1,在AppDelegate.swift里面(下面这个函数里面写)

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

//定义三个视图

　　　var oneview = Oneview()

        var twoview = Twoview()

        var threeview = ThreeView()

//导航栏

        var threenav : UINavigationController = UINavigationController(rootViewController: threeview)

        var oneNav :UINavigationController = UINavigationController(rootViewController: oneview)

        var twoNav :UINavigationController = UINavigationController(rootViewController: twoview)

 //tabbar

        var oneItem :UITabBarItem = UITabBarItem(tabBarSystemItem: UITabBarSystemItem.Bookmarks, tag: 0)

        var twoItem :UITabBarItem = UITabBarItem(tabBarSystemItem: UITabBarSystemItem.Downloads, tag: 1)

        var treeItem :UITabBarItem = UITabBarItem(tabBarSystemItem: UITabBarSystemItem.Favorites, tag: 2)

        oneview.tabBarItem = oneItem

        twoview.tabBarItem = twoItem

        threeview.tabBarItem = treeItem

　　　　var tc = UITabBarController()

        tc.tabBar.barTintColor = UIColor.blackColor()

        tc.viewControllers = [oneNav,twoNav,threenav]

        self.window?.rootViewController = tc;

　　return true

}