Develop Reference

Getting Data from JSON?

I want to get the username from this
Json url.
I have this code but it doesn't let me get the data saying
Json parsing error
Here is the code:
HttpHandler.java
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();
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity {
private String TAG = MainActivity.class.getSimpleName();
private ProgressDialog pDialog;
private ListView lv;
// URL to get contacts JSON
private static String url = "https://someLink";
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.list);
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(MainActivity.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 {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
JSONArray contacts = jsonObj.getJSONArray("");
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String name = c.getString("username");
// tmp hash map for single contact
HashMap<String, String> contact = new HashMap<>();
// adding each child node to HashMap key => value
contact.put("username", name);
// 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();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, contactList,
R.layout.list_item, new String[]{"username"}, new int[]{R.id.name});
lv.setAdapter(adapter);
}
}
}
This is an example i found on google and tried to change it a bit in my needs.I've put an empty JsonArray.I also tried other examples but i can't understand what is going wrong.
**
> New question
If my url is like this?What is the difference with the other?
**

You don't have an array to parse in the output. Your URL giving you an Object. Your code should be something like this
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
String name = jsonObj.getString("username");
//... now use the whereever you want
}
catch (final JSONException e) {
//... put your error log
}

Please edit your code in MainActivity to get the username from json string as follows :
if(jsonStr!=null)
{
JSONObject jsonObj = new JSONObject(jsonStr);
if(jsonObj !=null)
{
String name = jsonObj .getString("username");
}
}

i suggest you to use this one.
public class HttpGetResources extends AsyncTask<String, Void, Object> {
#SuppressLint("StaticFieldLeak")
private ProgressBar progressBar;
private static final String RAW_DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSSz";
private String urlString;
private String apiName;
private Class Response_Class;
private static final Gson GSON = new GsonBuilder().setDateFormat(RAW_DATE_FORMAT).create();
private Context context;
public HttpGetResources(Context context,Class Response_Class, String apiName, String urlString) {
this.Response_Class = Response_Class;
this.apiName = apiName;
this.urlString = urlString;
this.context=context;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected void onPostExecute(Object response) {
super.onPostExecute(response);
}
HttpURLConnection conn = null;
OutputStreamWriter out = null;
Object result = null;
BufferedReader buffer = null;
final ExecutorService executor = Executors.newCachedThreadPool(Executors.defaultThreadFactory());
static public Future<Object> future;
#SuppressWarnings("unchecked")
#Override
protected Object doInBackground(final String... params) {
// JsonObject res=null;
future = executor.submit(new Callable<Object>() {
#Override
public Object call() throws IOException {
try {
URL url = new URL(urlString + apiName);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json;charset=UTF-8");
conn.setConnectTimeout(3000);
conn.setReadTimeout(15000);
conn.setDoInput(true);
conn.setDoOutput(true);
out = new OutputStreamWriter(conn.getOutputStream());
out.write(params[0]);
out.flush();
out.close(); out=null;
buffer = new BufferedReader(new InputStreamReader(conn.getInputStream()));
// res= GSON.fromJson(buffer, JsonObject.class);
// result = new Gson().fromJson(res.toString(), Response_Class);
result = GSON.fromJson(buffer, Response_Class);
buffer.close(); buffer=null;
// result = new Gson().fromJson(res.toString(), Response_Class);
} catch (Exception e) {
//
} finally {
if (buffer!=null) {
try {
buffer.close();
} catch (Exception e) { //
}
}
if (out != null) {
try {
out.close();
} catch (Exception e) { //
}
}
if (conn != null) {
conn.disconnect();
}
}
return result;
}
});
try {
result = future.get(10, TimeUnit.SECONDS);
} catch (Exception ignored) {
}
return result;
}
}
--and call method--
public synchronized Object HttpGetRes(final Object REQUEST_CLASS, final Class RESPONSE_CLASS, final String
API_NAME, final String URL) {
if(isNetworkAvailable()) {
response = null;
try {
Log.e(API_NAME, "url: " + URL);
Log.e(REQUEST_CLASS.getClass().getSimpleName(), new Gson().toJson(REQUEST_CLASS));
HttpGetResources resource = new HttpGetResources(BaseContext,RESPONSE_CLASS, API_NAME,
URL);
response = resource.execute(new Gson().toJson(REQUEST_CLASS)).get();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
if (response != null) {
String x = new Gson().toJson(response);
Log.e(RESPONSE_CLASS.getSimpleName(), x);
return response;
} else {
}
}
return null;
}

Try to use GSON library in the future, it will auto convert the JSON object to a java object automatically for you. This will be useful to avoid parsing complex JSON objects or JSON arrays. https://github.com/google/gson

