HarmonyOS ArkTS开发中，异步回调，怎么切到主线程执行呢

@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
  loadData(){ 
    test1((data:ESObject)=>{ 
      this.message = data 
    }) 
  } 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
          .onClick(() => { 
            this.loadData() 
            hilog.info(0x0000, 'testTag', 'Test NAPI 2 + 3 = %{public}d', testNapi.add(2, 3)); 
          }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
} 
async function myAsyncFunction(): Promise<string> { 
  const result: string = await new Promise((resolve: Function) => { 
    setTimeout(() => { 
      resolve('Hello, world!'); 
    }, 3000); 
  }); 
  console.info(result); // 输出： Hello, world! 
  return result; 
} 
async function test1(onDataLoaded: (data:ESObject)=> void){ 
  let a = await myAsyncFunction().then((a)=>{ 
    console.log("xxxx1"+a) 
    return a; 
  }) 
  let data = "xxxx" 
  onDataLoaded(data); 
  console.log("xxxx2"+ a ) 
} 
//网络请求可以考虑这样封装一下 
async function fetchData(onDataLoaded: (data:ESObject)=> void){ 
  let httpRequest = http.createHttp(); 
  httpRequest.request( 
    "EXAMPLE_URL", 
    {}, 
    (err: BusinessError,data:http.HttpResponse)=>{ 
      if (!err) { 
        onDataLoaded(JSON.stringify(data.result)) 
      } 
    } 
  ); 
}