相对于WPF/Silverlight，UWP的动画系统可以说有大幅提高，不过本文无意深入讨论这些动画API，本文将介绍使用Shape做一些进度、等待方面的动画，除此之外也会介绍一些相关技巧。
1. 使用StrokeDashOffset做等待提示动画
圆形的等待提示动画十分容易做，只要让它旋转就可以了：
但是圆形以外的形状就不容易做了，例如三角形，总不能让它单纯地旋转吧：
要解决这个问题可以使用StrokeDashOffset。StrokeDashOffset用于控制虚线边框的第一个短线相对于Shape开始点的位移，使用动画控制这个数值可以做出边框滚动的效果：
<Page.Resources>
<Storyboard x:Name="ProgressStoryboard">
<DoubleAnimationUsingKeyFrames EnableDependentAnimation="True"
Storyboard.TargetProperty="(Shape.StrokeDashOffset)"
Storyboard.TargetName="triangle">
<EasingDoubleKeyFrame KeyTime="0:1:0"
Value="-500" />
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</Page.Resources>
<Grid Background="#FFCCCCCC">
<Grid Height="100"
HorizontalAlignment="Center">
<StackPanel Orientation="Horizontal"
VerticalAlignment="Center">
<TextBlock Text="L"
FontSize="55"
Margin="0,0,5,4" />
<local:Triangle x:Name="triangle"
Height="40"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue"
StrokeDashArray="4.045 4.045"
StrokeDashOffset="0.05"
StrokeDashCap="Round" />
<TextBlock Text="ading..."
FontSize="55"
Margin="5,0,0,4" />
</StackPanel>
</Grid>
</Grid>
需要注意的是Shape的边长要正好能被StrokeDashArray中短线和缺口的和整除，即 满足边长 / StrokeThickness % Sum( StrokeDashArray ) = 0，这是因为在StrokeDashOffset=0的地方会截断短线，如下图所示：
另外注意的是边长的计算，如Rectangle，边长并不是(Height + Width) * 2，而是(Height - StrokeThickness) * 2 + (Width- StrokeThickness) * 2，如下图所示，边长应该从边框正中间开始计算：
有一些Shape的边长计算还会受到Stretch影响，如上一篇中自定义的Triangle：
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
<Grid Height="50"
Width="50">
<local:Triangle Stretch="Fill"
StrokeThickness="5"
Stroke="RoyalBlue" />
</Grid>
<Grid Height="50"
Width="50"
Margin="10,0,0,0">
<local:Triangle Stretch="None"
StrokeThickness="5"
Stroke="RoyalBlue" />
</Grid>
</StackPanel>
2. 使用StrokeDashArray做进度提示动画
StrokeDashArray用于将Shape的边框变成虚线，StrokeDashArray的值是一个double类型的有序集合，里面的数值指定虚线中每一段以StrokeThickness为单位的长度。用StrokeDashArray做进度提示的基本做法就是将进度Progress通过Converter转换为分成两段的StrokeDashArray，第一段为实线，表示当前进度，第二段为空白。假设一个Shape的边长是100，当前进度为50，则将StrokeDashArray设置成{50，double.MaxValue}两段。
做成动画如下图所示：
<Page.Resources>
<Style TargetType="TextBlock">
<Setter Property="FontSize"
Value="12" />
</Style>
<local:ProgressToStrokeDashArrayConverter x:Key="ProgressToStrokeDashArrayConverter"
TargetPath="{Binding ElementName=Triangle}" />
<local:ProgressToStrokeDashArrayConverter2 x:Key="ProgressToStrokeDashArrayConverter2"
TargetPath="{Binding ElementName=Triangle}" />
<toolkit:StringFormatConverter x:Key="StringFormatConverter" />
<local:ProgressWrapper x:Name="ProgressWrapper" />
<Storyboard x:Name="Storyboard1">
<DoubleAnimation Duration="0:0:5"
To="100"
Storyboard.TargetProperty="Progress"
Storyboard.TargetName="ProgressWrapper"
EnableDependentAnimation="True" />
</Storyboard>
</Page.Resources>
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Viewbox Height="150">
<StackPanel Orientation="Horizontal">
<Grid>
<local:Triangle Height="40"
Width="40"
StrokeThickness="2"
Stroke="DarkGray" />
<local:Triangle x:Name="Triangle"
Height="40"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue"
StrokeDashArray="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource ProgressToStrokeDashArrayConverter}}" />
<TextBlock Text="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource StringFormatConverter},ConverterParameter='{}{0:0}'}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Margin="0,15,0,0" />
</Grid>
<Grid Margin="20,0,0,0">
<local:Triangle Height="40"
Width="40"
StrokeThickness="2"
Stroke="DarkGray" />
<local:Triangle x:Name="Triangle2"
