React Native For Android初体验

@author ASCE1885的 Github 简书 微博 CSDN
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React Native For Android提前发布了，代码托管在Github上面，本文是一个尝鲜体验，主要介绍环境配置的过程。

环境配置

目前React Native只支持在OS X系统上面进行开发，其他系统的筒靴们请掩泪飘过，同时，使用React Native开发的app只能运行在>= Android 4.1 (API 16) 和>= iOS 7.0的手机操作系统上面。

搭建React Native的开发环境涉及到几个工具，这里我们简单介绍一下：

Homebrew

Homebrew是一个方便开发者在MAC OS X系统上面安装Linux工具包的ruby脚本，而MAC OS X已经内置了ruby的解释环境，因此安装Homebrew只需执行以下脚本：

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

更多关于Homebrew的用法请参见官方文档。关于Homebrew的作者，还有一个趣闻：白板编程没写出反转二叉树，Homebrew 作者被谷歌拒掉了。

nvm

Node版本管理器，是一个简单的bash脚本，用来管理同一台电脑上的多个node.js版本，并可实现方便的版本间切换。我们可以使用Homebrew来安装nvm：

brew install nvm

然后打开.bashrc文件

vim $HOME/.bashrc

添加如下配置：

export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"  # This loads nvm

当然也可以选择官方的安装方法，就不用自己手动写.bashrc文件了：

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.26.1/install.sh | bash

或者

wget -qO- https://raw.githubusercontent.com/creationix/nvm/v0.26.1/install.sh | bash

这样配置之后，在Terminal输入nvm命令还是提示command not found，需要再次输入：

. ~/.nvm/nvm.sh

激活nvm，这一点比较奇怪，因为我们在.bashrc已经设置了才对。

Node.js

基于Chrome V8 JavaScript引擎实现的一个JavaScript运行时，可用于方便地搭建响应速度快、易于扩展的网络应用。Node.js 使用事件驱动， 非阻塞I/O 模型而得以轻量和高效，非常适合在分布式设备上运行的数据密集型的实时应用。通过nvm安装Node.js的命令如下：

nvm install node && nvm alias default node

不过可能由于网络或者服务不稳定，实际上使用这个命令安装可能会失败，就算成功也会花费较长的时间，因此建议到Node.js官网去直接下载pkg包：

watchman

Facebook 开源的一个文件监控服务，用来监视文件并且记录文件的改动情况，当文件变更它可以触发一些操作，例如执行一些命令等等。安装watchman，是为了规避node文件监控的一个bug，安装很简单，脚本如下：

brew install watchman

flow

Facebook 出品的一个用于 JavaScript 代码静态类型检查的工具，用于找出 JavaScript 代码中的类型错误。Flow 采用 OCaml 语言开发。安装脚本如下：

brew install flow

安装完成之后，可以执行如下命令更新 Homebrew 的信息，并升级所有可以升级的软件：

brew update && brew upgrade

Android开发环境要求

打开Android SDK Manager，确保如下工具和开发包已经安装：

SDK：

• Android SDK Build-tools version 23.0.1
• Android 6.0 (API 23)
• Android Support Repository

模拟器：

• Intel x86 Atom System Image (for Android 5.1.1 - API 22)
• Intel x86 Emulator Accelerator (HAXM installer)

React Native工程配置

安装react-native

npm install -g react-native-cli

在Terminal中运行以上脚本，成功后，就可以在Terminal中使用react-native这个命令了，这个脚本只需执行一次。

生成工程

react-native init AwesomeProject

在Terminal中执行以上脚本，它会下载React Native工程源码和依赖，并在AwesomeProject/iOS/AwesomeProject.xcodeproj目录中创建XCode工程，在AwesomeProject/android/app创建Android Studio工程。生成的示例工程目录如下所示：

至此，React Native配置完成。

Android Studio工程概览

使用Android Studio打开AwesomeProject/android/app，Gradle会去下载一系列依赖的函数包，这个过程视网速而定，可能会比较长时间。通过阅读源码我们可以发现，这些依赖的函数包主要有：

compile 'com.android.support:appcompat-v7:23.0.1'
compile 'com.facebook.fresco:fresco:0.6.1'
compile 'com.facebook.fresco:imagepipeline-okhttp:0.6.1'
compile 'com.fasterxml.jackson.core:jackson-core:2.2.3'
compile 'com.google.code.findbugs:jsr305:3.0.0'
compile 'com.squareup.okhttp:okhttp:2.4.0'
compile 'com.squareup.okhttp:okhttp-ws:2.4.0'
compile 'com.squareup.okio:okio:1.5.0'
compile 'org.webkit:android-jsc:r174650'

