我无法从Swift iOS中的appdelegate访问TabbarController

Question

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

    self.window?.backgroundColor = UIColor.white
    self.window?.makeKeyAndVisible()

    let tabBarController = UITabBarController()
    let myVC1 = ViewController(nibName: "ViewController", bundle: nil)
    let myVC2 = ViewController1(nibName: "ViewController1", bundle: nil)
    let controllers = [myVC1,myVC2]
    tabBarController.viewControllers = controllers
    window?.rootViewController = tabBarController
    let firstImage = UIImage(named: "Search")
    let secondImage = UIImage(named: "Search1")
    myVC1.tabBarItem = UITabBarItem(
        title: "Pie",
        image: firstImage,
        tag: 1)
    myVC2.tabBarItem = UITabBarItem(
        title: "Pizza",
        image: secondImage,
        tag:2)
    // Override point for customization after application launch.
    return true

A black screen appears whenever I run the app.

Answer 1

I think you did not pervoid UIWindow size window = UIWindow(frame: UIScreen.main.bounds) window?.rootViewController = UITabBarController()

or you some problem with setting root view controller.

Answer 2

You need to add window = UIWindow at the beginning of app Delegate didFinishLaunchingWithOptions: or else there isn't a frame size set. Thats why your getting the black screen.

window = UIWindow(frame: UIScreen.main.bounds)

self.window?.backgroundColor = UIColor.white


let tabBarController = UITabBarController()
let myVC1 = UIViewController()
let myVC2 = UIViewController()
let controllers = [myVC1,myVC2]