Silverlight 下苹果(Mac OS)风格按钮的实现
在 Silverlight 2 beta 2 下，可以通过 Style 和 ControlTemplate 对控件的观感 (look and feel) 进行定制。并且在最新的 Expression Blend 2.5 June 2008 preview 版本中，可以用可视化的方式来进行设计（一些细微的地方仍然要代码调整），这样就方便多了。本文介绍如何实现一个 Mac 风格的按钮。先看一下效果：
左边一排是普通按钮，右边一排是 Mac 风格的按钮。其中获得焦点的按钮在视觉上用一圈虚线框表示。
因为 Button 控件开放了一个 Template 属性，我们要做的就是创建一个 Style. 比如叫做 MacButton，然后让按钮实例去套用这个 Style 即可：
<Button Style="{StaticResource MacButton}"/>
而 Style 本质上是用来设置属性值的，Template 也是一个特殊的属性，它是 CcontrolTemplate. 在 Xaml 语法中可以这样写：
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
</ControlTemplate>
</Setter.Value>
</Setter>
所有控件的真实内容都在上面的 "...." 中定义即可。
再介绍一点基础知识
==========================
控件契约 (Control Contract)
Silverlight 2 beta 2 内置的每一种控件都有其自身的契约，我们在为控件创建 Style 时必须符合此契约的要求才能生效。
一般包含3个方面：
1) 属性
2) 控件可能用到的 UIElement. (用 TemplatePartAttribute 标记)
3) VisualState 对象 (用 TemplateVisualState 在控件上标记)
这里 VisualState 很有意思，表示控件的状态。并且状态可以分组，同一个组内的状态可以互相迁移。
比如 Button 有两组状态：一组是“普通”、“鼠标悬停”、“按下”、“禁用”；而另一组是“获得焦点”、“失去焦点”。
两组状态可以同时生效，互不影响。
在 ControlTemplate 内，我们可以定义各个状态以及状态间迁移时的动画 (用一个 Storyboard 定义)，以及状态之间迁移花费多少时间 (Duration) 等。
Button 控件的契约如下：
public class Button : Control
{
public static readonly DependencyProperty BackgroundProperty;
public static readonly DependencyProperty BorderBrushProperty;
public static readonly DependencyProperty BorderThicknessProperty;
public static readonly DependencyProperty ContentProperty;
public static readonly DependencyProperty ContentTemplateProperty;
public static readonly DependencyProperty FontFamilyProperty;
public static readonly DependencyProperty FontSizeProperty;
public static readonly DependencyProperty FontStretchProperty;
public static readonly DependencyProperty FontStyleProperty;
public static readonly DependencyProperty FontWeightProperty;
public static readonly DependencyProperty ForegroundProperty;
public static readonly DependencyProperty HorizontalContentAlignmentProperty;
public static readonly DependencyProperty PaddingProperty;
public static readonly DependencyProperty TextAlignmentProperty;
public static readonly DependencyProperty TextDecorationsProperty;
public static readonly DependencyProperty TextWrappingProperty;
public static readonly DependencyProperty VerticalContentAlignmentProperty;
public Brush Background { get; set; }
public Brush BorderBrush { get; set; }
public Thickness BorderThickness { get; set; }
public object Content { get; set; }
public DataTemplate ContentTemplate { get; set; }
public FontFamily FontFamily { get; set; }
public double FontSize { get; set; }
public FontStretch FontStretch { get; set; }
public FontStyle FontStyle { get; set; }
public FontWeight FontWeight { get; set; }
public Brush Foreground { get; set; }
public HorizontalAlignment HorizontalContentAlignment { get; set; }
public Thickness Padding { get; set; }
public TextAlignment TextAlignment { get; set; }
public TextDecorationCollection TextDecorations { get; set; }
public TextWrapping TextWrapping { get; set; }
public VerticalAlignment VerticalContentAlignment { get; set; }
}
关于动画的更多知识参考 Silverlight 2 beta 2 文档。
简单说一下创建这个样式的步骤：
在 ExpressionBlend 2.5 中，首先我们往界面上拖一个 Button. 然后在右键菜单中：
选择 "Edit a Copy" 后，就会自动创建一个指定名称的 Style, 其内容是 Button 的默认模板。
因为模板内容非常繁琐，我们如果自己全部手写很困难，所以我们选择在默认模板的基础上修改。
后续的步骤，主要是在模板的控件树中删除掉不必要的内容，并且修改一些画刷等设置，重新定义动画等等。不再一一详述，具体请看代码。
另外这里我发现的一个特别需要注意的问题，就是 Button 默认生成的模板中，其 Unfocused 状态的动画必须删除掉才行：
<vsm:VisualState x:Name="Unfocused">
<Storyboard>
<!-- 自动生成的模板下这里是有内容的，要删掉！-->
</Storyboard>
</vsm:VisualState>
否则，你会发现套用了该风格的所有按钮都无法失去焦点，页面上会出现若干个按钮同时为高亮状态的滑稽情景。
下面是例子的全部代码：
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="SilverlightApplication6.Page"
d:DesignWidth="640" d:DesignHeight="480" xmlns:vsm="clr-namespace:System.Windows;assembly=System.Windows">
<UserControl.Resources>
<vsm:Style x:Key="MacButton" TargetType="Button">
