在兴冲冲更新了Xcode11，并创建了项目之后，且发现真机和模拟器都黑屏了，怎么都不显示View了。 然后项目中比之前莫名其妙的多出来了两个文件: APPdelegate.m中也多了两段不明所以的代码：
#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. }经查询资料得知，IOS13之后，生命周期时间就开始由UISceneDelegate接管了，一时间真的是措手不及啊，不过适应之前可以先通过以下办法恢复到原来的项目结构：
删除info.plist中的Application Scene Manifest 删除项目中的Scenedelegate.h和Scenedelegate.m删除掉APPdelegate.m中的#pragma mark - UISceneSession lifecycle代码在APPdelegate.h中添加@property (strong, nonatomic) UIWindow * window;属性然后，老朋友就还是熟悉的项目，熟悉的味道了。
