Develop Reference

Unable to parse JSON data into Listview

im trying to parse data from SQL Database into Listview.
My PHP script is working because if i run it in the browser i get the content.
If im trying to get the data from my SQL Databse into the listview my app shows nothing.
Here is my MainActivity:
public class Locations extends AppCompatActivity implements AdapterView.OnItemClickListener {
ArrayList<productforloc> arrayList;
ListView lv;
private String TAG = Locations.class.getSimpleName();
private TextView addressField; //Add a new TextView to your activity_main to display the address
private LocationManager locationManager;
private String provider;
int i = 1;
private ProgressDialog pDialog;
String name;
// URL to get contacts JSON
private static String url = "Mylink";
ArrayList<HashMap<String, String>> contactList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.content_main);
Intent i = getIntent();
String cityname = i.getExtras().getString("cityname");
TextView city = (TextView) findViewById(R.id.ort);
city.setText(cityname);
pDialog = new ProgressDialog(Locations.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(true);
pDialog.show();
arrayList = new ArrayList<>();
lv = (ListView) findViewById(R.id.lv);
lv.setOnItemClickListener((AdapterView.OnItemClickListener) this);
runOnUiThread(new Runnable() {
#Override
public void run() {
new ReadJSON().execute(url);
}
});
final ImageButton filteropen = (ImageButton) findViewById(R.id.aufklaupen);
filteropen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
RelativeLayout filter = (RelativeLayout) findViewById(R.id.filterloc);
filter.setVisibility(View.VISIBLE);
ImageButton filterclose = (ImageButton) findViewById(R.id.zuklappen);
filterclose.setVisibility(View.VISIBLE);
filteropen.setVisibility(View.INVISIBLE);
}
});
final ImageButton filterclose = (ImageButton) findViewById(R.id.zuklappen);
filterclose.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
RelativeLayout filter = (RelativeLayout) findViewById(R.id.filterloc);
filter.setVisibility(View.INVISIBLE);
ImageButton filteropen = (ImageButton) findViewById(R.id.aufklaupen);
filteropen.setVisibility(View.VISIBLE);
filterclose.setVisibility(View.INVISIBLE);
}
});
}
class ReadJSON extends AsyncTask<String,Integer,String> {
#Override
protected String doInBackground(String... params) {
return readURL(params[0]);
}
#Override
protected void onPostExecute(String content) {
try{
JSONObject jo = new JSONObject(content);
JSONArray ja = jo.getJSONArray("contacts");
for(int i=0;i<ja.length();i++){
JSONObject po = ja.getJSONObject(i);
arrayList.add(new productforloc(
po.getString("imageurl"),
po.getString("name"),
po.getString("street"),
po.getString("postalcode"),
po.getString("musicstyle"),
po.getString("musicsecond"),
po.getString("entry"),
po.getString("opening"),
po.getString("agegroup"),
po.getString("urlbtn"),
po.getString("Fsk"),
po.getString("city"),
po.getString("bg")
));
}
} catch (JSONException e) {
e.printStackTrace();
}
final CustomListAdapterforloc adapter = new CustomListAdapterforloc(getApplicationContext(),R.layout.model,arrayList);
lv.setAdapter(adapter);
if(pDialog.isShowing()){
pDialog.dismiss();
}
}
}
private String readURL(String url){
StringBuilder content = new StringBuilder();
try{
URL uri = new URL(url);
URLConnection urlConnection = uri.openConnection();
BufferedReader bufferedReader= new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
String line;
while((line = bufferedReader.readLine()) !=null){
content.append(line+"\n");
}
bufferedReader.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return content.toString();
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
productforloc pForloc = arrayList.get(position);
Intent intent = new Intent();
intent.setClass(this,DetailActivity.class);
intent.putExtra("name",pForloc.getName());
intent.putExtra("imageurl",pForloc.getImage());
intent.putExtra("street",pForloc.getStreet());
intent.putExtra("postalcode",pForloc.getPostalcode());
intent.putExtra("entry",pForloc.getEntry());
intent.putExtra("agegroup",pForloc.getAgegroup());
intent.putExtra("opening",pForloc.getOpening());
intent.putExtra("urlbtn",pForloc.getUrlbtn());
intent.putExtra("Fsk",pForloc.getFsk());
intent.putExtra("city",pForloc.getCity());
intent.putExtra("musicstyle",pForloc.getMusicstyle());
intent.putExtra("musicsecond",pForloc.getMusicsecond());
intent.putExtra("bg",pForloc.getBg());
startActivity(intent);
}
/**
* Async task class to get json by making HTTP call
}
*/
}
and here is my Customlistadapter Activity:
public class CustomListAdapterforloc extends ArrayAdapter<productforloc>{
ArrayList<productforloc> products;
Context context;
int resource;
public CustomListAdapterforloc(Context context, int resource, List<productforloc> products) {
super(context, resource, products);
this.products = (ArrayList<productforloc>) products;
this.context = context;
this.resource = resource;
}
#NonNull
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView== null){
LayoutInflater layoutInflater = (LayoutInflater) getContext().getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
convertView = layoutInflater.inflate(R.layout.model,null,true);
}
productforloc product = getItem(position);
ImageView imageView = (ImageView) convertView.findViewById(R.id.imagelist);
Picasso.with(context).load(product.getImage()).into(imageView);
TextView txtName= (TextView) convertView.findViewById(R.id.namelist);
txtName.setText(product.getName());
return convertView;
}
}

