ios - 没有 Storyboard 的应用程序启动-UIViewController仍然不可见

Question

阅读https://medium.com/ios-os-x-development/ios-start-an-app-without-storyboard-5f57e3251a25之后
我已经执行了以下步骤

从项目

中删除 Main.storyboard和 LaunchScreen.storyboard

从下的主界面中删除主部署信息

从Main.storyboard

中删除对 LaunchScreen.storyboard和 Info.plist的引用

这是上述步骤的一些屏幕截图


在 AppDelegate.swift中，我做了以下修改

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow(frame: UIScreen.main.bounds)
        let viewController = ViewController()
        viewController.view.backgroundColor = UIColor.red
        window!.rootViewController = viewController
        window!.makeKeyAndVisible()
        
        print("application executed")
        
        return true
    }
}

当我启动模拟器时，将在控制台上打印“已执行的应用程序”。
该应用启动后，我预计会看到全屏红色。但是，我只能看到整个黑屏。
我可以知道我错过了哪些其他步骤吗？

Answer 1

您具有场景生命周期，因此应在SceneDelegate中创建窗口。
这是AppDelegate:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        return true
    }

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }
}

现在是 SceneDelegate

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

        if let windowScene = scene as? UIWindowScene {
            let viewController = ViewController()
            viewController.view.backgroundColor = UIColor.red

            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = viewController
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}