Xcode 新建iOS13以下项目（OC、Swift）

1.新建项目

2.解决ios13以下运行闪退问题

1）删除SceneDelegate.swift

官方文档：
In iOS 13 and later, use UISceneDelegate objects to respond to life-cycle events in a scene- 
based app.

这个场景呢，如果不使用ipad的多窗口就不建议使用

2）删除 Main.storyboard，不使用storyboard布局，打开info.plist，删除Main storyboard file base name和Application Scene Manifest选项。

3）删除appdelegate 中关于scene的2个代理

4）appdelegate中添加根导航

//swift
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        let screen = UIScreen.main.bounds        //获得设备尺寸
        self.window = UIWindow.init(frame: screen) //给“输出窗口“实例化并设置frame
        let viewController = ViewController() //实例化一个ViewController
        let navigationController = UINavigationController(rootViewController: viewController)  //为ViewController设置一个导航栏
        self.window?.rootViewController = navigationController//将“输出窗口”的根视图设置为导航栏
        self.window?.makeKeyAndVisible()       //  设置"输出窗口可见"
        return true
    }
}




//OC 
@interface AppDelegate ()
    @property (strong, nonatomic) UIWindow *window;
@end
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc]init];
    self.window.frame = [UIScreen mainScreen].bounds;
    LogInViewController *loginVC = [[LogInViewController alloc]initWithNibName:@"LogInViewController" bundle:nil];
    self.window.rootViewController = loginVC;
    [self.window makeKeyAndVisible];
    return YES;
}

参考自：https://www.xugj520.cn/archives/xcode-swift.html