Flutter混合Android

1.新建一个Android工程

好比工程名MyApplication

2.建立Flutter Module

在cd到当前project下运行命令：

E:\MyApplication
flutter create -t module my_flutter
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3.增长配置代码

在工程setttings.gradle中增长配置:

include ':app'
setBinding(new Binding([gradle: this]))
evaluate(new File(settingsDir, 'my_flutter/.android/include_flutter.groovy'))
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接下来在app的build.gradle增长依赖：

implementation project(':flutter')
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可能会报错：

Error: Invoke-customs are only supported starting with Android O (--min-api 26)
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在app的build.gradle的android标签下增长：

compileOptions{
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
}
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最后生成的目录结构：

通过上面3步就已经集成Flutter了，接着看看怎么在Android工程中建立Flutter的UI

4.Android中建立Flutter UI

Flutter提供两种方法引入，一个是View，一个是Fragment，看下View的代码：

public class FlutterActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_flutter);

        FlutterView view = Flutter.createView(this, getLifecycle(), "new_page");
        FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(
                FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT
        );
        addContentView(view, layoutParams);
    }
}
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第二个参数是Lifecycle对象，第三个参数是route，这个参数Flutter端能够经过window.defaultRouteName获取

看下Flutter侧的dart代码, 在my_flutter->lib目录下新建list.dart：

import 'package:flutter/material.dart';

class ListViewTest extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Widget divider1 = Divider(color: Colors.blue);
    Widget divider2 = Divider(color: Colors.green);

    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text('ListTest'),
      ),
      body: Center(
        child: ListView.separated(
            itemBuilder: (BuildContext context, int index) {
              return ListTile(
                title: Text("$index"),
              );
            },
            separatorBuilder: (BuildContext context, int index) {
              return index % 2 == 0 ? divider1 : divider2;
            },
            itemCount: 100),
      ),
    );
  }
}
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在main.dart中导出路由new_page:

import 'package:flutter/material.dart';
import 'list.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
      routes: {
        "new_page": (context) => ListViewTest(),
      },
    );
  }
}
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5.hot reload

进入到flutter module目录下, 执行命令 flutter attach 便可, 在这个命令窗口按r便可hot reload:

E:\MyApplication\my_flutter
λ flutter attach
Waiting for a connection from Flutter on vivo x27...
Done.
Syncing files to device vivo x27...                             1,125ms

🔥  To hot reload changes while running, press "r". To hot restart (and rebuild state), press "R".
An Observatory debugger and profiler on vivo 1819 is available at: http://127.0.0.1:55515/
For a more detailed help message, press "h". To detach, press "d"; to quit, press "q".


Initializing hot reload...
Reloaded 2 of 433 libraries in 969ms.
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6.总结

最后对比看下继承了Flutter和没有继承的Android工程打出来的Release包大小对比：

接入Flutter以后，包大小激增5M，主要是由于flutter.so这个so库。还有flutter_assets里是flutter工程产生的assets文件, isolate_snapshot_data、isolate_snapshot_instr、vm_snapshot_data、vm_snapshot_instr为特定平台的数据和指令.

Refs:

Android工程接入Flutter module

flutter接入现有的app详细介绍

Flutter(Android 混合开发)

如何进行Flutter混合开发

Flutter 的两种编译模式