i solved it using this code in my MAinActivity:
public class Locations extends AppCompatActivity {
private String TAG = Locations.class.getSimpleName();
private ProgressDialog pDialog;
private ListView lv;
// URL to get contacts JSON
private static String url = "http://partypeople.bplaced.net/loli.php";
ArrayList<HashMap<String, String>> contactList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
contactList = new ArrayList<>();
lv = (ListView) findViewById(R.id.lv);
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(Locations.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
#Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url);
Log.e(TAG, "Response from url: " + jsonStr);
if (jsonStr != null) {
try {
JSONArray contacts = new JSONArray(jsonStr);
// Getting JSON Array node
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String id = c.getString("id");
String name = c.getString("name");
String email = c.getString("email");
String address = c.getString("address");
String gender = c.getString("gender");
// tmp hash map for single contact
HashMap<String, String> contact = new HashMap<>();
// adding each child node to HashMap key => value
contact.put("id", id);
contact.put("name", name);
contact.put("email", email);
// adding contact to contact list
contactList.add(contact);
}
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json parsing error: " + e.getMessage(),
Toast.LENGTH_LONG)
.show();
}
});
}
} else {
Log.e(TAG, "Couldn't get json from server.");
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Couldn't get json from server. Check LogCat for possible errors!",
Toast.LENGTH_LONG)
.show();
}
});
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**3
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
Locations.this, contactList,
R.layout.model, new String[]{"name", "email",
"mobile"}, new int[]{R.id.namelist,
});
lv.setAdapter(adapter);
}
}
and used in my CustomlistadapterActivity:
public class HttpHandler {
private static final String TAG = HttpHandler.class.getSimpleName();
public HttpHandler() {
}
public String makeServiceCall(String reqUrl) {
String response = null;
try {
URL url = new URL(reqUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
// read the response
InputStream in = new BufferedInputStream(conn.getInputStream());
response = convertStreamToString(in);
} catch (MalformedURLException e) {
Log.e(TAG, "MalformedURLException: " + e.getMessage());
} catch (ProtocolException e) {
Log.e(TAG, "ProtocolException: " + e.getMessage());
} catch (IOException e) {
Log.e(TAG, "IOException: " + e.getMessage());
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
}
return response;
}
private String convertStreamToString(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line;
try {
while ((line = reader.readLine()) != null) {
sb.append(line).append('\n');
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
}
Thanks for your input

Override getCount method into adapter class.