Showing ProgressBar on parsing and downloading json result

In my App I am hitting a service which can have no result to n number of results(basically some barcodes). As of now I am using default circular progressbar when json is parsed and result is being saved in local DB(using sqlite). But if the json has large number of data it sometimes takes 30-45 min to parse and simultaneously saving that data in DB, which makes the interface unresponsive for that period of time and that makes user think the app has broken/hanged. For this problem I want to show a progressbar with the percentage stating how much data is parsed and saved so that user get to know the App is still working and not dead. I took help from this link but couldn't find how to achieve. Here's my Asynctask,
class BackGroundTasks extends AsyncTask<String, String, Void> {
private String operation, itemRef;
private ArrayList<Model_BarcodeDetail> changedBarcodeList, barcodeList;
private ArrayList<String> changeRefList;
String page;
public BackGroundTasks(String operation, String itemRef, String page) {
this.operation = operation;
this.itemRef = itemRef;
this.page = page;
}
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
if (dialog == null) {
dialog = ProgressDialog.show(mActivity, null,
"Please wait ...", true);
}
}
#Override
protected Void doInBackground(String... params) {
// TODO Auto-generated method stub
try{
if (!connection.HaveNetworkConnection()) {
dialog.dismiss();
connection.showToast(screenSize, "No Internet Connection.");
return null;
}
if (operation.equalsIgnoreCase("DownloadChangeItemRef")) {
changeRefList = DownloadChangeItemRef(params[1]);
if (changeRefList != null && !changeRefList.isEmpty()) {
RefList1.addAll(changeRefList);
}
}
if ((changeRefList != null && changeRefList.size() >0)) {
setUpdatedBarcodes(changedBarcodeList);
}
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
#SuppressLint("SimpleDateFormat")
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
}
}
ArrayList<String> DownloadChangeItemRef(String api_token) {
ArrayList<String> changedRefList = null;
HttpClient httpClient = new DefaultHttpClient();
HttpPost postRequest = new HttpPost(thoth_url + "/" + todaysDate
+ "?&return=json");
String url = thoth_url + "/" + todaysDate + "?&return=json";
String result = "";
try {
changedRefList = new ArrayList<String>();
ResponseHandler<String> responseHandler = new BasicResponseHandler();
result = httpClient.execute(postRequest, responseHandler);
JSONObject jsonObj = new JSONObject(result);
JSONArray jsonarray = jsonObj.getJSONArray("changes");
if (jsonarray.length() == 0) {
return null;
}
for (int i = 0; i < jsonarray.length(); i++) {
JSONObject obj = jsonarray.getJSONObject(i);
changedRefList.add(obj.getString("ref"));
}
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
// when there is no thoth url
Log.i("inclient: ", e.getMessage());
return null;
} catch (Exception e) {
// when there are no itemref
return null;
}
return changedRefList;
}
private boolean setUpdatedBarcodes(
final ArrayList<Model_BarcodeDetail> changedBarcodeList2) {
try {
BarcodeDatabase barcodeDatabase = new BarcodeDatabase(mActivity);
barcodeDatabase.open();
for (Model_BarcodeDetail model : changedBarcodeList2) {
barcodeDatabase.updateEntry(model, userId);
}
n++;
barcodeDatabase.close();
if (RefList1.equals(RefList)) {
if (dialog != null) {
dialog.dismiss();
}
connection.showToast(screenSize, "Barcodes updated successfully");
}
} catch (Exception e) {
Log.i("Exception caught in: ", "setDownloadedBarcodes method");
e.printStackTrace();
return false;
}
return true;
}

