Undefined Property

I am developing an android game.This is an actionscript for exit popup.

I keep getting this error 1120 : Access of undefined property Native Application

CODE :

import flash.events.MouseEvent;

MC1.visible = false;

//Movieclip name declared as MC1

btn_exit.addEventListener(MouseEvent.CLICK, onExit);//Exit Button on menu

function onExit(event:MouseEvent):void

{

          MC1.visible = true;

}

//Function on Button click

MC1.YesBtn.addEventListener(MouseEvent.CLICK, onYes);

function onYes(event:MouseEvent):void

{

NativeApplication.nativeApplication.exit();

}

MC1.NoBtn.addEventListener(MouseEvent.CLICK, onNo);

function onNo(event:MouseEvent):void

{

          MC1.visible = false;

}