flex状态之间的切换

<?xml version="1.0" encoding="utf-8"?>
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<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"
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?????????????????????????? minWidth="955" minHeight="600" xmlns:local="*" xmlns:myPacket="myPacket.*">
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??????? <s:states>
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??????????????? <s:State name="nomalA"/>
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??????????????? <s:State name ="nomalB"/>
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??????????????? <s:State name="nomalC"/>
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??????????????? <s:State name="nomalD"/>
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??????? </s:states>
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???????
??????? <s:transitions>
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??????????????? <s:Transition toState="nomalA">
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??????????????????????????????? <s:Sequence??????? target="{group1}">
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??????????????????????????????? <s:Fade alphaFrom="0" alphaTo="1" duration="4000"/>
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??????????????????????????????? </s:Sequence>
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??????????????? </s:Transition>
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??????????????? <s:Transition toState="nomalB">
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??????????????????????????????? <s:Sequence??????? target="{group2}">
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??????????????????????????????????????? <s:Fade alphaFrom="0" alphaTo="1" duration="4000"/>
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??????????????????????????????? </s:Sequence>
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??????????????? </s:Transition>
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??????? </s:transitions>
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??????? <fx:Script>
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??????????????? <![CDATA[
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??????????????????????? private var ADD:String = "add";
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??????????????????????? private var NORMALA:String = "nomalA";
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??????????????????????? private var NORMALB:String = "nomalB";
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??????????????????????? private var NORMALC:String = "nomalC";
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??????????????????????? private var NORMALD:String = "nomalD";

??????????????????????? protected function button1_clickHandler(event:MouseEvent):void
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??????????????????????? {
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??????????????????????????????? if(currentState == NORMALA)currentState = NORMALB;
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??????????????????????????????? else if(currentState == NORMALB)currentState = NORMALC;
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??????????????????????????????? else if(currentState == NORMALC)currentState = NORMALD;
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??????????????????????????????? else if(currentState == NORMALD)currentState = NORMALA;
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??????????????????????????????? else return;
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??????????????????????? }

??????????????? ]]>
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??????? </fx:Script>
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??????? <fx:Declarations>
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??????? </fx:Declarations>
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???????
??????? <s:Group id="group1" includeIn="nomalA">
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??????????????? <s:Button id="nostudent1" x="114" y="80" label="nostudent 1"/>
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??????? </s:Group>
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??????? <s:Group id="group2" includeIn="nomalB">
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??????????????? <s:Button id="nostudent2" x="114" y="80" label="nostudent 2"/>
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??????? </s:Group>
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??????? <s:Group id="group3" includeIn="nomalC">
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??????????????? <s:Button id="nostudent3" x="114" y="80" label="nostudent 3"/>
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??????? </s:Group>
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??????? <s:Group id="group4" includeIn="nomalD">
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??????????????? <s:Button id="nostudent4" x="114" y="80" label="nostudent 4"/>
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??????? </s:Group>
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???????
??????? <s:Button x="309" y="312" label="click" click="button1_clickHandler(event)"/>
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</s:Application>