Height="40"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue"
StrokeDashArray="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource ProgressToStrokeDashArrayConverter2}}" />
<TextBlock Text="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource StringFormatConverter},ConverterParameter='{}{0:0}'}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Margin="0,15,0,0" />
</Grid>
</StackPanel>
</Viewbox>
</Grid>
其中ProgressToStrokeDashArrayConverter和ProgressToStrokeDashArrayConverter2的代码如下：
public class ProgressToStrokeDashArrayConverter : DependencyObject, IValueConverter
{
/// <summary>
/// 获取或设置TargetPath的值
/// </summary>
public Path TargetPath
{
get { return (Path)GetValue(TargetPathProperty); }
set { SetValue(TargetPathProperty, value); }
}
/// <summary>
/// 标识 TargetPath 依赖属性。
/// </summary>
public static readonly DependencyProperty TargetPathProperty =
DependencyProperty.Register("TargetPath", typeof(Path), typeof(ProgressToStrokeDashArrayConverter), new PropertyMetadata(null));
public virtual object Convert(object value, Type targetType, object parameter, string language)
{
if (value is double == false)
return null;
var progress = (double)value;
if (TargetPath == null)
return null;
var totalLength = GetTotalLength();
var firstSection = progress * totalLength / 100 / TargetPath.StrokeThickness;
if (progress == 100)
firstSection = Math.Ceiling(firstSection);
var result = new DoubleCollection { firstSection, double.MaxValue };
return result;
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}
protected double GetTotalLength()
{
var geometry = TargetPath.Data as PathGeometry;
if (geometry == null)
return 0;
if (geometry.Figures.Any() == false)
return 0;
var figure = geometry.Figures.FirstOrDefault();
if (figure == null)
return 0;
var totalLength = 0d;
var point = figure.StartPoint;
foreach (var item in figure.Segments)
{
var segment = item as LineSegment;
if (segment == null)
return 0;
totalLength += Math.Sqrt(Math.Pow(point.X - segment.Point.X, 2) + Math.Pow(point.Y - segment.Point.Y, 2));
point = segment.Point;
}
totalLength += Math.Sqrt(Math.Pow(point.X - figure.StartPoint.X, 2) + Math.Pow(point.Y - figure.StartPoint.Y, 2));
return totalLength;
}
}
public class ProgressToStrokeDashArrayConverter2 : ProgressToStrokeDashArrayConverter
{
public override object Convert(object value, Type targetType, object parameter, string language)
{
if (value is double == false)
return null;
var progress = (double)value;
if (TargetPath == null)
return null;
var totalLength = GetTotalLength();
totalLength = totalLength / TargetPath.StrokeThickness;
var thirdSection = progress * totalLength / 100;
if (progress == 100)
thirdSection = Math.Ceiling(thirdSection);
var secondSection = (totalLength - thirdSection) / 2;
var result = new DoubleCollection { 0, secondSection, thirdSection, double.MaxValue };
return result;
}
}
由于代码只是用于演示，protected double GetTotalLength()写得比较将就。可以看到这两个Converter继承自DependencyObject，这是因为这里需要通过绑定为TargetPath赋值。
这里还有另一个类ProgressWrapper：
public class ProgressWrapper : DependencyObject
{
/// <summary>
/// 获取或设置Progress的值
/// </summary>
public double Progress
{
get { return (double)GetValue(ProgressProperty); }
set { SetValue(ProgressProperty, value); }
}
/// <summary>
/// 标识 Progress 依赖属性。
/// </summary>
public static readonly DependencyProperty ProgressProperty =
DependencyProperty.Register("Progress", typeof(double), typeof(ProgressWrapper), new PropertyMetadata(0d));
}
