WPF程序设计指南:Style

注：一下内容及代码基本来自Charles Petzold著，蔡学庸译，电子工业出版社出版的《Windows Presentation Foundation 程序设计指南》一书

1. Style概述

• Style是Property值的collection,这些Style的property值可以用在element上，Style可以一定程度弥补XAML无法使用循环语句的缺点。
• Style最重要的Property是Setters, Setters类型为SetterBaseCollection，这是SetterBase的集合，
• SetterBase是一个抽象类的子类有EventSetter和Setter

因此，最基本的Style格式是：

   <
   Style 
   ...
   >
   

   <
   Setter 
   ... 
   />
   

   <
   EventSetter 
   ... 
   />
   

   <
   Setter 
   ... 
   />
   

   </
   Style
   >
  

2. Style属性之一：Setters

• 一个或者多个Setter or EventSetter objects
• Setter主要用来设置element的一个与“值”相关的Property
• Setter主要有两个Property: Property 和 Value 

• 如果是在c#代码里，需要将Properyt设置为FontSizeProperty

• 如果需要将Value设置为null：Value="{x:Null}"

3. 关于对Property设置的优先级

•  如有一个仅供某个element使用的Style(这样设置用处不大，仅为举例) 

< Button xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
HorizontalAlignment ="Center" VerticalAlignment ="Center"
Foreground ="Red" >
< Button.Style >
< Style >
< Setter Property ="Button.FontSize" Value ="18pt" />
< Setter Property="Control.Foreground" Value="Blue" />
</ Style >
</ Button.Style >
Button with Local Style
</ Button >

• 如果像这样，在element中和Style中都对Foreground做设定，那么“局部设定”的优先级优先于Style的设定
• 而Style的优先级又高于从visual tree 继承来的Property设定

4. Style作为Resource使用

 如下，一个由Button控件和TextBlock element共用的Style

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style x:Key ="normal" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.Foreground" Value ="Blue" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />
< Setter Property ="Control.Padding" Value ="20, 10, 20, 10" />
</ Style >
</ StackPanel.Resources >

< Button Style ="{StaticResource normal}" >
Button on top of the stack
</ Button >

< TextBlock Style ="{StaticResource normal}" >
TextBlock in the middle of the stack
</ TextBlock >

< Button Style ="{StaticResource normal}" >
Button on the bottom of the stack
</ Button >
</ StackPanel >

 也可以为某个独有的Property定义一个Setter。例如：

< Setter Property ="Button.IsDefault" Value ="true" />

 只会设置Button的IsDefault，因为TextBlock不具有此属性

 5. 具有相同key的style

 可以在多个resource中使用相同的key来定义stlye。对于某个特定的element来说，它将沿视觉树往上搜索，采用第一个和key关联的style。 

< Grid xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< Grid.Resources >
< Style TargetType ="{x:Type Button}" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.Foreground" Value ="Blue" />
</ Style >
</ Grid.Resources >

< StackPanel >
< StackPanel.Resources >
< Style TargetType ="{x:Type Button}" >
< Setter Property ="Control.Foreground" Value ="Red" />
</ Style >
</ StackPanel.Resources >
< Button >
Button Number 1
</ Button >
< Button >
Button Number 2
</ Button >
< Button >
Button Number 3
</ Button >
</ StackPanel >
</ Grid >

 说明： 

这些按钮会使用在StackPanel中定义的style，前景色为红色，字体为默认值。

使用相同名称的style不会覆盖某些property的同时还去保留另外一些。

 6. Style属性之二：Resource

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >

< Style x:Key ="normal" >

<Style.Resources>
<LinearGradientBrush x:Key="gradbrush"
StartPoint="1,0" EndPoint="1,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="LightBlue" Offset="0" />
<GradientStop Color="Aquamarine" Offset="1" />
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
</ Style.Resources >

< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />
< Setter Property ="Control.Background"
Value ="{StaticResource gradbrush}" />
</ Style >
</ StackPanel.Resources >

< Button Style ="{StaticResource normal}" >
Button Number 1
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 2
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 3
</ Button >
</ StackPanel >

