Flex与后台交互的4种方法 HTTPService、URLLoader、WebService详解

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="initializeHandler(event)">
<mx:Script>
<![CDATA[
private function initializeHandler(event:Event):void {
countriesService.send();
}
private function changeHandler(event:Event):void {
statesService.send();
}
]]>
</mx:Script>
<!-- 载入纯静态的xml数据 -->
<mx:HTTPService id="countriesService" url="http://www.rightactionscript.com/states/xml/countries.xml" />
<!-- 载入由php生成的xml数据 -->
<mx:HTTPService id="statesService" url="http://www.rightactionscript.com/states/xml/states.php">
<!-- 以下标签就是要发送到服务端的数据了,可以这样理解:有一个名为country的变量,它的值为花括号{}里的内容 -->
<mx:request>
<country>{country.value}</country>
</mx:request>
</mx:HTTPService>
<mx:VBox>
<!-- 此控件的数据由第一个<mx:HTTPService/>控件接收的内容提供,并且由这个ComboBox控制着第二个ComboBox所要显示的内容 -->
<mx:ComboBox id="country" dataProvider="{countriesService.lastResult.countries.country}"
change="changeHandler(event)" />
<!-- 下面的ComboBox已经绑定了{statesService.lastResult.states.state},随它的数据改变而改变 -->
<mx:ComboBox dataProvider="{statesService.lastResult.states.state}" />
</mx:VBox>
</mx:Application>

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="initializeHandler(event)">
<mx:Script>
<![CDATA[
private var _countriesService:URLLoader;
private var _statesService:URLLoader;
private function initializeHandler(event:Event):void {
_countriesService = new URLLoader();
_countriesService.addEventListener(Event.COMPLETE, countriesCompleteHandler);
_countriesService.load(new URLRequest("http://www.rightactionscript.com/states/xml/countries.xml"));
_statesService = new URLLoader();
_statesService.addEventListener(Event.COMPLETE, statesCompleteHandler);
XML.ignoreWhitespace = true;
}
private function countriesCompleteHandler(event:Event):void {
var xml:XML = new XML(_countriesService.data);
country.dataProvider = xml.children();
}
private function statesCompleteHandler(event:Event):void {
var xml:XML = new XML(_statesService.data);
state.dataProvider = xml.children();
}
private function changeHandler(event:Event):void {
var request:URLRequest = new URLRequest("http://www.rightactionscript.com/states/xml/states.php");
var parameters:URLVariables = new URLVariables();
parameters.country = country.value;
request.data = parameters;
_statesService.load(request);
}
]]>
</mx:Script>
<mx:VBox>
<mx:ComboBox id="country" change="changeHandler(event)" />
<mx:ComboBox id="state" />
</mx:VBox>
</mx:Application>

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="initializeHandler(event)">
<mx:Script>
<![CDATA[
private function initializeHandler(event:Event):void {
statesService.getCountries();
}
private function changeHandler(event:Event):void {
statesService.getStates(country.value);
}
]]>
</mx:Script>
<mx:WebService id="statesService"
wsdl="http://www.rightactionscript.com/states/webservice/StatesService.php?wsdl">
<mx:operation name="getCountries" />
<mx:operation name="getStates" />
</mx:WebService>
<mx:VBox>
<mx:ComboBox id="country"
dataProvider="{statesService.getCountries.lastResult}" change="changeHandler(event)" />
<mx:ComboBox dataProvider="{statesService.getStates.lastResult}" />
</mx:VBox>
</mx:Application>