因为这里没有可供Storyboard操作的double属性，所以用这个类充当Storyboard和StrokeDashArray的桥梁。UWPCommunityToolkit中也有一个差不多用法的类BindableValueHolder，这个类通用性比较强，可以参考它的用法。
3. 使用Behavior改进进度提示动画代码
只是做个动画而已，又是Converter，又是Wrapper，又是Binding，看起来十分复杂，如果Shape上面有Progress属性就方便多了。这时候首先会考虑附加属性，在XAML用法如下：
<UserControl.Resources>
<Storyboard x:Name="Storyboard1">
<DoubleAnimation Duration="0:0:5"
To="100"
Storyboard.TargetProperty="(local:PathExtention.Progress)"
Storyboard.TargetName="Triangle" />
</Storyboard>
</UserControl.Resources>
<Grid x:Name="LayoutRoot"
Background="White">
<local:Triangle x:Name="Triangle"
Height="40"
local:PathExtention.Progress="0"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue" >
</local:Triangle>
</Grid>
但其实这是行不通的，XAML有一个存在了很久的限制：However, an existing limitation of the Windows Runtime XAML implementation is that you cannot animate a custom attached property.。这个限制决定了XAML不能对自定义附加属性做动画。不过，这个限制只限制了不能对自定义附加属性本身做动画，但对附加属性中的类的属性则可以，例如以下这种写法应该是行得通的：
<UserControl.Resources>
<Storyboard x:Name="Storyboard1">
<DoubleAnimation Duration="0:0:5"
To="100"
Storyboard.TargetProperty="(local:PathExtention.Progress)"
Storyboard.TargetName="TrianglePathExtention" />
</Storyboard>
</UserControl.Resources>
<Grid x:Name="LayoutRoot"
Background="White">
<local:Triangle x:Name="Triangle"
Height="40"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue" >
<local:PathHelper>
<local:PathExtention x:Name="TrianglePathExtention"
Progress="0" />
</local:PathHelper>
</local:Triangle>
</Grid>
更优雅的写法是利用XamlBehaviors，这篇文章很好地解释了XamlBehaviors的作用：
XAML Behaviors非常重要，因为它们提供了一种方法，让开发人员能够以一种简洁、可重复的方式轻松地向UI对象添加功能。他们无需创建控件的子类或重复编写逻辑代码，只要简单地增加一个XAML代码片段。
要使用Behavior改进现有代码，只需实现一个PathProgressBehavior：
public class PathProgressBehavior : Behavior<UIElement>
{
protected override void OnAttached()
{
base.OnAttached();
UpdateStrokeDashArray();
}
/// <summary>
/// 获取或设置Progress的值
/// </summary>
public double Progress
{
get { return (double)GetValue(ProgressProperty); }
set { SetValue(ProgressProperty, value); }
}
/*Progress DependencyProperty*/
protected virtual void OnProgressChanged(double oldValue, double newValue)
{
UpdateStrokeDashArray();
}
protected virtual double GetTotalLength(Path path)
{
/*some code*/
}
private void UpdateStrokeDashArray()
{
var target = AssociatedObject as Path;
if (target == null)
return;
double progress = Progress;
//if (target.ActualHeight == 0 || target.ActualWidth == 0)
// return;
if (target.StrokeThickness == 0)
return;
var totalLength = GetTotalLength(target);
var firstSection = progress * totalLength / 100 / target.StrokeThickness;
if (progress == 100)
firstSection = Math.Ceiling(firstSection);
var result = new DoubleCollection { firstSection, double.MaxValue };
target.StrokeDashArray = result;
}
}
XAML中如下使用：
<UserControl.Resources>
<Storyboard x:Name="Storyboard1">
<DoubleAnimation Duration="0:0:5"
To="100"
Storyboard.TargetProperty="Progress"
Storyboard.TargetName="PathProgressBehavior"
EnableDependentAnimation="True"/>
</Storyboard>
</UserControl.Resources>
<Grid x:Name="LayoutRoot"
Background="White">
<local:Triangle x:Name="Triangle"
Height="40"
local:PathExtention.Progress="0"
Width="40"
StrokeThickness="2"
Stroke="RoyalBlue" >
<interactivity:Interaction.Behaviors>
<local:PathProgressBehavior x:Name="PathProgressBehavior" />
</interactivity:Interaction.Behaviors>
</local:Triangle>
</Grid>
这样看起来就清爽多了。
4. 模仿背景填充动画
先看看效果：
其实这篇文章里并不会讨论填充动画，不过首先声明做填充动画会更方便快捷，这一段只是深入学习过程中的产物，实用价值不高。
上图三角形的填充的效果只需要叠加两个同样大小的Shape，前面那个设置Stretch="Uniform"，再通过DoubleAnimation改变它的高度就可以了。文字也是相同的原理，叠加两个相同的TextBlock，将前面那个放在一个无边框的ScrollViewer里再去改变ScrollViewer的高度。
