在我的应用程序中，我从登录屏幕导航到一个类，比如classA，如下所示：

classA *objUserHome = [[classA alloc]init];
        [self presentModalViewController:objUserHome animated:YES];
        [objUserHome release];

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ClassA有一个导航栏和一个选项卡栏（其中有5个选项卡），我以编程方式创建了我的选项卡栏如下：

- (void)viewDidLoad
{
    [super viewDidLoad];
    //Create tab bar controller and navigation bar controller
    
    tabBarController = [[UITabBarController alloc] init];
    
    NSMutableArray *arrControllers = [[NSMutableArray alloc] initWithCapacity:5];
    
    //Add PunchClock to tab View Controller
    PunchClock* objPunchClock = [[PunchClock alloc] initWithTabBar];
    NavigationController = [[UINavigationController alloc] initWithRootViewController:objPunchClock];
    NavigationController.navigationBar.tintColor = [UIColor brownColor];
    [arrControllers addObject:NavigationController];
    [NavigationController release];
    [objPunchClock release];
    
    //Add Time_Sheet to tab View Controller
    Time_Sheet* objTime_Sheet = [[Time_Sheet alloc] initWithTabBar];
    NavigationController = [[UINavigationController alloc] initWithRootViewController:objTime_Sheet];
    NavigationController.navigationBar.tintColor = [UIColor brownColor];
    [arrControllers addObject:NavigationController];
    [NavigationController release];
    [objTime_Sheet release];
    
    //Add PTO to tab View Controller
    PTO* objPTO = [[PTO alloc] initWithTabBar];
    NavigationController = [[UINavigationController alloc] initWithRootViewController:objPTO];
    NavigationController.navigationBar.tintColor = [UIColor brownColor];
    [arrControllers addObject:NavigationController];
    [NavigationController release];
    [objPTO release];
    
    //Add PunchClock to tab View Controller
    CrewPunch* objCrewPunch = [[CrewPunch alloc] initWithTabBar];
    NavigationController = [[UINavigationController alloc] initWithRootViewController:objCrewPunch];
    NavigationController.navigationBar.tintColor = [UIColor brownColor];
    [arrControllers addObject:NavigationController];
    [NavigationController release];
    [objCrewPunch release];
    
    //Add PunchClock to tab View Controller
    Reports* objReports = [[Reports alloc] initWithTabBar];
    NavigationController = [[UINavigationController alloc] initWithRootViewController:objReports];
    NavigationController.navigationBar.tintColor = [UIColor brownColor];
    [arrControllers addObject:NavigationController];
    [NavigationController release];
    [objReports release];
    
    // Add this view controller array into the tab bar
    
    //self .viewControllers = arrControllers;
     tabBarController .viewControllers = arrControllers;
   
    [arrControllers release];
    [self.view addSubview:[tabBarController view]];
    
   
}

型
和ClassA is inherited from UIViewController
现在的问题是，在导航到classA之后，classA的视图向下移动了大约4mm，如下图所示。为什么会这样呢？我该如何解决此问题？

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