Progress Bar not visible with Stand alone asynctask

I am trying to fetch some data from Web Server through JSON. I am using asynctask to do so. Normally it is taking 5-10 seconds to be shown in my ListView.
Hence I want to put spinner progress bar. My code is working fine only problem is the progress bar is not visible.
MyActivity code to call asyntask
try{
JSONObject output = new AsyncTaskJsonParse(this,status, A, B, city).execute().get();
try {
JSONObject output = new AsyncTaskJsonParse(ListViewDisplay.this,status, bgrp, antigen, city).execute().get();
JSONObject src = output.getJSONObject("data");
String flag = output.getString("success");
String flagmsg = output.getString("message");
if (flag == "1") {
JSONArray jarr_name = new JSONArray(src.getString("name"));
JSONArray jarr_fathername = new JSONArray(src.getString("fathername"));
JSONArray jarr_moh = new JSONArray(src.getString("moh"));
JSONArray jarr_city = new JSONArray(src.getString("city"));
JSONArray jarr_phone = new JSONArray(src.getString("phone"));
int n = jarr_name.length();
name_array = new String[n];
fathername_array = new String[n];
moh_array = new String[n];
phone_array = new String[n];
city_array = new String[n];
for (int i = 0; i < n; i++) {
name_array[i] = (String) jarr_name.get(i);
fathername_array[i] = (String) jarr_fathername.get(i);
moh_array[i] = (String) jarr_moh.get(i);
phone_array[i] = (String) jarr_phone.get(i);
city_array[i] = "Vadodara";
Log.d("Inside StringArray", i + "");
}
String msg = src.getString("name");
list = (ListView) findViewById(R.id.listView);
CustomListAdapter custAdaptor = new CustomListAdapter(this, name_array, fathername_array, mohalla_array, city_array, phone_array);
list.setAdapter(custAdaptor);
}else
{
Toast.makeText(this, "Data not found" + flagmsg, Toast.LENGTH_LONG).show();
}
}catch(ExecutionException e){
// TODO Auto-generated catch block
e.printStackTrace();
}
catch(InterruptedException e)
{
e.printStackTrace();
}catch(JSONException je)
{
}
Standalone asyntask with progressbar code
public class AsyncTaskJsonParse extends AsyncTask<String, String, JSONObject>
{
String A,B;
private String url = "abc.com/check.php";
List<NameValuePair> param=new ArrayList<NameValuePair>();
private Context context;
private ProgressDialog progress;
public AsyncTaskJsonParse(Context context,String A,String B,String antigen,String city)
{
this.A=A;
this.B=B;
this.city=city;
this.context=context;
progress=new ProgressDialog(context);
}
#Override
protected void onPreExecute() {
super.onPreExecute();
Log.e("In preexecution ", "Preexecution 1");
progress.setMessage("Processing...");
progress.setIndeterminate(true);
progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);
progress.setCancelable(true);
Log.e("In preexecution azam", "Preexecution 2");
progress.show();
if(progress.isShowing())
{
Log.d("In preexecution ", "Showing 2");
}
}
//rest of code i.e. doInBackground and postexecute come after this.
#Override
protected JSONObject doInBackground(String... arg0) {
// TODO Auto-generated method stub
try
{
JsonParsor parse=new JsonParsor();
Log.d("diInbackgrnd ","Dialog box");
jsonobj = parse.getJSONFromUrl(url, param);
}
catch(Exception e)
{
Log.e(TAG, " "+e );
}
return jsonobj;
}
#Override
protected void onPostExecute(JSONObject result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
//pDialog.dismiss();
if(progress.isShowing())
{
Log.e("In onPost ", "Showing 2");
}
progress.dismiss();
}
}
In my log I can see the message "In preexecution Showing 2". And the appliaction is working as expected but the Spinner progressbar is not visible.
Note: I did not add any progressbar component in any xml file. Does i need to add it? if yes then where and how?
class JsonParser.java
public class JsonParsor {
final String TAG = "JsonParser.java";
static InputStream is = null;
static JSONObject jObj = null;
static String str = "";
public JSONObject getJSONFromUrl(String url,List<NameValuePair> params) {
try {
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(url);
post.setEntity(new UrlEncodedFormEntity(params));
HttpResponse response = client.execute(post);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try
{
BufferedReader br=new BufferedReader(new InputStreamReader(is,"iso-8859-1"), 8);
StringBuilder builder=new StringBuilder();
String line=null;
while((line=br.readLine())!=null)
{
builder.append(line + "\n");
}
is.close();
str=builder.toString();
}
catch(Exception e)
{
}
try {
jObj=new JSONObject(str);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return jObj;
}
}

I suspect your problem is that your AsyncTask finishes immediately as parse.getJSONFromUrl... is also Async. So whats happening is that progress.dismiss(); in onPostExecute invoked also immediately.
Try removing progress.dismiss(); from onPostExecute and see what happens

This should work. But without the progress.setMessage("Processing...");
You can still set that.
#Override
protected void onPreExecute() {
super.onPreExecute();
dialog = new ProgressDialog(getActivity(),R.style.MyTheme);
dialog.setCancelable(false);
dialog.setProgressStyle(android.R.style.Widget_ProgressBar_Small);
dialog.show();
}

Asyntask not executing onPostExecute()