java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()

public class MainActivity extends AppCompatActivity {
ListView lv;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv=(ListView)findViewById(R.id.list_id);
new JsonTask().execute("https://www.dropbox.com/s/o8yqrfm08wfdh48/Hotels.txt?dl=0");
}
class JsonTask extends AsyncTask<String,String ,List<MovieModels>>{
#Override
protected List<MovieModels> doInBackground(String...Params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
URL url = new URL(Params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream= connection.getInputStream();
reader=new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer =new StringBuffer();
String line="";
while ((line=reader.readLine())!=null){
buffer.append(line);
}
String finaljson = buffer.toString();
JSONObject parentObject = new JSONObject(finaljson);
JSONArray parentArray =parentObject.getJSONArray("Hotels");
List<MovieModels> modelsList=new ArrayList<>();
for (int i=0; i<parentArray.length();i++) {
JSONObject finalobject = parentArray.getJSONObject(i);
MovieModels models= new MovieModels();
models.setImage(finalobject.getString("Image"));
models.setHotel_Name(finalobject.getString("Hotel_Name"));
modelsList.add(models);
}
return modelsList;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(List<MovieModels> result) {
super.onPostExecute(result);
Adapter adapter=new Adapter(getApplicationContext(),R.layout.row,result);
lv.setAdapter(adapter);
//to do set the data into list
}
}
public class Adapter extends ArrayAdapter{
private List<MovieModels> modelsList;
private int resource;
private LayoutInflater inflater;
public Adapter(Context context, int resource, List<MovieModels> objects) {
super(context, resource, objects);
modelsList= objects;
this.resource=resource;
inflater=(LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView==null){
convertView=inflater.inflate(R.layout.row,null);
}
ImageView imageView;
TextView textView;
imageView=(ImageView)convertView.findViewById(R.id.image_id);
textView=(TextView)convertView.findViewById(R.id.text_id);
ImageLoader.getInstance().displayImage(modelsList.get(position).getImage(),imageView);
textView.setText("Hotel_Name-"+modelsList.get(position).getHotel_Name());
return convertView;
}
}}
I have an error in the set adapter class, could anyone advise?

Create a class for your MovieModels like this:
public class MovieModels(){
private String imagePath, hotelName;
public MovieModels(String imagePath, String hotelName){
this.imagePath = imagePath;
this.hotelName = hotelName;
}
public String getImagePath(){
return imagePath;
}
public String getHotelName(){
return hotelName;
}
public void setImagePath(String imagePath){
this.imagePath = imagePath;
}
public void setHotelName(String hotelName){
this.hotelName = hotelName;
}
}
and then modify your doInBackground() method like this:
#Override
protected List<MovieModels> doInBackground(String...Params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
List<MovieModels> modelsList=new ArrayList<>();
try {
URL url = new URL(Params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream= connection.getInputStream();
reader=new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer =new StringBuffer();
String line="";
while ((line=reader.readLine())!=null){
buffer.append(line);
}
String finaljson = buffer.toString();
JSONObject parentObject = new JSONObject(finaljson);
JSONArray parentArray =parentObject.getJSONArray("Hotels");
for (int i=0; i<parentArray.length();i++) {
JSONObject finalobject = parentArray.getJSONObject(i);
String image = finalobject.getString("Image");
String hotelName = finalobject.getString("Hotel_Name");
modelsList.add(new MovieModels(image, hotelName));
}
return modelsList;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
and your postExecute() like this:
#Override
protected void onPostExecute(List<MovieModels> result) {
super.onPostExecute(result);
if (result == null) {
Log.e("MY APPLICATION", "No result to display");
}
Adapter adapter=new Adapter(getApplicationContext(),R.layout.row,result);
lv.setAdapter(adapter);
//to do set the data into list
}
Hope it helps!!!

You return null in your doInBackground and then sets it to the adapter.
You have 2 options to solve it:
Return an empty Array e.g return new ArrayList<>(); instead of return null
or
Check don't set the adapter in case its null. e.g:
#Override
protected void onPostExecute(List<MovieModels> result) {
super.onPostExecute(result);
if (result == null) {
//todo handle no result
return;
}
Adapter adapter=new Adapter(getApplicationContext(),R.layout.row,result);
lv.setAdapter(adapter);
//to do set the data into list
}
}
Edit:
In addition, as said in the comments, your JSON Key you are trying to get ("Hotel_Name") is not like the one of the JSON itself (its "Hotel Name" in the JSON). After you fix that you will see the list, though its still important to solve the exception first.

