mxml内嵌代码：

应用加载完成注册一下：creationComplete="reg()" public function reg():void{                if(flash.external.ExternalInterface.available){                var jsStr:String;                 jsStr =                     'eval(\'window.onbeforeunload = onbeforeunloadHandler;' +                        'function onbeforeunloadHandler(){
   ' +                            'var swfRef = document.'+FlexGlobals.topLevelApplication.className+' || window.'+FlexGlobals.topLevelApplication.className+';'+                            'swfRef.windowCloseHandler();' +                            'return "退出系统提示";' +                        '}\')';                flash.external.ExternalInterface.call(jsStr);                flash.external.ExternalInterface.addCallback('windowCloseHandler',externalWindowCloseHandler);            }        }                        public function externalWindowCloseHandler():void{            //    Alert.show("aaaaa");            }