WPF中的动画——（五）路径动画

原文:WPF中的动画——（五）路径动画

路径动画是一种专门用于将对象按照指定的Path移动的动画，虽然我们也可以通过控制动画的旋转和偏移实现对象的移动，但路径动画更专业，它的实现更加简洁明了。

路径动画中最常用的是MatrixAnimationUsingPath，它通常用于控制对象的MatrixTransform，一个简单的例子如下： 

       <Canvas >
           <Canvas.Resources>
               <PathGeometry x:Key="path" Figures="M 10,100 C 35,0 135,0 160,100 180,190 285,200 310,100" />
               <Storyboard x:Key="pathStoryboard" >
                   <MatrixAnimationUsingPath PathGeometry="{StaticResource path}"
                                             Storyboard.TargetName="ButtonMatrixTransform"
                                             Storyboard.TargetProperty="Matrix"
                                             DoesRotateWithTangent="True"
                                             Duration="0:0:5" RepeatBehavior="Forever" >
                   </MatrixAnimationUsingPath>
               </Storyboard>
           </Canvas.Resources>
           
           <Canvas.Triggers>
               <EventTrigger RoutedEvent="Control.Loaded">
                   <BeginStoryboard Storyboard="{StaticResource pathStoryboard}" />
               </EventTrigger>
           </Canvas.Triggers>
           
           <Path Data="{StaticResource path}" Stroke="Black" StrokeThickness="1" />
           
           <Button Width="50" Height="20" >
               <Button.RenderTransform>
                   <MatrixTransform x:Name="ButtonMatrixTransform" />
               </Button.RenderTransform>
           </Button>
       </Canvas>

 

注意这儿有一个DoesRotateWithTangent的属性，设置上它后，对象在移动的过程中还能根据路径的坡度旋转，非常有用。

除了MatrixAnimationUsingPath外，另外还有两种路径动画：PointAnimationUsingPath和DoubleAnimationUsingPath。PointAnimationUsingPath用于靠中心点确定位置的形状， 

       <Canvas >
           <Canvas.Resources>
               <PathGeometry x:Key="path" Figures="M 10,100 C 35,0 135,0 160,100 180,190 285,200 310,100" />
               <Storyboard x:Key="pathStoryboard" >
                   <PointAnimationUsingPath PathGeometry="{StaticResource path}"
                                             Storyboard.TargetName="ellipse"
                                             Storyboard.TargetProperty="Center"
                                             Duration="0:0:5" RepeatBehavior="Forever" >
                   </PointAnimationUsingPath>
               </Storyboard>
           </Canvas.Resources>
           
           <Canvas.Triggers>
               <EventTrigger RoutedEvent="Control.Loaded">
                   <BeginStoryboard Storyboard="{StaticResource pathStoryboard}" />
               </EventTrigger>
           </Canvas.Triggers>
           
           <Path Data="{StaticResource path}" Stroke="Black" StrokeThickness="1" />
           
           <Path Fill="Orange">
               <Path.Data>
                   <EllipseGeometry x:Name="ellipse" Center="5,5" RadiusX="12" RadiusY="12"/>
               </Path.Data>
           </Path>
       </Canvas>
 

 

 DoubleAnimationUsingPath则是通过X、Y和Angle三个属性联合实现路径的变化，一般在TranslateTransform中使用，如下就是一个简单的例子： 

  <Canvas >
           <Canvas.Resources>
               <PathGeometry x:Key="path" Figures="M 10,100 C 35,0 135,0 160,100 180,190 285,200 310,100" />
               <Storyboard x:Key="pathStoryboard" >
                   <DoubleAnimationUsingPath PathGeometry="{StaticResource path}"
                                             Storyboard.TargetName="translateTransform"
                                             Storyboard.TargetProperty="X"
                                             Source="X"
                                             Duration="0:0:5" RepeatBehavior="Forever" >
                   </DoubleAnimationUsingPath>
                   <DoubleAnimationUsingPath PathGeometry="{StaticResource path}"
                                             Storyboard.TargetName="translateTransform"
                                             Storyboard.TargetProperty="Y"
                                             Source="Y"
                                             Duration="0:0:5" RepeatBehavior="Forever" >
                   </DoubleAnimationUsingPath>
               </Storyboard>
           </Canvas.Resources>
           
           <Canvas.Triggers>
               <EventTrigger RoutedEvent="Control.Loaded">
                   <BeginStoryboard Storyboard="{StaticResource pathStoryboard}" />
               </EventTrigger>
           </Canvas.Triggers>
           
           <Path Data="{StaticResource path}" Stroke="Black" StrokeThickness="1" />
           
           <Path Fill="Orange">
               <Path.Data>
                   <EllipseGeometry x:Name="ellipse" Center="5,5" RadiusX="12" RadiusY="12"/>
               </Path.Data>
               <Path.RenderTransform>
                   <TranslateTransform x:Name="translateTransform" />
               </Path.RenderTransform>
           </Path>
       </Canvas>

 

 这个实现的效果和MatrixAnimationUsingPath类似，但比它用法复杂，很难找到它的使用场景，但由于它的控制维度更多，可能一般用于需要更多的控制的地方吧。