How to parse JSON dat with HTTP Post method in android studio

JSONParser.class
package com.example.diptiagravat.myapplication;
public class JSONParser {
public String getJSON(String url, int timeout) {
HttpURLConnection c = null;
try {
URL u = new URL(url);
c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.setRequestProperty("Content-length", "0");
c.setUseCaches(false);
c.setAllowUserInteraction(false);
c.setConnectTimeout(timeout);
c.setReadTimeout(timeout);
c.connect();
int status = c.getResponseCode();
switch (status) {
case 200:
case 201:
BufferedReader br = new BufferedReader(new InputStreamReader(c.getInputStream()));
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
br.close();
return sb.toString();
}
} catch (MalformedURLException ex) {
Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);
} finally {
if (c != null) {
try {
c.disconnect();
} catch (Exception ex) {
Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);
}
}
}
return null;
}
public String sendHTTPData(String urlpath, String id) {
HttpURLConnection connection = null;
try {
URL url=new URL(urlpath);
connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setDoInput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/json");
connection.setRequestProperty("Accept", "application/json");
OutputStreamWriter streamWriter = new OutputStreamWriter(connection.getOutputStream());
streamWriter.write(id);
streamWriter.flush();
StringBuilder stringBuilder = new StringBuilder();
if (connection.getResponseCode() == HttpURLConnection.HTTP_OK){
InputStreamReader streamReader = new InputStreamReader(connection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(streamReader);
String response = null;
while ((response = bufferedReader.readLine()) != null) {
stringBuilder.append(response + "\n");
}
bufferedReader.close();
Log.d("test", stringBuilder.toString());
return stringBuilder.toString();
} else {
Log.e("test", connection.getResponseMessage());
return null;
}
} catch (Exception exception){
Log.e("test", exception.toString());
return null;
} finally {
if (connection != null){
connection.disconnect();
}
}
}
}
MainActivity.java
package com.example.diptiagravat.myapplication;
public class MainActivity extends AppCompatActivity {
private TextView txtid, txtcname;
Spinner spcnt, spstate;
public ArrayList<String> clist;
ArrayAdapter<String> cad;
public ArrayList<String> slist;
ArrayAdapter<String> sad;
public String strcnt;
private static String url = "http://urmiinfotech.com/demo/ifirst/app_api/get_country_list.php";
private static String stateUrl = "http://urmiinfotech.com/demo/ifirst/app_api/get_state_list.php";
private static final String TAG_USER = "country";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "country_name";
private ArrayList<Country> clistModels;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
CountryAsyncTask countryAsyncTask= new CountryAsyncTask();
countryAsyncTask.execute();
}
private void initViews() {
txtid = (TextView) findViewById(R.id.tvid);
txtcname = (TextView) findViewById(R.id.tvcname);
spcnt = (Spinner) findViewById(R.id.spcnt);
spstate = (Spinner) findViewById(R.id.spstate);
clist = new ArrayList<String>();
slist = new ArrayList<String>();
}
public class CountryAsyncTask extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... params) {
// TODO Auto-generated method stub
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = null;
try {
json = new JSONObject(jParser.getJSON(url, 5000));
} catch (JSONException e) {
e.printStackTrace();
}
return json.toString();
}
#Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
Log.i("Result Ravi", result);
try {
JSONObject obj = new JSONObject(result);
JSONArray cntArray = obj.getJSONArray("country");
if (cntArray.length() > 0) {
for (int i = 0; i < cntArray.length(); i++) {
final JSONObject temp = cntArray.getJSONObject(i);
// txtid.setText(temp.getString("id"));
// txtcname.setText(temp.getString("country_name"));
Country country = new Gson().fromJson(temp.toString(), Country.class);
clist = new ArrayList<String>();
clistModels = new ArrayList<Country>();
clistModels.add(new Country(temp.optString("id"), temp.optString("country_name"), "", null));
clist.add(temp.getString("country_name"));
cad = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item, clist);
spcnt.setAdapter(cad);
spcnt.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
strcnt = clistModels.get(position).getId();
//strcnt = parent.getItemAtPosition(position).toString();
Log.i("id", strcnt);
new StatesAsyncTask().execute();
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
// txtid.setText(temp.getString(country.getId()));
// txtcname.setText(temp.getString(country.getCountryName()));
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public class StatesAsyncTask extends AsyncTask<Void, Void, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(Void... params) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = null;
try {
json = new JSONObject(jParser.sendHTTPData(stateUrl, strcnt));
} catch (JSONException e) {
e.printStackTrace();
}
return json.toString();
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
try {
JSONObject obj = new JSONObject(s);
JSONArray stArray = obj.getJSONArray("statelist");
if (stArray.length() > 0) {
for (int i = 0; i < stArray.length(); i++) {
final JSONObject temp = stArray.getJSONObject(i);
// txtid.setText(temp.getString("id"));
// txtcname.setText(temp.getString("country_name"));
Statelist stlist = new Gson().fromJson(temp.toString(), Statelist.class);
slist = new ArrayList<String>();
// clistModels = new ArrayList<Country>();
//clistModels.add(new Country(temp.optString("id"), temp.optString("country_name"), "", null));
slist.add(temp.getString("state_name"));
sad = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item, slist);
spstate.setAdapter(sad);
spstate.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
// strcnt = clistModels.get(position).getId();
//strcnt = parent.getItemAtPosition(position).toString();
// Log.i("id", strcnt);
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
// txtid.setText(temp.getString(country.getId()));
// txtcname.setText(temp.getString(country.getCountryName()));
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
My response is null?

