iOS 8 Swift导航栏标题,按钮未显示在基于选项卡的应用程序中

Question

我正在尝试按照本教程,这个答案,以及在iOS 8/Swift中基于选项卡的应用程序中为每个选项卡创建导航栏的答案,但我的导航栏上没有显示标题或按钮.

这是我到目前为止:

// AppDelegate.swift
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {            
    let tabBarController = UITabBarController()

    let vc1 = ViewController()
    let vc2 = ViewController()
    let vc3 = ViewController()

    let nc1 = UINavigationController(rootViewController: vc1)
    let nc2 = UINavigationController(rootViewController: vc2)
    let nc3 = UINavigationController(rootViewController: vc3)

    let controllers = [nc1,nc2,nc3]

    tabBarController.viewControllers = controllers

    nc1.tabBarItem = UITabBarItem(title: "item1", image: nil, tag: 1)
    nc2.tabBarItem = UITabBarItem(title: "item2", image: nil, tag: 1)
    nc3.tabBarItem = UITabBarItem(title: "item3", image: nil, tag: 1)

    window = UIWindow(frame: UIScreen.mainScreen().bounds)
    window?.rootViewController = tabBarController
    window?.makeKeyAndVisible()

    return true
}

// ViewController.swift
class ViewController: UIViewController, UINavigationBarDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let navigationBar = UINavigationBar(frame: CGRectMake(0, 0, self.view.frame.size.width, 44))
        navigationBar.backgroundColor = UIColor.blueColor()
        navigationBar.delegate = self;

        let navigationItem = UINavigationItem()
        navigationItem.title = "Title"

        let leftButton =  UIBarButtonItem(title: "Left Button", style:   UIBarButtonItemStyle.Plain, target: self, action: nil)
        let rightButton = UIBarButtonItem(title: "Right Button", style: UIBarButtonItemStyle.Plain, target: self, action: nil)

        navigationItem.leftBarButtonItem = leftButton
        navigationItem.rightBarButtonItem = rightButton

        navigationBar.items = [navigationItem]

    }

    func positionForBar(bar: UIBarPositioning) -> UIBarPosition {
        return UIBarPosition.TopAttached
    }
}

但我只是在模拟器的顶部有一个空白的导航栏.

Answer 1

UINavigationBar当你已经提供了一个自定义时,你正在制作一个自定义UINavigationController.

请尝试在您的ViewController:

override func viewDidLoad() {
    super.viewDidLoad()

    self.title = "Title"

    let navigationBar = navigationController!.navigationBar
    navigationBar.tintColor = UIColor.blueColor()

    let leftButton =  UIBarButtonItem(title: "Left Button", style: UIBarButtonItemStyle.Plain, target: self, action: nil)
    let rightButton = UIBarButtonItem(title: "Right Button", style: UIBarButtonItemStyle.Plain, target: self, action: nil)

    navigationItem.leftBarButtonItem = leftButton
    navigationItem.rightBarButtonItem = rightButton
}