Flutter混合开发和Android动态更新实践
感谢闲鱼的文章给的思路：
本篇是实践性文章包含两部分
将Flutter工程编译后的文件集成到Android项目
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
Flutter库
主要是flutter.jar，文件位于Flutter SDK目录下flutter/bin/cache/artifacts/engine
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
Flutter Plugin编译文件(暂时没用到，待补充)
集成步骤
在原生项目中新建一个module例如fluttermodule
将flutter.jar放入libs文件夹
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
}
}
将application指定为FlutterApplication或者自定义类集成FlutterApplication
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">
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);
}
}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
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
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。
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