HttpURLConnection is deprecated in Android Lollipop, so please try to use DefaultHttpClient instead. Also, check your logs, this is at your onPostExecute():
Log.i("Result Ravi", result);
For DefaultHttpClient check this post.
Another way is to try Retrofit

retrieve arraylist from AsyncTask class object after the doInBackground method is finished

i have classes in my projects that only does the server operations such as getting and putting data. i have class which populating list and then method to get this list. the problem is that i'm calling the "getList" method and the background operation hasent finished then i get null from the "getList" method
this is my AsyncTask class, as you can see the "getList" suppose to give me the list completed
public class GetRoomatesListActivity extends AsyncTask<String, String, String> {
private ArrayList<RoomateModel> tmpList;
private ArrayList<RoomateModel> completeList;
DBHelper db;
Context context;
public GetRoomatesListActivity(Context context){
this.context = context;
}
#Override
protected String doInBackground(String... params) {
db = DBHelper.getInstance(context);
HttpURLConnection connection = null;
BufferedReader reader = null;
tmpList = new ArrayList<RoomateModel>();
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
String finalJson = buffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("result");//creates array of Roomates of the selected apartment
for (int i = 0; i < parentArray.length(); i++) {
JSONObject finalObject = parentArray.getJSONObject(i);//get the cuttent json object which is representaion of roomate object
String Fname = finalObject.getString("firstName");
String Lname = finalObject.getString("lastName");
String phone = finalObject.getString("phone");
RoomateModel item = new RoomateModel(Fname, Lname, phone);//creates roomates model with the current item data from the array
tmpList.add(item);//adds the roomate to the list of roomates
//add the roomates to local data base
db.addRoomate(item,apartment);
}
return null;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
completeList = tmpList;
}
public ArrayList<RoomateModel> getList(){
return completeList;
}
}
and this is the class which im trying to get the list to in order to use it but its retrieving null
public class roomatesScreen extends Activity {
ListView items;
ArrayList<RoomateModel> list; //list to compare with the list rerived from GetRoomatesListActivity
RoomatesAdapter adapter;
DBHelper db;
ApartmentModel apartment;
SharedPreferences preferences;
GetRoomatesListActivity r;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.roomates_list);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
items = (ListView) findViewById(R.id.roomatesList);
db = DBHelper.getInstance(this);
Bundle bundle = getIntent().getExtras();
int number = bundle.getInt("number");
apartment = new ApartmentModel(number);// creates apartment model with the user's apartment number
final String num = Integer.toString(number);
r = new GetRoomatesListActivity(this);
r.execute("this is the link to my query" + num);
list = r.getList(); //here list is null
adapter = new RoomatesAdapter(roomatesScreen.this, list);
items.setAdapter(adapter);//here application crushes because of nullPointerExpeption

The best way is to perform the update on UI is in PostExecute method of AsyncTask..
At the time you are accessing it, the control is in the doInBackground method. So your list is null at that time.
put this
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
adapter = new RoomatesAdapter(roomatesScreen.this, tmpList);
items.setAdapter(adapter);/
}
into the onPostExecute().
2nd solution
Initialize the list when you are setting it to adapter. like:
list = new ArrayList();
and rest work (update the list and call notifyDataSetChanged() on adapter object) in onPostExecute().

