public void start() {
        if (active != null){
            // execute possibly pending setCurrent 
            Displayable d = Display.getDisplay(active).getCurrent();
            if(d != null){
                Display.getDisplay(active).setCurrent(d);
            }
                
            try{
                active.startApp();
            }
            catch(Exception e){
                e.printStackTrace();
            }
        }
    }