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

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

//判断网路是否畅通加权限

         if(NetWorkUtil.isNetAvailable(MainActivity.this)){//网络畅通

            //开始请求数据

         }else{

             Toast.makeText(MainActivity.this, "目前没网请检查网络权限", 0).show();

         }

public class NetWorkUtil {

      public static boolean isNetAvailable(Context context){

            //获得网络管理器

            ConnectivityManager connM =

                    (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

            NetworkInfo netInfo = connM.getActiveNetworkInfo();//得到网络详情

            if(netInfo == null || !netInfo.isAvailable())

                return false;

            return true;

        }

}