Change doInBackground() method return type
public class GetRoomatesListActivity extends AsyncTask<String, String, ArrayList<Object>> {
private ArrayList<RoomateModel> tmpList;
private ArrayList<RoomateModel> completeList;
DBHelper db;
Context context;
public GetRoomatesListActivity(Context context){
this.context = context;
}
#Override
protected ArrayList<Object> doInBackground(String... params) {
db = DBHelper.getInstance(context);
HttpURLConnection connection = null;
BufferedReader reader = null;
tmpList = new ArrayList<RoomateModel>();
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
String finalJson = buffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("result");//creates array of Roomates of the selected apartment
for (int i = 0; i < parentArray.length(); i++) {
JSONObject finalObject = parentArray.getJSONObject(i);//get the cuttent json object which is representaion of roomate object
String Fname = finalObject.getString("firstName");
String Lname = finalObject.getString("lastName");
String phone = finalObject.getString("phone");
RoomateModel item = new RoomateModel(Fname, Lname, phone);//creates roomates model with the current item data from the array
tmpList.add(item);//adds the roomate to the list of roomates
//add the roomates to local data base
db.addRoomate(item,apartment);
}
return null;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
completeList = tmpList;
}
public ArrayList<RoomateModel> getList(){
return completeList;
}
}

Show data in listview with Asynctask

I success show my data from web service JSON in listview, but I want to add Asyntask.
Where I can put code Asyntask in my code.
This my code to show data in list view
public class Jadwal_remix extends ListActivity {
String v_date;
JSONArray r_js = null;
ArrayList<HashMap<String, String>> myArray = new ArrayList<HashMap<String,String>>();
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.main);
String status ="";
String date = "";
String result = "";
String url = "http://10.0.2.2/remix/view_list.php";
JSONParser jParser = new JSONParser();
JSONObject json = jParser.AmbilJson(url);
try
{
r_js = json.getJSONArray("view_list");
for (int i =0; i < r_js.length(); i++)
{
String my_array = "";
JSONObject ar = r_js.getJSONObject(i);
status = ar.getString("st");
date = ar.getString("date");
result = ar.getString("result");
if (status.trim().equals("er"))
{
my_array += "Sorry "+result;
HashMap<String, String> map = new HashMap<String, String>();
map.put("result", my_array);
myArray.add(map);
}
else
{
my_array += "Date : "+date+" "+"Result : "+result;
HashMap<String, String> map = new HashMap<String, String>();
map.put("result", my_array);
myArray.add(map);
}
}
}
catch (JSONException e)
{
e.printStackTrace();
}
adapter_listview();
}
public void adapter_listview() {
ListAdapter adapter = new SimpleAdapter(this, jadwalRemix,R.layout.my_list,new String[] { "result"}, new int[] {R.id.txtResult});
setListAdapter(adapter);
}
}
And this JSONParser
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject AmbilJson(String url) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
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();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
Where can I put code for Asyntask?
Ok, I get sample code, and my code now like this
public class Jadwal_remix extends ListActivity {
String v_date;
JSONArray r_js = null;
ArrayList<HashMap<String, String>> myArray = new ArrayList<HashMap<String,String>>();
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.main);
private class myProses extends AsyncTask<Void, Void, Void> {
ProgressDialog dialog;
protected void onPreExecute() {
dialog = ProgressDialog.show(Jadwal_remix.this, "", "Loading... Please wait", true);
}
protected Void doInBackground(Void... params) {
String status ="";
String date = "";
String result = "";
String url = "http://10.0.2.2/remix/view_list.php";
JSONParser jParser = new JSONParser();
JSONObject json = jParser.AmbilJson(url);
try
{
r_js = json.getJSONArray("view_list");
for (int i =0; i < r_js.length(); i++)
{
String my_array = "";
JSONObject ar = r_js.getJSONObject(i);
status = ar.getString("st");
date = ar.getString("date");
result = ar.getString("result");
if (status.trim().equals("er"))
{
my_array += "Sorry "+result;
HashMap<String, String> map = new HashMap<String, String>();
map.put("result", my_array);
myArray.add(map);
}
else
{
my_array += "Date : "+date+" "+"Result : "+result;
HashMap<String, String> map = new HashMap<String, String>();
map.put("result", my_array);
myArray.add(map);
}
}
}
catch (JSONException e)
{
e.printStackTrace();
}
return null;
protected void onPostExecute(Void unused) {
adapter_listview();
dialog.dismiss();
}
}
public void adapter_listview() {
ListAdapter adapter = new SimpleAdapter(this, jadwalRemix,R.layout.my_list,new String[] { "result"}, new int[] {R.id.txtResult});
setListAdapter(adapter);
}
}
I'm get problem when server is die, it still loading.
How I can show message ex: can't connect to server?

