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)
代码
<
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
代码
<
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。
代码
<
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
代码
<
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：
代码
<
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。
代码
<
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：
代码
< 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
代码
<
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
代码
<
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
代码
<
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
- 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”
- 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）
- 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
- System.Windows..::.TriggerBase
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
代码
<
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
代码
<
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。
代码
<
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
代码
<
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