Android - JSON mySQL query gives NetworkOnMainThreadException

Question

I am trying to run this activity in order to query a database for populating a table. I have tried to follow a snippet I found online, the only problem is, no matter what, I get "connectionandroid.os.NetworkOnMainThreadException" error.

I have tried to put in an handler, as suggested in many forums, using AsyncTask and do it in background, but still nothing. I know the error appears when a long query is sent to a database, but this query takes 0.1s, probably. I have the db locally, although accessing it with public IP, and the db is extremely small.

Here my PHP code:

<?php

$hostname_localhost ="localhost";
$database_localhost ="DB";
$username_localhost ="root";
$password_localhost ="pwd";

mysql_connect($hostname_localhost,$username_localhost,$password_localhost);

mysql_select_db($database_localhost);

$sql=mysql_query("select * from friendlist where Id1 = 1");
while($row=mysql_fetch_assoc($sql))
$output[]=$row;
print(json_encode($output));
mysql_close();
?>

The code works, as if I go to the page, I see displayed the results (I only have 3 rows for the moment).

Here is the java part:

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.net.ParseException;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

public class MySQLAndroidActivity extends ListActivity {

JSONArray jArray;
String result = null;
InputStream is = null;
StringBuilder sb=null;
HttpResponse response;
HttpEntity entity;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
//http post
try{
HttpClient httpclient = new DefaultHttpClient();

 HttpPost httppost = new HttpPost("http://X.X.X.X/test.php");

 httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
response = httpclient.execute(httppost);

 entity = response.getEntity();


 is = entity.getContent();

 }catch(Exception e){
     Log.e("log_tag", "Error in http connection"+e.toString());
     System.exit(1);
}

//convert response to string
try{
  BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
   sb = new StringBuilder();
   sb.append(reader.readLine() + "\n");

   String line="0";
   while ((line = reader.readLine()) != null) {
                  sb.append(line + "\n");
    }
    is.close();
    result=sb.toString();
    }catch(Exception e){
          Log.e("log_tag", "Error converting result "+e.toString());
    }
//parsing data
String idfriend;
String id1;
String id2;
try{
  jArray = new JSONArray(result);
  JSONObject json_data=null;
  for(int i=0;i<jArray.length();i++){
         json_data = jArray.getJSONObject(i);
         idfriend=json_data.getString("Idfriend");
         id1=json_data.getString("Id1");
         id2=json_data.getString("Id2");


         System.out.println("id1: " + id1);
     }
  }
  catch(JSONException e1){
   Toast.makeText(getBaseContext(), "No Id found" ,Toast.LENGTH_LONG).show();
  } catch (ParseException e1) {
   e1.printStackTrace();
 }
}
}

I tried also using a simple Activity and not a ListActivity.

I have an almost similar code, but that one uses a different method. In fact, it doesnt get the result, on php, it just returns a characters whether there are 0 or more rows retrieved. In this case I need something on a higher level, as I will need to get the values of some specific fields.

EDIT:

As requested, the stacktrace:

  Error in http connectionandroid.os.NetworkOnMainThreadException
  04-17 06:44:17.921: W/System.err(24207): java.lang.Exception
  04-17 06:44:17.921: W/System.err(24207):  at       com.mysql.android.MySQLAndroidActivity.onCreate(MySQLAndroidActivity.java:56)
  04-17 06:44:17.921: W/System.err(24207):  at       android.app.Activity.performCreate(Activity.java:4465)
  04-17 06:44:17.921: W/System.err(24207):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
  04-17 06:44:17.921: W/System.err(24207):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
  04-17 06:44:17.921: W/System.err(24207):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
  04-17 06:44:17.921: W/System.err(24207):  at android.app.ActivityThread.access$600(ActivityThread.java:123)
  04-17 06:44:17.921: W/System.err(24207):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
  04-17 06:44:17.921: W/System.err(24207):  at android.os.Handler.dispatchMessage(Handler.java:99)
  04-17 06:44:17.921: W/System.err(24207):  at android.os.Looper.loop(Looper.java:137)
  04-17 06:44:17.931: W/System.err(24207):  at android.app.ActivityThread.main(ActivityThread.java:4424)
  04-17 06:44:17.931: W/System.err(24207):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-17 06:44:17.931: W/System.err(24207):  at java.lang.reflect.Method.invoke(Method.java:511)
  04-17 06:44:17.931: W/System.err(24207):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
  04-17 06:44:17.931: W/System.err(24207):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
  04-17 06:44:17.931: W/System.err(24207):  at dalvik.system.NativeStart.main(Native Method)

EDIT2:

Here is something very similar to the version I did with the AsyncTask (I am creating it on the fly, without a compiler, so it might not be perfect; but it is very similar to the one I did before):

  @Override
   public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);

      new LoadTask().execute();

  }



 private class LoadTask extends AsyncTask<Void, Integer, Void> {
            @Override
            protected void onPreExecute() {

            }

            @Override
            protected Void doInBackground(Void... params) {
                    synchronized (this) {

                    Looper.prepare();       
                    doStuff() //this method basically contains what it is inside the onCreate.

