当我在appdelegate swift中设置Tabbar时，如何设置viewcontroller的rootview？

Question

我在AppDelegate中设置了UITabBarController，并将根视图设置为tab bar对象。 但我需要将根视图设置为另一个视图控制器而不会丢失标签栏的功能。 我怎样才能做到这一点？

  let vc1 = ConstituencyViewController()
    //vc1.view.backgroundColor = UIColor.orange
    vc1.tabBarItem.title = "Search"
    vc1.tabBarItem.image = UIImage(named: "Search")

    // Set up the second View Controller
    let vc2 = ConstDetailViewController()
    //vc2.view.backgroundColor = UIColor.purple
    vc2.tabBarItem.title = "User"
    vc2.tabBarItem.image = UIImage(named: "Street View")

    // Set up the Tab Bar Controller to have two tabs
    let tabBarController = UITabBarController()

    tabBarController.viewControllers = [vc1, vc2]

    // Make the Tab Bar Controller the root view controller
    window?.rootViewController = tabBarController
    window?.makeKeyAndVisible()

Answer 1

 let appDelegate = UIApplication.shared.delegate as! AppDelegate

    let vc1 = ConstDetailViewController()
            //vc1.view.backgroundColor = UIColor.orange
            vc1.tabBarItem.title = "Search"
            vc1.tabBarItem.image = UIImage(named: "Search")

    let vc2 = OptionsViewController()

    vc2.tabBarItem.title = "Search"
    vc2.tabBarItem.image = UIImage(named: "Street View")

            // Set up the second View Controller

            //vc2.view.backgroundColor = UIColor.purple

            // Set up the Tab Bar Controller to have two tabs
            let tabBarController = UITabBarController()

            tabBarController.viewControllers = [vc1,vc2]
    appDelegate.window?.rootViewController = tabBarController
    appDelegate.window?.makeKeyAndVisible()