File Upload using AS3 SDK

Hello,

i can not upload file using Flex/Air SDK.
below is my code. not getting response with uploadCompleteHandler() function after uploading file.

private function upoadBtnClick(e:MouseEvent):void {
fr = new FileReference();
fr.addEventListener( Event.SELECT, selectHandler );
fr.addEventListener( DataEvent.UPLOAD_COMPLETE_DATA, uploadCompleteHandler );
fr.browse();
}
private function selectHandler(event:Event):void {
Backendless.FileService.upload(fr, ‘test’)
}
private function uploadCompleteHandler( event:DataEvent ):void {
trace( "File URL is " + event.data );
}

can you please help me? i need to do it asap.
Thanks Kinjal.