                    }

                    return null;
            }

       }
       }

- I recall that I was forced to use 'Looper.prepare();'. So I added it before 'doStuff();'

EDIT 2:

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.net.ParseException;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Looper;
import android.util.Log;
import android.widget.Toast;

public class MySQLAndroidActivity extends ListActivity {

    JSONArray jArray;
    String result = null;
    InputStream is = null;
    StringBuilder sb = null;
    HttpResponse response;
    HttpEntity entity;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);


        new LoadTask.execute();

    }



    private class LoadTask extends AsyncTask < Void, Integer, Void > {@Override
        protected void onPreExecute() {

        }

        @Override
        protected Void doInBackground(Void...params) {

            Looper.prepare();

            doStuff();



            return null;


        }
    }


    public void doStuff() {
        ArrayList < NameValuePair > nameValuePairs = new ArrayList < NameValuePair > ();
        //http post
        try {
            HttpClient httpclient = new DefaultHttpClient();

            HttpPost httppost = new HttpPost("http://X.X.X.X/test.php");

            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            response = httpclient.execute(httppost);

            entity = response.getEntity();


            is = entity.getContent();

        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection" + e.toString());
            System.exit(1);
        }


        //convert response to string
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
            sb = new StringBuilder();
            sb.append(reader.readLine() + "\n");

            String line = "0";
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            result = sb.toString();
        } catch (Exception e) {
            Log.e("log_tag", "Error converting result " + e.toString());
        }
        //parsing data
        String idfriend;
        String id1;
        String id2;
        try {
            jArray = new JSONArray(result);
            JSONObject json_data = null;

            System.out.println("Length " + jArray.length());
            Log.d("DB", "Length " + jArray.length());

            for (int i = 0; i < jArray.length(); i++) {

                System.out.println("counter " + i);
                json_data = jArray.getJSONObject(i);
                idfriend = json_data.getString("Idfriend");
                id1 = json_data.getString("Id1");
                id2 = json_data.getString("Id2");


                System.out.println("id1: " + id1);
            }
        } catch (JSONException e1) {
            Log.d("DB", "Error somewhere");
        } catch (ParseException e1) {
            e1.printStackTrace();
        }
    }
}

Thanks in advance,

N.

Answer 1

You should read abou model-view-controller pattern (look it up in google). This pattern defines that you should implement separately the view (user interfaces) from model (database accesses. Read about Dao pattern) and from controller (the logic that runs the application, for example these are the main classes).

Hope this helps you!

Answer 2

I heard that starting from ICS, it is not allowed to perform network operations on UI (main) thread. Therefore, you must need to perform this operation in a separate thread. So either use AsyncTask, Thread or HandlerThread with Looper and Handler to perform web operation. If you try it on a device running froyo or gingerbread, it would be fine but not on ICS.

Regarding your attempt to run it via handler or AsyncTask, it depends on how you did it. Paste that code so i see the problem.

---

Update

public class MySQLAndroidActivity extends ListActivity {

    private static final String url = "http://X.X.X.X/test.php";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity2);

        LoadTask t = new LoadTask();
        t.execute(null);

    }

    private static class LoadTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {

        }

        @Override
        protected Void doInBackground(Void... params) {
            doStuff();

            return null;
        }
    }





    public static void doStuff() {
        JSONArray jArray;
        String result = null;
        InputStream is = null;
        StringBuilder sb = null;
        HttpResponse response;
        HttpEntity entity;

        ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
        // http post
        try {
            HttpClient httpclient = new DefaultHttpClient();

            HttpPost httppost = new HttpPost(url);

            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            response = httpclient.execute(httppost);

            entity = response.getEntity();

            is = entity.getContent();

        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection" + e.toString());
            System.exit(1);
        }

        // convert response to string
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
            sb = new StringBuilder();
            sb.append(reader.readLine() + "\n");

            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
            is.close();
            result = sb.toString();

            Log.i("json string", result);
        } catch (Exception e) {
            Log.e("log_tag", "Error converting result " + e.toString());
        }


        // parsing data
        String idfriend;
        String id1;
        String id2;
        try {
            jArray = new JSONArray(result);
            JSONObject json_data = null;

            System.out.println("Length " + jArray.length());
            Log.d("DB", "Length " + jArray.length());

            for (int i = 0; i < jArray.length(); i++) {

                System.out.println("counter " + i);
                json_data = jArray.getJSONObject(i);
                idfriend = json_data.getString("idfriend");
                id1 = json_data.getString("id1");
                id2 = json_data.getString("id2");

                System.out.println("id1: " + id1);
            }
        } catch (JSONException e1) {
            Log.d("DB", "Error somewhere");
        } catch (ParseException e1) {
            e1.printStackTrace();
        }
    }

}

*There were some method calling issues and the most important was that you were fetching keys out from JSONObject as Idfriend, Id1, Id2 which is wrong because in your json string the keys are like idfriend, id1, id2. Its case-sensitive, thats why it was crashing.