Flutter混合开发和Android动态更新实践

感谢闲鱼和csdn的文章给的思路：

闲鱼flutter混合工程持续集成的最佳实践

深入理解 Flutter 的编译原理与优化

Flutter混合开发和动态更新的探索历程 Android版

本篇是实践性文章包含两部分

1. 将Flutter工程编译后的文件集成到Android项目
2. 将Flutter代码热更新

不涉及源码和理论，想要了解的话可以阅读上面的文章

将Flutter工程编译后的文件集成到Android项目

​ 因为Flutter无法完全替代原生绝大部分项目都是Flutter和Native混合开发的模式，所以存在一部分同学只做Native开发，并不熟悉Flutter技术。如果直接采用Flutter工程来开发，那这部分原生开发同学也需要配置Flutter环境，学习Flutter。

​ 由于上述原因，所以采用flutter项目和原生项目相互独立开发，将flutter项目编译后的文件以module的形式集成到Android项目中。

原理：Android项目依赖flutter的文件

1. Flutter库

   主要是flutter.jar，文件位于Flutter SDK目录下flutter/bin/cache/artifacts/engine

2. Flutter工程编译文件

   isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr、flutter_assets下所有文件

   位于Flutter工程build/app/intermediates/flutter/release/下

3. Flutter Plugin编译文件(暂时没用到，待补充)

集成步骤

1. 在原生项目中新建一个module例如fluttermodule

2. 将flutter.jar放入libs文件夹

3. 将isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr和flutter_assets下所有文件放入assets/flutter_assets/下

   为了方便可以在flutter项目中用gradle脚本实现，例如

   task copyAndroidFlutterModule << {
       println "project.rootDir = ${project.rootDir}/"
   
       println "buildDir = ${this.buildDir}/"
       def flutterOutputDir = "${this.buildDir}/flutter_android_output/flutter_module/"
       def flutterPluginFile = new File(flutterOutputDir)
       if (!flutterPluginFile.exists()) {
           flutterPluginFile.mkdirs()
       } else {
           flutterPluginFile.deleteDir()
       }
       def flutterReleaseBuildDir = "${this.buildDir}/app/intermediates/flutter/release/"
       println "flutterReleaseBuildDir=$flutterReleaseBuildDir"
       //复制snapshot_data和snapshot_instr
       project.copy {
           from flutterReleaseBuildDir
           include "*snapshot_data"
           include "*snapshot_instr"
           into flutterOutputDir
       }
       //复制flutter_assets
       project.copy {
           from "${flutterReleaseBuildDir}flutter_assets/"
           into flutterOutputDir
       }
   }
   

4. 将application指定为FlutterApplication或者自定义类集成FlutterApplication

   <application
           android:allowBackup="true"
           android:icon="@mipmap/ic_launcher"
           android:label="@string/app_name"
           android:name="io.flutter.app.FlutterApplication"
           android:roundIcon="@mipmap/ic_launcher_round"
           android:supportsRtl="true"
           android:theme="@style/AppTheme">
     </application>
   

5. 新建Activity继承FlutterActivity

   package com.gmail.jackxuechen.fluttermodel;
   
   import android.os.Bundle;
   import io.flutter.app.FlutterActivity;
   
   public class FlutterRootActivity extends FlutterActivity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       GeneratedPluginRegistrant.registerWith(this);
     }
   }
   

6. 集成成功

Android动态更新

原理：替换/data/data/包名/app_flutter/flutter_assets/

下的isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr即可实现flutter项目的更新

为了方便可以写个gradle脚本将flutter工程编译的isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr文件放到一个单独文件夹

task copyAndroidFlutterAssets << {
    println "project.rootDir = ${project.rootDir}/"
    println "buildDir = ${this.buildDir}/"
    def flutterOutputDir = "${this.buildDir}/flutter_android_output/flutter_assets/"
    def flutterPluginFile = new File(flutterOutputDir)
    if (!flutterPluginFile.exists()) {
        flutterPluginFile.mkdirs()
    } else {
        flutterPluginFile.deleteDir()
    }
    def flutterReleaseBuildDir = "${this.buildDir}/app/intermediates/flutter/release/"
    println "flutterReleaseBuildDir=$flutterReleaseBuildDir"
    //复制snapshot_data和snapshot_instr
    project.copy {
        from flutterReleaseBuildDir
        include "*snapshot_data"
        include "*snapshot_instr"
        into flutterOutputDir
    }
}

注意事项

1. vm_snapshot_data、vm_snapshot_instr和flutter sdk版本有关，生成更新文件时应保持和集成到原生项目中的flutter sdk版本一致

2. 因为isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr可能是在FlutterApplication中处理(需要看源码目前还没研究到)的。如果直接替换相关文件而没有冷启动，可能会导致崩溃，不过可以通过升级逻辑实现冷启更新，类型腾讯tinker。

3. 如果flutter项目中添加新的依赖原生的插件，则无法通过替换flutter编译后的文件升级，强制升级会崩溃