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Android

一步一步开发天气 App

Kotlin​

学习新语言：

  1. 搭建环境，入口函数，打印字符串，Hello World!
  2. 变量、常量、枚举
  3. 表达式、控制流程
  4. 函数、高阶函数
  5. 集合及集合的操作
  6. 类、静态成员、继承、扩展(extension)
  7. 逐步调试

Hello World Playground

Kotlin 是由捷克的 JetBrains 软件公司开发的一种静态类型的、面向对象的编程语言。它与 Java 语言具有互操作性，而且该语言十分简洁，并得到 Android Studio 的支持。事实上，Kotlin 在您的设备中需要使用 JVM。

If lambdas are nothing more than nameless functions, then closures are little more than lambdas with a context.

Kotlin is a modern statically typed programming language.（静态类型语言 vs 动态类型语言）

Android KTX is a set of Kotlin extensions that are included with Android Jetpack and other Android libraries.

A language is statically-typed if the type of a variable is known at compile-time instead of at run-time: C, C++, C#, Java, Swift, Kotlin, ...

A language is dynamically-typed if the type of a variable is checked during run-time: JavaScript, Dart, Objective-C, PHP, Python, Ruby, ...

A strongly-typed language is one in which variables are bound to specific data types, and will result in type errors if types do not match up as expected in the expression — regardless of when type checking occurs.（与类型检查发生在编译期还是运行期无关） e.g Python, Java, etc.

A weakly-typed language is a language in which variables are not bound to a specific data type; they still have a type, but type safety constraints are lower compared to strongly-typed languages. e.g PHP, C, etc.

All Strongly-typed languages are Statically-typed, not all Weakly-typed languages are Dynamically-typed. 强类型语言的变量类型一定是在编译期就确定了。

Most of these rules affect variable assignment, return values and function calling.

Jetpack​

Jetpack is a suite of libraries, tools, and guidance. Jetpack comprises the androidx.* package libraries, unbundled from the platform APIs. This means that it offers backward compatibility and is updated more frequently than the Android platform.

AndroidX is a major improvement to the original Android Support Library, which is no longer maintained.

adb​

Android Debug Bridge 是一种客户端-服务器程序，包括以下三个组件：

  • 客户端：用于发送命令。客户端在开发计算机上运行。您可以通过发出 adb 命令来从命令行终端调用客户端。
  • 守护进程 (adbd)：在设备上运行命令。守护进程在每个设备上作为后台进程运行。
  • 服务器：管理客户端和守护进程之间的通信。服务器在开发机器上作为后台进程运行。

操作系统分布

Android API Levels

Android 9.0 Pie, Aug 6, 2018 (iOS 12, September 17, 2018)

安卓分支​

原生安卓——Google 为自家安卓设备 Pixel 系列提供的系统，由谷歌负责安全补丁升级和系统更新；

Android One——Google 为非 Google 硬件提供的原生安卓，由谷歌负责安全补丁升级和系统更新；

Android Go——取代 Android One 成为专为低端设备优化的安卓系统，由 OEM 厂商在接受 Google 推送后负责安全补丁升级和系统更新。

机型​

国内的原厂系统接近原生，而且口碑还可以的基本上就是一加了，但是一加 6 变成 AB 分区后，刷机什么的比较麻烦，之前的机型还可以。华为锁了 bootloader，不能自己解锁，OV 两家也是很少有 rom，基本上只有小米比较适合搞机。

Android Studio​