在appdelegate中设置初始viewcontroller-迅速

Question

我想从appdelegate设置初始viewcontroller。我找到了一个很好的答案，但是在目标C中，我无法迅速实现同一目标。通过情节提要以编程方式设置初始视图控制器- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions{    self.window = [[UIWindow alloc] initWithFrame:UIScreen.mainScreen.bounds];    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];    UIViewController *viewController = // determine the initial view controller here and instantiate   it with [storyboard instantiateViewControllerWithIdentifier:<storyboard id>];    self.window.rootViewController = viewController;    [self.window makeKeyAndVisible];    return YES;}有人能帮忙吗？我希望初始Viewcontroller依赖于使用条件语句满足的某些条件。

Answer 1

我使用此线程帮助我将目标C转换为swift，并且可以完美地工作。

在Swift中实例化并呈现一个viewController

Swift 2代码：

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

    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

    let storyboard = UIStoryboard(name: "Main", bundle: nil)

    let initialViewController = storyboard.instantiateViewControllerWithIdentifier("LoginSignupVC")

    self.window?.rootViewController = initialViewController

    self.window?.makeKeyAndVisible()

    return true

}

Swift 3代码：

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

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

    let storyboard = UIStoryboard(name: "Main", bundle: nil)

    let initialViewController = storyboard.instantiateViewController(withIdentifier: "LoginSignupVC")

    self.window?.rootViewController = initialViewController

    self.window?.makeKeyAndVisible()

    return true

}

Answer 2

尝试这个。例如：您应该UINavigationController用作初始视图控制器。然后，您可以将任何视图控制器设置为情节提要中的根。

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

    // Override point for customization after application launch.

    let storyboard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)

    let navigationController:UINavigationController = storyboard.instantiateInitialViewController() as UINavigationController

    let rootViewController:UIViewController = storyboard.instantiateViewControllerWithIdentifier("VC") as UIViewController

    navigationController.viewControllers = [rootViewController]

    self.window?.rootViewController = navigationController

    return true

}

看到我的故事板屏幕。

Answer 3

对于Swift 3，Swift 4：

从情节提要实例化根视图控制器：

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

        // this line is important

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

        // In project directory storyboard looks like Main.storyboard,

        // you should use only part before ".storyboard" as it's name,

        // so in this example name is "Main".

        let storyboard = UIStoryboard.init(name: "Main", bundle: nil)

        // controller identifier sets up in storyboard utilities

        // panel (on the right), it called Storyboard ID

        let viewController = storyboard.instantiateViewController(withIdentifier: "YourViewControllerIdentifier") as! YourViewController

        self.window?.rootViewController = viewController

        self.window?.makeKeyAndVisible()        

        return true

    }

如果要UINavigationController用作根用户：

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

        // this line is important

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

        let storyboard = UIStoryboard.init(name: "Main", bundle: nil)

        let viewController = storyboard.instantiateViewController(withIdentifier: "YourViewControllerIdentifier") as! YourViewController

        let navigationController = UINavigationController.init(rootViewController: viewController)

        self.window?.rootViewController = navigationController

        self.window?.makeKeyAndVisible()        

        return true

    }

从XIB实例化根视图控制器：

几乎一样，但是不是一行

let storyboard = UIStoryboard.init(name: "Main", bundle: nil)

let viewController = storyboard.instantiateViewController(withIdentifier: "YourViewControllerIdentifier") as! YourViewController

你必须写

let viewController = YourViewController(nibName: "YourViewController", bundle: nil)