React Native 分包实践

1. 实现思路

1. RN从本地中读取bundle文件进行显示
2. 将JS文件进行分包打包
3. Native实现页面跳转，每个包跳转都为一个新的Activity
4. 进行bundle文件基础包与功能包的拆分，使用Google的diff_match_patch算法生成差异文件
5. 网络下载差异文件进行合并
6. 展示新页面

2. 操作步骤

Android 
1. 修改MainApplication
2. 修改MainActivity
3. 创建LocalReactActivityDelegate
4. 打第一bundle
react-native bundle --platform android --dev false --entry-file index.js --bundle-output bundle/index.android.bundle --assets-dest bundle/assets/

5. 打第二个bundle
react-native bundle --platform android --dev false --entry-file src/indexNet.js --bundle-output bundle/index1.android.bundle --assets-dest bundle/assets/
其中indexNet.js是新页面的入口文件
6. 使用google-diff-match-patch进行差异比对

3. 本地加载实现

1). 修改MainApplication

public class MainApplication extends Application {
  
  private static MainApplication sInstance;
  
  /**
   * 获取当前对象
   */
  public static MainApplication getInstance() {
    return sInstance;
  }
  
  @Override
  public void onCreate() {
    super.onCreate();
    sInstance = this;
    SoLoader.init(this, /* native exopackage */ false);
  }
}

这里主要是将Application中实现的接口取消，转由MainActivity中提供.

2). 修改MainActivity

public class MainActivity extends ReactActivity {

    /**
     * Returns the name of the main component registered from JavaScript.
     * This is used to schedule rendering of the component.
     */
    @Override
    protected String getMainComponentName() {
        return "Unpacking";
    }
    
    @Override
    protected ReactActivityDelegate createReactActivityDelegate() {
        return new LocalReactActivityDelegate(this, getMainComponentName());
    }
}

这里实现ReactActivity中的createReactActivityDelegate方法，自定义代理设置

3). LocalReactActivityDelegate代理代码

/**
 * 本地ReactActivity代理
 */
class LocalReactActivityDelegate(activity: Activity, @Nullable mainComponentName: String) :
        ReactActivityDelegate(activity, mainComponentName) {
  
  private val mReactNativeHost: ReactNativeHost = object : ReactNativeHost(MainApplication.getInstance()) {
    /**
     * 返回ReactPackage对象
     */
    override fun getPackages(): MutableList<ReactPackage> = Arrays.asList(
            MainReactPackage(),
            CustomPackage()
    )
  
    /**
     * 是否为开发
     */
    override fun getUseDeveloperSupport(): Boolean = BuildConfig.DEBUG
  
    /**
     * 返回JSBundle文件路径
     */
    override fun getJSBundleFile(): String? = "${Environment.getExternalStorageDirectory()}/bundle/index.android.bundle"
  }
  
  /**
   * 返回ReactNativeHost对象
   */
  override fun getReactNativeHost(): ReactNativeHost = mReactNativeHost
}

4). Native实现页面跳转

I. 创建CustomPackage

/**
 * 自定义ReactPackage
 */
class CustomPackage : ReactPackage {
  /**
   * 创建本地模块
   */
  override fun createNativeModules(reactContext: ReactApplicationContext?): MutableList<NativeModule>
    = Arrays.asList(PageModule(reactContext))
  
  /**
   * 创建视图管理者
   */
  override fun createViewManagers(reactContext: ReactApplicationContext?): MutableList<ViewManager<View, ReactShadowNode<*>>>
    = Collections.emptyList()
  
}

5). 创建PageMoudle

/**
 * 页面管理模块
 */
@ReactModule(name = "PageModule")
class PageModule(reactContext: ReactApplicationContext?) : ReactContextBaseJavaModule(reactContext) {
  override fun getName(): String = "PageModule"
  
  /**
   * 开启网络上的模块页面
   */
  @ReactMethod
  fun startNetActivity() {
    val intent = Intent(currentActivity, NetActivity::class.java)
    currentActivity?.startActivity(intent)
  }
  
}

6). NetActivity页面

/**
 * 新页面
 */
class NetActivity : ReactActivity() {
  override fun getMainComponentName(): String? {
    return "NetActivity"
  }
  
  override fun createReactActivityDelegate(): ReactActivityDelegate =
          object: ReactActivityDelegate(this, mainComponentName) {
            override fun getReactNativeHost(): ReactNativeHost = object : ReactNativeHost(MainApplication.getInstance()) {
              override fun getPackages(): MutableList<ReactPackage> = Arrays.asList(MainReactPackage())
  
              override fun getUseDeveloperSupport(): Boolean = BuildConfig.DEBUG
  
              override fun getJSBundleFile(): String? = "${Environment.getExternalStorageDirectory()}/bundle/index1.android.bundle"
            }
          }
}

7). RN中使用

修改App.js文件

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View, NativeModules, TouchableOpacity} from 'react-native';

const PageModule = NativeModules.PageModule;

const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' + 'Cmd+D or shake for dev menu',
  android:
    'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});

type Props = {};
export default class App extends Component<Props> {
    startPage() {
        PageModule.startNetActivity()
    }
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>Welcome to React Native!</Text>
        <Text style={styles.instructions}>To get started, edit App.js</Text>
        <Text style={styles.instructions}>{instructions}</Text>
                <TouchableOpacity
                    onPress={() => this.startPage()}
                >
                    <Text style={styles.instructions}>开启新页面</Text>
                </TouchableOpacity>
      </View>
    );
  }
}

const 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,
  },
});

8). 执行打包

react-native bundle --platform android --dev false --entry-file index.js --bundle-output bundle/index.android.bundle --assets-dest bundle/assets/

