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Why do I have java.lang.NullPointerException at multiple libraries in Android in trying to Parse JSON

I am trying to parse a JSON format in my Android Application. I am fairly new in developing android applications so I am referring to a lot of tutorials. I followed the steps in this tutorial : http://mobilesiri.com/json-parsing-in-android-using-android-studio/
Here is my MainActivity.java class :
package com.example.carlajoyce.parsejson;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class MainActivity extends ListActivity {
private static String url = "http://tech.ccare.jrhernani.com/tech/workorders";
private static final String TAG_WORKORDERINFO = "workorders";
private static final String TAG_ID = "id";
private static final String TAG_SUBJECT = "subject";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_INITIATED = "initiated";
private static final String TAG_FINISHED = "finished";
private static final String TAG_CREATEDAT = "created_at";
private static final String TAG_UPDATEDAT = "updated_at";
private static final String TAG_TICKETID = "ticket_id";
private static final String TAG_CREATEDBYID = "createdBy_id";
private static final String TAG_TECHNICIANID = "technician_id";
private static final String TAG_WORKORDERREFID = "workorderref_id";
private static final String TAG_WORKORDERSTATUSID = "workorderstatus_id";
private static final String TAG_DEPARTMENTID = "department_id";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new GetWorkOrders().execute();
}
/**
*Async task class to get JSON by making HTTP call
*/
private class GetWorkOrders extends AsyncTask<Void, Void, Void> {
/*HashMap for ListView*/
ArrayList<HashMap<String, String>> workOrderList;
ProgressDialog pDialog;
#Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
#Override
protected Void doInBackground(Void... arg0) {
/*Creating service handler class instance*/
WebRequest webreq = new WebRequest();
/* Making a request to url and getting response*/
String jsonStr = webreq.makeWebServiceCall(url, WebRequest.GETRequest);
Log.d("Response: ", "> " + jsonStr);
workOrderList = ParseJSON(jsonStr);
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
/*Dismiss the progress dialog*/
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, workOrderList,
R.layout.list_item, new String[]{TAG_SUBJECT, TAG_DESCRIPTION}, new int[]{R.id.subject, R.id.description});
setListAdapter(adapter);
}
}
private ArrayList<HashMap<String, String>> ParseJSON(String json) {
if (json != null) {
try {
// Hashmap for ListView
ArrayList<HashMap<String, String>> workOrderList = new ArrayList<HashMap<String, String>>();
JSONObject jsonObj = new JSONObject(json);
// Getting JSON Array node
JSONArray workOrders = jsonObj.getJSONArray(TAG_WORKORDERINFO);
// looping through All WorkOrders
for (int i = 0; i < workOrders.length(); i++) {
JSONObject c = workOrders.getJSONObject(i);
String id = c.getString(TAG_ID);
String subject = c.getString(TAG_SUBJECT);
String description = c.getString(TAG_DESCRIPTION);
String initiated = c.getString(TAG_INITIATED);
String finished = c.getString(TAG_FINISHED);
String created_at = c.getString(TAG_CREATEDAT);
String updated_at = c.getString(TAG_UPDATEDAT);
String ticket_id = c.getString(TAG_TICKETID);
String createdBy_id = c.getString(TAG_CREATEDBYID);
String technician_id = c.getString(TAG_TECHNICIANID);
String workorderref_id = c.getString(TAG_WORKORDERREFID);
String workorderstatus_id = c.getString(TAG_WORKORDERSTATUSID);
String department_id = c.getString(TAG_DEPARTMENTID);
// tmp hashmap for single student
HashMap<String, String> workOrder = new HashMap<String, String>();
// adding each child node to HashMap key => value
workOrder.put(TAG_ID,id);
workOrder.put(TAG_SUBJECT, subject);
workOrder.put(TAG_DESCRIPTION, description);
workOrder.put(TAG_INITIATED, initiated);
workOrder.put(TAG_FINISHED, finished);
workOrder.put(TAG_CREATEDAT, created_at);
workOrder.put(TAG_UPDATEDAT, updated_at);
workOrder.put(TAG_TICKETID, ticket_id);
workOrder.put(TAG_CREATEDBYID, createdBy_id);
workOrder.put(TAG_TECHNICIANID, technician_id);
workOrder.put(TAG_WORKORDERREFID, workorderref_id);
workOrder.put(TAG_WORKORDERSTATUSID, workorderstatus_id);
workOrder.put(TAG_DEPARTMENTID, department_id);
// adding student to students list
workOrderList.add(workOrder);
}
return workOrderList;
} catch (JSONException e) {
e.printStackTrace();
return null;
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url.");
return null;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
I have a basic understanding of how the code works and I fixed some problems that occurred without having to ask here but I met a problem on I don't know where to begin. I am hoping you can tell me the reason for these errors:
02-16 17:51:31.294 6378-6378/com.example.carlajoyce.parsejson E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.carlajoyce.parsejson, PID: 6378
java.lang.NullPointerException
at android.widget.SimpleAdapter.getCount(SimpleAdapter.java:93)
at android.widget.ListView.setAdapter(ListView.java:480)
at android.app.ListActivity.setListAdapter(ListActivity.java:265)
at com.example.carlajoyce.parsejson.MainActivity$GetWorkOrders.onPostExecute(MainActivity.java:93)
at com.example.carlajoyce.parsejson.MainActivity$GetWorkOrders.onPostExecute(MainActivity.java:49)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:801)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:617)
at dalvik.system.NativeStart.main(Native Method)
NOTE: I also downloaded the code the tutorial provided and it works just fine.
Thanks in advance.