Working ASyncTask tutorial,
Full ASyncTask Eclipse Project,
and here's some code that I think, when mixed with the above sample, will get you the result with the list that you desire (you'll have to adapt it to your needs a bit, though (pay attention to the list stuff, even though this is from a custom Dialog:
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Kies Facebook-account");
builder.setNegativeButton("Cancel", this);
LayoutInflater inflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View dialogLayout = inflater.inflate(R.layout.dialog, null);
builder.setView(dialogLayout);
final String[] items = {"Red", "Green", "Blue" };
builder.setAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, items),
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Log.v("touched: ", items[which].toString());
}}
);
return builder.create();
}

This is my code please try this one,
MAinActivity.java
public class MyActivity extends Activity {
private ListView contests_listView;
private ProgressBar pgb;
ActivitiesBean bean;
ArrayList<Object> listActivities;
ActivityAdapter adapter;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listview);
contests_listView = (ListView) findViewById(R.id.activity_listView);
pgb = (ProgressBar) findViewById(R.id.contests_progressBar);
listActivities = new ArrayList<Object>();
new FetchActivitesTask().execute();
}
public class FetchActivitesTask extends AsyncTask<Void, Void, Void> {
int i =0;
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
pgb.setVisibility(View.VISIBLE);
}
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
String url = "Your URL Here";
String strResponse = util.makeWebCall(url);
try {
JSONObject objResponse = new JSONObject(strResponse);
JSONArray jsonnodes = objResponse.getJSONArray(nodes);
for (i = 0; i < jsonnodes.length(); i++)
{
String str = Integer.toString(i);
Log.i("Value of i",str);
JSONObject jsonnode = jsonnodes.getJSONObject(i);
JSONObject jsonnodevalue = jsonnode.getJSONObject(node);
bean = new ActivitiesBean();
bean.title = jsonnodevalue.getString(title);
bean.image = jsonnodevalue.getString(field_activity_image_fid);
listActivities.add(bean);
}
}
catch (JSONException e) {
e.printStackTrace();
}
return null;
}
#Override
public void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
pgb.setVisibility(View.GONE);
displayAdapter();
}
}
public void displayAdapter()
{
adapter = new ActivityAdapter(this, listActivities);
contests_listView.setAdapter(adapter);
contests_listView.setOnItemClickListener(new OnItemClickListener() {
//#Override
public void onItemClick(AdapterView<?> arg0, View arg1,
int position, long id) {
// your onclick Activity
}
});
}
}
util.class
public static String makeWebCall(String url) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpRequest = new HttpGet(url);
// HttpPost post = new HttpPost(url);
try {
HttpResponse httpResponse = client.execute(httpRequest);
final int statusCode = httpResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
return null;
}
HttpEntity entity = httpResponse.getEntity();
InputStream instream = null;
if (entity != null) {
instream = entity.getContent();
}
return iStream_to_String(instream);
}
catch (IOException e) {
httpRequest.abort();
// Log.w(getClass().getSimpleName(), "Error for URL =>" + url, e);
}
return null;
}
public static String iStream_to_String(InputStream is1) {
BufferedReader rd = new BufferedReader(new InputStreamReader(is1), 4096);
String line;
StringBuilder sb = new StringBuilder();
try {
while ((line = rd.readLine()) != null) {
sb.append(line);
}
rd.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String contentOfMyInputStream = sb.toString();
return contentOfMyInputStream;
}
}
ActivityBean.java
public class ActivitiesBean implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
public String title;
public String image;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}