打开mainstoryboard，首先选择要启动的视图，然后打开Utilities—> Attributes。在“视图控制器”下面，你会看到“Is initial View Controller”单选按钮。选择它。

——对修改后的问题:

也许你可以试试这个:在你的初始视图的ViewDidLoad部分写一个方法，当这个方法在应用程序启动时运行，方法触发一个到另一个视图的segue。

(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions你可以通过编程方式设置(BOOL)应用程序中的关键窗口的rootViewController

例如:

- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    if (shouldShowAnotherViewControllerAsRoot) {
        UIStoryboard *storyboard = self.window.rootViewController.storyboard;
        UIViewController *rootViewController = [storyboard instantiateViewControllerWithIdentifier:@"rootNavigationController"];
        self.window.rootViewController = rootViewController;
        [self.window makeKeyAndVisible];
    }

    return YES;
}

Xcode 12.4 Swift 5

在SceneDelegate.Swift

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
    let window = UIWindow(windowScene: windowScene)
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    window.rootViewController = storyboard.instantiateViewController(withIdentifier: "UserViewController") as! UserViewController
    
    self.window = window
    window.makeKeyAndVisible()
}

你可以添加视图控制器场景将要显示的条件

Swift 4, Xcode 9

在AppDelegate.swift文件中

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let firstVC = storyboard.instantiateViewController(withIdentifier: "firstViewController") as! firstViewController
    self.window?.rootViewController = firstVC
}

找到了简单的解决方案-不需要从故事板和编辑项目信息选项卡中删除“初始视图控制器检查”，并使用makeKeyAndVisible，只是放置

self.window.rootViewController = rootVC;

in

- (BOOL) application:didFinishLaunchingWithOptions:

 func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        self.window = UIWindow(frame: UIScreen.main.bounds)
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        if (PreferenceHelper.getAccessToken() != "") {
            let initialViewController = storyboard.instantiateViewController(withIdentifier: "your View Controller Identifier")
            self.window?.rootViewController = initialViewController
        } else {
            let initialViewController = storyboard.instantiateViewController(withIdentifier: "your View Controller identifier")
            self.window?.rootViewController = initialViewController
        }
        self.window?.makeKeyAndVisible()
        return true
    }

/*
use your view Controller identifier must use it doubles quotes**strong text**