I think you should first initialize adapter and view with empty list, so move this:
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, workOrderList,
R.layout.list_item, new String[]{TAG_SUBJECT, TAG_DESCRIPTION}, new int[]{R.id.subject, R.id.description});
setListAdapter(adapter);
to onCreate() in MainActivity, and when job is finished - in onPostExecute() just notify adapter that data set changed.
adapter.notifyDataSetChanged();
Please let me know if it works for you.

It happens if the workOrderList is null.
You have to initialize this list before calling the constructor of your adapter.
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, workOrderList,
R.layout.list_item, new String[]{TAG_SUBJECT, TAG_DESCRIPTION}, new int[]{R.id.subject, R.id.description});
It happens because your ParseJSON (called in the doInBackground method) can return null

How to Set ImageView in AsyncTask

I understand that we cannot set ImageView in AsyncTask. But I need to add the ImageView into HashMap and the HashMap need to add into an ArrayList inside the for loop. I cannot do that in onPostExecute(). Does anyone know how to do?
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Base64;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class AllProductsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://192.168.1.132/retEqp.php";
ImageView iv;
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "equipments";
private static final String TAG_PID = "item_ID";
private static final String TAG_NAME = "item_Name";
private static final String TAG_DESC = "item_Desc";
private static final String TAG_LOC = "item_Location";
private static final String TAG_STATUS = "item_Status";
private static final String TAG_IMAGE = "item_Image";
// products JSONArray
JSONArray equipments = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
iv = (ImageView)findViewById(R.id.img2);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
// Starting new intent
Intent previousScreen = new Intent(getApplicationContext(), NewProductActivity.class);
//Sending the data to NewProductActivity
previousScreen.putExtra("id",pid);
setResult(1000, previousScreen);
finish();
// starting new activity and expecting some response back
}
});
}
// Response from Edit Product Activity
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
#Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
// Log.d("All Products: ", json.toString());
try {
equipments = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < equipments.length(); i++) {
JSONObject c = equipments.getJSONObject(i);
// Storing each json item in variable
String id = "ID: "+c.getString(TAG_PID);
String name = "Name: "+c.getString(TAG_NAME);
String desc = "Description: "+c.getString(TAG_DESC);
String loc = "Location: "+c.getString(TAG_LOC);
String status = "Status: "+c.getString(TAG_STATUS);
String image = c.getString(TAG_IMAGE);
byte[] rawImage = Base64.decode(image, Base64.DEFAULT);
Bitmap bmp12 = BitmapFactory.decodeByteArray(rawImage, 0, rawImage.length);
iv.setImageBitmap(bmp12);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
// map.put(TAG_IMAGE, rawImage.length);
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
map.put(TAG_DESC, desc);
map.put(TAG_LOC, loc);
map.put(TAG_STATUS, status);
map.put(TAG_IMAGE, iv.toString());
// adding HashList to ArrayList
productsList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AllProductsActivity.this, productsList,
R.layout.list_item, new String[] { TAG_IMAGE,TAG_PID,
TAG_NAME,TAG_DESC,TAG_LOC,TAG_STATUS},
new int[] {R.id.img,R.id.pid, R.id.name,R.id.desc,R.id.loc,R.id.status});
// updating listview
setListAdapter(adapter);
}
});
}
}
}

