func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        
        
        let tab = MyTabbarController()
        let rootVC = UINavigationController(rootViewController: tab)
        self.window?.rootViewController = rootVC
        
        return true
    }

import Foundation
import UIKit
class MyTabbarController: UITabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        let firstVC = FirstViewController()
        firstVC.title = "第一"
        
        let secondVC = SecondViewController()
        secondVC.title = "第二"
        
        self.viewControllers = [firstVC,secondVC]
        
        //默认选中的是游戏主界面视图
        self.selectedIndex = 0
        
        
    }
}

import Foundation
import UIKit
class FirstViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        self.view.backgroundColor = UIColor.blue
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

import Foundation
import UIKit
class SecondViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        self.view.backgroundColor = UIColor.gray
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}