不过如果我们反编译AwesomeProject生成的apk，或者在Android Studio中查看AwesomeProject的External Libraries，会发现事实上最终打进apk包的函数包不止上面这些，可以看到External Libraries的截图如下：

最终生成的debug版本apk大小为7.2M，体积还是比较大的。

当然，打开app/build.gradle文件，可以看到该module只依赖react-native的一个jar包，其他依赖的函数包对于开发者来说是透明的：

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId "com.awesomeproject"
        minSdkVersion 16
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        ndk {
            abiFilters "armeabi-v7a", "x86"
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:23.0.0'
    compile 'com.facebook.react:react-native:0.11.+'
}

打开示例工程唯一的类MainActivity，可以发现已经针对React Native做了一层封装调用，默认帮我们维护了React Native的生命周期。

package com.awesomeproject;

import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;

import com.facebook.react.LifecycleState;
import com.facebook.react.ReactInstanceManager;
import com.facebook.react.ReactRootView;
import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
import com.facebook.react.shell.MainReactPackage;
import com.facebook.soloader.SoLoader;

public class MainActivity extends Activity implements DefaultHardwareBackBtnHandler {

    private ReactInstanceManager mReactInstanceManager;
    private ReactRootView mReactRootView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mReactRootView = new ReactRootView(this);

        mReactInstanceManager = ReactInstanceManager.builder()
                .setApplication(getApplication())
                .setBundleAssetName("index.android.bundle")
                .setJSMainModuleName("index.android")
                .addPackage(new MainReactPackage())
                .setUseDeveloperSupport(BuildConfig.DEBUG)
                .setInitialLifecycleState(LifecycleState.RESUMED)
                .build();

        mReactRootView.startReactApplication(mReactInstanceManager, "AwesomeProject", null);

        setContentView(mReactRootView);
    }

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_MENU && mReactInstanceManager != null) {
            mReactInstanceManager.showDevOptionsDialog();
            return true;
        }
        return super.onKeyUp(keyCode, event);
    }

    @Override
    public void invokeDefaultOnBackPressed() {
      super.onBackPressed();
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (mReactInstanceManager != null) {
            mReactInstanceManager.onPause();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        if (mReactInstanceManager != null) {
            mReactInstanceManager.onResume(this);
        }
    }
}

工程目录下的index.android.js是基于React写的js主模块代码：

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 */
'use strict';

var React = require('react-native');
var {
  AppRegistry,
  StyleSheet,
  Text,
  View,
} = React;

var AwesomeProject = React.createClass({
  render: function() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          Welcome to React Native!
        </Text>
        <Text style={styles.instructions}>
          To get started, edit index.android.js
        </Text>
        <Text style={styles.instructions}>
          Shake or press menu button for dev menu
        </Text>
      </View>
    );
  }
});

var styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);

而package.json是工程的依赖和元数据配置文件：

{
  "name": "AwesomeProject",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node_modules/react-native/packager/packager.sh"
  },
  "dependencies": {
    "react-native": "^0.11.0"
  }
}

最后说一句，想要学习React Native For Android，最好是具有Javascript和React的相关经验。

更新：很多人反馈说执行react-native init命令创建工程会卡死在这里，猜测可能是前面的环境配置出现问题导致，我使用该命令创建一个新的工程只需几分钟，执行后的日志记录如下，供参考：

Last login: Thu Sep 24 11:05:42 on ttys002
N/A: version "node" is not yet installed
guhaoxindeMacBook-Pro:~ guhaoxin$ cd ~/Desktop/
guhaoxindeMacBook-Pro:Desktop guhaoxin$ mkdir reactnative
guhaoxindeMacBook-Pro:Desktop guhaoxin$ cd reactnative/
guhaoxindeMacBook-Pro:reactnative guhaoxin$ react-native init asce1885
This will walk you through creating a new React Native project in /Users/guhaoxin/Desktop/reactnative/asce1885
 
> bufferutil@1.2.1 install /Users/guhaoxin/Desktop/reactnative/asce1885/node_modules/react-native/node_modules/ws/node_modules/bufferutil
> node-gyp rebuild

  CXX(target) Release/obj.target/bufferutil/src/bufferutil.o
  SOLINK_MODULE(target) Release/bufferutil.node
 
> utf-8-validate@1.2.1 install /Users/guhaoxin/Desktop/reactnative/asce1885/node_modules/react-native/node_modules/ws/node_modules/utf-8-validate
> node-gyp rebuild

  CXX(target) Release/obj.target/validation/src/validation.o
  SOLINK_MODULE(target) Release/validation.node
 
> spawn-sync@1.0.13 postinstall /Users/guhaoxin/Desktop/reactnative/asce1885/node_modules/react-native/node_modules/yeoman-generator/node_modules/cross-spawn/node_modules/spawn-sync
> node postinstall

