摘要:

介绍Xcode新建的SwiftUI模版项目结构、跟普通Storyboard模版项目的差异、SwiftUI项目的app启动流程、UIScene概念介绍、AppDelegate.swift和Info.plist的差异

1.项目模版

Interface: SwiftUI

Life Cycle: UIKit App Delegate

Language: Swift

Life Cycle选择UIKit App Delegate是为了项目模版有app生命周期，方便跟普通app生命周期做比较

 2.差异性

1）AppDelegate.swift

import UIKit

@main

class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        // Override point for customization after application launch.

        return true

    }

    // MARK: UISceneSession Lifecycle

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {

        // Called when a new scene session is being created.

        // Use this method to select a configuration to create the new scene with.

        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)

    }

    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {

        // 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.

    }

}

app原本的生命周期不见了？增加了UISceneSession的生命周期！

swiftUI增加了Scene场景的概念，app可以切换scene场景

scene场景：pc电脑或某些iPad可以在一个app软件里面打开多个window窗口，一个window窗口就是对应一个scene场景，如火狐浏览器可以同时打开多个窗口，一个窗口显示百度首页，一个窗口显示火狐首页，如下：