[TIMOB-2899] [Exit/Back Button] problem with exit app without back button !

Hi,
I read a lot of things with back button and exit button, but nothing answer me.
Is it possible to do an EXIT Button which exit app like pressing back button in a light window ?
I give you a code that works but only when you launch it a second time (don't know why) !
app.js

// this sets the background color of the master UIView (when there are no windows/tab groups on it)
Titanium.UI.setBackgroundColor('#000');
Ti.include('mainCloseView.js');
var FTimer = null;
function DoTimeout()
{
//  clearTimeout(FTimer);

DoCloseMainWin();

}
DoMainCloseView();
FTimer = setTimeout( DoTimeout, 5000);

mainCloseView.js

var MainCloseWin = null;
function DoMainCloseView()
{

MainCloseWin = Titanium.UI.createWindow({
title:'TabViewLogin',
exitOnClose:true,
navBarHidden: true
});
MainCloseWin.open();

}
function DoCloseMainWin(){

MainCloseWin.close();

}

With or without navBarHidden it's the same thing.
ty