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Strange NullPointException [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I'm trying to display data from mysql database with recycler-view ans card-view, but i'm facing this error message:
java.lang.NullPointerException: Attempt to invoke interface method
'int java.util.List.size()' on a null object reference
Everything seems to work properly because I'm able to display data retrieved on (Log) in my loop, and when I'm trying to add data on my List data_list, every thing is OK, because I'm able to know the number of lines returned by my data_list
Log.e("number of lines return", String.valueOf(data_list.size()));
But when i'm trying to reach the data_list on my Custom Adapter:
#Override
public int getItemCount() {
return my_data.size();
}
It warns me i can't access my_data because it's null.
The part of my code which retrieves data from my database:
private void load_data_from_server(final int id) {
//Log.e("iddddsss", String.valueOf(id));
AsyncTask<Integer,Void,Void> task =new AsyncTask<Integer, Void, Void>(){
#Override
protected Void doInBackground(Integer... integers) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url("http://www.unhabitatrdcongo.org/Recycler-android-mySQL/index2.php?id="+id)
.build();
try {
Response response = client.newCall(request).execute();
JSONArray array = new JSONArray(response.body().string());
for (int i=0; i<array.length(); i++){
JSONObject object = array.getJSONObject(i);
Integer idd = object.getInt("id");
String des = object.getString("description").toString();
String im =object.getString("image").toString();
MyData data = new MyData(idd, des, im);
Log.e("errr", data.getDescription().toString());
data_list.add(data);
}
Log.e("number of lines read", String.valueOf(data_list.size()));
} catch (IOException e) {
e.printStackTrace();
Log.e("erreur IO EXCEPTION", e.toString());
} catch (JSONException e) {
System.out.print("End of content");
Log.e("erreur JSON",e.toString());
}
return null;
}

Generally, my_data has not been assigned yet while executing getItemCount (). This method is called in the adapter construct this.my_data = data_list;

Most likely the List<MyData> data_listthat the class is getting is null, and then, when this.my_data = data_list; you are doing this this.my_data = null;
Try to check that.

make java wait until variable changes

I want to make my code wait until there is a change anywhere in my class to the variable finaloutcomes. Is there any way to do this? I am carrying this out within an Asynctask, which I posted below.
public HashMap<String,String> checkbetoutcome() {
new LoadAllGamet().execute();
// INSERT CODE HERE
return finaloutcomes;
}
ASYNCTASK
class LoadAllGamet extends AsyncTask<String, String, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
protected String doInBackground(String... args) {
// HttpParams httpParameters = new BasicHttpParams();
// HttpConnectionParams.setConnectionTimeout(httpParameters, 250000);
//HttpConnectionParams.setSoTimeout(httpParameters, 250000);
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(url_check_bet);
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("param", bet));
// Log.d("CURRENTITEM", currentitem);
try {
post.setEntity(new UrlEncodedFormEntity(params));
} catch (IOException ioe) {
ioe.printStackTrace();
}
try {
HttpResponse response = client.execute(post);
Log.d("Http Post Responsecxxx:", response.toString());
HttpEntity httpEntity = response.getEntity();
InputStream is = httpEntity.getContent();
JSONObject jObj = null;
String json = "";
client.getConnectionManager().closeExpiredConnections();
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
if (!line.startsWith("<", 0)) {
if (!line.startsWith("(", 0)) {
sb.append(line + "\n");
}
}
}
is.close();
json = sb.toString();
json = json.substring(json.indexOf('{'));
// Log.d("sbsssssssssss", json);
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
allgames = jObj.getJSONArray("bets");
// Log.d("WHAT IS MY ARRAY?", allgames.toString());
for (Integer i = 0; i < allgames.length(); i++) {
HashMap<String,String> statuses = new HashMap<>();
JSONObject c = allgames.getJSONObject(i);
JSONArray currentbet = c.getJSONArray("bet");
Log.d("Single array",currentbet.toString());
// Storing each json item in variable
for (Integer a = 0; a < currentbet.length();a++) {
JSONObject d = currentbet.getJSONObject(a);
String Result = d.getString("Result");
String id = d.getString("gid");
Log.d("RESULTS",Result);
statuses.put(id, Result);
}
allbetsmap.add(i, statuses);
Log.d("ddd", statuses.toString());
Log.d("AAA", allbetsmap.get(i).toString());
}
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
}
catch (IOException e) {
e.printStackTrace();
}
return "";
}
#Override
protected void onPostExecute(String param) {
Log.d("SIZE",Integer.toString(allbetsmap.size()));
//ArrayList<Map<String,String>> allbetsmap = new ArrayList<>();
//ArrayList<Map<String,String>> passtocheck = new ArrayList<>();
if (allbetsmap.size() == passtocheck.size()) {
for (int i = 0; i < allbetsmap.size();i++) {
if (allbetsmap.get(i).size() == passtocheck.get(i).size()) {
String finaloutcome = "won";
for (String a : allbetsmap.get(i).keySet()) {
String f = allbetsmap.get(i).get(a);
if(f.equals("null")) {
finaloutcome = "open";
}
else if (! (f.equals(passtocheck.get(i).get(a)))) {
finaloutcome = "lost";
break;
}
}
finaloutcomes.put(Integer.toString(i),finaloutcome);
}
}
}
Log.d("Vital",finaloutcomes.toString());
}
}

