iphone 如何获取整个屏幕的大小

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    MenuViewController *menuController = [[MenuViewController alloc] initWithNibName:@"MenuView" bundle:nil];
    self.menuViewController = menuController;
    [menuController release];

    menuViewController.view.frame = [UIScreen mainScreen].applicationFrame;
    [window addSubview:[menuViewController view]];
    [window makeKeyAndVisible];

    return YES;
}