Error on fetching data from Mysql DB with JSON and PHP

I am learning to build android applications and I need some help whit getting data from MySQL. I followed this tutorial to do it but I get this error:

Error org.json.JSONEXception: Value of type java.lang.String cannot be converted to JSONObject

On my MainActivity I have one button which when is clicked open second activity. The second activity must get and show data from DB. This is the code of second activity Restaurant.java

public class Restaurants extends Activity {
     private String jsonResult;
     private String url = "http://10.0.2.2/app1/GetRestaurants.php";
     private ListView listView;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.restaurants);
         listView = (ListView) findViewById(R.id.listView1);
         accessWebService();
     }

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

    // Async Task to access the web
    private class JsonReadTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... params) {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(params[0]);
    try {
        HttpResponse response = httpclient.execute(httppost);
        jsonResult = inputStreamToString(
        response.getEntity().getContent()).toString();
    }

    catch (ClientProtocolException e) {
           e.printStackTrace();
    } catch (IOException e) {
           e.printStackTrace();
      }
    return null;
 }

 private StringBuilder inputStreamToString(InputStream is) {
     String rLine = "";
     StringBuilder answer = new StringBuilder();
     BufferedReader rd = new BufferedReader(new InputStreamReader(is));

 try {
    while ((rLine = rd.readLine()) != null) {
    answer.append(rLine);
 }
}

 catch (IOException e) {
 // e.printStackTrace();
    Toast.makeText(getApplicationContext(),
    "Error..." + e.toString(), Toast.LENGTH_LONG).show();
 }
    return answer;
 }

     @Override
     protected void onPostExecute(String result) {
     ListDrwaer();
   }
 }// end async task

 public void accessWebService() {
    JsonReadTask task = new JsonReadTask();
    // passes values for the urls string array
    task.execute(new String[] { url });
 }

 // build hash set for list view
 public void ListDrwaer() {
     List<Map<String, String>> restaurantList = new ArrayList<Map<String, String>>();

 try {
     JSONObject jsonResponse = new JSONObject(jsonResult);
     JSONArray jsonMainNode = jsonResponse.optJSONArray("restoranti");

     for (int i = 0; i < jsonMainNode.length(); i++) {
     JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
     String name = jsonChildNode.optString("name");
     String menu = jsonChildNode.optString("menu");
     String outPut = name + "-" + menu;
     restaurantList.add(createRestaurants("restoranti", outPut));
   }
 } catch (JSONException e) {
      Toast.makeText(getApplicationContext(), "Error " + e.toString(),
      Toast.LENGTH_SHORT).show();
  }

 SimpleAdapter simpleAdapter = new SimpleAdapter(this, restaurantList,
    android.R.layout.simple_list_item_1,
    new String[] { "restoranti" }, new int[] { android.R.id.text1 });
    listView.setAdapter(simpleAdapter);
 }

 private HashMap<String, String> createRestaurants(String name, String menu) {
      HashMap<String, String> restaurantNameNo = new HashMap<String, String>();
      restaurantNameNo.put(name, menu);
      return restaurantNameNo;
 }
}

This is the restaurants.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="14dp" >
</ListView>

Please let me know if need to post some more code. Many thank's for help.

I also found this answer to the post which is almost similar and tried to make the same but didn't work for me. Same error and blank page.