Ios UINavigationBar在iPhone旋转后消失

我有一个应用程序可以在didFinishLaunchingWithOptions方法中设置UINavigationController，如下所示：

 main_iPhone *mainiPhone = [[main_iPhone alloc] initWithNibName:@"main_iPhone" bundle:nil];
mainiPhone.navigationItem.title = @"TitleHere";

UIBarButtonItem *botaoSobre = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:mainiPhone action:@selector(goToAboutView)];
mainiPhone.navigationItem.rightBarButtonItem = botaoSobre;

navController = [[UINavigationController alloc] initWithRootViewController:mainiPhone];
navController.navigationBar.tintColor = [UIColor orangeColor];
navController.navigationBar.translucent = NO;

[self.window addSubview:navController.view];
[self.window makeKeyAndVisible];
return YES;

- (void)willAnimateRotationToInterfaceOrientation:

运行应用程序时，导航栏仅在纵向模式下正确显示。但是，当我旋转设备以横向移动时，导航栏消失。当我旋转回到纵向时，导航栏也不会回来

PS:My mainiPhone.xib文件有两个视图，一个在纵向模式，一个在横向模式。我在主iPhone内切换视图。m如下所示：

 main_iPhone *mainiPhone = [[main_iPhone alloc] initWithNibName:@"main_iPhone" bundle:nil];
mainiPhone.navigationItem.title = @"TitleHere";

UIBarButtonItem *botaoSobre = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:mainiPhone action:@selector(goToAboutView)];
mainiPhone.navigationItem.rightBarButtonItem = botaoSobre;

navController = [[UINavigationController alloc] initWithRootViewController:mainiPhone];
navController.navigationBar.tintColor = [UIColor orangeColor];
navController.navigationBar.translucent = NO;

[self.window addSubview:navController.view];
[self.window makeKeyAndVisible];
return YES;

- (void)willAnimateRotationToInterfaceOrientation:

UIInterfaceOrientation界面定向持续时间： NSTimeInterval持续时间{

if (interfaceOrientation == UIInterfaceOrientationPortrait) {
    self.view = self.portrait; 
    self.view.transform = CGAffineTransformIdentity;
    self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(0)); 
    self.view.bounds = CGRectMake(0.0, 0.0, 320.0, 460.0);


} else if (interfaceOrientation == UIInterfaceOrientationLandscapeLeft) {
    self.view = self.landscape; 
    self.view.transform = CGAffineTransformIdentity; 
    self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(-90)); 
    self.view.bounds = CGRectMake(0.0, 0.0, 480.0, 300.0);


} else if (interfaceOrientation ==  UIInterfaceOrientationPortraitUpsideDown) { 
    self.view = self.portrait; 
    self.view.transform = CGAffineTransformIdentity; 
    self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(180)); 
    self.view.bounds = CGRectMake(0.0, 0.0, 320.0, 460.0);


} else if (interfaceOrientation == UIInterfaceOrientationLandscapeRight) { 

    self.view = self.landscape; 
    self.view.transform = CGAffineTransformIdentity; 
    self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(90)); 
    self.view.bounds = CGRectMake(0.0, 0.0, 480.0, 300.0);
}

}

另外，我的shouldAutorotateToInterfaceOrientation方法只返回YES

我做错了什么？

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提前非常感谢

如果我添加UINavigationController*navC=[self-navigationController]；作为WillAnimateRotationInterfaceOrientation方法的第一行，它返回nil。不知何故，当设备旋转时，我在didFinishLaunchingWithOptions方法中创建的导航控制器丢失了，但我不知道为什么。