<Page.Resources>
<Style TargetType="TextBlock">
<Setter Property="FontSize"
Value="12" />
</Style>
<local:ProgressToHeightConverter x:Key="ProgressToHeightConverter"
TargetContentControl="{Binding ElementName=ContentControl}" />
<local:ReverseProgressToHeightConverter x:Key="ReverseProgressToHeightConverter"
TargetContentControl="{Binding ElementName=ContentControl2}" />
<toolkit:StringFormatConverter x:Key="StringFormatConverter" />
<local:ProgressWrapper x:Name="ProgressWrapper" />
<Storyboard x:Name="Storyboard1">
<DoubleAnimation Duration="0:0:5"
To="100"
Storyboard.TargetProperty="Progress"
Storyboard.TargetName="ProgressWrapper"
EnableDependentAnimation="True" />
</Storyboard>
</Page.Resources>
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid>
<local:Triangle Height="40"
Width="40"
StrokeThickness="2"
Fill="LightGray" />
<local:Triangle Height="40"
Width="40"
Stretch="Fill"
StrokeThickness="2"
Stroke="RoyalBlue" />
<ContentControl x:Name="ContentControl"
VerticalAlignment="Bottom"
HorizontalAlignment="Center"
Height="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource ProgressToHeightConverter}}">
<local:Triangle x:Name="Triangle3"
Height="40"
Width="40"
StrokeThickness="2"
Fill="RoyalBlue"
Stretch="Uniform"
VerticalAlignment="Bottom" />
</ContentControl>
<TextBlock Text="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource StringFormatConverter},ConverterParameter='{}{0:0}'}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Margin="0,12,0,0"
Foreground="White" />
<ContentControl x:Name="ContentControl2"
Height="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource ReverseProgressToHeightConverter}}"
VerticalAlignment="Top"
HorizontalAlignment="Center">
<ScrollViewer BorderThickness="0"
Padding="0,0,0,0"
VerticalScrollBarVisibility="Disabled"
HorizontalScrollBarVisibility="Disabled"
VerticalAlignment="Top"
Height="40">
<Grid Height="40">
<TextBlock Text="{Binding Progress,Source={StaticResource ProgressWrapper},Converter={StaticResource StringFormatConverter},ConverterParameter='{}{0:0}'}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Margin="0,12,0,0" />
</Grid>
</ScrollViewer>
</ContentControl>
</Grid>
</Grid>
ProgressToHeightConverter和ReverseProgressToHeightConverter的代码如下：
public class ProgressToHeightConverter : DependencyObject, IValueConverter
{
/// <summary>
/// 获取或设置TargetContentControl的值
/// </summary>
public ContentControl TargetContentControl
{
get { return (ContentControl)GetValue(TargetContentControlProperty); }
set { SetValue(TargetContentControlProperty, value); }
}
/// <summary>
/// 标识 TargetContentControl 依赖属性。
/// </summary>
public static readonly DependencyProperty TargetContentControlProperty =
DependencyProperty.Register("TargetContentControl", typeof(ContentControl), typeof(ProgressToHeightConverter), new PropertyMetadata(null));
public object Convert(object value, Type targetType, object parameter, string language)
{
if (value is double == false)
return 0d;
var progress = (double)value;
if (TargetContentControl == null)
return 0d;
var element = TargetContentControl.Content as FrameworkElement;
if (element == null)
return 0d;
return element.Height * progress / 100;
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}
}
public class ReverseProgressToHeightConverter : DependencyObject, IValueConverter
{
/// <summary>
/// 获取或设置TargetContentControl的值
/// </summary>
public ContentControl TargetContentControl
{
