Xcode11之后新创建的工程会多出两个文件SceneDelegate。那么我们如何让它变回之前的那样的工程呢。

一、将这两个文件删除。
会报错There is no scene delegate set. A scene delegate class must be specified to use a main storyboard file.
二、将Info.plist -> Open As -> Source Code将划框的部分删除。

image.png

三、将AppDelegate.m中的UISceneSession lifecycle注释掉或者删掉。

pragma mark - UISceneSession lifecycle

- (UISceneConfiguration *)application:(UIApplication *)application configurationForConnectingSceneSession:(UISceneSession *)connectingSceneSession options:(UISceneConnectionOptions *)options {
    // Called when a new scene session is being created.
    // Use this method to select a configuration to create the new scene with.
    return [[UISceneConfiguration alloc] initWithName:@"Default Configuration" sessionRole:connectingSceneSession.role];
}

- (void)application:(UIApplication *)application didDiscardSceneSessions:(NSSet<UISceneSession *> *)sceneSessions {
    // Called when the user discards a scene session.
    // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
    // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
}

四、在didFinishLaunchingWithOptions中加入UIWindow。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.backgroundColor = [UIColor whiteColor];

    self.window.rootViewController = [[ViewController alloc] init];;
    
    [self.window makeKeyAndVisible];
    return YES;
}

在AppDelegate.h中加入@property (strong, nonatomic) UIWindow *window;
这样就又回到我们熟悉的代码了。

swift的AppDelegate中window

    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        
        self.window = UIWindow(frame: UIScreen.main.bounds)
        self.window?.backgroundColor = UIColor.white
        
        self.window?.rootViewController = ViewController()
        self.window?.makeKeyAndVisible()
        
        return true
    }

原文链接：https://blog.csdn.net/weixin_43864837/article/details/104232482