You can't access the UI in a background thread.
The idea behind AsyncTask is that doInBackground does the background work, then you can return something that will be passed as a parameter to onPostExecute which is executed in the main thread.
In this case you have to return the parsed model objects from doInBackground (I would create a custom class), receive in onPostExecute. Also, create a custom adapter, which will take care of creating views. You should generate bitmaps there (probably you have to put the parsing to bitmap in another async task).

JSON data not shown on second time an activity is opened

I have an activity that retreives objects from JSON.
The first time the activity is shown, all works fine.
But if the user goes forward and back and opens it again, then any data is shown.
This is my code:
package com.solinpromex.casajuventudtrescantos;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.StringTokenizer;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListView;
public class DondeEsta_T1_MainActivity extends Activity {
// Declare Variables
private static final String TAG_NAME = "nombreCategoria";
private static final String TAG_ID = "idPrueba";
private String name = "Categoria";
private String id = "id";
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
DondeEsta_T1_ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String ID_DES= "id_des";
static String TITULO_DES = "titulo_des";
static String CATEGORIAS_DES = "categoria_des";
static String LUGAR_DES = "lugar_des";
static String LATITUD_DES = "latitud_des";
static String LONGITUD_DES = "longitud_des";
static String IMAGEN_DES = "imagen_des";
static String DESCRIPCION_DES = "descripcion_des";
static String WEB_DES = "web_des";
static String MAIL_DES = "mail_des";
static String TEL_DES = "tel_des";
static String LUGAR_CORTO = "lugar_corto";
static String idPrueba = "idPrueba";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v("MVASCO", "context is null!");
// getting intent data
Intent in = getIntent();
// Get JSON values from previous intent
name = in.getStringExtra(TAG_NAME);
id = in.getStringExtra(TAG_ID);
idPrueba =in.getStringExtra(idPrueba);
setContentView(R.layout.dondeesta_t1_listview_main);
// Execute DownloadJSON AsyncTask
//new DownloadJSON().execute();
}
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
}
#Override
protected Void doInBackground(Void... params) {
// Create an array
// Log.v("categoria para pasar a la URL", id_categoria_donde_esta);
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL("http://.hidden url.../app_php_files/recuperar_categorias_donde_esta_t1.php?cat="+idPrueba);
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("Categorias");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("id_des", jsonobject.getString("id_des"));
map.put("titulo_des", jsonobject.getString("titulo_des"));
map.put("categoria_des", jsonobject.getString("categoria_des"));
map.put("lugar_des", jsonobject.getString("lugar_des"));
map.put("latitud_des", jsonobject.getString("latitud_des"));
map.put("longitud_des", jsonobject.getString("longitud_des"));
map.put("descripcion_des", jsonobject.getString("descripcion_des"));
map.put("web_des", jsonobject.getString("web_des"));
map.put("mail_des", jsonobject.getString("mail_des"));
map.put("imagen_des", "http://www.solinpromex.com/casajuventud/sitios/"+jsonobject.getString("imagen_des"));
map.put("tel_des", jsonobject.getString("tel_des"));
map.put("lugar_corto", jsonobject.getString("lugar_corto"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new DondeEsta_T1_ListViewAdapter(DondeEsta_T1_MainActivity.this, arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
}
}
#Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
new DownloadJSON().execute();
}
}
What am I doing wrong?