get { return (ContentControl)GetValue(TargetContentControlProperty); }
set { SetValue(TargetContentControlProperty, value); }
}
/// <summary>
/// 标识 TargetContentControl 依赖属性。
/// </summary>
public static readonly DependencyProperty TargetContentControlProperty =
DependencyProperty.Register("TargetContentControl", typeof(ContentControl), typeof(ReverseProgressToHeightConverter), new PropertyMetadata(null));
public object Convert(object value, Type targetType, object parameter, string language)
{
if (value is double == false)
return double.NaN;
var progress = (double)value;
if (TargetContentControl == null)
return double.NaN;
var element = TargetContentControl.Content as FrameworkElement;
if (element == null)
return double.NaN;
return element.Height * (100 - progress) / 100;
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}
}
再提醒一次，实际上老老实实做填充动画好像更方便些。
5. 将动画应用到Button的ControlTemplate
同样的技术，配合ControlTemplate可以制作很有趣的按钮：
PointerEntered时，按钮的边框从进入点向反方向延伸。PointerExited时，边框从反方向向移出点消退。要做到这点需要在PointerEntered时改变边框的方向，使用了ChangeAngleToEnterPointerBehavior：
public class ChangeAngleToEnterPointerBehavior : Behavior<Ellipse>
{
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.PointerEntered += OnAssociatedObjectPointerEntered;
AssociatedObject.PointerExited += OnAssociatedObjectPointerExited;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.PointerEntered -= OnAssociatedObjectPointerEntered;
AssociatedObject.PointerExited -= OnAssociatedObjectPointerExited;
}
private void OnAssociatedObjectPointerExited(object sender, PointerRoutedEventArgs e)
{
UpdateAngle(e);
}
private void OnAssociatedObjectPointerEntered(object sender, PointerRoutedEventArgs e)
{
UpdateAngle(e);
}
private void UpdateAngle(PointerRoutedEventArgs e)
{
if (AssociatedObject == null || AssociatedObject.StrokeThickness == 0)
return;
AssociatedObject.RenderTransformOrigin = new Point(0.5, 0.5);
var rotateTransform = AssociatedObject.RenderTransform as RotateTransform;
if (rotateTransform == null)
{
rotateTransform = new RotateTransform();
AssociatedObject.RenderTransform = rotateTransform;
}
var point = e.GetCurrentPoint(AssociatedObject.Parent as UIElement).Position;
var centerPoint = new Point(AssociatedObject.ActualWidth / 2, AssociatedObject.ActualHeight / 2);
var angleOfLine = Math.Atan2(point.Y - centerPoint.Y, point.X - centerPoint.X) * 180 / Math.PI;
rotateTransform.Angle = angleOfLine + 180;
}
}
这个类命名不是很好，不过将就一下吧。
为了做出边框延伸的效果，另外需要一个类EllipseProgressBehavior：
public class EllipseProgressBehavior : Behavior<Ellipse>
{
/// <summary>
/// 获取或设置Progress的值
/// </summary>
public double Progress
{
get { return (double)GetValue(ProgressProperty); }
set { SetValue(ProgressProperty, value); }
}
/// <summary>
/// 标识 Progress 依赖属性。
/// </summary>
public static readonly DependencyProperty ProgressProperty =
DependencyProperty.Register("Progress", typeof(double), typeof(EllipseProgressBehavior), new PropertyMetadata(0d, OnProgressChanged));
private static void OnProgressChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
var target = obj as EllipseProgressBehavior;
double oldValue = (double)args.OldValue;
double newValue = (double)args.NewValue;
if (oldValue != newValue)
target.OnProgressChanged(oldValue, newValue);
}
protected virtual void OnProgressChanged(double oldValue, double newValue)
{
UpdateStrokeDashArray();
}
protected virtual double GetTotalLength()
{
if (AssociatedObject == null)
return 0;
return (AssociatedObject.ActualHeight - AssociatedObject.StrokeThickness) * Math.PI;
}
