以编程方式设置时无法显示我的 uitabbar

Question

因此，我一直在到处寻找有关如何以编程方式创建 uitabbar 的示例。我尽力从每个示例中获取我需要的内容，并将我希望的应用程序的外观组合在一起：一个带有 2 个选项卡的选项卡栏的欢迎屏幕。

我有一个用于欢迎屏幕的视图控制器，其中有一个 UIButton 可以继续：

-(IBAction)aMethod:(id)sender {

    MyTabProjectViewController *controller = [[MyTabProjectViewController alloc] initWithNibName:nil bundle:nil];
    controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self presentModalViewController:controller animated:YES];
    }

Then in my MyTabProjectViewController.m I do this:


    - (void)viewDidLoad
    {
        [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    //Setting up the view
    UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    contentView.backgroundColor = [UIColor whiteColor];
    self.view = contentView;    

    //Declaring all view controllers
    FirstView *first = [[FirstView alloc] init];
    SecondView *second = [[SecondView alloc] init];

    //Set titles for the view controllers
    first.title = @"First";
    second.title = @"Second";


    UITabBarController *tabBarController = [[UITabBarController alloc] init];
    tabBarController.view.frame = CGRectMake(0, 0, 320, 460);


    UINavigationController *nvc1 = [[UINavigationController alloc] initWithRootViewController:first];
    UINavigationController *nvc2 = [[UINavigationController alloc] initWithRootViewController:second];

    nvc1.navigationBar.barStyle = UIBarStyleBlack;
    nvc2.navigationBar.barStyle = UIBarStyleBlack;


    NSArray *controllers = [[NSArray alloc] initWithObjects:nvc1, nvc2, nil];

    self.tabBarController.viewControllers = controllers;

    [self.view addSubview:tabBarController.view];    
    }

由于某种原因，没有任何效果。当我单击按钮转到 MyTabProjectViewController 时，我看到一个空白页面。

Answer 1

尝试添加

tabBarController.selectedIndex = 0;

Answer 2

您实例化 UITabBarController 的新实例并将 ViewControllers 列表设置为另一个实例，只需将行： 替换

self.tabBarController.viewControllers = controllers;

为行：

tabBarController.viewControllers = controllers;