I am new to Android programming. I have gone through most of the Android developer docs by Google. Here is my question:

What i am trying to do: From the first Login page of my app, I am trying to fetch a json file located in a server and parse the results to check whether the login was successful or not.
I am unable to parse the json in the following class. Please suggest what is wrong. I have checked all the other questions from past few days on stackoverflow but not much help. please help.

LoginActivity.java

```
package com.practice.serverdashboard;

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.app.Service;
import android.content.Context;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.EditText;
import android.widget.Toast;

public class LoginActivity extends Activity {

    public EditText username;
    private EditText password;

    private static final String TAG = "MyActivity";

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

        username = (EditText) findViewById(R.id.txt_username);   
        password = (EditText) findViewById(R.id.txt_password);   

        //Showing the keypad
         InputMethodManager mgr = (InputMethodManager)this.getSystemService(Service.INPUT_METHOD_SERVICE);
         mgr.showSoftInput(username, InputMethodManager.SHOW_IMPLICIT);     
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_login, menu);
        return true;
    }

    public void callLoginService(View v)
    {
        //Hidding the keypad
        InputMethodManager mgr = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
        mgr.hideSoftInputFromWindow(username.getWindowToken(), 0);
        mgr.hideSoftInputFromWindow(password.getWindowToken(), 0);

        String loginUrlString="http://freakageekinternaltest.com:2200/mgmt/JSP/login.jsp?userId="+username.getText()+"&pws="+password.getText();
        Log.e("log_tag", "The URL is :: "+loginUrlString);
        //calling the login URL
        //GetJson gJ=new GetJson();
        //gJ.execute(loginUrlString);
        JSONObject json=getJSONfromURL(loginUrlString);

        AlertDialog.Builder adb = new AlertDialog.Builder(
                LoginActivity.this);
                adb.setTitle("Login Service");
                adb.setMessage("Testing...");
                adb.setPositiveButton("Ok", null);
                adb.show(); 

    }

public JSONObject getJSONfromURL(String url){

    //initialize
    InputStream is = null;
    String result = "";
    JSONObject jArray = null;

    //http post
    try{
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

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

    //convert response to string
    try{
        BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        result=sb.toString();

        Log.e("log_tag", "result is:: "+result);

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

    //try parse the string to a JSON object
    try{
            jArray = new JSONObject(result);
    }catch(JSONException e){
        Log.e("log_tag", "Error parsing data "+e.toString());
    }

    AlertDialog.Builder adb = new AlertDialog.Builder(
            LoginActivity.this);
            adb.setTitle("Login Service");
            adb.setMessage("Success...");
            adb.setPositiveButton("Ok", null);
            adb.show(); 

    return jArray;
}

}

```

Here is the logcat output:

```
02-13 11:13:15.173: E/log_tag(6083): The URL is :: http://freakageekinternaltest.com:2200/mgmt/JSP/login.jsp?userId=test567&pws=test@pps
02-13 11:13:15.183: E/log_tag(6083): Error in http connection android.os.NetworkOnMainThreadException
02-13 11:13:15.183: E/log_tag(6083): Error converting result java.lang.NullPointerException: lock == null
02-13 11:13:15.183: E/log_tag(6083): Error parsing data org.json.JSONException: End of input at character 0 of 

```

I have checked out the AsyncTask also, because of the NetworkOnMainThreadException exception( with help from stackoverflow). But i dont know where to start and how to use Async class in my LoginActivity.java class. Please help. Thanking you in advacnce.

Here is the json that i am trying to fetch from a server and parse:

```
{"LOGIN":"TRUE","userId":"Web Administrator","userAccessType":"ALL"}

```

@gabe: thx for ur early reply gabe. Is it mandatory to do networking operations in the background? Since i am trying to fetch login details from server, what will my app will do when it just sits there waiting for the server response? Also, considering my above code, what to do to implement AsyncTask class? I have gone through the docs mentioned by u. But i tried making a new class which extends AsyncTask. In that class, i did all the networking operation in the doInBackground method and thn used the onPostExecute method to send back the results to LoginActivity.java class. However, since this background operations are done on a new class which extends the AsyncTask class, so i am unable to use the controls defined in my main\_activity.xml file. So how to implement all this? Thx again.

Hello again!
Now i have modified my code as suggested in the answers.

```
private class RetreiveDataAsynctask extends AsyncTask<String,Void,JSONObject> {

        @Override
        protected JSONObject doInBackground(String... loginURL) {
            JSONObject obj = getJSONfromURL(loginURL);
            return obj;
        }

        @Override
        protected void onPostExecute(JSONObject obj) {
             //Do all ur UI related stuff as this will be executing in ui thread

            super.onPostExecute(obj);
        }

    }

```

And in the onCreate method, i am calling like this:

```
RetreiveDataAsynctask mRetreiveData = new RetreiveDataAsynctask();
        mRetreiveData.execute(loginUrlString);

```

But, its giving error in this line:

```
JSONObject obj = getJSONfromURL(loginURL);

```

Can somebody tell me what is wrong with this code? The rest of the parsing functions remains same as specified above.
Thx in advance.