当我按下视图控制器时，UITabbar消失

Question

这是我的应用代表：

    // Initialize your five tab controllers.  with each tab has its own navigation controller
    HomePageView *homePageView = [[HomePageView alloc]init];
    UINavigationController *nav1 = [[UINavigationController alloc]initWithRootViewController:homePageView];
    [nav1.navigationBar setTitleTextAttributes:@{NSForegroundColorAttributeName : [UIColor whiteColor]}];

    // Set nav Bar to be completely transparent
    [nav1.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    nav1.navigationBar.shadowImage = [UIImage new];
    nav1.navigationBar.translucent = YES;

    //Set Title
    nav1.tabBarItem.title = @"Home";

    ProfileViewController *profileViewController=[[ProfileViewController alloc]init];
    UINavigationController *nav2 = [[UINavigationController alloc]initWithRootViewController:profileViewController];

    // Set Title
    nav2.tabBarItem.title = @"Profile";

    // Set nav Bar to be completely transparent
    [nav2.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    nav2.navigationBar.shadowImage = [UIImage new];
    nav2.navigationBar.translucent = YES;

    FeedViewController *feedViewController=[[FeedViewController alloc]init];
    UINavigationController *nav3 = [[UINavigationController alloc]initWithRootViewController:feedViewController];

    // Set nav Bar to be completely transparent
    [nav3.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    nav3.navigationBar.shadowImage = [UIImage new];
    nav3.navigationBar.translucent = YES;

    // Set Title
    nav3.tabBarItem.title = @"Feeds";

    ListeningSessionViewController *listeningSessionViewController= [[ListeningSessionViewController alloc]init];
    UINavigationController *nav4 = [[UINavigationController alloc]initWithRootViewController:listeningSessionViewController];

    // Set nav Bar to be completely transparent
    [nav4.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    nav4.navigationBar.shadowImage = [UIImage new];
    nav4.navigationBar.translucent = YES;

    // set Title
    nav4.tabBarItem.title = @"Mussion";

    RecievedViewController *recievedViewController =[[RecievedViewController alloc]init];
    UINavigationController *nav5 = [[UINavigationController alloc]initWithRootViewController:recievedViewController];

    // Set nav Bar to be completely transparent
    [nav5.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    nav5.navigationBar.shadowImage = [UIImage new];
    nav5.navigationBar.translucent = YES;

    // Set Title
    nav5.tabBarItem.title = @"Recieved";

    // Set selected tab bar background
    UIImage *whiteBackground = [UIImage imageNamed:@"whiteBackground"];
    [[UITabBar appearance] setSelectionIndicatorImage:whiteBackground];

    self.tabC.tabBar.translucent = YES;

    // initialize tabbarcontroller,set your viewcontrollers and change its color.
    self.tabC = [[UITabBarController alloc]init];
    NSArray* controllers = [NSArray arrayWithObjects: nav1,nav2,nav3,nav4,nav5, nil];
    [self.tabC setViewControllers: controllers animated:NO];

    //[_window addSubview:self.tabC.view];
    [self.window setRootViewController:self.tabC];

    // Show window
    [self.window makeKeyAndVisible];

    return YES;
}

当我从其中一个标签栏控制器推送视图控制器时，例如HomePageView，标签栏消失：

SearchSongViewController *Search_MusicTableView = [[SearchSongViewController alloc] init];
    Search_MusicTableView.modalTransitionStyle=UIModalTransitionStyleCrossDissolve;
    [self.navigationController presentModalViewController:Search_MusicTableView animated:YES];

当我呈现模态视图或甚至推动另一个视图控制器时，标签栏消失了，请问这是为什么？以及如何解决它，非常感谢！