12.WPF动画

动画的就是在UI元素上施加一些Timeline实例。WPF把简单的动画称为AnimationTimeline，复杂的动画称为Storyboard。

简单的独立动画

简单线性动画

WPF中动画系统中Dloble类型的属性用的最多，所以以DoubleAnimationBase为例

• 变化时间（Duration）：必须制定，类型为Duration
• 变化终点（To）：如果没有指定，采用上一次动画的终点或者默认值
• 变化幅度（By）：如果指定了变化终点，变化幅度将被忽略
• 变化起点（From）：如果没有指定变化起点，则以变化目标的属性当前值为起点

<Grid>
    <Button Width="80" Height="80" HorizontalAlignment="Left" VerticalAlignment="Top" Click="Button_Click">
        <Button.RenderTransform>
            <TranslateTransform X="0" Y="0" x:Name="tt"></TranslateTransform>
        </Button.RenderTransform>
    </Button>
</Grid>

改变TranslateTransform对象X,Y的属性就会让Button的显示位置（非实际位置）改变

private void Button_Click(object sender, RoutedEventArgs e)
{
    DoubleAnimation daX = new DoubleAnimation();
    DoubleAnimation daY = new DoubleAnimation();
    //指定起点
    daX.From = 0;
    daY.From = 0;
    //指定终点
    Random r = new Random();
    daX.To = r.NextDouble() * 300;
    daY.To = r.NextDouble() * 300;
    //指定时长
    Duration duration = new Duration(TimeSpan.FromMilliseconds(300));
    daX.Duration = duration;
    daY.Duration = duration;
    //动画主体是TranslateTransform变形，而不是Button
    this.tt.BeginAnimation(TranslateTransform.XProperty, daX);
    this.tt.BeginAnimation(TranslateTransform.YProperty, daY);
}

高级动画控制

除了From、To等属性还具有一下高级属性

属性	描述
AccelerationRatio	加速度，0-1且与DecelerationRatio和不大于1
DecelerationRatio	减速度，0-1且与DecelerationRatio和不大于1
SpeedRatio	快进和慢进
AutoReverse	倒放
RepeatBehavior	重复，0为不播放，n为播放n次。RepeatBehavior.Forever为循环
BeginTime	播放前等待时间
EasingFunction	缓冲式渐变

只需在上面的代码中加入

BounceEase be = new BounceEase();
be.Bounces = 3;//弹跳3次
be.Bounciness = 3;//弹跳程度，值越大反弹越低
daY.EasingFunction = be;

关键帧

将上面案例的Button设置按照Z字型移动

private void Button_Click(object sender, RoutedEventArgs e)
{

    DoubleAnimationUsingKeyFrames dakX = new DoubleAnimationUsingKeyFrames();
    DoubleAnimationUsingKeyFrames dakY = new DoubleAnimationUsingKeyFrames();

    //设置动画总时长
    dakX.Duration = new Duration(TimeSpan.FromMilliseconds(900));
    dakY.Duration = new Duration(TimeSpan.FromMilliseconds(900));
    //创建，添加关键帧
    LinearDoubleKeyFrame x_kf_1 = new LinearDoubleKeyFrame();
    LinearDoubleKeyFrame x_kf_2 = new LinearDoubleKeyFrame();
    LinearDoubleKeyFrame x_kf_3 = new LinearDoubleKeyFrame();
    x_kf_1.KeyTime = KeyTime.FromPercent(0.33);
    x_kf_1.Value = 200;
    x_kf_2.KeyTime = KeyTime.FromPercent(0.66);
    x_kf_2.Value = 0;
    x_kf_3.KeyTime = KeyTime.FromPercent(1);
    x_kf_3.Value = 200;
    dakX.KeyFrames.Add(x_kf_1);
    dakX.KeyFrames.Add(x_kf_2);
    dakX.KeyFrames.Add(x_kf_3);

