Android Array list returns Null after adding values

Question

I am trying to add values to array list for ploting xAxis value in mpandroid chart but while debugging array list returns Null

While adding in forloop it shows value but after the end of forloop array list is empty Help me

Code

private ArrayList<String> getXAxisValues() {
final ArrayList<String> xAxis = new ArrayList<>();
final Intent intent = getIntent();
final String getUserId =  intent.getStringExtra("UserId");
new Thread(new Runnable() {
    public void run() {
        HttpRequest req = null;
        try {
            req = new HttpRequest("http://abc.sc.in/abc.php");
            final String response = req.preparePost().withData("answerUserId="+getUserId).sendAndReadString();


            JSONArray myObjects = null;
            try {
                myObjects = new JSONArray(response);

                for (int ji = 1; ji < myObjects.length(); ji++) {
                    JSONObject jsonobject = myObjects.getJSONObject(ji);
                    final String Date = jsonobject.getString("date(answerDate)");
                    System.out.println("Date Response =====>: " + Date);
                   // The Values of Date (2 Dates [21,23]) here are shown while adding
                    xAxis.add(Date); 

                }

            } catch (JSONException e) {
                e.printStackTrace();
            }






        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}).start();


System.out.println("Here It shows [] after adding values ==============================>" + xAxis);

return xAxis;

}

actually your thread is not executed and before that you are returning xAxis — Pavya
– Pavya, Commented Nov 24, 2015 at 6:45
@user3676184 Is there any possibility of adding return inside thread or after thread execution — Vinod Kumar
– Vinod Kumar, Commented Nov 24, 2015 at 6:47

Pavya · Accepted Answer · 2015-11-24 06:53:01Z

2

create AsynchTask task that will return arraylist like

public class DemoAsynch extends AsyncTask<Context, Integer, ArrayList<String>>{

}

After that

ArrayList<String> abc = new DemoAsynch().execute().get();

in abc you will get all list and also pass your id whatever you required to that asynch

answered Nov 24, 2015 at 6:53

Pavya

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1 Comment

ρяσѕρєя K Over a year ago

Calling get() method will hang Main Ui Thread which will cause "ANR" Dialog. so call execute() method without get() method and use onPostExecute

ρяσѕρєя K · Accepted Answer · 2015-11-24 06:54:32Z

2

While adding in forloop it shows value but after the end of forloop array list is empty

Because getXAxisValues() method return value after calling Thread.start() instead of wait until run method execution finish.

Either use Callable and Future classes to get status of running Thread before getting value or in Android, best way is do it using AsyncTask by implementing doInBackground and onPostExecute methods

answered Nov 24, 2015 at 6:54

ρяσѕρєя K

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1 Comment

Vinod Kumar Over a year ago

Upvote for listing possible ways ..I'll replace it with async thanks

Suresh Atta · Accepted Answer · 2015-11-24 06:56:04Z

2

I am not an Android guru but you missed the concept.

You really need to understand how an asynchronous call works. You are printing values and then the response coming back .

Try printing after the response came

for (int ji = 1; ji < myObjects.length(); ji++) {
                    JSONObject jsonobject = myObjects.getJSONObject(ji);
                    final String Date = jsonobject.getString("date(answerDate)");
                    System.out.println("Date Response =====>: " + Date);
                   // The Values of Date (2 Dates [21,23]) here are shown while adding
                    xAxis.add(Date); 
    System.out.println("Here It shows [] after adding values ==============================>" + xAxis);


                }

edited Nov 24, 2015 at 6:56

answered Nov 24, 2015 at 6:43

Suresh Atta

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2 Comments

Vinod Kumar Over a year ago

How can I do that ? can u modify and show how it will work ?

Suresh Atta Over a year ago

@vinod I already did. Look at the line System.out.println("Here It shows [] after adding values ==============================>" + xAxis);

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