判断是否联网

代码：

ConnectivityManager cm = (ConnectivityManager) getActivity().getSystemService(getActivity().CONNECTIVITY_SERVICE);

           NetworkInfo mm=cm.getActiveNetworkInfo();

           if(mm!=null){

         //有网 请求网络

            }else if(mm==null){

         //没网络 

       }

记得加权限

<uses-permission android:name="android.permission.INTERNET"></uses-permission><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>

ConnectivityManager cm = (ConnectivityManager) this.getSystemService(this.CONNECTIVITY_SERVICE);NetworkInfo mm = cm.getActiveNetworkInfo();if(mm != null){    //有网请求网络    new MyAsyncTask().execute(url);}else{    //无网络    List<Bean2> list2 = dao.select();    for (int i = 0; i < list2.size(); i++) {        String name = list2.get(i).carrier_name;        String phone = list2.get(i).carrier_phone;        list.add(new Bean2(name ,phone));    }    ma = new MyAdapter(list,MainActivity.this  ) ;    lv.setAdapter(ma);}