iOS Appdelegate与SceneDelegate下创建根视图

iOS13之前，Appdelegate的职责全权处理App生命周期和UI生命周期；
iOS13之后，Appdelegate的职责是：
1、处理 App 生命周期
2、新的 Scene Session 生命周期
一，SceneDelegate下的根视图
Appdelegate不在负责UI生命周期，所有UI生命周期交给SceneDelegate处理：
（1）SceneDelegate.h 文件下@property (strong, nonatomic) UIWindow * window;
（2）-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions进行初始化，转交给
SceneDelegate的willConnectToSession:方法进行根控制器设置

• (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 =[[UINavigationController alloc]initWithRootViewController:[ViewController new]];
  [self.window makeKeyAndVisible];
  }
  二。删除SceneDelegate
  1，直接删除SceneDelegate.h、SceneDelegate.m文件
  2，info.plist文件中删除Application Scene Manifest
  

3，删除SceneDelegate在AppDelegate中的代理

#pragma mark - UISceneSession lifecycle

• (UISceneConfiguration *)application:(UIApplication *)application configurationForConnectingSceneSession:(UISceneSession *)connectingSceneSession options:(UISceneConnectionOptions *)options {
  }

• (void)application:(UIApplication *)application didDiscardSceneSessions:(NSSet<UISceneSession *> *)sceneSessions {
  }
  4，在AppDelegate.h添加@property (strong, nonatomic) UIWindow * window;
  5，

• (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];self.window.backgroundColor = [UIColor whiteColor];
  ViewController *rootVC = [[ViewController alloc]init];
  UINavigationController *navigationC = [[UINavigationController alloc]initWithRootViewController:rootVC];
  navigationC.navigationBar.barStyle = UIBarStyleDefault;
  navigationC.navigationBar.tintColor = [UIColor blackColor];
  navigationC.navigationBar.barTintColor = [UIColor whiteColor];
  self.window.rootViewController = navigationC;
  [self.window makeKeyAndVisible];
  if (@available(iOS 13.0, *)) {
  self.window.overrideUserInterfaceStyle = UIUserInterfaceStyleLight;//强制关闭深色模式
  }
  return YES;
  }