 以上代码，如果不使用Resource，就要将value打散：

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style x:Key ="normal" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />
< Setter Property ="Control.Background" >
<Setter.Value>
<LinearGradientBrush StartPoint="1,0" EndPoint="1,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="LightBlue" Offset="0" />
<GradientStop Color="Aquamarine" Offset="1" />
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
</Setter.Value>
</ Setter >
</ Style >
</ StackPanel.Resources >

< Button Style ="{StaticResource normal}" >
Button Number 1
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 2
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 3
</ Button >
</ StackPanel >

7. Style属性之三：TargetType

TargetType，指定此style被用到何种类型的element上。

被应用的element必须“类型完全符合”，例如，如果TargetType为Control，则此Sytle不会采用到Button或者label控件上。

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >

< Style TargetType ="{x:Type Button}" >
< Setter Property ="FontSize" Value ="24" />
< Setter Property ="Foreground" Value ="Blue" />
</ Style >

< Style TargetType ="{x:Type TextBlock}" >
< Setter Property ="Foreground" Value ="Red" />
</ Style >

</ StackPanel.Resources >

<Button>
Button with Text Content
</Button >

<TextBlock>
TextBlock Text
</TextBlock >

<Button>
<TextBlock>
Button with TextBlock Content
</TextBlock>
</Button >
</ StackPanel >

说明：

第一个element：<Button>采用第一个style。前景色为蓝色，字体为24

第二个element：<TextBlock>采用第二个style。前景色为红色，字体为默认值
第三个element：<Button>中的<TextBlock>，前景色会采用第二个style（红色），而字体为24。原因是Sytle比“property继承”优先级高，所以前景色用第二个style，但是由于该style中没有对字体设定，所以会继承视觉树上其父亲的此property。

 

注：

• 可以在指定TargertType的同时指定Key
• 只要指定了TargertType，特定Type的element就一定会使用特定的style（同一个TargetType的style，有的style有key，有的style没有key，那么没有指定key的element也会用没有指定key的style）
• 如果多个style被定义在同一个resource section，他们的key不可以重复

8. Style属性之四：BasedOn

    BasedOn有类似“继承”的作用，可以修改已有的Style：

• 通过指定已有的Style的key，或者TargetType来实现：

  < StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
  < StackPanel.Resources >
  
  < Style x:Key ="normal" >
  < Setter Property ="Control.FontSize" Value ="24" />
  < Setter Property ="Control.Foreground" Value ="Blue" />
  < Setter Property ="Control.HorizontalAlignment" Value ="Center" />
  < Setter Property ="Control.Margin" Value ="24" />
  < Setter Property ="Control.Padding" Value ="20, 10, 20, 10" />
  </ Style >
  
  < Style TargetType ="{x:Type Button}" >
  < Setter Property ="Control.FontSize" Value ="24" />
  < Setter Property ="Control.Foreground" Value ="Blue" />
  < Setter Property ="Control.HorizontalAlignment" Value ="Center" />
  < Setter Property ="Control.Margin" Value ="24" />
  </ Style >
  
  < Style x:Key="hotbtn"
  TargetType="{x:Type Button}"
  BasedOn ="{StaticResource {x:Type Button}}" >
  < Setter Property ="Control.Foreground" Value ="Red" />
  </ Style >
  
  < Style x:Key="newbtn"

  BasedOn ="{StaticResource normal}" >
  < Setter Property ="Control.Foreground" Value ="Red" />
  </ Style >
  
  </ StackPanel.Resources >
  
  < Button Style ="{StaticResource normal}" >
  Button Number 1
  </ Button >
  
  < Button Style ="{StaticResource hotbtn}" >
  Button Number 2
  </ Button >
  
  < Button Style ="{StaticResource newbtn}" >
  Button Number 3
  </ Button >
  </ StackPanel >

    注：如果已有的Style既有key又有TargetType，那么baseon的style也要都指定

• baseon的时候，TargetType也可以用继承

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >

< Style TargetType ="{x:Type Control}" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.Foreground" Value ="Blue" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />
</ Style >

< Style TargetType ="{x:Type Button}"
BasedOn ="{StaticResource {x:Type Control}}" >
< Setter Property ="Control.Foreground" Value ="Red" />
</ Style >