This is my Asyntask code which is not firing the onPostExecute() Any one has any idea why this might be happening???
EDIT: The Asyntask is called this way
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FacebookSdk.sdkInitialize(getApplicationContext());
callbackManager = CallbackManager.Factory.create();
setContentView(R.layout.activity_main);
.
.
textView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), SignUp.class);
startActivity(intent);
}
});
textView2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), Feedback.class);
startActivity(intent);
}
});
fbLoginButton = (LoginButton) findViewById(R.id.login_button);
fbLoginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
#Override
public void onSuccess(LoginResult loginResult) {
token=loginResult.getAccessToken().getToken().toString();
Log.v("tag", "Token:\n" + token);
try {
get_profile();
}catch (Exception ex) {
String error = ex.getMessage();
}
}
#Override
public void onCancel() {
Toast.makeText(MainActivity.this, "Login cancelled by user!", Toast.LENGTH_LONG).show();
System.out.println("Facebook Login failed!!");
}
#Override
public void onError(FacebookException e) {
Toast.makeText(MainActivity.this, "Login unsuccessful!", Toast.LENGTH_LONG).show();
System.out.println("Facebook Login failed!!");
}
});
}
The get_profile(); method is defined like this
//Method to get profile details
public void get_profile() throws UnsupportedEncodingException {
try {
// Calling async task to get json
new FetchOperation().execute();
} catch (Exception e) {
e.printStackTrace();
}
}
This is inside the Main class too
//Asynctask to get Getting fb profile details
private class FetchOperation extends AsyncTask<Void, Void, String> {
String fb_token;
#Override
protected void onPreExecute() {
super.onPreExecute();
// Get user defined values
fb_token = token;
}
#Override
protected String doInBackground(Void... params) {
String response = "";
String Urls = "https://graph.facebook.com/me?access_token=";
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet(Urls +token);
HttpEntity httpEntity = null;
HttpResponse httpResponse = null;
try {
httpResponse = httpclient.execute(httpget);
} catch (ClientProtocolException e) {
e.printStackTrace();
Log.v("Response", "Hi From e1 : " + e.toString());
} catch (IOException e) {
e.printStackTrace();
}
try {
httpEntity = httpResponse.getEntity();
response = EntityUtils.toString(httpEntity);
Log.v("Response", "Hi From 2 : "+response.toString());
return response;
} catch (IOException e) {
e.printStackTrace();
Log.v("Response", "Hi From e2 : " + e.toString());
}
return null;
}
#Override
protected void onPostExecute(String jsonStr) {
super.onPostExecute(jsonStr);
Log.v("tag", "Result:" + jsonStr);
if (jsonStr != null) {
try{
JSONObject jsonObj = new JSONObject(jsonStr);
String email = jsonObj.getString("email");
String firstName = jsonObj.getString("first_name");
String lastName = jsonObj.getString("last_name");
String gender = jsonObj.getString("gender");
String country = jsonObj.getString("locale");
id = jsonObj.getString("id");
user = firstName.concat(" ");
user = user.concat(lastName);
image = "http://graph.facebook.com/" + id + "/picture?type=large";
Log.v("Fb name", "Bla bla Name : " + user);
new UploadOperation().execute();
}
catch (JSONException e) {
e.printStackTrace();
}
}
else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
}
}
This is the last lines of the logcat
06-29 14:30:49.927 2091-2091/com.example.kmi_dev.fbloginsample V/tag﹕ Token:
CA****************************************************************xr
06-29 14:30:50.697 2091-2135/com.example.kmi_dev.fbloginsample V/Response﹕ Hi From 2 : {"id":"910***********6","first_name":"Shivanshu","gender":"male","last_name":"Verma","link":"https:\/\/www.facebook.com\/app_scoped_user_id\/910***********6\/","locale":"en_GB","name":"Shivanshu Verma","timezone":5.5,"updated_time":"2015-06-22T04:17:39+0000","verified":true}
06-29 14:31:23.827 2091-2098/com.example.kmi_dev.fbloginsample W/art﹕ Suspending all threads took: 10ms
I intend to fire another asyntask which will then save the data fetched by this asyntask into the database.

Make these changes, it will work -
private class FetchOperation extends AsyncTask<Void, Void, String>
change to - private class FetchOperation extends AsyncTask<Void, String, String> , because, you are trying to return String.
response = EntityUtils.toString(httpEntity);
change to - response = EntityUtils.toString(httpEntity).toString();
at the next line of this you have actually done it.
At the very end of doInBackground method where return null;
change to - return response;
4.No need to call super in onPostExecute()
5.Inside onPostExecute() check jsonStr is null or not and do whatever you want to do if null and if contains json data.

Your JSONObject does not contain a JSONString "email", so it is falling over at line
String email = jsonObj.getString("email");
and going straight to catch block.