    LinearDoubleKeyFrame y_kf_1 = new LinearDoubleKeyFrame();
    LinearDoubleKeyFrame y_kf_2 = new LinearDoubleKeyFrame();
    LinearDoubleKeyFrame y_kf_3 = new LinearDoubleKeyFrame();
    y_kf_1.KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(300));
    y_kf_1.Value = 0;
    y_kf_2.KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(600));
    y_kf_2.Value = 180;
    y_kf_3.KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(900));
    y_kf_3.Value = 180;
    dakY.KeyFrames.Add(y_kf_1);
    dakY.KeyFrames.Add(y_kf_2);
    dakY.KeyFrames.Add(y_kf_3);

    //执行动画
    tt.BeginAnimation(TranslateTransform.XProperty, dakX);
    tt.BeginAnimation(TranslateTransform.YProperty, dakY);
}

路径动画

让目标沿着给定的路径移动，使用DoubleAnimationUsingPath，需要一个PathGeometry来指定路径，PathGeometry的另一个重要属性是Source，枚举值为X\Y\Angle，例如Angle则表示关注曲线上每一点处切线方向的变化。

实例：让一个Button沿着路径移动

<Grid x:Name="layoutRoot">
    <Grid.Resources>
        <!--移动路径-->
        <PathGeometry x:Key="movePath" Figures="M 0,50 C 300,-100 300,400 600,120"></PathGeometry>
    </Grid.Resources>
    <Button Content="Move" Width="80" Height="80" HorizontalAlignment="Left" VerticalAlignment="Top" Click="Button_Click">
        <Button.RenderTransform>
            <TranslateTransform X="0" Y="0" x:Name="tt"></TranslateTransform>
        </Button.RenderTransform>
    </Button>
</Grid>

private void Button_Click(object sender, RoutedEventArgs e)
{
    //从XAML代码中获取移动路径数据
    PathGeometry pg = this.layoutRoot.FindResource("movePath") as PathGeometry;
    Duration duration = new Duration(TimeSpan.FromMilliseconds(600));

    //创建动画
    DoubleAnimationUsingPath dpX = new DoubleAnimationUsingPath();
    dpX.Duration = duration;
    dpX.PathGeometry = pg;
    dpX.Source = PathAnimationSource.X;

    DoubleAnimationUsingPath dpY = new DoubleAnimationUsingPath();
    dpY.Duration = duration;
    dpY.PathGeometry = pg;
    dpY.Source = PathAnimationSource.Y;

    dpX.AutoReverse = true;
    dpX.RepeatBehavior = RepeatBehavior.Forever;
    dpY.AutoReverse = true;
    dpY.RepeatBehavior = RepeatBehavior.Forever;

    //执行动画
    this.tt.BeginAnimation(TranslateTransform.XProperty,dpX);
    this.tt.BeginAnimation(TranslateTransform.YProperty,dpY); 
}

场景

场景就是并行执行一组动画，WPF会把一组动画组织在Stroyboard中，安排好它们的协作关系。

制作3个小球执行不同动画的场景

<Window x:Class="WpfApplication1.Window64"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window64" Height="159" Width="461">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="38" />
            <RowDefinition Height="38" />
            <RowDefinition Height="38" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="60" />
        </Grid.ColumnDefinitions>
        <!--跑道(红)-->
        <Border Grid.Row="0" BorderBrush="Gray" BorderThickness="1">
            <Ellipse Width="36" Height="36" Fill="Red" HorizontalAlignment="Left" x:Name="ballR">
                <Ellipse.RenderTransform>
                    <TranslateTransform X="0" Y="0" x:Name="ttR">
                    </TranslateTransform>
                </Ellipse.RenderTransform>
            </Ellipse>
        </Border>
        <!--跑道(绿)-->
        <Border Grid.Row="1" BorderBrush="Gray" BorderThickness="1,0,1,1">
            <Ellipse Width="36" Height="36" Fill="Green" HorizontalAlignment="Left" x:Name="ballG">
                <Ellipse.RenderTransform>
                    <TranslateTransform X="0" Y="0" x:Name="ttG">
                    </TranslateTransform>
                </Ellipse.RenderTransform>
            </Ellipse>
        </Border>
        <!--跑道(蓝)-->
        <Border Grid.Row="2" BorderBrush="Gray" BorderThickness="1,0,1,1">
            <Ellipse Width="36" Height="36" Fill="Blue" HorizontalAlignment="Left" x:Name="ballB">
                <Ellipse.RenderTransform>
                    <TranslateTransform X="0" Y="0" x:Name="ttB">
                    </TranslateTransform>
                </Ellipse.RenderTransform>
            </Ellipse>
        </Border>
        <!--按钮-->
        <Button Content="Go" Grid.RowSpan="3" Grid.Column="1" Click="Button_Click"/>
    </Grid>
</Window>

