Worker和宿主线程的即时消息通信

在ArkTS中，Worker相对于Taskpool存在一定的差异性，有数量限制但是可以长时间存在。一个Worker中可能会执行多个不同的任务，每个任务的执行时长或返回结果可能都不同，宿主线程需要根据情况调用Worker中的不同方法，Worker则需要及时地将结果返回给宿主线程。

下面以Worker响应"hello world"请求为例说明。

首先，创建一个执行任务的Worker。创建方法可参考创建worker的注意事项。

import { ErrorEvent, MessageEvents, ThreadWorkerGlobalScope, worker } from '@kit.ArkTS';
import { CopyEntry } from '../Sendable/CopyEntry';

const workerPort: ThreadWorkerGlobalScope = worker.workerPort;

// ...

// Worker接收宿主线程的消息，做相应的处理
workerPort.onmessage = (e: MessageEvents) => {
  let obj: CopyEntry[] = e.data;
  console.info(`The type of the first set of data is ${obj[0].type}.`);
}

import { ErrorEvent, MessageEvents, ThreadWorkerGlobalScope, worker } from '@kit.ArkTS';
import { CopyEntry } from '../Sendable/CopyEntry';

const workerPort: ThreadWorkerGlobalScope = worker.workerPort;

// ...

// Worker接收宿主线程的消息，做相应的处理
workerPort.onmessage = (e: MessageEvents) => {
  let obj: CopyEntry[] = e.data;
  console.info(`The type of the first set of data is ${obj[0].type}.`);
}

这里的宿主线程是UI主线程，在宿主线程中创建Worker对象，当点击Button时调用postMessage方法向Worker线程发送消息，Worker线程将通过注册的onmessage回调处理宿主线程发送的消息。

import { worker } from '@kit.ArkTS';
import { BusinessError } from '@kit.BasicServicesKit';

function promiseCase() {
  let p: Promise<void> = new Promise<void>((resolve: Function, reject: Function) => {
    setTimeout(() => {
      resolve(1);
    }, 100)
  }).then(undefined, (error: BusinessError) => {
  })
  return p;
}

async function postMessageTest() {
  let ss = new worker.ThreadWorker('entry/ets/workers/Worker.ets');
  let res = undefined;
  let flag = false;
  let isTerminate = false;
  ss.onexit = () => {
    isTerminate = true;
  }
  // 接收Worker线程发送的消息
  ss.onmessage = (e) => {
    res = e.data;
    flag = true;
    console.info('worker:: res is  ' + res);
  }
  // 给Worker线程发送消息
  ss.postMessage('hello world');
  while (!flag) {
    await promiseCase();
  }

  ss.terminate();
  while (!isTerminate) {
    await promiseCase();
  }
}

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';

  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            postMessageTest();
            this.message = 'success';
          })
      }
      .width('100%')
    }
    .height('100%')
  }
}

import { worker } from '@kit.ArkTS';
import { BusinessError } from '@kit.BasicServicesKit';

function promiseCase() {
  let p: Promise<void> = new Promise<void>((resolve: Function, reject: Function) => {
    setTimeout(() => {
      resolve(1);
    }, 100)
  }).then(undefined, (error: BusinessError) => {
  })
  return p;
}

async function postMessageTest() {
  let ss = new worker.ThreadWorker('entry/ets/workers/Worker.ets');
  let res = undefined;
  let flag = false;
  let isTerminate = false;
  ss.onexit = () => {
    isTerminate = true;
  }
  // 接收Worker线程发送的消息
  ss.onmessage = (e) => {
    res = e.data;
    flag = true;
    console.info('worker:: res is  ' + res);
  }
  // 给Worker线程发送消息
  ss.postMessage('hello world');
  while (!flag) {
    await promiseCase();
  }

  ss.terminate();
  while (!isTerminate) {
    await promiseCase();
  }
}

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';

  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            postMessageTest();
            this.message = 'success';
          })
      }
      .width('100%')
    }
    .height('100%')
  }
}

在示例代码中，Worker接收宿主线程的消息，并处理后将结果返回给宿主线程。实现了宿主线程与Worker之间的即时通信，使宿主线程能够方便地使用Worker的运行结果。