Flex中的CSS： （3）CSS会被编译器转换为什么样的AS代码--交集：

解说：

s|Button#btn??????????? 这种形式的CSS将作用在id为btn的按钮上。其他的按钮不受影响。

s|Button.MyStyle????? 这种形式的CSS将作用在指定类型选择器“MyStyle”的按钮上。其他的按钮不受影响。

这种形式的定义称为：交集

?

test1.mxml

<?xml version="1.0" encoding="utf-8"?>
<!-- styles/SelectorsTest.mxml -->
<s:Application 
	xmlns:fx="http://ns.adobe.com/mxml/2009" 
	xmlns:mx="library://ns.adobe.com/flex/mx" 
	xmlns:s="library://ns.adobe.com/flex/spark">    
	<s:layout>
		<s:VerticalLayout/>
	</s:layout>
	
	<fx:Style>
		@namespace s "library://ns.adobe.com/flex/spark";
		@namespace mx "library://ns.adobe.com/flex/mx";
		
		s|Button#btn{
			font-size:20px;
		}
		
	</fx:Style>
	
	<fx:Script>
		<![CDATA[

			public function showSelectors():void {            
				
				var selectors:Array = styleManager.selectors;
				msg.text = "所有的选择器列表如下(" + selectors.length + ")n";
				for (var i:int = 0; i < selectors.length; i++) {
					msg.text += "n" + selectors[i];      
				}
			}
		]]>
	</fx:Script>    
	<s:Group id="group1" width="511" height="396">
		<s:TextArea id="msg" x="1" y="28" width="100%" height="359"/>
		<s:Button id="btn" label="Show Selectors" click="showSelectors()"/>
	</s:Group>
	
	<s:Group id="group2" width="511">
		<s:Button label="test" click="showSelectors()"/>
	</s:Group>
</s:Application>

执行结果如下：

?

编译器生成的代码如何呢：

        var conditions:Array;
        var condition:CSSCondition;
        var selector:CSSSelector;
        selector = null;
        conditions = null;
        conditions = [];
        condition = new CSSCondition("id","btn");
        conditions.push(condition); 
        selector = new CSSSelector("spark.components.Button",conditions,selector);
        // spark.components.Button#btn
        style = styleManager.getStyleDeclaration("spark.components.Button#btn");
        if (!style)
        {
            style = new CSSStyleDeclaration(selector,styleManager);
        }

        if (style.factory == null)
        {
            style.factory = function():void
            {
                this.fontSize = 20;
            };
        }

?

?

如果把CSS定义改为：s|Button#btn -->? #btn，执行结果没有变化，但是自动生成的代码会有变化，看看是怎样的吧：

注意到变化了吗？

        var conditions:Array;
        var condition:CSSCondition;
        var selector:CSSSelector;
        selector = null;
        conditions = null;
        conditions = [];
        condition = new CSSCondition("id","btn");
        conditions.push(condition); 
        selector = new CSSSelector("",selector);
        // #btn
        style = styleManager.getStyleDeclaration("#btn");
        if (!style)
        {
            style = new CSSStyleDeclaration(selector,styleManager);
        }

        if (style.factory == null)
        {
            style.factory = function():void
            {
                this.fontSize = 20;
            };
        }