HttpURLConnection连接网络问题

错误提示如下：

HttpURLConnection连接网络时，提示“Cleartext HTTP traffic to www.imooc.com not permitted ”

代码如下：

package util;

import android.content.Context;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class HttpUtil {

   public static String getDataFromNet(String urlStr){
       try {
           URL url = new URL(urlStr);
           HttpURLConnection conn = (HttpURLConnection) url.openConnection();
           conn.setConnectTimeout(30*1000);
           conn.setRequestMethod("GET");
           conn.connect();
           //如果请求成功，则读取数据
           if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){
               InputStreamReader inputStreamReader = new InputStreamReader(conn.getInputStream());
               BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
               StringBuilder stringBuilder = new StringBuilder();
               String line;
               while((line = bufferedReader.readLine())!=null){
                   stringBuilder.append(line);
               }
               inputStreamReader.close();
               bufferedReader.close();
               conn.disconnect();
               return stringBuilder.toString();
           }
       } catch (MalformedURLException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }
       return null;
   }
}