 
> fsevents@1.0.0 install /Users/guhaoxin/Desktop/reactnative/asce1885/node_modules/react-native/node_modules/babel/node_modules/chokidar/node_modules/fsevents
> node-pre-gyp install --fallback-to-build

  SOLINK_MODULE(target) Release/.node
  CXX(target) Release/obj.target/fse/fsevents.o
  SOLINK_MODULE(target) Release/fse.node
  COPY /Users/guhaoxin/Desktop/reactnative/asce1885/node_modules/react-native/node_modules/babel/node_modules/chokidar/node_modules/fsevents/lib/binding/Release/node-v46-darwin-x64/fse.node
  TOUCH Release/obj.target/action_after_build.stamp
react-native@0.11.0 node_modules/react-native
├── absolute-path@0.0.0
├── progress@1.1.8
├── graceful-fs@4.1.2
├── stacktrace-parser@0.1.3
├── react-timer-mixin@0.13.3
├── wordwrap@1.0.0
├── underscore@1.7.0
├── image-size@0.3.5
├── semver@4.3.6
├── yargs@1.3.2
├── debug@2.1.0 (ms@0.6.2)
├── immutable@3.7.5
├── bser@1.0.0 (node-int64@0.4.0)
├── optimist@0.6.1 (wordwrap@0.0.3, minimist@0.0.10)
├── source-map@0.1.31 (amdefine@1.0.0)
├── promise@7.0.4 (asap@2.0.3)
├── chalk@1.0.0 (escape-string-regexp@1.0.3, ansi-styles@2.1.0, supports-color@1.3.1, strip-ansi@2.0.1, has-ansi@1.0.3)
├── worker-farm@1.3.1 (xtend@4.0.0, errno@0.1.4)
├── rebound@0.0.12
├── sane@1.2.0 (watch@0.10.0, minimist@1.2.0, exec-sh@0.2.0, minimatch@0.2.14, walker@1.0.7, fb-watchman@1.6.0)
├── connect@2.8.3 (methods@0.0.1, uid2@0.0.2, fresh@0.1.0, cookie-signature@1.0.1, pause@0.0.1, bytes@0.2.0, buffer-crc32@0.2.1, qs@0.6.5, cookie@0.1.0, send@0.1.2, formidable@1.0.14)
├── uglify-js@2.4.16 (uglify-to-browserify@1.0.2, async@0.2.10, optimist@0.3.7, source-map@0.1.34)
├── ws@0.8.0 (options@0.0.6, ultron@1.0.2, bufferutil@1.2.1, utf-8-validate@1.2.1)
├── regenerator@0.8.36 (private@0.1.6, through@2.3.8, commoner@0.10.3, recast@0.10.25, esprima-fb@15001.1.0-dev-harmony-fb, defs@1.1.0)
├── jstransform@11.0.1 (object-assign@2.1.1, base62@1.1.0, source-map@0.4.4, esprima-fb@15001.1.0-dev-harmony-fb, commoner@0.10.3)
├── module-deps@3.5.6 (inherits@2.0.1, shallow-copy@0.0.1, duplexer2@0.0.2, minimist@0.2.0, concat-stream@1.4.10, parents@1.0.1, subarg@0.0.1, readable-stream@1.1.13, through2@0.4.2, resolve@0.7.4, stream-combiner2@1.0.2, browser-resolve@1.9.1, JSONStream@0.7.4, detective@3.1.0)
├── joi@5.1.0 (topo@1.0.3, isemail@1.2.0, hoek@2.16.3, moment@2.10.6)
├── yeoman-environment@1.2.7 (escape-string-regexp@1.0.3, log-symbols@1.0.2, diff@1.4.0, text-table@0.2.0, untildify@2.1.0, mem-fs@1.1.0, globby@2.1.0, grouped-queue@0.3.0, lodash@3.10.1, inquirer@0.8.5)
├── yeoman-generator@0.20.3 (read-chunk@1.0.1, detect-conflict@1.0.0, yeoman-welcome@1.0.1, path-is-absolute@1.0.0, path-exists@1.0.0, yeoman-assert@2.1.0, rimraf@2.4.3, async@1.4.2, text-table@0.2.0, xdg-basedir@2.0.0, user-home@2.0.0, mime@1.3.4, dargs@4.0.1, run-async@0.1.0, nopt@3.0.4, mkdirp@0.5.1, shelljs@0.5.3, istextorbinary@1.0.2, through2@2.0.0, diff@2.1.2, glob@5.0.14, underscore.string@3.2.2, findup-sync@0.2.1, pretty-bytes@2.0.1, cli-table@0.3.1, dateformat@1.0.11, mem-fs-editor@2.0.4, github-username@2.0.0, cross-spawn@2.0.0, class-extend@0.1.1, download@4.2.0, html-wiring@1.2.0, gruntfile-editor@1.0.0, lodash@3.10.1, sinon@1.17.0, inquirer@0.8.5)
├── react-tools@0.14.0-beta1 (commoner@0.10.3)
