HarmonyOS网络监听问题

import connection from '@ohos.net.connection'; 
import { BusinessError } from "@ohos.base"; 
import { hilog } from '@kit.PerformanceAnalysisKit'; 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
 
  onPageShow(): void { 
    this.init(); 
  } 
 
  init(){ 
    let netCon: connection.NetConnection = connection.createNetConnection(); 
    netCon.register((error: BusinessError) => { 
      if(error==undefined){ 
        hilog.info(0x0000,"网络状态","注册成功") 
      }else { 
        hilog.info(0x0000,"网络状态","注册失败 error is %s",JSON.stringify(error)) 
      } 
 
 
    }); 
 
    // 订阅网络可用事件。调用register后，才能接收到此事件通知 
    netCon.on('netAvailable', (data: connection.NetHandle) => { 
      hilog.info(0x0000,"网络状态",'网络状态可用 ' + JSON.stringify(data)); 
    }); 
    // 订阅网络不可用事件。调用register后，才能接收到此事件通知 
    netCon.on('netUnavailable', () => { 
      hilog.info(0x0000,"网络状态",'网络状态不可用1 '); 
    }); 
    netCon.on('netLost', () => { 
      hilog.info(0x0000,"网络状态",'网络状态不可用2 '); 
    }); 
 
    // 订阅网络连接信息变化事件。调用register后，才能接收到此事件通知 
    netCon.on('netConnectionPropertiesChange', (data: connection.NetConnectionPropertyInfo) => { 
      hilog.info(0x0000,"网络状态","Succeeded to get data: " + JSON.stringify(data)); 
    }); 
 
    connection.getDefaultNet().then((netHandle)=>{ 
      connection.reportNetDisconnected(netHandle).then(()=> { 
        hilog.info(0x0000,"网络状态",'reportNetDisconnected '); 
      }); 
    }); 
 
  } 
 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}