<vsm:Setter Property="IsEnabled" Value="true"/>
<vsm:Setter Property="IsTabStop" Value="true"/>
<vsm:Setter Property="Background" Value="#FF003255"/>
<vsm:Setter Property="Foreground" Value="#FF313131"/>
<vsm:Setter Property="MinWidth" Value="5"/>
<vsm:Setter Property="MinHeight" Value="5"/>
<vsm:Setter Property="Margin" Value="0"/>
<vsm:Setter Property="HorizontalContentAlignment" Value="Center"/>
<vsm:Setter Property="VerticalContentAlignment" Value="Center"/>
<vsm:Setter Property="Cursor" Value="Arrow"/>
<vsm:Setter Property="TextAlignment" Value="Left"/>
<vsm:Setter Property="TextWrapping" Value="NoWrap"/>
<vsm:Setter Property="FontSize" Value="11"/>
<vsm:Setter Property="Template">
<vsm:Setter.Value>
<ControlTemplate TargetType="Button">
<Grid>
<Grid.Resources>
<Color x:Key="LinearBevelLightStartColor">#FFFFFFFF</Color>
<Color x:Key="LinearBevelLightEndColor">#F4E2E0E0</Color>
<Color x:Key="LinearBevelDarkStartColor">#E0E5E5E5</Color>
<Color x:Key="LinearBevelDarkEndColor">#B2FFFFFF</Color>
<Color x:Key="MouseOverLinearBevelDarkEndColor">#7FFC1717</Color>
<Color x:Key="HoverLinearBevelLightStartColor">#FCFFFFFF</Color>
<Color x:Key="HoverLinearBevelLightEndColor">#EAFFFFFF</Color>
<Color x:Key="HoverLinearBevelDarkStartColor">#D8FFFFFF</Color>
<Color x:Key="HoverLinearBevelDarkEndColor">#4CFFFFFF</Color>
<Color x:Key="CurvedBevelFillStartColor">#B3FFFFFF</Color>
<Color x:Key="CurvedBevelFillEndColor">#3CFFFFFF</Color>
<SolidColorBrush x:Key="BorderBrush" Color="#FF5E5E5E"/>
<SolidColorBrush x:Key="AccentBrush" Color="#FF000000"/>
<SolidColorBrush x:Key="DisabledBrush" Color="#A5FFFFFF"/>
<LinearGradientBrush x:Key="FocusedStrokeBrush" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#B2FFFFFF" Offset="0"/>
<GradientStop Color="#51FFFFFF" Offset="1"/>
<GradientStop Color="#66FFFFFF" Offset="0.325"/>
<GradientStop Color="#1EFFFFFF" Offset="0.325"/>
</LinearGradientBrush>
</Grid.Resources>
<vsm:VisualStateManager.VisualStateGroups>
<vsm:VisualStateGroup x:Name="CommonStates">
<vsm:VisualStateGroup.Transitions>
<vsm:VisualTransition Duration="00:00:00.2000000" To="MouseOver"/>
<vsm:VisualTransition Duration="0:0:0.1" To="Pressed"/>
<vsm:VisualTransition Duration="00:00:00.2000000" From="Normal" To="MouseOver"/>
</vsm:VisualStateGroup.Transitions>
<vsm:VisualState x:Name="Normal">
<Storyboard/>
</vsm:VisualState>
<vsm:VisualState x:Name="MouseOver">
<Storyboard>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#c8d5ed" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#97c2ee" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#6eadee" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#aff9ff" />
</ColorAnimationUsingKeyFrames>
</Storyboard>
</vsm:VisualState>
<vsm:VisualState x:Name="Pressed">
<Storyboard>
<DoubleAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="BackgroundGradient" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Offset)">
<SplineDoubleKeyFrame KeyTime="0" Value=".2"/>
</DoubleAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#bac5e8" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#7bb2e9" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#4d9ae7" />
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames
Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops).(GradientStop.Color)">
<SplineColorKeyFrame KeyTime="0" Value="#85eaff" />
</ColorAnimationUsingKeyFrames>
</Storyboard>
</vsm:VisualState>
<vsm:VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="DisabledVisual" Storyboard.TargetProperty="Opacity">
<SplineDoubleKeyFrame KeyTime="0" Value="1"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</vsm:VisualState>
</vsm:VisualStateGroup>
<vsm:VisualStateGroup x:Name="FocusStates">