Ok, forget what I wrote before. I didn't realize you were writing code for android. Here is an improved version of LoadAllGamet. There are two important things here. 1. define as much as possible locally i.e. inside a method or - if that's not possible - inside the class. 2. return the result instead of putting it into some variable.
class LoadAllGamet extends AsyncTask<String, Void, HashMap<String,String>> {
protected HashMap<String,String> doInBackground(String ... args) {
HashMap<String,String> finaloutcomes = new HashMap<>(),
HashMap<Integer, HashMap<String,String>> allbetsmap = new HashMap<>();
HttpClient client = new DefaultHttpClient();
...
Log.d("SIZE",Integer.toString(allbetsmap.size()));
if (allbetsmap.size() == passtocheck.size()) {
...
}
Log.d("Vital",finaloutcomes.toString());
return finaloutcomes;
}
}
Whenever you want to do something that might take some time you should not run
that in the UI thread of you App since it can block your UI.
Instead run it asynchronously. One way of doing this is to use AsyncTask.
Let's assume you want to do something and while that something is being processed
you also want to update the UI (e.g. progress bars) from time to time. And once you
are finished you want to do something else with the result.
Here is one way of writing this.
void doSomething() {
new AsyncTask<String, Progress, Result>() {
protected Result doInBackground(String... args) {
//some code
publishProgress(values);
//some more code
return result;
}
protected void onProgressUpdate(Progress ... values) {
updateProgessBars(values);
}
protected void onPostExecute(Result result) {
doSomethingElse(result);
}
}.execute();
}
The String in new AsyncTask<String, Progress, Result> is the type of the
arguments to doInBackground. Often however you don't really need that unless
you want to pass arguments into execute.
Progress is the type of the values you want to send to onProgressUpdate. That
one you only need if you want to update your UI while the background processing
is still going on.
Result is of course your result type. Whatever you want to happen after
the doInBackground is finished you write into onPostExecute.

parsing a specific JSON data format

i have this small problem,i am making a android application n use a .php file to call java script file that returns me a JSON output..now my problem is the output is in a valid JSON format, now i am confused as to how to parse the values.
the output is
["15.493511","73.818659"]
where the 1st value is the latitude value and the 2nd being longitude value..
what i want to do is parse this is on fetching this value in the asynctask i want to split these values ans assign them to variables. any idea how i could do this.
Thank you in advance.

well its a json array
<?php
$val = '["15.493511","73.818659"]';
$arrVal = json_decode($val, true);
print_r($arrVal);
$latitude = $arrVal[0];
$longitude = $arrVal[1]
This will output:
array(15.493511, 73.818659);

as you said i want to do is parse this is on fetching this value in the asynctask means you need to parse the json data in android application.
JSONArray jObject = new JSONArray(result); //result is the json data you received
String lat = jObject.getString(0);
String long = jObject.getString(1);
updated the answer as suggested by spring-breaker

Do something like below,
private class MyAsyncTask extends AsyncTask<String, String, String>
{
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
String data="["15.493511","73.818659"]"; // Assuming that it is your static data
try {
JSONArray myArray=new JSONArray(data);
String lattitude=myArray.getString(0);
String longitudetude=myArray.getString(1);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
//update your UI or do your task;
}
}
}
And execute the AsyncTask like following,
new MyAsyncTask().execute();

