private Boolean isOnline()  {     ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);      NetworkInfo ni = cm.getActiveNetworkInfo();     if(ni != null && ni.isConnected())    {//        Toast.makeText(this, "网络连接正常", 1000).show();        return true;    }     else{        Toast.makeText(this, "网络连接失败请点击菜单设置", 3000).show();    }     return false;     }

 最后最关键的是 别忘记在AndroidManifest.xml中注册。