UITabBarController加载之后不显示sub view controller

原代码：

    fileprivate func createSubiewControllers() {

        let newsVC = NewsViewController()

        let newsItem = UITabBarItem(title: "动态", image: UIImage(named: "TabNewsNormal"), selectedImage: UIImage(named: "TabNewsPressed"));

        newsVC.tabBarItem = newsItem

        let discoverVC = DiscoverViewController()

        let discoverItem = UITabBarItem(title: "发现", image: UIImage(named: "TabDiscoverNormal"), selectedImage: UIImage(named: "TabDiscoverPressed"));

        discoverVC.tabBarItem = discoverItem

        let nullVC = UIViewController()

        let nullItem = UITabBarItem()

        nullVC.tabBarItem = nullItem

        let messageVC = MessageViewController()

        let messageItem = UITabBarItem(title: "消息", image: UIImage(named: "TabMessageNormal"), selectedImage: UIImage(named: "TabMessagePressed"));

        messageVC.tabBarItem = messageItem

        let meVC = MeViewController()

        let meItem = UITabBarItem(title: "我", image: UIImage(named: "TabMeNormal"), selectedImage: UIImage(named: "TabMePressed"));

        meVC.tabBarItem = meItem

        self.viewControllers = [newsVC, discoverVC, nullVC, messageVC, meVC]

        let tabBarHeight = self.tabBar.frame.size.height

        let addButton = UIButton(type: .custom)

        if let addImage = UIImage(named: "TabAddButton") {

            addButton.frame = CGRect(x: , y: , width: addImage.size.width * (tabBarHeight - ) / addImage.size.height, height: tabBarHeight - )

            addButton.setImage(addImage, for: .normal)

        }

        addButton.layer.masksToBounds = true

        addButton.layer.cornerRadius =

        var center = self.tabBar.center

        center.y = self.tabBar.frame.size.height /

        addButton.center = center

        self.tabBar.addSubview(addButton)

    }

效果：

没有显示第一个“动态”viewController。

UITabBarController加载之后不显示sub view controller

原因：

self.viewControllers中要放UINavigationController所以将

self.viewControllers = [newsVC, discoverVC, nullVC, messageVC, meVC]

改为

        let navNewsVC = UINavigationController(rootViewController: newsVC)

        let navDiscoverVC = UINavigationController(rootViewController: discoverVC)

        let navMessageVC = UINavigationController(rootViewController: messageVC)

        let navMeVC = UINavigationController(rootViewController: meVC)

        self.viewControllers = [navNewsVC, navDiscoverVC, nullVC, navMessageVC, navMeVC]

即可正确显示。