<vsm:VisualState x:Name="Focused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="FocusVisual" Storyboard.TargetProperty="Visibility">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<vsm:Visibility>Visible</vsm:Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</vsm:VisualState>
<vsm:VisualState x:Name="Unfocused">
<Storyboard>
</Storyboard>
</vsm:VisualState>
</vsm:VisualStateGroup>
</vsm:VisualStateManager.VisualStateGroups>
<Rectangle x:Name="Background" Fill="{TemplateBinding Background}" RadiusX="11" RadiusY="11"/>
<Rectangle x:Name="BackgroundGradient" Stroke="{StaticResource BorderBrush}" StrokeThickness="1" RadiusX="11" RadiusY="11" Margin="-1,-1,-1,-1">
<Rectangle.Fill>
<LinearGradientBrush EndPoint="0.7,1" StartPoint="0.7,0">
<GradientStop Color="{StaticResource LinearBevelLightStartColor}" Offset="0"/>
<GradientStop Color="{StaticResource LinearBevelLightEndColor}" Offset="0.326"/>
<GradientStop Color="{StaticResource LinearBevelDarkStartColor}" Offset="0.344"/>
<GradientStop Color="#FFFFFFFF" Offset="0.786"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<Grid x:Name="FocusVisual" Visibility="Collapsed">
<Rectangle Margin="-2,1,-2,-2" Stroke="{StaticResource AccentBrush}" StrokeThickness="1" StrokeDashArray="1.5 1.5" RadiusX="3" RadiusY="3" />
</Grid>
<ContentPresenter Margin="4,5,4,4" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" Padding="{TemplateBinding Padding}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" TextAlignment="{TemplateBinding TextAlignment}" TextDecorations="{TemplateBinding TextDecorations}" TextWrapping="{TemplateBinding TextWrapping}"/>
<Rectangle x:Name="DisabledVisual" IsHitTestVisible="false" Opacity="0" Fill="{StaticResource DisabledBrush}" RadiusX="4" RadiusY="4"/>
</Grid>
</ControlTemplate>
</vsm:Setter.Value>
</vsm:Setter>
</vsm:Style>
</UserControl.Resources>
<Canvas x:Name="LayoutRoot" Background="White">
<Button x:Name="Button1" TabIndex="0" Height="23" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Top" Width="63" Content="Button1" Canvas.Top="30" Canvas.Left="44"/>
<Button x:Name="Button2" TabIndex="1" Height="37" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Top" Width="120" Content="Button2" Canvas.Top="68.5" Canvas.Left="43"/>
<Button x:Name="Button3" TabIndex="2" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Top" Content="Button3" Width="195" Height="65" Canvas.Top="122" Canvas.Left="43"/>
<Button x:Name="Button4" TabIndex="3" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Stretch" Content="Button4" IsEnabled="False" Width="195" Canvas.Top="209" Canvas.Left="43" Height="65"/>
<Button x:Name="Button5" TabIndex="4" Height="23" HorizontalAlignment="Right" Margin="0,0,0,0" VerticalAlignment="Top" Content="Button1" Width="63" Canvas.Top="30" Canvas.Left="269" Style="{StaticResource MacButton}"/>
<Button x:Name="Button6" TabIndex="5" Height="37" HorizontalAlignment="Right" Margin="0,0,0,0" VerticalAlignment="Top" Content="Button2" Width="120" Canvas.Top="68.5" Canvas.Left="269" Style="{StaticResource MacButton}"/>
<Button x:Name="Button7" TabIndex="6"HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Top" Content="Button3" Height="65" Canvas.Top="122" Canvas.Left="269" Width="195" Style="{StaticResource MacButton}"/>
<Button x:Name="Button8" TabIndex="7" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Content="Button4" IsEnabled="False" Canvas.Top="209" Canvas.Left="269" Width="195" Height="65" Style="{StaticResource MacButton}"/>
</Canvas>
</UserControl>
关于 Expression Blend 的使用教程，这里有几个参考：
http://blog.joycode.com/scottgu/archive/2008/06/09/115138.aspx
http://timheuer.com/blog/archive/2008/06/04/skinning-silverlight-controls-made-easier.aspx
http://timheuer.com/blog/archive/2008/06/04/silverlight-introduces-visual-state-manager-vsm.aspx
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