如何判断当前网络能否上网

import { connection } from '@kit.NetworkKit'; 
import { BusinessError } from '@kit.BasicServicesKit'; 
 
export class NetJudge{ 
  public static conn:connection.NetConnection|undefined= undefined; 
 
  private static JUDGE_NET_TAG:string = 'NetJudge.currNet.isUseful'; 
 
  public static netFlag:string = 'false' 
 
  private  static init(){ 
    NetJudge.conn = connection.createNetConnection(); 
    NetJudge.conn.register(()=>{ 
      console.info('connection register success') 
    }) 
 
    NetJudge.conn.on('netAvailable',(data)=>{ 
      console.info('NetJudge  netAvailable ') 
      AppStorage.setOrCreate(NetJudge.JUDGE_NET_TAG, NetJudge.judgeHasNet()) 
    }) 
 
    NetJudge.conn.on('netUnavailable',()=>{ 
      console.info('NetJudge  netUnavailable ') 
      AppStorage.setOrCreate(NetJudge.JUDGE_NET_TAG, NetJudge.judgeHasNet()) 
    }) 
 
    NetJudge.conn.on('netCapabilitiesChange', (data: connection.NetCapabilityInfo) => { 
      AppStorage.setOrCreate(NetJudge.JUDGE_NET_TAG, NetJudge.judgeHasNet()) 
    }) 
 
    // 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 
    NetJudge.conn.on('netConnectionPropertiesChange', (data: connection.NetConnectionPropertyInfo) => { 
      AppStorage.setOrCreate(NetJudge.JUDGE_NET_TAG, NetJudge.judgeHasNet()) 
    }); 
 
    NetJudge.conn.on('netLost',()=>{ 
      AppStorage.setOrCreate(NetJudge.JUDGE_NET_TAG, NetJudge.judgeHasNet()) 
    }) 
 
  } 
 
  public static regist(){ 
    if(NetJudge.conn == undefined){ 
      NetJudge.init() 
    } 
  } 
 
  public static judgeHasNet(): boolean { 
    try { // 获取当前网络连接 
      let netHandle = connection.getDefaultNetSync() 
 
      // 0-100 为系统预留的连接 
      if (!netHandle || netHandle.netId < 100) { 
        return false; 
      } 
 
      // 获取连接的属性 
      let netCapa = connection.getNetCapabilitiesSync(netHandle); 
      let cap = netCapa.networkCap; 
      if (!cap) { 
        return false; 
      } 
 
      for (let em of cap) { 
        if (connection.NetCap.NET_CAPABILITY_VALIDATED == em) { 
          return true; 
        } 
      } 
    } catch (e) { 
      let err = e as BusinessError 
      console.info('get netInfo error ：' + JSON.stringify(err)) 
    } 
    return false; 
  } 
}