frameworks/projects/spark/asdoc/en_US/spark/components/examples/CheckBoxExample.mxml

<?xml version="1.0"?>
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  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
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      http://www.apache.org/licenses/LICENSE-2.0

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  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
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-->
<!-- Simple example to demonstrate the Spark CheckBox control -->
<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">

    <fx:Script>
        <![CDATA[
           [Bindable]
           public var totalCost:Number = 4.50;

           // This event handler adds/removes the cost of condiments to/from the total cost.
           private function modifyBurger(evt:MouseEvent):void {
               // Add 0.25 to the total cost for every condiment. Delete 0.25 for
               // every condiment removed.
               if(CheckBox(evt.target).selected) {
                   totalCost += 0.25;
               } else {
                   totalCost -= 0.25;
               }
               // Format the totalCost and then display it in a label.
               totalString.text = usdFormatter.format(totalCost);
             }
        ]]>
    </fx:Script>

    <fx:Declarations>
        <mx:CurrencyFormatter id="usdFormatter" precision="2" currencySymbol="$"
                decimalSeparatorFrom="." decimalSeparatorTo="." useNegativeSign="true"
                useThousandsSeparator="true" alignSymbol="left"/>
    </fx:Declarations>

    <s:Panel title="Spark CheckBox Control Example"
            width="75%" height="75%"
            horizontalCenter="0" verticalCenter="0">
        <s:VGroup left="10" right="10" top="10" bottom="10">
            <s:Label text="Hamburger Base Price: $4.50" />
            <s:Label text="Select condiments for your hamburger (0.25 each):" />
            <s:CheckBox id="lettuceCB" label="Pickles" click="modifyBurger(event);"/>
            <s:CheckBox id="tomatoCB" label="Tomato" click="modifyBurger(event);"/>
            <s:CheckBox id="pickleCB" label="Lettuce" click="modifyBurger(event);"/>
            <s:CheckBox id="mayoCB" label="Mayonnaise" click="modifyBurger(event);"/>

            <mx:Spacer height="20" />
            <s:HGroup>
                <s:Label text="Total Price: " />
                <s:Label id="totalString" text="$4.50"/>
            </s:HGroup>
        </s:VGroup>
    </s:Panel>

</s:Application>