HarmonyOS 如何实现后台执行任务

参考代码如下：

import { backgroundTaskManager } from '@kit.BackgroundTasksKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { wantAgent, WantAgent } from '@kit.AbilityKit';
@Entry
@Component
struct Index {
  @State message: string = 'ContinuousTask';
  private  intervalID: number = -1

  // 通过getContext方法，来获取page所在的UIAbility上下文。
  private context: Context = getContext(this);

  startContinuousTask() {
    let wantAgentInfo: wantAgent.WantAgentInfo = {
      // 点击通知后，将要执行的动作列表
      // 添加需要被拉起应用的bundleName和abilityName
      wants: [
        {
          bundleName: "com.example.myapplication",
          abilityName: "com.example.myapplication.EntryAbility"
        }
      ],
      // 指定点击通知栏消息后的动作是拉起ability
      actionType: wantAgent.OperationType.START_ABILITY,
      // 使用者自定义的一个私有值
      requestCode: 0,
      // 点击通知后，动作执行属性
      actionFlags: [wantAgent.WantAgentFlags.UPDATE_PRESENT_FLAG]
    };

    // 通过wantAgent模块下getWantAgent方法获取WantAgent对象
    wantAgent.getWantAgent(wantAgentInfo).then((wantAgentObj: WantAgent) => {
      backgroundTaskManager.startBackgroundRunning(this.context,
        backgroundTaskManager.BackgroundMode.DATA_TRANSFER, wantAgentObj).then(() => {
        // 此处执行具体的长时任务逻辑，如放音等。
        this.intervalID = setInterval(()=>{
          console.info(`下载一次用户数据`)
        },3000)
        console.info(`Succeeded in operationing startBackgroundRunning.`);
      }).catch((err: BusinessError) => {
        console.error(`Failed to operation startBackgroundRunning. Code is ${err.code}, message is ${err.message}`);
      });
    });
  }

  stopContinuousTask() {
    backgroundTaskManager.stopBackgroundRunning(this.context).then(() => {
      console.info(`Succeeded in operationing stopBackgroundRunning.`);
    }).catch((err: BusinessError) => {
      console.error(`Failed to operation stopBackgroundRunning. Code is ${err.code}, message is ${err.message}`);
    });
  }

  build() {
    Row() {
      Column() {
        Text("Index")
          .fontSize(50)
          .fontWeight(FontWeight.Bold)

        Button() {
          Text('申请长时任务').fontSize(25).fontWeight(FontWeight.Bold)
        }
        .type(ButtonType.Capsule)
        .margin({ top: 10 })
        .backgroundColor('#0D9FFB')
        .width(250)
        .height(40)
        .onClick(() => {
          // 通过按钮申请长时任务
          this.startContinuousTask();
        })

        Button() {
          Text('取消长时任务').fontSize(25).fontWeight(FontWeight.Bold)
        }
        .type(ButtonType.Capsule)
        .margin({ top: 10 })
        .backgroundColor('#0D9FFB')
        .width(250)
        .height(40)
        .onClick(() => {
          // 此处结束具体的长时任务的执行

          // 通过按钮取消长时任务
          this.stopContinuousTask();
        })
      }
      .width('100%')
    }
    .height('100%')
  }
}