put this
Intent in = getIntent();
// Get JSON values from previous intent
name = in.getStringExtra(TAG_NAME);
id = in.getStringExtra(TAG_ID);
idPrueba =in.getStringExtra(idPrueba);
into the Method onResume then it should work i think
Take also a look in this overview of the Lifecycle of an Activity
http://www.android-app-market.com/wp-content/uploads/2012/03/Android-Activity-Lifecycle.png

List view activity showing objects only the first time it is opened

In my Android app I have a list view activity showing MySQL objects downloaded from a web server via JSON.
I have detected following issue: the first time the activity is shown, the JSON objects are shown fine, but if the user goes back to the previous activity and then opens the list view activity again, any object is shown on the list and no error is thrown.
I need your help to solve this issue. Here is the activity code:
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class ofertas_list extends ListActivity {
private ProgressDialog pDialog;
// JSON node keys
private static final String TAG_NAME = "nombreCategoria";
private static final String TAG_ID = "idCategoria";
private static final String TAG_CATEGORIAS = "Categorias";
// URL to get contacts JSON
private static String url = "http://xxxxxxxx/android_ofertaslist.php?id=";
// JSON Node names
private static final String TAG_NOMBREEMPRESA = "nombreEmpresa";
private static final String TAG_IDEMPRESA = "idEmpresa";
private static final String TAG_DESCRIPCIONEMPRESA = "descripcionEmpresa";
private static final String TAG_STRIMAGEN = "strImagen";
private static final String TAG_DIRECCIONEMPRESA = "direccionEmpresa";
private static final String TAG_TELEFONOEMPRESA = "telefonoEmpresa";
private static final String TAG_FACEBOOKEMPRESA = "facebookEmpresa";
private static final String TAG_EMAILEMPRESA = "emailEmpresa";
private static final String TAG_TEXTOOFERTA = "textoOferta";
private static final String TAG_HORARIOEMPRESA = "horarioEmpresa";
private static final String TAG_CATEGORIAEMPRESA = "categoriaEmpresa";
private static final String TAG_LATITUDEMPRESA = "latitudEmpresa";
private static final String TAG_LONGITUDEMPRESA = "longitudEmpresa";
private static final String TAG_VALORACIONEMPRESA = "valoracionEmpresa";
// contacts JSONArray
JSONArray contacts = null;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_categorias);
// getting intent data
Intent in = getIntent();
// JSON node keys
// Get JSON values from previous intent
String name = in.getStringExtra(TAG_NAME);
String email = in.getStringExtra(TAG_ID);
// URL to get contacts JSON
this.url = url+email;
this.setTitle(name);
contactList = new ArrayList<HashMap<String, String>>();
ListView lv = getListView();
// Listview on item click listener
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
//cambiar por los nuevos campos
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String cost = ((TextView) view.findViewById(R.id.email))
.getText().toString();
//Starting single contact activity
//cambiar por los nuevos campos
Intent in = new Intent(getApplicationContext(),
SingleContactActivity.class);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_ID, cost);
startActivity(in);
}
});
// Calling async task to get json
new GetContacts().execute();
}
/**
* Async task class to get json by making HTTP call
* */
private class GetContacts extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(ofertas_list.this);
