IOS AppDelegate

ios程序启动顺序

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("application:构造函数")
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
        print("applicationWillResignActive:程序即将取消激活状态")
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        print("applicationDidEnterBackground:程序进入后台")
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        print("applicationWillEnterForeground:程序即将进入前台")
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        print("applicationDidBecomeActive:程序被激活");
        view?.removeFromSuperview()
    }

    func applicationWillTerminate(_ application: UIApplication) {
        print("applicationWillTerminate:程序关闭");
    }

·启动程序时顺序：构造函数->程序被激活

程序启动.png

·进入切换程序界面（双击home键）执行：程序即将取消激活状态

切换界面.png

·从切换界面返回程序执行：程序被激活
·返回桌面（单击home键）执行顺序：程序即将取消激活状态->程序进入后台

返回桌面.png

·从桌面回到程序：程序即将进入前台->程序被激活
*例：如果想让app在进程切换界面不显示程序内容的话，可以在applicationWillResignActive的时候放一张图在覆盖window，然后在applicationDidBecomeActive的时候去掉

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("application:构造函数")
        view = UIView(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: UIScreen.main.bounds.size.height))
        view?.backgroundColor = UIColor.red
        return true
    }

func applicationWillResignActive(_ application: UIApplication) {
        print("applicationWillResignActive:程序即将取消激活状态")
        self.window?.addSubview(view!)
        self.window?.bringSubview(toFront: view!)
    }

func applicationDidBecomeActive(_ application: UIApplication) {
        print("applicationDidBecomeActive:程序被激活");
        view?.removeFromSuperview()
    }

切换.gif