Flex 与 javascript交互,该如何解决

Flex 与 javascript交互

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"  creationComplete="initApp();"
   xmlns:s="library://ns.adobe.com/flex/spark" 
   xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Declarations>
<!-- 将非可视元素（例如服务、值对象）放在此处 -->
</fx:Declarations>
<fx:Script>
<![CDATA[
//Flex
import flash.external.ExternalInterface;

import mx.controls.Alert;

public function javaScriptFun(value:String):String{
return "调用Flex函数成功1" + value;
}

public function initApp():void{
ExternalInterface.addCallback("myFlexFun",javaScriptFun);
btn.addEventListener(MouseEvent.CLICK, callJs);
}

public function callJs(event:MouseEvent):void{
//应该如何召唤javascript函数？
var str:String =  ExternalInterface.call("sendToFlex","Flex");
if(str == null){
Alert.show("召唤失败");
}else{
Alert.show(str);
}
}
]]>
</fx:Script>
<s:Button x="204" y="173" label="召唤JavaScriptFun" id="btn" width="153"/>
</s:Application>

<script type="text/javascript">
            window.onload = function () {
                document.getElementById("swfHtml").innerHTML = getSWFHTML();
            }
            function callApp() {
                var x;
                if (navigator.appName.indexOf("Microsoft") != -1) {
                    x = document.getElementById("MyFlexApp").myFlexFun();
//x = document.getElementById("MyFlexApp").myFlexFun("test"); 这样传递参数出错，应该如何传参？
                }
                else {
                    x = document.getElementById("MyFlexApp").myFlexFun();
                }
                alert(x);
            }
            function getSWFHTML() {
                var swfNode = "";
                if (navigator.plugins && navigator.mimeTypes && navigator.mimeTypes.length) {
                    // Netscape浏览器插件体系结构
                    swfNode = '<embed type="application/x-shockwave-flash" src="flex/FlexProject2.swf" '; 
 
                    swfNode += 'id="MyFlexApp" name="MyFlexApp" ';
                    swfNode += 'allowScriptAccess="sameDomain" ';
                    swfNode += 'FlashVars ="param1=one&param2=2&param3=3&param4=four"';
                    swfNode += '/>';
                } else { // IE
                    swfNode = '<object id="MyFlexApp" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000">';
                    swfNode += '<param name="movie" value="flex/FlexProject2.swf" />';
                    swfNode += '<param name="FlashVars" value="param1=one&param2=2&param3=3&param4=four" />';
                    swfNode += '<param name="allowScriptAccess" value="sameDomain" />';
                    swfNode += "</object>";
                }
                return swfNode;
            }
            function sendToFlex(value) {
                return "返回给Flex值：" + value;
            }
        </script>

<input onclick="callApp();" value="调用Flex" type="button" />