< Style TargetType ="{x:Type Label}"
BasedOn ="{StaticResource {x:Type Control}}" >
< Setter Property ="Control.Foreground" Value ="Green" />
</ Style >

< Style TargetType ="{x:Type TextBox}"
BasedOn ="{StaticResource {x:Type Control}}" >
</ Style >
</ StackPanel.Resources >

< Button >
Button Control
</ Button >

< Label >
Label Control
</ Label >

< TextBox >
TextBox Control
</ TextBox >
</ StackPanel >

9. 使用Style的内在约束

• 不能定义没有dependency property支持的值，例如不能指定一个stackpanel所具有的孩子个数（应该使用Template）
• setter不支持派生自Visual或ContentElement的Value（例如将一张图片设为使用该style的Button的Content）。因为在特定的style中引用到的任何对象，都只会被创建一次，成为该style的一部分，所以会被使用该style的element所共有。

10. 将数据绑定应用到Style

•  Setter 中的 Value属性可以是一个数据绑定

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style TargetType ="{x:Type Button}" >

< Setter Property ="FontSize"
Value ="{Binding ElementName=scroll, Path=Value}" />

< Setter Property ="HorizontalAlignment" Value ="Center" />
< Setter Property ="Margin" Value ="24" />
</ Style >
</ StackPanel.Resources >

< ScrollBar Name="scroll" Orientation ="Horizontal" Margin ="24"
Minimum ="11" Maximum ="100" Value ="24" />

< Button >
Button Number 1
</ Button >

< Button >
Button Number 2
</ Button >

< Button >
Button Number 3
</ Button >
</ StackPanel >

以上Button的Fontsize的Value被绑定到一个名为“scroll”的ScrollBar的Value Property上。

•  也可以搭配RelativeSource

    
   <
   Setter 
   Property
   ="X2"
    
 Value
   ="{Binding RelativeSource={RelativeSource self}, 
 Path=X1}"
    
   />
  

以上代码将x2属性的值绑定为和x1一样。

11. Style中的事件处理 ：EventSetter

 EventerSetter和Setter级别相同，用来为特定的routed事件设定事件处理函数

可以在多个element间共享一个事件处理函数

< Window.Resources >
< Style TargetType ="{x:Type Button}" >
< Setter Property ="FontSize" Value ="24" />
< Setter Property ="HorizontalAlignment" Value ="Center" />
< Setter Property ="Margin" Value ="24" />
<EventSetter Event="Click" Handler="ButtonOnClick" />
</ Style >
</ Window.Resources >

< StackPanel >
< Button >
Button Number 1
</ Button >

< Button >
Button Number 2
</ Button >

< Button >
Button Number 3
</ Button >
</ StackPanel >
</ Window >

12. Style的第五个属性：Triggers

1. Triggers设定element或控件如何响应“此element property 的改变”，或者“数据绑定的改变”，或者“事件的发生”
2. Setter和Trigger都涉及“要被设定的”property。Setter是在element第一次创建时进行property设定，Trigger只有当某些事情发生时，才会去设定property（也就是说某些事情触发使得此property改变）
3. Triggers属性的类型是TriggerCollection，这是TriggerBase对象的collection, 派生自TriggerBase类型的Trigger有五种：
   • System.Windows..::.TriggerBase  
            System.Windows..::.DataTrigger  
           System.Windows..::.EventTrigger     （主要用于图形动画）
           System.Windows..::.MultiDataTrigger   
           System.Windows..::.MultiTrigger  
           System.Windows..::.Trigger

一下依次介绍除EventTrigger之外的各种Trigger

• Trigger

Trigger是最常见的，用来指定control或element应该如何响应特定的propertyd的改变，这些property常常都涉及到用户的输入，例如IsMouseOver property

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style x:Key ="normal" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />

< Style.Triggers >
< Trigger Property="Control.IsMouseOver" Value="true">
<Setter Property="Control.FontStyle" Value="Italic" />
<Setter Property="Control.Foreground" Value="Blue" />
</Trigger >

< Trigger Property="Button.IsPressed" Value="true">
<Setter Property="Control.Foreground" Value="Red" />
</Trigger >
</Style.Triggers >
</ Style >
</ StackPanel.Resources >

< Button Style ="{StaticResource normal}" >
Button Number 1
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 2
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 3
</ Button >
</ StackPanel >

