Flutter鸿蒙下原生视图的使用说明

一、背景介绍

在跨平台开发中，Flutter 通过 PlatformView 机制允许开发者嵌入原生平台的视图组件。对于鸿蒙（HarmonyOS）系统，同样可以通过类似机制实现 Flutter 与原生组件的无缝整合。本文将介绍如何在 Flutter 应用中嵌入鸿蒙原生视图，并实现双向通信。

二、 PlatformView 机制

Flutter 通过 PlatformView 接口将原生视图渲染到 Flutter 的 widget 树中。对于鸿蒙系统，我们需要：

1、创建鸿蒙原生组件：使用 Java/JS 编写 HarmonyOS 的 UI 组件。

2、建立通信桥梁：通过 MethodChannel 实现 Flutter 与原生端的双向通信。

2、处理布局与生命周期：协调 Flutter 与原生视图的布局和渲染。

---

三、实现步骤

1、创建 Flutter 插件项目：

flutter create --template=plugin harmony_view

2、鸿蒙原生端实现

使用 DevEco Studio工具打开 harmony_view\ohos项目,在harmony_view\ohos\entry\src\main\ets\entryability目录下实现代码

2.1、新建CustomView.ets文件，CustomView用于在Flutter Widget里显示

@Component
struct ButtonComponent {
    @Prop params: Params
    customView: CustomView = this.params.platformView as CustomView
    @StorageLink('numValue') storageLink: string = "first"
    @State bkColor: Color = Color.Red

    build() {
      Column() {
        Button("发送数据给Flutter")
          .border({ width: 2, color: Color.Blue})
          .backgroundColor(this.bkColor)
          .onTouch((event: TouchEvent) => {
            console.log("nodeController button on touched")
          })
          .onClick((event: ClickEvent) => {
            this.customView.sendMessage();
            console.log("nodeController button on click")
           })

        Text(`来自Flutter的数据 : ${this.storageLink}`)
          .onTouch((event: TouchEvent) => {
            console.log("nodeController text on touched")
          })

        }.alignItems(HorizontalAlign.Center)
         .justifyContent(FlexAlign.Center)
         .direction(Direction.Ltr)
         .width('100%')
         .height('100%')
    }
}

2.2、定义一个builder方法，放入2.1的自定义Component组件

@Builder
function ButtonBuilder(params: Params) {
   ButtonComponent({ params: params })
     .backgroundColor(Color.Yellow)
}

2.3、继承PlatformView实现一个自定义的Customview，实现getView接口，返回WrappedBuilder(ButtonBuilder)，放入2.2的的builder方法

import MethodChannel, {
        MethodCallHandler,
        MethodResult
        } from '@ohos/flutter_ohos/src/main/ets/plugin/common/MethodChannel';
import PlatformView, { Params } from '@ohos/flutter_ohos/src/main/ets/plugin/platform/PlatformView';
import common from '@ohos.app.ability.common';
import { BinaryMessenger } from '@ohos/flutter_ohos/src/main/ets/plugin/common/BinaryMessenger';
import StandardMethodCodec from '@ohos/flutter_ohos/src/main/ets/plugin/common/StandardMethodCodec';
import MethodCall from '@ohos/flutter_ohos/src/main/ets/plugin/common/MethodCall';

@Observed
export class CustomView extends PlatformView implements MethodCallHandler {
    numValue: string = "test";

    methodChannel: MethodChannel;
    index: number = 1;

    constructor(context: common.Context, viewId: number, args: ESObject, message: BinaryMessenger) {
        super();
        console.log("nodeController viewId:" + viewId)
        // 注册消息通道，消息通道根据具体需求添加，代码仅作为示例
        this.methodChannel = new MethodChannel(message, `com.rex.custom.ohos/customView${viewId}`, StandardMethodCodec.INSTANCE);
        this.methodChannel.setMethodCallHandler(this);
    }

