iOS13中AppDelegate的職責發現了改變：

iOS13之前，Appdelegate的職責全權處理App生命周期和UI生命周期；
iOS13之后，Appdelegate的職責是：
1、處理 App 生命周期
2、新的 Scene Session 生命周期

Appdelegate不在負責UI生命周期，所有UI生命周期交給SceneDelegate處理：

因此初始化window方法需要改變：
現在不再Appdelegate的- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions進行初始化，轉交給SceneDelegate的willConnectToSession:方法進行根控制器設置

- (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions {
    UIWindowScene *windowScene = (UIWindowScene *)scene;
    self.window = [[UIWindow alloc] initWithWindowScene:windowScene];
    self.window.frame = windowScene.coordinateSpace.bounds;
    self.window.rootViewController = [UITabBarController new];
    [self.window makeKeyAndVisible];
}

想繼續全部使用AppDelegate也是可以的，刪除SceneDelegate

1，直接刪除SceneDelegate.h、SceneDelegate.m文件

2，info.plist文件中刪除Application Scene Manifest

8FD21B88-3FEC-47BA-9B84-AD396C7390D8.png

3，刪除SceneDelegate在AppDelegate中的代理

#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.
}

4，在AppDelegate.h添加@property (strong, nonatomic) UIWindow * window;

5，沒了。