HarmonyOS主线程子线程切换问题

import { taskpool } from '@kit.ArkTS'; 
import { emitter } from '@kit.BasicServicesKit'; 
@Concurrent 
function printArgs(args: number): number { 
  console.info("printArgs: " + args); 
  // 子线程处理逻辑 
  console.info("this is child thread: " + args); 
  return args + 5; 
} 
function testChildThread(num: number) { 
  taskpool.execute(printArgs, num).then((value: Object) => { 
    console.info("taskpool result: " + value); 
    // 子线程处理后返回数据给主线程 
    // 定义一个eventId为1111的事件，事件优先级为Low 
    let event: emitter.InnerEvent = { 
      eventId: 1111, 
      priority: emitter.EventPriority.LOW 
    }; 
    let eventData: emitter.EventData = { 
      data: { 
        content: 'c', 
        id: 1, 
        isEmpty: false, 
        num: value 
      } 
    }; 
    // 发送eventId为1111的事件，事件内容为eventData 
    emitter.emit(event, eventData); 
  }); 
} 
function testTaskPool() { 
  console.log("this is start... main thread") 
  let num = 20; 
  // 定义一个eventId为1111的事件 
  let event: emitter.InnerEvent = { 
    eventId: 1111 
  }; 
  // 收到eventId为1111的事件后执行该回调 
  let callback = (eventData: emitter.EventData): void => { 
    console.info('event callback:' + JSON.stringify(eventData)); 
    // 执行主线程拿到子线程数据后的逻辑 
    console.info("num====" + eventData?.data?.num) 
    num = eventData?.data?.num ? eventData?.data?.num : 0; 
  }; 
  // 订阅eventId为1111的事件 
  emitter.on(event, callback); 
  testChildThread(num); 
  console.log("this is end... main thread, num==" + num) 
} 
@Entry 
@Component 
struct Index { 
  build() { 
    Row() { 
      Column() { 
        Button("点我") 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
          .onClick(() => { 
            testTaskPool(); 
          }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}