使用 ArkTs 开发 Flutter 鸿蒙平台插件

news/2024/10/22 18:40:42

使用 ArkTs 开发 Flutter 鸿蒙平台插件

本文讲述如何开发一个 Flutter 鸿蒙插件，如何实现 Flutter 与鸿蒙的混合开发，以及双端消息通信。

Flutter侧，编写 MethodChannel

const MethodChannel _methodChannel = MethodChannel('xxx.com/app');/// 获取tokenstatic Future<dynamic> getToken() {return _methodChannel.invokeMethod("getPrefs", 'token');}/// 设置tokenstatic Future<dynamic> setToken(String token) {return _methodChannel.invokeMethod("setPrefs", {'key': 'token', 'value': token});}

代码生命了一个 methodChannel, 并实现了 token 存错的调用方法。

ArkTs侧，实现调用

编写 src/main/ets/entryability/EntryAbility.ets


import { FlutterAbility, FlutterEngine } from '@ohos/flutter_ohos';
import { GeneratedPluginRegistrant } from '../plugins/GeneratedPluginRegistrant';
import ForestPlugin from './ForestPlugin';
import { BusinessError } from '@kit.BasicServicesKit';
import { window } from '@kit.ArkUI';
import { preferences } from '@kit.ArkData';let dataPreferences: preferences.Preferences | null = null;export default class EntryAbility extends FlutterAbility {onWindowStageCreate(windowStage: window.WindowStage): void {super.onWindowStageCreate(windowStage);preferences.getPreferences(this.context, 'forestStore', (err: BusinessError, val: preferences.Preferences) => {if (err) {console.error("Failed to get preferences. code =" + err.code + ", message =" + err.message);return;}dataPreferences = val;console.info("Succeeded in getting preferences1.");})}configureFlutterEngine(flutterEngine: FlutterEngine) {super.configureFlutterEngine(flutterEngine)GeneratedPluginRegistrant.registerWith(flutterEngine)this.addPlugin(new ForestPlugin());}
}export {dataPreferences};

该文件使的原生页面在加载时，配置 Flutter 引擎，注册插件。 Flutter初始化时，同时初始化了首选项dataPreferences，以备后用。

编写 src/main/ets/entryability/ForestPlugin.ets

import { Any, BasicMessageChannel, EventChannel, FlutterManager, FlutterPlugin, Log, MethodCall, MethodChannel, StandardMessageCodec} from '@ohos/flutter_ohos';
import { FlutterPluginBinding } from '@ohos/flutter_ohos/src/main/ets/embedding/engine/plugins/FlutterPlugin';
import { batteryInfo } from '@kit.BasicServicesKit';
import { MethodCallHandler, MethodResult } from '@ohos/flutter_ohos/src/main/ets/plugin/common/MethodChannel';
import { preferences } from '@kit.ArkData';
import { BusinessError } from '@kit.BasicServicesKit';
import {dataPreferences} from './EntryAbility';
import router from '@ohos.router'
import { webviewRouterParams } from '../pages/Webview';const TAG = "[flutter][plugin][forest]";export default class ForestPlugin implements FlutterPlugin {private channel?: MethodChannel;private basicChannel?: BasicMessageChannel<Any>;private api = new ForestApi();private dataPreferences: preferences.Preferences | null = null;onAttachedToEngine(binding: FlutterPluginBinding): void {this.channel = new MethodChannel(binding.getBinaryMessenger(), "xxx.com/app");this.channel.setMethodCallHandler({onMethodCall : (call: MethodCall, result: MethodResult) => {console.log(`${TAG}-->[${call.method}]: ${JSON.stringify(call.args)}`);switch (call.method) {case "getPrefs":this.api.getPrefs(String(call.args), result);break;case "setPrefs":let key = String(call.argument("key"));let value = String(call.argument("value"));this.api.setPrefs(key, value);default:result.notImplemented();break;}}})}//···onDetachedFromEngine(binding: FlutterPluginBinding): void {Log.i(TAG, "onDetachedFromEngine");this.channel?.setMethodCallHandler(null);}getUniqueClassName(): string {return "ForestPlugin";}

以上代码实现了一个插件类，其核心实现了FlutterPlugin中的 onAttachedToEngine方法，该方法在 Flutter 引擎加载成功后调用。

onMethodCall中接收来自 Flutter 的消息调用，分别实现了 'getPrefs' 和 'setPrefs' 两个回掉，其中 getPrefs有返回值，通过 result.success(val);（见下）异步返回，
setPrefs没有返回值。

以下为 ForestApi的具体实现，使用了 HarmonyOS 中的首选项 API 设置和读取数据。

class ForestApi {getPrefs(key: string, result: MethodResult) {dataPreferences?.get(key, '', (err: BusinessError, val: preferences.ValueType) => {if (err) {console.error(`${TAG} Failed to get value of ${key}. code =` + err.code + ", message =" + err.message);result.success('');}console.info(`${TAG} Succeeded in getting value of ${key}:${val}.`);result.success(val);})}setPrefs(key: string, value: string) {dataPreferences?.put(key, value, (err: BusinessError) => {if (err) {console.error(`${TAG} Failed to put value of ${key}. code =` + err.code + ", message =" + err.message);return;}console.info(`${TAG} Succeeded in putting value of ${key}.`);})}clearPrefs(key: string) {dataPreferences?.delete(key, (err: BusinessError) => {if (err) {console.error("Failed to delete the key 'startup'. code =" + err.code + ", message =" + err.message);return;}console.info(`Succeeded in deleting the key ${key}.`);})}
}

注意事项

1.双端初始化methodChannel中的名称必须保持一致，如 xxx.com/app.
2.arkTS侧通过 result.success(val) 返回数据，该过程是异步的，故在 Dart 侧需要使用 await 或者回调函数取值。
3.通信中默认只支持基础的数据类型，复杂类型的需要进行序列化或编解码。
4.在Dart 侧接收的数据为 dymanic 类型，需要进行数据类型转换。