pDialog.setMessage("Cargando datos...");
pDialog.setCancelable(false);
pDialog.show();
}
#Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
contacts = jsonObj.getJSONArray(TAG_CATEGORIAS);
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String nombreEmpresa = c.getString(TAG_NOMBREEMPRESA);
String descripcionEmpresa = c.getString(TAG_DESCRIPCIONEMPRESA);
String strImagen = c.getString(TAG_STRIMAGEN);
String direccionEmpresa = c.getString(TAG_DIRECCIONEMPRESA);
String telefonoEmpresa = c.getString(TAG_TELEFONOEMPRESA);
String facebookEmpresa = c.getString(TAG_FACEBOOKEMPRESA);
String emailEmpresa = c.getString(TAG_EMAILEMPRESA);
String textoOferta = c.getString(TAG_TEXTOOFERTA);
String horarioEmpresa = c.getString(TAG_HORARIOEMPRESA);
String categoriaEmpresa = c.getString(TAG_CATEGORIAEMPRESA);
String valoracionEmpresa = c.getString(TAG_VALORACIONEMPRESA);
String latitudEmpresa = c.getString(TAG_LATITUDEMPRESA);
String longitudEmpresa = c.getString(TAG_LONGITUDEMPRESA);
String idEmpresa = c.getString(TAG_IDEMPRESA);
// Phone node is JSON Object
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_IDEMPRESA, idEmpresa);
contact.put(TAG_NOMBREEMPRESA, nombreEmpresa);
contact.put(TAG_DESCRIPCIONEMPRESA,descripcionEmpresa);
contact.put(TAG_STRIMAGEN,strImagen);
contact.put(TAG_DIRECCIONEMPRESA,direccionEmpresa);
contact.put(TAG_TELEFONOEMPRESA,telefonoEmpresa);
contact.put(TAG_FACEBOOKEMPRESA,facebookEmpresa);
contact.put(TAG_EMAILEMPRESA,emailEmpresa);
contact.put(TAG_TEXTOOFERTA,textoOferta);
contact.put(TAG_HORARIOEMPRESA,horarioEmpresa);
contact.put(TAG_CATEGORIAEMPRESA,categoriaEmpresa);
contact.put(TAG_VALORACIONEMPRESA,valoracionEmpresa);
contact.put(TAG_LATITUDEMPRESA,latitudEmpresa);
contact.put(TAG_LONGITUDEMPRESA,longitudEmpresa);
// adding contact to contact list
contactList.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
ofertas_list.this, contactList,
R.layout.list_item_ofertas, new String[] { TAG_NOMBREEMPRESA, TAG_DIRECCIONEMPRESA}, new int[] { R.id.name,
R.id.email });
setListAdapter(adapter);
}
}
}
UPDATED CODE:
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class ofertas_list extends ListActivity {
private ProgressDialog pDialog;
// JSON node keys
private static final String TAG_NAME = "nombreCategoria";
private static final String TAG_ID = "idCategoria";
private static final String TAG_CATEGORIAS = "Categorias";
// URL to get contacts JSON
private static String url = "http://xxxxxxx/android_ofertaslist.php?id=";
// URL to get contacts JSON
// private static String url = "http://mujercanariasigloxxi.appgestion.eu/app_php_files/android_ofertaslist.php";
// JSON Node names
private static final String TAG_NOMBREEMPRESA = "nombreEmpresa";
private static final String TAG_IDEMPRESA = "idEmpresa";
private static final String TAG_DESCRIPCIONEMPRESA = "descripcionEmpresa";
private static final String TAG_STRIMAGEN = "strImagen";
private static final String TAG_DIRECCIONEMPRESA = "direccionEmpresa";
private static final String TAG_TELEFONOEMPRESA = "telefonoEmpresa";
private static final String TAG_FACEBOOKEMPRESA = "facebookEmpresa";
private static final String TAG_EMAILEMPRESA = "emailEmpresa";
private static final String TAG_TEXTOOFERTA = "textoOferta";
private static final String TAG_HORARIOEMPRESA = "horarioEmpresa";
private static final String TAG_CATEGORIAEMPRESA = "categoriaEmpresa";
private static final String TAG_LATITUDEMPRESA = "latitudEmpresa";