    onMethodCall(call: MethodCall, result: MethodResult): void {
        // 接受Dart侧发来的消息
        let method: string = call.method;
        let link1: SubscribedAbstractProperty<number> = AppStorage.link('numValue');
        switch (method) {
            case 'getMessageFromFlutterView':
                let value: ESObject = call.args;
                this.numValue = value;
                link1.set(value)
                console.log("nodeController receive message from dart: " + this.numValue);
                result.success(true);
                break;
        }
    }

    public sendMessage = () => {
        console.log("nodeController sendMessage")
        //向Dart侧发送消息
        this.methodChannel.invokeMethod('getMessageFromOhosView', 'natvie - ' + this.index++);
    }

    getView(): WrappedBuilder<[Params]> {
        return new WrappedBuilder(ButtonBuilder);
    }

    dispose(): void {
    }
}

---

2.4、实现一个自定义的PlatformViewFactory，在其create方法中创建自定义的PlatformView的实例

import common from '@ohos.app.ability.common';
import MessageCodec from '@ohos/flutter_ohos/src/main/ets/plugin/common/MessageCodec';
import PlatformViewFactory from '@ohos/flutter_ohos/src/main/ets/plugin/platform/PlatformViewFactory';
import { BinaryMessenger } from '@ohos/flutter_ohos/src/main/ets/plugin/common/BinaryMessenger';
import PlatformView from '@ohos/flutter_ohos/src/main/ets/plugin/platform/PlatformView';
import { CustomView } from './CustomView';

export class CustomFactory extends PlatformViewFactory {
  message: BinaryMessenger;

  constructor(message: BinaryMessenger, createArgsCodes: MessageCodec<Object>) {
    super(createArgsCodes);
    this.message = message;
  }

  public create(context: common.Context, viewId: number, args: Object): PlatformView {
    return new CustomView(context, viewId, args, this.message);
  }
}

1.5、新建一个继承于FlutterPlugin的CustomPlugin插件，在onAttachedToEngine中，注册自定义的PlatformViewFactory

import  { FlutterPlugin,
  FlutterPluginBinding } from '@ohos/flutter_ohos/src/main/ets/embedding/engine/plugins/FlutterPlugin';
import StandardMessageCodec from '@ohos/flutter_ohos/src/main/ets/plugin/common/StandardMessageCodec';
import { CustomFactory } from './CustomFactory';

export class CustomPlugin implements FlutterPlugin {
  getUniqueClassName(): string {
    return 'CustomPlugin';
  }

  onAttachedToEngine(binding: FlutterPluginBinding): void {
    binding.getPlatformViewRegistry()?.
    registerViewFactory('com.rex.custom.ohos/customView', new CustomFactory(binding.getBinaryMessenger(), StandardMessageCodec.INSTANCE));
  }

  onDetachedFromEngine(binding: FlutterPluginBinding): void {}
}

3、Flutter 端实现

用AndroidStudio工具打开harmony_view项目在harmony_view\lib目录下实现代码，新建CustomOhosView.dart，用于显示Native侧的CustomView的Widget OhosView组件就是桥接PlatformView的关键。

• viewType：传递给Native侧，告知插件需要创建那个PlatformView，这个PlatformView需要在插件初始化时注册。
• onPlatformViewCreated：PlatformView创建成功时的回调。
• creationParams：传递给PlatformView的初始化参数。3.1、实现CustomOhosView，使用OhosView组件，viewType需要和ets侧FlutterPlugin做registerViewFactory操作时指定的viewType一致

3.1、实现CustomOhosView，使用OhosView组件，viewType需要和ets侧FlutterPlugin做registerViewFactory操作时指定的viewType一致

import 'dart:async';

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

typedef OnViewCreated = Function(CustomViewController);

///自定义OhosView
class CustomOhosView extends StatefulWidget {
  final OnViewCreated onViewCreated;

  const CustomOhosView(this.onViewCreated, {Key? key}) : super(key: key);