You are getting JSON Array.
So your code can be something like this..
String latitude=jsonarray.getString(0);
String longitude=jsonarray.getString(1);

try below code:-
JSONArray j = new JSONArray("ur value");
for (int i = 0; i < j.length(); i++)
{
System.out.println(j.get(i));
}

Android - Parsing Twitter JSON for image url

I'm currently trying to put a twitter feed into my app and currently everything works except when I try to get the image url field from the JSON returned.
Here is my code to parse the JSON:
public ArrayList<Tweet> getTweets() {
String searchUrl =
"http://twitter.com/statuses/user_timeline/vogella.json";
ArrayList<Tweet> tweets =
new ArrayList<Tweet>();
HttpClient client = new DefaultHttpClient();
HttpGet get = new HttpGet(searchUrl);
ResponseHandler<String> responseHandler =
new BasicResponseHandler();
String responseBody = null;
try {
responseBody = client.execute(get, responseHandler);
} catch(Exception ex) {
ex.printStackTrace();
}
JSONObject jsonObject = null;
Log.e("", "responseBody = " + responseBody);
JSONArray arr = null;
try {
arr = new JSONArray(responseBody);
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
for (int i = 0; i < arr.length(); i++) {
try {
jsonObject = arr.getJSONObject(i);
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Tweet tweet = null;
try {
tweet = new Tweet(
jsonObject.getString("profile_image_url"),
jsonObject.getString("text"),
jsonObject.getString("created_at")
);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
tweets.add(tweet);
}
return tweets;
}
And here is the error I get:
02-14 00:19:18.672: W/System.err(809): org.json.JSONException:JSONObject["profile_image_url"] not found.
Despite the "profile_image_url" being present - click the link to see the JSON - LINK. Everything else in the feed appears to be retrievable so why cant I get the image url?

Your jsonObject variable refers to the top level array element of your response, which contains elements like in_reply_to_status_id, geo, etc. The profile_image_url property is not a property in that top level array element, but rather a child element of the user property.
[
{
"in_reply_to_status_id":null,
"in_reply_to_user_id_str":null,
...
"geo":null,
"user":
{
"profile_background_image_url":"http:\/\/a3.twimg.com\/profile_background_images\/112136794\/twilk_background_4c1620bca9ed3.jpg",
...
}
},
...
]
To access the profile_background_image_url, you would have to do something roughly like the following:
JSONObject userObject = jsonObject.getJSONObject ("user");
String url = userObject.getString("profile_image_url");

here is the cause:
[
{
"user":{
"profile_image_url":"http:\/\/a3.twimg.com\/profile_images\/1249241027 \/LarsVogel10_normal.png",
},
"created_at":"Mon Feb 13 22:34:09 +0000 2012",
"text":"Fun evening at speaker dinner at #jfokus."
},
{
..
...
profile_image_url is under "user", while "text" and "created_at" are above

I'm PRETTY sure that to do this you have to read the JSON from the URL that has the 'profile_image_url' variable. The twitter.com/statuses/ URL doesn't have that variable I don't think. This shows that the 'profile_image_url' is at /profile_images/. Just letting you know that changing your URL to that might be able to find it. :P