--platform: 平台
--dev: 是否为开发模式
--entry-file: 入口文件
--bundle-output: bundle输出路径，这里注意bundle文件夹必须存在
--assets-dest: 资源文件存放路径

9). 测试

I. 生成之后将bundle文件夹拷贝至sdcard下
II. 如果想要在调试时可用，务必修改android/app/build.gradle文件,将bundleInDebug设置为false, 设置为false之后即不将bundle文件打包进app

project.ext.react = [
        entryFile    : "index.js",
        bundleInDebug: false
]

III. 运行
注：此时无法开启新的页面，因为新页面的js文件不存在

4. 开启新页面

1). RN中创建入口文件indexNet.js

/** @format */

import {AppRegistry} from 'react-native';
import NetJs from './NetJs';
import {name as appName} from './NetActivity';

AppRegistry.registerComponent(appName, () => NetJs);

2). RN中创建NetActivity.json文件

{
  "name": "NetActivity",
  "displayName": "NetActivity"
}

注：此处的name和displayName应当与NetActivity.kt中的getMainComponentName方法返回的一致。

3). NetJs.js文件内容

import React, {PureComponent} from 'react';
import {
    StyleSheet, Text,
    View
} from 'react-native';

/**
 * @FileName: NetJs
 * @Author: mazaiting
 * @Date: 2018/10/9
 * @Description:
 */
class NetJs extends PureComponent {
    render() {
        return (
            <View style={styles.container}>
                <Text>Welcome mazaiting!</Text>
            </View>
        )
    }
}

/**
 * 样式属性
 */
const styles = StyleSheet.create({
    container: {
        backgroundColor: '#DDD'
    }
});

/**
 * 导出当前Module
 */
module.exports = NetJs;

4). 打包

react-native bundle --platform android --dev false --entry-file src/indexNet.js --bundle-output bundle/index1.android.bundle --assets-dest bundle/assets/

5). 拷贝文件

将bundle文件夹直接拷贝到sdcard目录下，此时再重新运行APP, 即可成功显示页面。

6). 带来的问题

初始包太大，每个包都讲RN基础内容打包，此时应该比较差异，进行差异化分解。

5. 差异化

1). diff-match-patch主页

2). 测试页面

3). 依赖

  implementation 'google-diff-match-patch:google-diff-match-patch:0.1'

4). 代码使用

const val FILE1 = "index.android"
const val FILE2 = "index1.android"
const val FILE3 = "$FILE2-$FILE1.patch"

const val FILE_DIR = "E:\\android\\React-Native-Study\\Unpacking\\bundle\\"
const val SUFFIX = ".bundle"

object Patch {
  @JvmStatic
  fun main(args: Array<String>) {
    val file1 = "$FILE_DIR$FILE1$SUFFIX"
    val file2 = "$FILE_DIR$FILE2$SUFFIX"
    val file3 = "$FILE_DIR$FILE3"
    val patch = productPatch(file1, file2)
    
    productFile(file1, file3, patch)
  }
  
  /**
   * 生成文件
   * @param fileOri 源文件
   * @param fileDest 目标文件
   * @param patchString 差异字符串
   */
  private fun productFile(fileOri: String, fileDest: String, patchString: String?) {
    // 创建对象
    val patch = diff_match_patch()
    // 读取文件
    val file1 = readFile(fileOri)
    // 获取补丁内容
    val patchText = patch.patch_fromText(patchString)
    // 应用补丁
    val patchApply = patch.patch_apply(LinkedList(patchText), file1)
    
    println("===============================================")
    println("结果：" + patchApply[0])
    // 写入文件内容
    writeResult(fileDest, patchApply[0].toString())
    println("===============================================")
    // 获取执行结果数组，true为成功，false为失败
    val patchResult: BooleanArray = patchApply[1] as BooleanArray
    val result = StringBuilder()
    patchResult.forEach { result.append("$it  ") }
    
    println("result: $result")
  }
  
  /**
   * 写入文件
   * @param fileDest 目标文件
   * @param string 文件内容
   */
  private fun writeResult(fileDest: String, string: String) {
    // Read a file from disk and return the text contents.
    val output = FileWriter(fileDest)
    val writer = BufferedWriter(output)
    try {
      writer.write(string)
    } finally {
      writer.close()
      output.close()
    }
  }
  
  /**
   * 生成差异patch
   * @param fileOri 源文件
   * @param fileDest 目标文件
   * @return 差异字符串
   */
  private fun productPatch(fileOri: String, fileDest: String): String? {
    // 创建对象
    val diff = diff_match_patch()
    // 读取基础文件内容
    val file1 = readFile(fileOri)
    // 读取目标文件内容
    val file2 = readFile(fileDest)
    // 进行差异化
    val diffString = diff.diff_main(file1, file2, true)
    // 数组长度大于2执行
    if (diffString.size > 2) {
      diff.diff_cleanupSemantic(diffString)
    }
    
    println(diffString)
    
    println("===============================================")
    // 生成patch内容
    val patchString = diff.patch_make(file1, diffString)
    println(patchString)
    
    println("===============================================")
    // 将patch内容转为字符串
    val patchText = diff.patch_toText(patchString)
    println(patchText)
    
    return patchText
  }
  
  /**
   * 读取文件
   * @param filename 文件名
   * @return 文件内容
   */
  @Throws(IOException::class)
  private fun readFile(filename: String): String {
    // Read a file from disk and return the text contents.
    val sb = StringBuilder()
    val input = FileReader(filename)
    val bufRead = BufferedReader(input)
    try {
      var line = bufRead.readLine()
      while (line != null) {
        sb.append(line).append('\n')
        line = bufRead.readLine()
      }
    } finally {
      bufRead.close()
      input.close()
    }
    return sb.toString()
  }
}