  @override
  State<CustomOhosView> createState() => _CustomOhosViewState();
}

class _CustomOhosViewState extends State<CustomOhosView> {
  late MethodChannel _channel;

  @override
  Widget build(BuildContext context) {
    return _getPlatformFaceView();
  }

  Widget _getPlatformFaceView() {
    return OhosView(
      viewType: 'com.rex.custom.ohos/customView',
      onPlatformViewCreated: _onPlatformViewCreated,
      creationParams: const <String, dynamic>{'initParams': 'hello world'},
      creationParamsCodec: const StandardMessageCodec(),
    );
  }

  void _onPlatformViewCreated(int id) {
    _channel = MethodChannel('com.rex.custom.ohos/customView$id');
    final controller = CustomViewController._(
      _channel,
    );
    widget.onViewCreated(controller);
  }
}

3.2、在CustomOhosView所在文件中新建CustomViewController，用于实现Dart侧与Native侧的交互

class CustomViewController {
  final MethodChannel _channel;
  final StreamController<String> _controller = StreamController<String>();

  CustomViewController._(
    this._channel,
  ) {
    _channel.setMethodCallHandler(
      (call) async {
        switch (call.method) {
          case 'getMessageFromOhosView':
            // 从native端获取数据
            final result = call.arguments as String;
            _controller.sink.add(result);
            break;
        }
      },
    );
  }

  Stream<String> get customDataStream => _controller.stream;

  // 发送数据给native
  Future<void> sendMessageToOhosView(String message) async {
    await _channel.invokeMethod(
      'getMessageFromFlutterView',
      message,
    );
  }
}

3.3、修改harmony_view\lib\main.dart文件中的代码写测试

import 'dart:math';

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

void main() {
  runApp(const MaterialApp(home: MyHome()));
}

class MyHome extends StatelessWidget {
  const MyHome({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: CustomExample(),
    );
  }
}

class CustomExample extends StatefulWidget {
  const CustomExample({Key? key}) : super(key: key);

  @override
  State<CustomExample> createState() => _CustomExampleState();
}

class _CustomExampleState extends State<CustomExample> {
  String receivedData = '';
  CustomViewController? _controller;

  void _onCustomOhosViewCreated(CustomViewController controller) {
    _controller = controller;
    _controller?.customDataStream.listen((data) {
      //接收到来自OHOS端的数据
      setState(() {
        receivedData = '来自ohos的数据：$data';
      });
    });
  }

  Widget _buildOhosView() {
    return Expanded(
      child: Container(
        color: Colors.blueAccent.withAlpha(60),
        child: CustomOhosView(_onCustomOhosViewCreated),
      ),
      flex: 1,
    );
  }

  Widget _buildFlutterView() {
    return Expanded(
      child: Stack(
        alignment: AlignmentDirectional.bottomCenter,
        children: [
          Column(
            mainAxisAlignment: MainAxisAlignment.center,
            mainAxisSize: MainAxisSize.max,
            children: [
              TextButton(
                onPressed: () {
                  final randomNum = Random().nextInt(10);
                  _controller
                      ?.sendMessageToOhosView('flutter - $randomNum ');
                },
                child: const Text('发送数据给ohos'),
              ),
              const SizedBox(height: 10),
              Text(receivedData),
            ],
          ),
          const Padding(
            padding: EdgeInsets.only(bottom: 15),
            child: Text(
              'Flutter - View',
              style: TextStyle(
                fontSize: 20,
                fontWeight: FontWeight.bold,
              ),
            ),
          ),
        ],
      ),
      flex: 1,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        _buildOhosView(),
        _buildFlutterView(),
      ],
    );
  }
}

---

四、总结

通过 PlatformView 集成鸿蒙原生视图，开发者可以：

• 保留 Flutter 跨平台优势
• 充分利用鸿蒙系统特性
• 实现渐进式混合开发

未来随着 HarmonyOS 生态的发展，这种混合开发模式将显著提升应用的功能扩展能力。