与HTML相似，Flex允许在MXML标签中通过CSS样式来设置组件的外观。到flex4.5后已经基本上支持了HTML中的所有CSS的应用方式，这里主要来列举下flex4.5中CSS选择器的使用方法。 CSS选择器可以包括，标签选择器、类别选择器、ID选择器、交集选择器、并集选择器、后代选择器、全局选择器、伪类等，这些样式应用都已经在flex得到支持。
1、标签选择器： 标签选择器是根据MXML文件中组件的类型来设置的，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
s|TextInput{
color: #FF0000;
}
s|Button{
color: #FFFF00;
}
</fx:Style>
<s:VGroup>
<s:TextInput text="text input"/>
<s:Button label="button"/>
</s:VGroup>
</s:Application>
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2、类别选择器： 类别选择器是以一个点开头，后面加上组件中通过styleName设置的样式名来表示的类别选择器，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
.btn2{
color: #FF0000;
}
</fx:Style>
<s:VGroup>
<s:Button label="button1"/>
<s:Button label="button2" styleName="btn2"/>
</s:VGroup>
</s:Application>
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3、ID选择器： ID选择器是以#开头，后面加上组件中设置的ID名来表示的类别选择器，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
#btn1{
color: #FF0000;
}
.btn2{
color: #FF00FF;
}
</fx:Style>
<s:VGroup>
<s:Button id="btn1" label="button1"/>
<s:Button label="button2" styleName="btn2"/>
</s:VGroup>
</s:Application>
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4、交集选择器： 交集选择器由两个选择器直接连接构成，其结果是选中二者各自元素范围的交集，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
s|Button#btn1{
color: #FF0000;
}
s|Button.btn2{
color: #FF00FF;
}
</fx:Style>
<s:VGroup>
<s:Button id="btn1" label="button1"/>
<s:Button label="button2" styleName="btn2"/>
<s:Button label="button3"/>
</s:VGroup>
</s:Application>
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5、并集选择器： 并集选择器是多个选择器通过逗号连接而成的，并集选择器同时选中各个基本选择器所选择的范围，任何形式的选择器都可以，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
s|Button#btn1,s|Button.btn2{
color: #FF0000;
}
</fx:Style>
<s:VGroup>
<s:Button id="btn1" label="button1"/>
<s:Button label="button2" styleName="btn2"/>
<s:Button label="button3"/>
</s:VGroup>
</s:Application>
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6、后代选择器： 后代选择器也叫派生选择器，可以使用后代选择器给一个元素里的子元素定义样式，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
s|HGroup s|TextInput{
color: #FF0000;
}
</fx:Style>
<s:VGroup>
<s:HGroup verticalAlign="middle">
<s:Label text="Text Input 1"/>
<s:TextInput text="sample"/>
</s:HGroup>
<s:TextInput text="sample"/>
</s:VGroup>
</s:Application>
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7、全局选择器： 全局选择器global可以将样式应用到所有的组件，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
global{
color: #FF0000;
}
</fx:Style>
<s:VGroup>
<s:Label text="label"/>
<s:TextInput text="text input"/>
<s:Button label="button"/>
</s:VGroup>
</s:Application>
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8：伪类： 伪类是用来设置组件在不同状态下的样式，示例如下：
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<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
s|Button:up{
color: #FF0000;
}
s|Button:down{
color: #FF00FF;
}
s|Button:over{
color: #0000FF;
}
</fx:Style>
<s:VGroup>
<s:Button label="button"/>
</s:VGroup>
</s:Application>
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