UINavigationBar不显示?

我正在开发一个应用程序 UINavigationController 在rooViewController中 xib UIView ,代码编写如下。

@implementation RootViewController
@synthesize introductionView, WheelView;

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.navigationController setNavigationBarHidden:YES];
}

#pragma mark 
#pragma mark strart up screen:

-(void)startIntroductionScreen{
    if(window == nil) {
        window = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
    }
    [window addSubview: introductionView];
    [window makeKeyAndVisible]; 
}

-(void)WheelScreen{
    [window addSubview:carnivalWheelView];
    [window makeKeyAndVisible]; 
    self.navigationController.navigationBar.hidden = NO;    
    [self.navigationItem setLeftBarButtonItem:[[UIBarButtonItem alloc] initWithTitle:@"Setting" style:UIBarButtonItemStylePlain target:nil action:nil] animated:YES];
}

#pragma mark 
#pragma mark IBAction:

-(IBAction)breakGlass:(id)sender{
    [self startIntroductionScreen];
}

-(IBAction)anotherView:(id)sender{
    [self WheelScreen];
}

在上面的代码中,当 -(void)WheelScreen IBAction 调用的另一个视图 UINaviagtionBar 未显示。

提前谢谢你。