0912-从启动iOS的app的生命周期说起，Responding to the Launch of Your App必须清楚的前提知识点：

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我是靠谱客的博主奋斗红酒，最近开发中收集的这篇文章主要介绍0912-从启动iOS的app的生命周期说起，Responding to the Launch of Your App必须清楚的前提知识点：，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

必须清楚的前提知识点：

1、All apps have an associated process, represented by the UIApplication object. 进程对应

        ---每一个app在ios系统中都有一个进程对应，而在这个进程就是用UIApplication object来表征。

       --whose job is to respond to important events happening within that process。

       --主要工作是与app重要的事件进行响应

2、When the user first launches your app on a device, the system displays your launch storyboard until your app is ready to display its UI. 默认提供启动闪屏

- - 在启动你的app时，ios会主动提供一个launch storyboard来展示你公司的logo，图片这些，就是启动画面。为app的后台初始化运行争取时间，同时也是给一个用户错觉，以为自己启动得很快。

Add views to your launch storyboard, and use Auto Layout constraints to size and position those views so that they adapt to the underlying environment.

--所以你可以在launch storyboard 中添加你的视图

3、（重点）Put your app's launch-time initialization code in one or both of the following methods: 先行方法

application(_:willFinishLaunchingWithOptions:) //还未就绪，准备阶段
application(_:didFinishLaunchingWithOptions:) //已经就绪，随时可以运行

--UIKit calls these methods at the beginning of your app’s launch cycle. Use them to:

Initialize your app's data structures.

Verify that your app has the resources it needs to run.

--所以UIKit会先执行这两个方法（或其一），然后再初始化你的视图，你应该在这两个方法体能写你的初始化代码，资源，数据什么的

//其中的参数UIApplication.LaunchOptionsKey是Keys used to access values in the launch options dictionary passed to your app at initialization time. 字典类型中的一个元素，在初始化时间内，传递给你的app信息

使用示例：
class AppDelegate: UIResponder, UIApplicationDelegate,
CLLocationManagerDelegate {
let locationManager = CLLocationManager()
func application(_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions:
[UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// If launched because of new location data,
//
start the visits service right away.
if let keys = launchOptions?.keys {
if keys.contains(.location) {
locationManager.delegate = self
locationManager.startMonitoringVisits()
}
}
return true
}
// other methods…
}

遵守写代码约定，高效代码

1、Move Long-Running Tasks off the Main Thread。去重就轻

--不要把你的繁重任务写在主线程内，主线程应该尽快展示页面，给用户的良好体验。所以你应该：

Defer the initialization of features that are not needed immediately.

---延迟你属性那些东西的初始化，除非这些东西立马要用到，不然就给我延迟初始化

Move important, long-running tasks off your app’s main thread. For example, run them asynchronously on a global dispatch queue.

---又长又臭的执行任务不要加到主线程中，可以挂在异步的全局的分发队列中