Android ทำ Register เพื่อ connect ไปยัง mysql แต่ error แบบนี้แก้ไขยังไงครับ

package com.example.puen.connectmysqltest;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

public class Register extends Activity{
    EditText ET_NAME,ET_USER_NAME,ET_USER_PASS;
    String name,user_name,user_pass;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register_layout);
        ET_NAME = (EditText)findViewById(R.id.name);
        ET_USER_NAME = (EditText)findViewById(R.id.new_user_name);
        ET_USER_PASS = (EditText)findViewById(R.id.new_user_pass);


    }
public void userReg(View view)
    {
        name = ET_NAME.getText().toString();
        user_name = ET_USER_NAME.getText().toString();
        user_pass = ET_USER_PASS.getText().toString();
        String method ="register";
        BackgroundTask backgroundTask=new BackgroundTask(this);
        backgroundTask.execute(method,name,user_name,user_pass);
        finish();

    }


}

package com.example.puen.connectmysqltest;

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

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

/**
 * Created by puen on 4/4/2016.
 */
public class BackgroundTask extends AsyncTask<String,Void,String> {
Context ctx;
    BackgroundTask(Context ctx)
    {
        this.ctx= ctx;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        String reg_url ="http://10.0.2.2/webapp/register.php";
        String login_url ="http://10.0.2.2/webapp/login.php";
        String method = params[0];
        if(method.equals("register"))
        {
            String name = params[1];
                String user_name= params[2];
                String user_pass= params[3];
            try {
                URL url = new URL(reg_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                httpURLConnection.setRequestMethod("POST");
               // httpURLConnection.setDoOutput(true);
                OutputStream os = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(os,"UTF-8"));
              String data = URLEncoder.encode("user","UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+"&"+
                      URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8")+"&"+
                      URLEncoder.encode("user_pass","UTF-8")+"="+URLEncoder.encode(user_pass,"UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                os.close();
                InputStream IS = httpURLConnection.getInputStream();
                IS.close();
                return "Registration Seccess...";
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(ctx,result,Toast.LENGTH_LONG).show();
    }
}