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token
static Future<dynamic> getToken() {
return _methodChannel.invokeMethod("getPrefs", 'token');
}
/// 设置token
static 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。