private void Button_Click(object sender, RoutedEventArgs e)
{
    Duration duration = new Duration(TimeSpan.FromMilliseconds(600));

    //红色小球匀速运动
    DoubleAnimation daRx = new DoubleAnimation();
    daRx.Duration = duration;
    daRx.To = 400;

    //绿色小球做变速运动
    DoubleAnimationUsingKeyFrames dakGx = new DoubleAnimationUsingKeyFrames();
    dakGx.Duration = duration;
    SplineDoubleKeyFrame kfg = new SplineDoubleKeyFrame(400,KeyTime.FromPercent(1));
    kfg.KeySpline = new KeySpline(1,0,0,1);
    dakGx.KeyFrames.Add(kfg);

    //蓝色小球变速运动
    DoubleAnimationUsingKeyFrames dakBx = new DoubleAnimationUsingKeyFrames();
    dakBx.Duration = duration;
    SplineDoubleKeyFrame kfb = new SplineDoubleKeyFrame(400,KeyTime.FromPercent(1));
    kfb.KeySpline = new KeySpline(0,1,1,0);
    dakBx.KeyFrames.Add(kfb);

    //创建场景
    Storyboard storyBoard = new Storyboard();
    Storyboard.SetTargetName(daRx,"ttR");
    Storyboard.SetTargetProperty(daRx, new PropertyPath(TranslateTransform.XProperty));

    Storyboard.SetTargetName(dakGx, "ttG");
    Storyboard.SetTargetProperty(dakGx, new PropertyPath(TranslateTransform.XProperty));

    Storyboard.SetTargetName(dakBx, "ttB");
    Storyboard.SetTargetProperty(dakBx, new PropertyPath(TranslateTransform.XProperty));

    storyBoard.Duration = duration;
    storyBoard.Children.Add(daRx);
    storyBoard.Children.Add(dakBx);
    storyBoard.Children.Add(dakGx);

    storyBoard.Begin(this);
    storyBoard.Completed += (a, b) => { MessageBox.Show(ttR.X.ToString()); };
}

也可以直接使用XAML晚上上面的动画，Stroyboard一般都放在UI元素的Trigger中，Trigger在触发时会执行<BeginStoryboard>标签中的实例。

<Button Content="Go" Grid.RowSpan="3" Grid.Column="1" Click="Button_Click">
    <Button.Triggers>
        <EventTrigger RoutedEvent="Button.Click">
            <BeginStoryboard>
                <Storyboard Duration="0:0:0.6">
                    <!--红色小球动画-->
                    <DoubleAnimation Duration="0:0:0.6" To="400" Storyboard.TargetName="ttR" Storyboard.TargetProperty="X">
                        
                    </DoubleAnimation>
                    <!--绿色小球动画-->
                    <DoubleAnimationUsingKeyFrames Duration="0:0:0.6" Storyboard.TargetProperty="X" Storyboard.TargetName="ttG">
                        <SplineDoubleKeyFrame KeyTime="0:0:0.6" Value="400" KeySpline="1,0,0,1"></SplineDoubleKeyFrame>
                    </DoubleAnimationUsingKeyFrames>
                    <!--蓝色小球动画-->
                    <DoubleAnimationUsingKeyFrames Duration="0:0:0.6" Storyboard.TargetName="ttB" Storyboard.TargetProperty="X">
                        <SplineDoubleKeyFrame KeyTime="0:0:0.6" Value="400" KeySpline="0,1,1,0"></SplineDoubleKeyFrame>
                    </DoubleAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Button.Triggers>
</Button>