX.Source = PathAnimationSource.X;
animationX.Duration = new Duration(TimeSpan.FromSeconds(2));
DoubleAnimationUsingPath animationY = new DoubleAnimationUsingPath();
animationY.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationY.Source = PathAnimationSource.Y;
animationY.Duration = animationX.Duration;
DoubleAnimationUsingPath animationAngle = new DoubleAnimationUsingPath();
animationAngle.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
animationAngle.Source = PathAnimationSource.Angle;
animationAngle.Duration = animationX.Duration;
Storyboard story = new Storyboard();
story.RepeatBehavior = RepeatBehavior.Forever;
story.AutoReverse = true;
story.Children.Add(animationX);
story.Children.Add(animationY);
story.Children.Add(animationAngle);
Storyboard.SetTargetName(animationX, "translate");
Storyboard.SetTargetName(animationY, "translate");
Storyboard.SetTargetName(animationAngle, "rotate");
Storyboard.SetTargetProperty(animationX, new PropertyPath(TranslateTransform.XProperty));
Storyboard.SetTargetProperty(animationY, new PropertyPath(TranslateTransform.YProperty));
Storyboard.SetTargetProperty(animationAngle, new PropertyPath(RotateTransform.AngleProperty));
story.Begin(this);
效果图如下:
关于路径动画,先介绍到这里,不过其实实现上面的的动画更为常用的方式是使用MatrixAnimationUsingPath,可以参考以下代码:
Canvas.SetTop(this.border1, -this.border1.ActualHeight / 2);
this.border1.RenderTransformOrigin = new Point(0.5, 0.5);
MatrixTransform matrix = new MatrixTransform();
this.border1.RenderTransform = matrix;
NameScope.SetNameScope(this, new NameScope());
this.RegisterName("matrix", matrix);
MatrixAnimationUsingPath matrixAnimation = new MatrixAnimationUsingPath();
matrixAnimation.PathGeometry = this.path1.Data.GetFlattenedPathGeometry();
matrixAnimation.Duration = new Duration(TimeSpan.FromSeconds(2));
matrixAnimation.RepeatBehavior = RepeatBehavior.Forever;
matrixAnimation.AutoReverse = true;
matrixAnimation.IsOffsetCumulative = !matrixAnimation.AutoReverse;
matrixAnimation.DoesRotateWithTangent = true;//旋转
Storyboard story = new Storyboard();
story.Children.Add(matrixAnimation);
Storyboard.SetTargetName(matrixAnimation, "matrix");
Storyboard.SetTargetProperty(matrixAnimation, new PropertyPath(MatrixTransform.MatrixProperty));
story.Begin(this);
下载Demo:https://files.cnblogs.com/zhouyinhui/PathAnimationDemo.rar