How to eliminate the empty strings inside the object in android json parsing

Hi friends i like to parse the json from url and also like to elimate the null values field and only show the object which has value if anyone known syntax for that means please guide me thanks in advance.
JSON Structure
{
"daftar_rs": [
{
"Name": "exe1",
"URL": "http://samir-mangroliya.blogspot.in/p/android-json-parsing-tutorial.html"
},
{
"Name": "exe2",
"URL": "https://code.google.com/p/json-io/"
},
{
"Name": "exe3",
"URL": ""
},
{
"Name": "exe4",
"URL": "http://stackoverflow.com/questions/10964203/android-removing-jsonobject"
},
{
"Name": "exe5",
"URL": ""
},
{
"Name": "exe6",
"URL": ""
}
],
"success": 1
}
MainActivity
public class MainActivity extends Activity {
ListView lv;
List<String> titleCollection = new ArrayList<String>();
List<String> urlCollection = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.listView1);
// we will using AsyncTask during parsing
new AsyncTaskParseJson().execute();
lv.setOnItemClickListener(new OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
String linkUrl = urlCollection.get(arg2);
Intent webViewIntent = new Intent(MainActivity.this, WebViewActivity.class);
webViewIntent.putExtra("url", linkUrl);
startActivity(webViewIntent);
}
});
}
public void loadContents()
{
ArrayAdapter<String> adapter =new ArrayAdapter<String>(getBaseContext(), android.R.layout.simple_list_item_1,titleCollection);
lv.setAdapter(adapter);
}
// you can make this class as another java file so it will be separated from your main activity.
public class AsyncTaskParseJson extends AsyncTask<String, String, String> {
final String TAG = "AsyncTaskParseJson.java";
// set your json string url here
String yourJsonStringUrl = "http://192.168.1.167/vinandrophp/vinex.php";
// contacts JSONArray
JSONArray dataJsonArr = null;
#Override
protected void onPreExecute() {}
#Override
protected String doInBackground(String... arg0) {
try {
// instantiate our json parser
JsonParser jParser = new JsonParser();
// get json string from url
JSONObject json = jParser.getJSONFromUrl(yourJsonStringUrl);
// loop through all users
for (int i = 0; i < dataJsonArr.length(); i++) {
JSONObject c = dataJsonArr.getJSONObject(i);
// Storing each json item in variable
titleCollection.add(c.getString("Name"));
urlCollection.add(c.getString("URL"));
// show the values in our logcat
Log.e(TAG, "Name: " + titleCollection
+ ", URL: " + urlCollection);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String strFromDoInBg) {
loadContents();
}
}
}
JsonParser.java
public class JsonParser {
final String TAG = "JsonParser.java";
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
public JSONObject getJSONFromUrl(String url) {
// make HTTP request
try {
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(TAG, "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e(TAG, "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}

Just check it inside your code.
String linkUrl = urlCollection.get(arg2);
if (linkUrl== null || linkUrl.equals("")){
// null
}
else{
// not null so put to extras and start intent
Intent webViewIntent = new Intent(MainActivity.this, WebViewActivity.class);
webViewIntent.putExtra("url", linkUrl);
startActivity(webViewIntent);
}

try below code
for (int i = 0; i < dataJsonArr.length(); i++)
{
JSONObject c = dataJsonArr.getJSONObject(i);
// Storing each json item in variable
String Name = c.getString("Name");
String Url = c.getString("URL")
if(!TextUtils.isEmpty(Name) && !TextUtil.isEmpty(Url))
{
titleCollection.add(Name);
urlCollection.add(Url));
}
// show the values in our logcat
Log.e(TAG, "Name: " + titleCollection + ", URL: " + urlCollection);
}

try below code:-
if(c.getString("URL").equals("") || c.isNULL("URL"))
{
// do nothing
}
else
{
titleCollection.add(c.getString("Name"));
urlCollection.add(c.getString("URL"));
}

Change for loop as
for (int i = 0; i < dataJsonArr.length(); i++) {
JSONObject c = dataJsonArr.getJSONObject(i);
// Storing each json item in variable
String name = c.getString("Name");
String url = c.getString("URL");
if(name != null && !(name.equals(""))
&& url != null && !(url.equals(""){
titleCollection.add(c.getString("Name"));
urlCollection.add(c.getString("URL"));
}
// show the values in our logcat
Log.e(TAG, "Name: " + titleCollection
+ ", URL: " + urlCollection);
}

Try replace keys and values with regular expression if the key is empty in the JsonParser class.
json=json.replaceAll("\\n",""); //you should do not have any new lines after commas
json=json.replaceAll(",\\W*\"\\w+\":\\W?(\"\"|null)","");