Documentation URL

https://developer.apple.com/documentation/uikit/core_app/managing_your_app_s_life_cycle?language=objc

APP生命周期状态

管理生命周期事件

https://developer.apple.com/documentation/uikit/core_app/managing_your_app_s_life_cycle?language=objc

Launch

初始化APP准备启动；

APP启动时序
执行一次APP配置

Activation

APP显示到前台

准备[ApplicationDelegate applicationDidBecomeActive:]

当APP处于active状态时，回调

[ApplicationDelegate applicationWillEnterForeground:]

如果APP已经处于background，怎会先调用该方法，之后再回调applicationDidBecomeActive:方法；

[ViewController viewWillAppear:]

更新视图内容

[ViewController viewDidAppear:]

在视图出现在屏幕上后回调；

Deactivation

APP处于background，被阻塞；

[ApplicationDelegate applicationWillResignActive:]

首先调用该方法 ；在该过程中会中断app操作和保存用户关键数据；

[ApplicationDelegate applicationDidEnterBackground:]

APP进入background回调该方法；

Background executionTermination