第一种简单的(就在AppDelegate里的)
let vc1 = ViewController()
let nav1 = UINavigationController(rootViewController: vc1)
nav1.tabBarItem = UITabBarItem(title: "", image: UIImage(named: ""), selectedImage: UIImage(named: ""))
let vc2 = erViewController()
let nav2 = UINavigationController(rootViewController: vc2)
nav2.tabBarItem = UITabBarItem(title: "", image: UIImage(named: ""), selectedImage: UIImage(named: ""))
let tbv = UITabBarController()
tbv.viewControllers = [nav1,nav2]
//tbv.selectedViewController = nav2
self.window?.rootViewController = tbv
第二种麻烦的
第一步
创建MainViewController（UITabBarController）、FirstViewController、SecondViewController、ThirdViewController、FourthViewController、AddViewController六个类，其中MainViewController继承于UITabBarController，AddViewController可以是ViewController也可以是个View。
AppDelegate里
self.window?.rootViewController = mainViewController()
mainViewController里
viewDidLoad()里：
self.addChildVC(childVC: firstViewController(), childTitle: "First", imageName: "xiaoXi", selectedImageName: "xiaoXi_H")
self.addChildVC(childVC: secondViewController(), childTitle: "Second", imageName: "", selectedImageName: "")
self.addChildVC(childVC: thirdViewController(), childTitle: "third", imageName: "", selectedImageName: "")
/// 添加子控制器
private func addChildVC(childVC: UIViewController, childTitle: String, imageName: String, selectedImageName:String)
{
let navigation = UINavigationController(rootViewController: childVC)
navigation.navigationBar.tintColor = UIColor.white //item 字体颜色
navigation.navigationBar.barTintColor = UIColor.yellow //背景颜色
childVC.title = childTitle
childVC.tabBarItem.tag = 1
childVC.tabBarItem.image = UIImage(named: imageName)?.withRenderingMode(.alwaysOriginal)
childVC.tabBarItem.selectedImage = UIImage(named: selectedImageName)?.withRenderingMode(.alwaysOriginal)
self.addChildViewController(navigation)
}
最后是这样：