├── babel-core@5.8.21 (slash@1.0.0, try-resolve@1.0.1, babel-plugin-remove-debugger@1.0.1, babel-plugin-remove-console@1.0.1, babel-plugin-property-literals@1.0.1, babel-plugin-eval@1.0.1, babel-plugin-jscript@1.0.4, babel-plugin-inline-environment-variables@1.0.1, babel-plugin-undefined-to-void@1.1.6, babel-plugin-member-expression-literals@1.0.1, shebang-regex@1.0.0, to-fast-properties@1.0.1, trim-right@1.0.1, babel-plugin-react-constant-elements@1.0.3, babel-plugin-react-display-name@1.0.3, path-exists@1.0.0, path-is-absolute@1.0.0, fs-readdir-recursive@0.1.2, babel-plugin-constant-folding@1.0.1, babel-plugin-proto-to-assign@1.0.4, babel-plugin-dead-code-elimination@1.0.2, babel-plugin-runtime@1.0.7, private@0.1.6, globals@6.4.1, esutils@2.0.2, convert-source-map@1.1.1, js-tokens@1.0.1, babylon@5.8.23, resolve@1.1.6, bluebird@2.10.1, json5@0.4.0, babel-plugin-undeclared-variables-check@1.0.2, source-map@0.4.4, output-file-sync@1.1.1, source-map-support@0.2.10, home-or-tmp@1.0.0, debug@2.2.0, is-integer@1.0.6, repeating@1.1.3, line-numbers@0.2.0, lodash@3.10.1, detect-indent@3.0.1, minimatch@2.0.10, core-js@1.1.4, regexpu@1.3.0, regenerator@0.8.35)
└── babel@5.8.21 (slash@1.0.0, path-is-absolute@1.0.0, path-exists@1.0.0, fs-readdir-recursive@0.1.2, convert-source-map@1.1.1, commander@2.8.1, source-map@0.4.4, output-file-sync@1.1.1, glob@5.0.14, lodash@3.10.1, chokidar@1.1.0)
Setting up new React Native app in /Users/guhaoxin/Desktop/reactnative/asce1885
   create .flowconfig
   create .gitignore
   create .watchmanconfig
   create index.ios.js
   create index.android.js
   create ios/main.jsbundle
   create ios/asce1885/AppDelegate.h
   create ios/asce1885/AppDelegate.m
   create ios/asce1885/Base.lproj/LaunchScreen.xib
   create ios/asce1885/Images.xcassets/AppIcon.appiconset/Contents.json
   create ios/asce1885/Info.plist
   create ios/asce1885/main.m
   create ios/asce1885Tests/asce1885Tests.m
   create ios/asce1885Tests/Info.plist
   create ios/asce1885.xcodeproj/project.pbxproj
   create ios/asce1885.xcodeproj/xcshareddata/xcschemes/asce1885.xcscheme
   create android/app/build.gradle
   create android/app/proguard-rules.pro
   create android/app/src/main/AndroidManifest.xml
   create android/app/src/main/res/values/strings.xml
   create android/app/src/main/res/values/styles.xml
   create android/build.gradle
   create android/gradle.properties
   create android/settings.gradle
   create android/app/src/main/res/mipmap-hdpi/ic_launcher.png
   create android/app/src/main/res/mipmap-mdpi/ic_launcher.png
   create android/app/src/main/res/mipmap-xhdpi/ic_launcher.png
   create android/app/src/main/res/mipmap-xxhdpi/ic_launcher.png
   create android/gradle/wrapper/gradle-wrapper.jar
   create android/gradle/wrapper/gradle-wrapper.properties
   create android/gradlew
   create android/gradlew.bat
   create android/app/src/main/java/com/asce1885/MainActivity.java
**To run your app on iOS:**
   Open /Users/guhaoxin/Desktop/reactnative/asce1885/ios/asce1885.xcodeproj in Xcode
   Hit Run button
**To run your app on Android:**
   Have an Android emulator running, or a device connected
   cd /Users/guhaoxin/Desktop/reactnative/asce1885
   react-native run-android
guhaoxindeMacBook-Pro:reactnative guhaoxin$ cd asce1885/
guhaoxindeMacBook-Pro:asce1885 guhaoxin$ ls
android   index.android.js index.ios.js  ios   node_modules  package.json
guhaoxindeMacBook-Pro:asce1885 guhaoxin$ 

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