Flutter动态化（基于Android）

动态化方式

1. DSL语言动态化，服务端动态下发dom（暂不分析）

2. 动态替换打包后的产物

动态化效果

修改前

image.png

修改后：

image.png

flutter打包后结构

源码结构

image

打包后结构

.

├── AndroidManifest.xml

├── assets

│ └── flutter_assets

│ ├── AssetManifest.json

│ ├── assets

│ │ └── images

│ │ ├── test.jpeg

│ │ └── test_test.png

│ ├── FontManifest.json

│ ├── fonts

│ │ └── MaterialIcons-Regular.ttf

│ ├── NOTICES

│ └── packages

│ └── cupertino_icons

│ └── assets

│ └── CupertinoIcons.ttf

├── classes.dex

├── lib

│ ├── arm64-v8a

│ │ ├── libapp100.so

│ │ └── libflutter.so

│ ├── armeabi-v7a

│ │ ├── libapp.so

│ │ └── libflutter.so

│ └── x86_64

│ ├── libapp.so

│ └── libflutter.so

├── res

│ ├── drawable

│ │ ├── launch_background.xml

│ │ ├── notification_bg_low.xml

│ │ ├── notification_bg.xml

│ │ ├── notification_icon_background.xml

│ │ ├── notification_tile_bg.xml

│ │ └── toast_bg.xml

│ ├── mipmap-hdpi-v4

│ │ └── ic_launcher.png

│ ├── mipmap-mdpi-v4

│ │ └── ic_launcher.png

│ ├── mipmap-xhdpi-v4

│ │ └── ic_launcher.png

│ ├── mipmap-xxhdpi-v4

│ │ └── ic_launcher.png

│ └── mipmap-xxxhdpi-v4

│ └── ic_launcher.png

└── resources.arsc

flutter加载原理

image

1. FlutterActivity 壳中创建delegate 分发;

2. 在onCreate中创建引擎，引擎中初始化flutterLoader;注册插件，插件是通过反射方式注册

3. FlutterLoader 配置加载打包dart后的产物;

4. FlutterJNI 根据路径加载对应的so;

5. FlutterLoader 启动初始化方法;调用FlutterJNI 加载flutter release中的so（debug版本加载assets下的产物，分为JIT模式和release模式）

6. FlutterActivity oncreate方法中 配置window背景，

7. FlutterActivity oncreate方法中 创建flutterview，设置splashview，执行setContentView

动态化方案

1. 修改FlutterLoader 对象，使其指向自定义的FlutterLoader对象

如何修改：

在Application 中通过反射修改对象指针

public class BaseApplication  extends FlutterApplication {

    public static Application instance;

    @Override
    public void onCreate() {
        instance=this;
        try {
            //替换成自定义的Flutter加载类 干预Flutter的加载
            FlutterLoader flutterLoader = new CustomFlutterLoader();
            Field field = FlutterLoader.class.getDeclaredField("instance");
            field.setAccessible(true);//
            field.set(null, flutterLoader);
        } catch (Exception e) {
            e.printStackTrace();
        }
        super.onCreate();
    }

    @Override
    protected void attachBaseContext(Context base) {
        super.attachBaseContext(base);
        instance=this;
    }
}

2. CustomFlutterLoader修改

public void ensureInitializationComplete(@NonNull Context applicationContext, @Nullable String[] args) {
    ……
        List<String> shellArgs = new ArrayList<>();
        shellArgs.add("--icu-symbol-prefix=_binary_icudtl_dat");

        ApplicationInfo applicationInfo = getApplicationInfo(applicationContext);
        shellArgs.add("--icu-native-lib-path=" + applicationInfo.nativeLibraryDir + File.separator + DEFAULT_LIBRARY);

        if (args != null) {
            Collections.addAll(shellArgs, args);
        }
        loadNewFlutterSo(applicationContext);
        String kernelPath = null;
        …………
        String appStoragePath = PathUtils.getFilesDir(applicationContext);
        String engineCachesPath = PathUtils.getCacheDirectory(applicationContext);
        FlutterJNI.nativeInit(applicationContext, shellArgs.toArray(new String[0]),
                kernelPath, appStoragePath, engineCachesPath,System.currentTimeMillis());

        initialized = true;
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}

3. 加载so路径

private String[] loadNewFlutterSo(Context context) throws IOException {
    String[] result=null;
    final File dir = context.getDir("jniLibs", Context.MODE_PRIVATE);
    List<File> files = FileUtils.listFilesInDirWithFilter(dir, pathname -> pathname.getName().startsWith(FileUtils.TIMESTAMP_PREFIX), (o1, o2) -> {
        if (o1.isDirectory() && o2.isFile())
            return -1;
        if (o1.isFile() && o2.isDirectory())
            return 1;
        return o2.getName().compareTo(o1.getName());
    });
    if (!files.isEmpty()) {
        //获取最新的Flutter so
        File file = files.get(0);
        FlutterSoEntity entity = DynamicUpdateExtractor.readSoInfo(file);
        String flutterSoPath = FileUtils.generateSoFileName(entity);
        File soFile = new File(dir,flutterSoPath);
        if (soFile.exists() && Utils.getFileMD5(soFile).equals(entity.fileMd5)) {
            result=new String[2];
            result[0]=soFile.getAbsolutePath();
            result[1]=soFile.getName();
            ThreadPool.getInstance().execute(new Runnable() {
                @Override
                public void run() {
                    DynamicUpdateExtractor.deleteOtherFlutterSoFile(dir.getAbsolutePath(),entity);
                }
            });
        }
    }
    return result;
}

动态化缺陷

1. 本地图片暂无法替换

2. 替换so后需要重启

Q&A

Android native动态化方案

ReactNative动态化方案
参考源码：
https://github.com/heshiqi/flutter_dynamic_update