private static final String TAG_LONGITUDEMPRESA = "longitudEmpresa";
private static final String TAG_VALORACIONEMPRESA = "valoracionEmpresa";
#Override
public void onResume(){
super.onResume();
new GetContacts().execute();
}
// contacts JSONArray
JSONArray contacts = null;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_categorias);
// getting intent data
Intent in = getIntent();
// JSON node keys
// Get JSON values from previous intent
String name = in.getStringExtra(TAG_NAME);
String email = in.getStringExtra(TAG_ID);
// URL to get contacts JSON
this.url = url+email;
this.setTitle(name);
contactList = new ArrayList<HashMap<String, String>>();
ListView lv = getListView();
// Listview on item click listener
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
//cambiar por los nuevos campos
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String cost = ((TextView) view.findViewById(R.id.email))
.getText().toString();
//Starting single contact activity
//cambiar por los nuevos campos
Intent in = new Intent(getApplicationContext(),
SingleContactActivity.class);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_ID, cost);
startActivity(in);
}
});
// Calling async task to get json
new GetContacts().execute();
}
/**
* Async task class to get json by making HTTP call
* */
private class GetContacts extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(ofertas_list.this);
pDialog.setMessage("Cargando datos...");
pDialog.setCancelable(false);
pDialog.show();
}
#Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
contacts = jsonObj.getJSONArray(TAG_CATEGORIAS);
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String nombreEmpresa = c.getString(TAG_NOMBREEMPRESA);
String descripcionEmpresa = c.getString(TAG_DESCRIPCIONEMPRESA);
String strImagen = c.getString(TAG_STRIMAGEN);
String direccionEmpresa = c.getString(TAG_DIRECCIONEMPRESA);
String telefonoEmpresa = c.getString(TAG_TELEFONOEMPRESA);
String facebookEmpresa = c.getString(TAG_FACEBOOKEMPRESA);
String emailEmpresa = c.getString(TAG_EMAILEMPRESA);
String textoOferta = c.getString(TAG_TEXTOOFERTA);
String horarioEmpresa = c.getString(TAG_HORARIOEMPRESA);
String categoriaEmpresa = c.getString(TAG_CATEGORIAEMPRESA);
String valoracionEmpresa = c.getString(TAG_VALORACIONEMPRESA);
String latitudEmpresa = c.getString(TAG_LATITUDEMPRESA);
String longitudEmpresa = c.getString(TAG_LONGITUDEMPRESA);
String idEmpresa = c.getString(TAG_IDEMPRESA);
// Phone node is JSON Object
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_IDEMPRESA, idEmpresa);
contact.put(TAG_NOMBREEMPRESA, nombreEmpresa);
contact.put(TAG_DESCRIPCIONEMPRESA,descripcionEmpresa);
contact.put(TAG_STRIMAGEN,strImagen);
contact.put(TAG_DIRECCIONEMPRESA,direccionEmpresa);
contact.put(TAG_TELEFONOEMPRESA,telefonoEmpresa);
contact.put(TAG_FACEBOOKEMPRESA,facebookEmpresa);
contact.put(TAG_EMAILEMPRESA,emailEmpresa);
contact.put(TAG_TEXTOOFERTA,textoOferta);
contact.put(TAG_HORARIOEMPRESA,horarioEmpresa);
contact.put(TAG_CATEGORIAEMPRESA,categoriaEmpresa);
contact.put(TAG_VALORACIONEMPRESA,valoracionEmpresa);
contact.put(TAG_LATITUDEMPRESA,latitudEmpresa);
contact.put(TAG_LONGITUDEMPRESA,longitudEmpresa);
// adding contact to contact list
contactList.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
ofertas_list.this, contactList,
R.layout.list_item_ofertas, new String[] { TAG_NOMBREEMPRESA, TAG_DIRECCIONEMPRESA}, new int[] { R.id.name,
R.id.email });
setListAdapter(adapter);
}
}
}

