【高心星出品】
多线程Worker和@Sendable的使用方法
Worker在HarmonyOS中提供了一种多线程的实现方式，它允许开发者在后台线程中执行长耗时任务，从而避免阻塞主线程并提高应用的响应性。
@Sendable 注解主要用于标记那些需要在多线程环境中共享的数据对象或函数。被 @Sendable 标记的对象或函数可以在不同的线程之间高效地传输数据，这主要得益于 ArkTS 的序列化和反序列化机制。
开发步骤
【案例需求】 接下来要实现一个案例，创建两个子线程，一个子线程负责数据求和，一个子线程负责数据相减，UI线程提供共享数据给这两个子线程，子线程运行结果返回给UI线程。
创建两个worker。
在ets/下创建一个workers目录，在该目录下创建worker。这两个worker负责接受UI线程传过来的数据，并且负责子线程运行实体，并将结果发送给UI线程。
- addworker的代码
import { ErrorEvent, MessageEvents, ThreadWorkerGlobalScope, worker } from '@kit.ArkTS';
import { Temp } from '../pages/Index';
const workerPort: ThreadWorkerGlobalScope = worker.workerPort;
/**
* Defines the event handler to be called when the worker thread receives a message sent by the host thread.
* The event handler is executed in the worker thread.
*
* @param event message data
*/
// 线程运行实体
function add(temp:Temp){
let a=temp.a
let b=temp.b
temp.a+=5
return a+b
}
// 子线程接受UI线程信息并处理
workerPort.onmessage = async (event: MessageEvents) => {
if(event)
{
// 模拟线程睡眠2s
await new Promise((resolve:(v:number)=>void)=>{
setTimeout(()=>{resolve(10)},2000)
})
// 解析获取ui线程发送的数据
let t=event.data as Temp
// 子线程向UI线程发送消息
workerPort.postMessage(add(t))
}
};
/**
* Defines the event handler to be called when the worker receives a message that cannot be deserialized.
* The event handler is executed in the worker thread.
*
* @param event message data
*/
workerPort.onmessageerror = (event: MessageEvents) => {
};
/**
* Defines the event handler to be called when an exception occurs during worker execution.
* The event handler is executed in the worker thread.
*
* @param event error message
*/
workerPort.onerror = (event: ErrorEvent) => {
};
- jianworker的代码
import { ErrorEvent, MessageEvents, ThreadWorkerGlobalScope, worker } from '@kit.ArkTS';
import { Temp } from '../pages/Index';
const workerPort: ThreadWorkerGlobalScope = worker.workerPort;
/**
* Defines the event handler to be called when the worker thread receives a message sent by the host thread.
* The event handler is executed in the worker thread.
*
* @param event message data
*/
// 线程运行实体
function jian(t:Temp){
let a=t.a
let b=t.b
t.a-=5
return Math.abs(a-b)
}
// 子线程接受UI线程的信息 并运行
workerPort.onmessage = async (event: MessageEvents) => {
if(event){
// 模拟线程睡眠2s
await new Promise((resolve:(v:string)=>void)=>{
setTimeout(()=>{
resolve('a')
},2000)
})
let t=event.data as Temp
// 向UI线程发送消息
workerPort.postMessage(jian(t))
}
};
/**
* Defines the event handler to be called when the worker receives a message that cannot be deserialized.
* The event handler is executed in the worker thread.
*
* @param event message data
*/
workerPort.onmessageerror = (event: MessageEvents) => {
};
/**
* Defines the event handler to be called when an exception occurs during worker execution.
* The event handler is executed in the worker thread.
*
* @param event error message
*/
workerPort.onerror = (event: ErrorEvent) => {
};
- Index.ets代码
import { MessageEvents, worker } from "@kit.ArkTS";
@Sendable
export class Temp {
a: number
b: number
constructor(a: number, b: number) {
this.a = a;
this.b = b;
}
}
@Entry
@Component
struct Index {
@State message: string = 'Hello World';
// UI线程和其他两个子线程共享的数据
private temp = new Temp(10, 20)
//创建了两个线程
private addthread = new worker.ThreadWorker('entry/ets/workers/addworker.ets')
private jianthread = new worker.ThreadWorker('entry/ets/workers/jianworker.ets')
aboutToAppear(): void {
// UI线程中接受两个子线程发送的信息
this.addthread.onmessage = (event: MessageEvents) => {
console.log('gxxt add ', event.data as number)
console.log('gxxt 当前的temp值： ',JSON.stringify(this.temp))
}
this.jianthread.onmessage = (event: MessageEvents) => {
console.log('gxxt jian ', event.data as number)
console.log('gxxt 当前的temp值： ',JSON.stringify(this.temp))
}
}
build() {
Column({ space: 20 }) {
Button('加线程')
.width('60%')
.onClick(() => {
this.addthread.postMessageWithSharedSendable(this.temp)
})
Button('减线程')
.width('60%')
.onClick(() => {
this.jianthread.postMessageWithSharedSendable(this.temp)
})
}
.height('100%')
.width('100%')
.justifyContent(FlexAlign.Center)
}
}
项目通过点击两个按钮启动两个线程，并将共享数据temp发送给两个子线程，两个子线程分别执行相加和相减，同时还更新共享数据的原始值，通过观察运算结果和共享数据的变化，我们能掌握worker的开发方式。
运行结果
02-28 09:10:59.798 3292-3292 A03d00/JSAPP com.gxx.workdemo I gxxt add运算结果： 30
02-28 09:10:59.799 3292-3292 A03d00/JSAPP com.gxx.workdemo I gxxt 当前的temp值： {"a":15,"b":20}
02-28 09:11:04.877 3292-3292 A03d00/JSAPP com.gxx.workdemo I gxxt jian运算结果 5
02-28 09:11:04.877 3292-3292 A03d00/JSAPP com.gxx.workdemo I gxxt 当前的temp值： {"a":10,"b":20}
刚一开始进行运算的时候add线程面对的a为10，b为20，计算结果为30，add线程同时a=a+5操作，所以此时UI线程得到的a为15；然后jian线程运行结果为|15-20|，jian线程同时a=a-5,所以此时UI线程得到的a为10.