Permissions Error - Trying to get friends using android facebook sdk

I am trying to add a feature to my android app that allows users to "checkin" with other people tagged to the checkin.
I have the checkins method working no problem and can tag some one by adding the user ID as a parameter (see code below)
public void postLocationTagged(String msg, String tags, String placeID, Double lat, Double lon) {
Log.d("Tests", "Testing graph API location post");
String access_token = sharedPrefs.getString("access_token", "x");
try {
if (isSession()) {
String response = mFacebook.request("me");
Bundle parameters = new Bundle();
parameters.putString("access_token", access_token);
parameters.putString("place", placeID);
parameters.putString("Message",msg);
JSONObject coordinates = new JSONObject();
coordinates.put("latitude", lat);
coordinates.put("longitude", lon);
parameters.putString("coordinates",coordinates.toString());
parameters.putString("tags", tags);
response = mFacebook.request("me/checkins", parameters, "POST");
Toast display = Toast.makeText(this, "Checkin has been posted to Facebook.", Toast.LENGTH_SHORT);
display.show();
Log.d("Tests", "got response: " + response);
if (response == null || response.equals("") ||
response.equals("false")) {
Log.v("Error", "Blank response");
}
} else {
// no logged in, so relogin
Log.d(TAG, "sessionNOTValid, relogin");
mFacebook.authorize(this, PERMS, new LoginDialogListener());
}
} catch(Exception e) {
e.printStackTrace();
}
}
This works fine (I've posted it in case it is of help to anyone else!), the problem i am having is i am trying to create a list of the users friends so they can select the friends they want to tag. I have the method getFriends (see below) which i am then going to use to generate an AlertDialog that the user can select from which in turn will give me the id to use in the above "postLocationTagged" method.
public void getFriends(CharSequence[] charFriendsNames,CharSequence[] charFriendsID, ProgressBar progbar) {
pb = progbar;
try {
if (isSession()) {
String access_token = sharedPrefs.getString("access_token", "x");
friends = charFriendsNames;
friendsID = charFriendsID;
Log.d(TAG, "Getting Friends!");
String response = mFacebook.request("me");
Bundle parameters = new Bundle();
parameters.putString("access_token", access_token);
response = mFacebook.request("me/friends", parameters, "POST");
Log.d("Tests", "got response: " + response);
if (response == null || response.equals("") ||
response.equals("false")) {
Log.v("Error", "Blank response");
}
} else {
// no logged in, so relogin
Log.d(TAG, "sessionNOTValid, relogin");
mFacebook.authorize(this, PERMS, new LoginDialogListener());
}
} catch(Exception e) {
e.printStackTrace();
}
}
When i look at the response in the log it reads:
"got responce: {"error":{"type":"OAuthException", "message":"(#200) Permissions error"}}"
I have looked through the graphAPI documentation and searched for similar questions but to no avail! I'm not sure if i need to request extra permissions for the app or if this is something your just not allowed to do! Any help/suggestions would be greatly appreciated.

You might need the following permissions:
user_checkins
friends_checkins
read_friendlists
manage_friendlists
publish_checkins
Check the related ones from the API docs. Before that, make sure that which line causes this permission error and try to fix it.

The solution is to implement a RequestListener when making the request to the Facebook graph API. I have the new getFriends() method (see below) which uses the AsyncGacebookRunner to request the data.
public void getFriends(CharSequence[] charFriendsNames,String[] sFriendsID, ProgressBar progbar) {
try{
//Pass arrays to store data
friends = charFriendsNames;
friendsID = sFriendsID;
pb = progbar;
Log.d(TAG, "Getting Friends!");
//Create Request with Friends Request Listener
mAsyncRunner.request("me/friends", new FriendsRequestListener());
} catch (Exception e) {
Log.d(TAG, "Exception: " + e.getMessage());
}
}
The AsyncFacebookRunner makes the the request using the custom FriendsRequestListener (see below) which implements the RequestListener class;
private class FriendsRequestListener implements RequestListener {
String friendData;
//Method runs when request is complete
public void onComplete(String response, Object state) {
Log.d(TAG, "FriendListRequestONComplete");
//Create a copy of the response so i can be read in the run() method.
friendData = response;
//Create method to run on UI thread
FBConnectActivity.this.runOnUiThread(new Runnable() {
public void run() {
try {
//Parse JSON Data
JSONObject json;
json = Util.parseJson(friendData);
//Get the JSONArry from our response JSONObject
JSONArray friendArray = json.getJSONArray("data");
//Loop through our JSONArray
int friendCount = 0;
String fId, fNm;
JSONObject friend;
for (int i = 0;i<friendArray.length();i++){
//Get a JSONObject from the JSONArray
friend = friendArray.getJSONObject(i);
//Extract the strings from the JSONObject
fId = friend.getString("id");
fNm = friend.getString("name");
//Set the values to our arrays
friendsID[friendCount] = fId;
friends[friendCount] = fNm;
friendCount ++;
Log.d("TEST", "Friend Added: " + fNm);
}
//Remove Progress Bar
pb.setVisibility(ProgressBar.GONE);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FacebookError e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
Feel free to use any of this code in your own projects, or ask any questions about it.

You can private static final String[] PERMISSIONS = new String[] {"publish_stream","status_update",xxxx};xxx is premissions