You should probably perform the "new GetContacts().execute();" call in onResume(). See the Android documentation to get more familiar with the Android Activity lifecyle.
onCreate() is only called when the Activity is created. In your testing, the Activity is probably usually still alive, so onCreate() will not always be called when re-entering the Activity.

Put your new GetContacts().execute() in onResume() method.
onCreate() is called when you start Activity for the first time. If you leave activity, without killing it, and come back, your app goes thru onStart() ->onResume()`
Put onResume right before onCreate and remove new GetContacts().execute(); from onCreate().
...
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
#Override
public void onResume(){
super.onResume();
new GetContacts().execute();
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_categorias);
...

My aSyncTask is not working

my asynctask is not working. The dialog wont dismiss and the list is not being updated (i think because onPostExecute is not being called).I googled it, but without result.
package com.example.whs;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class Albums extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
// Array for the list
ArrayList<HashMap<String, String>> itemList;
// url to get the items
private static String url_all_products = "<my url here>";
// JSON variables
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
private static final String TAG_ITEMS = "items";
private static final String TAG_NAME = "name";
private static final String TAG_ID = "id";
private static final String TAG_USERNAME = "username";
//JSON array
JSONArray items = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_albums);
// HashMap for the items
itemList = new ArrayList<HashMap<String, String>>();
// Loading the items on the background
new LoadAllItems().execute();
// Get list-view
ListView lv = getListView();
// On item click
lv.setOnItemClickListener(new OnItemClickListener(){
public void onItemClick(AdapterView<?> parent, View view, int position, long id){
//do
}
});
}
// class for loading all items
class LoadAllItems extends AsyncTask<String, String, String> {
// Before
#Override
protected void onPreExecute(){
super.onPreExecute();
pDialog = new ProgressDialog(Albums.this);
pDialog.setMessage("Albums laden...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
// Get the products
#Override
protected String doInBackground(String... params) {
// Build Parameters
List<NameValuePair> params1 = new ArrayList<NameValuePair>();
//Get the JSON string
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params1);
// Check for response
Log.d("All Items: ", json.toString());
try {
// check for success tag
int success = json.getInt(TAG_SUCCESS);
if(success == 1) {
// found the items
items = json.getJSONArray(TAG_ITEMS);
// loop through the items
for (int i = 0; items.length() > i; i++){
// Get the item in variable c
JSONObject c = items.getJSONObject(i);
// Store in a variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String username = c.getString(TAG_USERNAME);
if(username == ""){
username = "onbekend";
}
// Create the HashMap
HashMap<String, String> map = new HashMap<String, String>();
// add it
map.put(TAG_ID, id);
map.put(TAG_USERNAME, username);
map.put(TAG_NAME, name);
// to arraylist
itemList.add(map);
}
}else{
// nothing found
Intent i = new Intent(getApplicationContext(), Index.class);
// close the previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e){
e.printStackTrace();
}
return null;
}
}
protected void onPostExecute(String result){
// dismiss dialog
pDialog.dismiss();
runOnUiThread(new Runnable(){
public void run(){
// Add adapter to the list
MenuAdapter adapter = new MenuAdapter(Albums.this, itemList);
ListView list = (ListView)findViewById(R.id.list);
list.setAdapter(adapter);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.albums, menu);
return true;
}
}
the loop is working correctly.
How to fix this?

1) you are trying to start an activity within the background thread, don't do this.
2) you are probably getting a json exception, just log more things so you can see what is happening
these may be why it never reaches onPostExecute

you can not perform UI related action in doInBackGround(), like you are strating a new activity in doInBaclground,
Intent i = new Intent(getApplicationContext(), Index.class);
// close the previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);