SwiftUI 应用在支持 iOS 13 时不运行

Question

应用程序在部署目标为 15.2 时运行良好，但后来我需要将部署目标更改为 iOS 13 以支持更多设备。在 iOS 14+ 上仍然可以正常工作，但是当它在模拟器上运行在 iOS 13 上时会崩溃并出现异常 Thread 1: signal SIGABRT。控制台没有显示调试信息：

CoreSimulator 802.6 - Device: iPhone 11 (iOS 13.0) (6CCC2B89-002B-4E83-8175-C244984BFC46) - Runtime: iOS 13.0 (17A577) - DeviceType: iPhone 11
Message from debugger: Terminated due to signal 9

以下是 WeatherApp.swift 文件代码的相关部分以及错误的屏幕截图：

@main
struct WeatherAppWrapper {
    static func main() {
        if #available(iOS 14.0, *) {
            WeatherApp.main()
        }
        else {
            UIApplicationMain(CommandLine.argc, CommandLine.unsafeArgv, nil, NSStringFromClass(SceneDelegate.self))
        }
    }
}

struct WeatherApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    @StateObject var loginStatus = UserLoginStatus()
    
    @available(iOS 14.0, *)
    var body: some Scene {
        WindowGroup {
            NavigationView{
                if Methods.UserAccount.getFromUserDefaults()["username"] != nil {
                    MainView(loggedIn: $loginStatus.loggedIn)
                    LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)
                } else {
                    LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)
                    MainView(loggedIn: $loginStatus.loggedIn)
                }
            }
        }
    }

    class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate, MessagingDelegate {
        func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

            //Some app-specific setup code
            ...
            
            return true
        }
        
    }
}

class UserLoginStatus: ObservableObject {
    @Published var loggedIn: Bool {
        didSet {
            print("The value of loggedIn changed from \(oldValue) to \(loggedIn)")
        }
    }
    
    init () {
        loggedIn = false
    }
}

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    @StateObject var loginStatus = UserLoginStatus()

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let mainView = MainView(loggedIn: $loginStatus.loggedIn)
        let loginView = LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            
            if Methods.UserAccount.getFromUserDefaults()["username"] != nil {
                window.rootViewController = UIHostingController(rootView: mainView)
            } else {
                window.rootViewController = UIHostingController(rootView: loginView)
            }
            
            self.window = window
            window.makeKeyAndVisible()
        }
    }
    
}

另外，这里是Info.plist文件的截图，具体展开相关区域：

Answer 1

根据 Apple docs，StateObject 仅适用于 iOS 14+。

Answer 2

StateObject 可从 SwiftUI 2.0 (iOS 14) 获得，旨在在视图中工作，而不是在 class 中工作（如 SceneDelegate）

对于提供的场景，一个可能的解决方案是在顶层（在委托或主视图中）仅将 logicState 用作属性，但将其完全注入子视图（而不是仅仅绑定）并在内部进行观察。

所以它应该看起来像

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var loginStatus = UserLoginStatus() // << just hold here

// ...

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let mainView = MainView(loginStatus: loginStatus) // << here !!

和

struct MainView: View {
    @ObservedObject var loginStatus: UserLoginStatus   // << injected here

// ...
}

类似的可以在WeatherApp

中完成

SwiftUI 应用在支持 iOS 13 时不运行

SwiftUI app doesn't run when supporting iOS 13

xcode

ios

swift

swiftui

SwiftUI 应用在支持 iOS 13 时不 运行

SwiftUI app doesn't run when supporting iOS 13

xcode

ios

swift

swiftui

SwiftUI 应用在支持 iOS 13 时不运行