private void UpdateStrokeDashArray()
{
if (AssociatedObject == null || AssociatedObject.StrokeThickness == 0)
return;
//if (target.ActualHeight == 0 || target.ActualWidth == 0)
// return;
var totalLength = GetTotalLength();
totalLength = totalLength / AssociatedObject.StrokeThickness;
var thirdSection = Progress * totalLength / 100;
var secondSection = (totalLength - thirdSection) / 2;
var result = new DoubleCollection { 0, secondSection, thirdSection, double.MaxValue };
AssociatedObject.StrokeDashArray = result;
}
}
套用到ControlTemplate如下：
<ControlTemplate TargetType="Button">
<Grid x:Name="RootGrid">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="0:0:1"
To="Normal">
<Storyboard>
<DoubleAnimationUsingKeyFrames EnableDependentAnimation="True"
Storyboard.TargetProperty="(local:EllipseProgressBehavior.Progress)"
Storyboard.TargetName="EllipseProgressBehavior">
<EasingDoubleKeyFrame KeyTime="0:0:1"
Value="0">
<EasingDoubleKeyFrame.EasingFunction>
<QuinticEase EasingMode="EaseOut" />
</EasingDoubleKeyFrame.EasingFunction>
</EasingDoubleKeyFrame>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
<VisualTransition GeneratedDuration="0:0:1"
To="PointerOver">
<Storyboard>
<DoubleAnimationUsingKeyFrames EnableDependentAnimation="True"
Storyboard.TargetProperty="(local:EllipseProgressBehavior.Progress)"
Storyboard.TargetName="EllipseProgressBehavior">
<EasingDoubleKeyFrame KeyTime="0:0:1"
Value="100">
<EasingDoubleKeyFrame.EasingFunction>
<QuinticEase EasingMode="EaseOut" />
</EasingDoubleKeyFrame.EasingFunction>
</EasingDoubleKeyFrame>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
</VisualStateGroup.Transitions>
<VisualState x:Name="Normal">
<Storyboard>
<PointerUpThemeAnimation Storyboard.TargetName="RootGrid" />
</Storyboard>
</VisualState>
<VisualState x:Name="PointerOver">
<Storyboard>
<PointerUpThemeAnimation Storyboard.TargetName="RootGrid" />
</Storyboard>
<VisualState.Setters>
<Setter Target="EllipseProgressBehavior.(local:EllipseProgressBehavior.Progress)"
Value="100" />
</VisualState.Setters>
</VisualState>
<VisualState x:Name="Pressed">
<Storyboard>
<PointerDownThemeAnimation Storyboard.TargetName="RootGrid" />
</Storyboard>
</VisualState>
<VisualState x:Name="Disabled" />
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<ContentPresenter x:Name="ContentPresenter"
AutomationProperties.AccessibilityView="Raw"
ContentTemplate="{TemplateBinding ContentTemplate}"
ContentTransitions="{TemplateBinding ContentTransitions}"
Content="{TemplateBinding Content}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
Padding="{TemplateBinding Padding}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" />
<Ellipse Fill="Transparent"
Stroke="{TemplateBinding BorderBrush}"
StrokeThickness="2">
<interactivity:Interaction.Behaviors>
<local:ChangeAngleToEnterPointerBehavior />
<local:EllipseProgressBehavior x:Name="EllipseProgressBehavior" />
</interactivity:Interaction.Behaviors>
</Ellipse>
</Grid>
</ControlTemplate>
注意：我没有鼓励任何人自定义按钮外观的意思，能用系统自带的动画或样式就尽量用系统自带的，没有设计师的情况下又想UI做得与众不同通常会做得很难看。想要UI好看，合理的布局、合理的颜色、合理的图片就足够了。
6. 结语
在学习Shape的过程中觉得好玩就做了很多尝试，因为以前工作中做过不少等待、进度的动画，所以这次就试着做出本文的动画。
XAML的传统动画并没有提供太多功能，主要是ColorAnimation、DoubleAnimation、PointAnimation三种，不过靠Binding和Converter可以弥补这方面的不足，实现很多需要的功能。
本文的一些动画效果参考了SVG的动画。话说回来，Windows 10 1703新增了SvgImageSource，不过看起来只是简单地将SVG翻译成对应的Shape，然后用Shape呈现，不少高级特性都不支持（如下图阴影的滤镜），用法如下：
<Image>
<Image.Source>
<SvgImageSource UriSource="feoffset_1.svg" />
</Image.Source>
</Image>
SvgImageSource：
原本的Svg：