说明：

   1. 当property的值被改变回去时，被Trigger修改的Property也会恢复他们原始的状态

   2. 以上两个Trigger的次序对效果有所影响，如果两个Trigger对相同的property做设定，后一个会覆盖前一个。如果以上两个Trigger对调，文字不会变成红色，因为press的时候，IsMouseOver肯定是为True的。

• MultiTrigger

MultiTrigger只有在两个或者多个事件都成立时才会被触发

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style x:Key ="normal" >
< Setter Property ="Control.FontSize" Value ="24" />
< Setter Property ="Control.HorizontalAlignment" Value ="Center" />
< Setter Property ="Control.Margin" Value ="24" />

< Style.Triggers >
< Trigger Property ="Button.IsPressed" Value ="True" >
< Setter Property ="Control.Foreground" Value ="Red" />
</ Trigger >

< MultiTrigger >
<MultiTrigger.Conditions >
<Condition Property="Control.IsMouseOver" Value="True" />
<Condition Property="Button.IsPressed" Value="False" />
</MultiTrigger.Conditions >
<Setter Property="Control.FontStyle" Value="Italic" />
<Setter Property="Control.Foreground" Value="Blue" />
</ MultiTrigger >

</ Style.Triggers >
</ Style >
</ StackPanel.Resources >

< Button Style ="{StaticResource normal}" >
Button Number 1
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 2
</ Button >

< Button Style ="{StaticResource normal}" >
Button Number 3
</ Button >
</ StackPanel >

 鼠标移动到按钮上：文字蓝色

 点击按钮：文字红色

 鼠标移动到按钮上方且按钮没有被按下：文字斜体

• DateaTrigger

DataTrigger与Trigger类似，只是用Binding取代了Property，Binding通常引用到另一个element。

< StackPanel xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
< StackPanel.Resources >
< Style TargetType ="{x:Type Button}" >
< Setter Property ="FontSize" Value ="24" />
< Setter Property ="HorizontalAlignment" Value ="Center" />
< Setter Property ="Margin" Value ="24" />

< Style.Triggers >
< DataTrigger Binding ="{Binding ElementName=txtbox,
Path=Text.Length}"
Value ="0" >
< Setter Property="IsEnabled" Value="False" />
</DataTrigger >
</ Style.Triggers >
</ Style >
</ StackPanel.Resources >

< TextBox Name ="txtbox" HorizontalAlignment ="Center"
Width ="2in" Margin ="24" />

< Button >
Button Number 1
</ Button >

< Button >
Button Number 2
</ Button >

< Button >
Button Number 3
</ Button >

</ StackPanel >

以上设定，只有当TextBox中的字符数不为0，Button才会Enable

• MultiDataTrigger

只有在多个绑定条件都成立时，才会触发事件

< StackPanel.Resources >
< Style TargetType ="{x:Type CheckBox}" >
< Setter Property ="HorizontalAlignment" Value ="Center" />
< Setter Property ="Margin" Value ="12" />
</ Style >


< Style TargetType ="{x:Type Button}" >
< Setter Property ="FontSize" Value ="24" />
< Setter Property ="HorizontalAlignment" Value ="Center" />
< Setter Property ="Margin" Value ="12" />
< Setter Property ="IsEnabled" Value ="False" />

< Style.Triggers >
<MultiDataTrigger>
< MultiDataTrigger.Conditions >
<Condition Binding="{Binding ElementName=chkbox1,
Path=IsChecked}"
Value="True" />
<Condition Binding="{Binding ElementName=chkbox2,
Path=IsChecked}"
Value="True" />
</ MultiDataTrigger.Conditions >
< Setter Property="IsEnabled" Value="True" />
</MultiDataTrigger >
</ Style.Triggers >
</ Style >
</ StackPanel.Resources >

< CheckBox Name ="chkbox1" >
Check 1
</ CheckBox >

< CheckBox Name ="chkbox2" >
Check 2
</ CheckBox >

< Button >
Button Number 1
</ Button >

< Button >
Button Number 2
</ Button >

< Button >
Button Number 3
</ Button >

</ StackPanel >

 以上设定，只有两个checkbox都被选中，才会时按钮enable