Android AsyncTask return multiple values in doInBackground to be used for onPostExecute

Question

I just read and tested the AsyncTask recently and now I need to know how can I pass multiple values in onPostExecute part. Well I use a JSON parser to get values from web but the values I get from the JSON are multiple values where I pass those values into an array separated by the column headers of each data fetched and this is the part where I supposed to return it for the onPostExecute use. But as far as I know you can only use the return once per run (correct me if I'm wrong please).

Well here's my code so far:

public class GetInfo extends AsyncTask<String, Void, List<String>>{

        private final String TAG = null;
        InputStream is = null;
        StringBuilder sb=null;
        List<String> list = new ArrayList<String>();

        @Override
        protected List<String> doInBackground(String... url) {
            String result = "";

            ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

                //CONNECT TO DATABASE
                 try{
                         HttpClient httpclient = new DefaultHttpClient();
                         HttpPost httppost = new HttpPost(url[0]);
                         httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                         HttpResponse response = httpclient.execute(httppost);
                         HttpEntity entity = response.getEntity();
                         is = entity.getContent();
                         Log.v(TAG, "connected");
                 }catch(Exception e){
                         Log.v(TAG, "run failed");

                         Log.e("log_tag", "Error in http connection "+e.toString());
                 }

                 //BUFFERED READER FOR INPUT STREAM
                try{
                     BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                     sb = new StringBuilder();
                     String line = "0";

                     while ((line = reader.readLine()) != null) {
                             sb.append(line + "\n");
                     }
                     is.close();
                     result=sb.toString();
                     Log.v(TAG, "buffered read");
                 }catch(Exception e){
                     Log.v(TAG, "buffered error");
                         Log.e("log_tag", "Error converting result "+e.toString());
                 }

                //CONVERT JSON TO STRING
                try{
                     Log.v(TAG, result);

                         JSONArray jArray = new JSONArray(result);
                         JSONObject json_data=null;

                         for(int i=0;i<jArray.length();i++){
                             Log.v(TAG, "loop start");

                                 json_data = jArray.getJSONObject(i);
                                 list.add(json_data.getString("id"));
                                 list2.add(json_data.getString("city"));
                                 Log.v(TAG, "list added");
                         }

                 }catch(JSONException e){
                     Log.v(TAG, "rest failed");
                         Log.e("log_tag", "Error parsing data "+e.toString());
                 }

                 Log.v(TAG, list.toString());

                return list; //I also need to return the list2 here

        }

        @Override
        protected void onPostExecute(List<String> result) {
            cities = result; //lost in this part hahaha!
            showCities();
        }

    }

Well to add, this code works fine when I return only one String Array (the list) but I get confused now in the second part. Also cities are declared in the Main class and the ShowCities() only used for display. So I don't bother adding the codes.

Answer 1

you can Do One thing Make your ArrayList as Static and access it when you want it.

public static List<String> LIST = new ArrayList<String>();
public static List<String> LIST1 = new ArrayList<String>();

public class GetInfo extends AsyncTask<String, Void, List<String>>{

        private final String TAG = null;
        InputStream is = null;
        StringBuilder sb=null;


        @Override
        protected List<String> doInBackground(String... url) {
            String result = "";

            ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

                //CONNECT TO DATABASE
                 try{
                         HttpClient httpclient = new DefaultHttpClient();
                         HttpPost httppost = new HttpPost(url[0]);
                         httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                         HttpResponse response = httpclient.execute(httppost);
                         HttpEntity entity = response.getEntity();
                         is = entity.getContent();
                         Log.v(TAG, "connected");
                 }catch(Exception e){
                         Log.v(TAG, "run failed");

                         Log.e("log_tag", "Error in http connection "+e.toString());
                 }

                 //BUFFERED READER FOR INPUT STREAM
                try{
                     BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                     sb = new StringBuilder();
                     String line = "0";

                     while ((line = reader.readLine()) != null) {
                             sb.append(line + "\n");
                     }
                     is.close();
                     result=sb.toString();
                     Log.v(TAG, "buffered read");
                 }catch(Exception e){
                     Log.v(TAG, "buffered error");
                         Log.e("log_tag", "Error converting result "+e.toString());
                 }

                //CONVERT JSON TO STRING
                try{
                     Log.v(TAG, result);

                         JSONArray jArray = new JSONArray(result);
                         JSONObject json_data=null;

                         for(int i=0;i<jArray.length();i++){
                             Log.v(TAG, "loop start");

                                 json_data = jArray.getJSONObject(i);
                                 LIST.add(json_data.getString("id"));
                                 LIST1.add(json_data.getString("city"));
                                 Log.v(TAG, "list added");
                         }

                 }catch(JSONException e){
                     Log.v(TAG, "rest failed");
                         Log.e("log_tag", "Error parsing data "+e.toString());
                 }

                 Log.v(TAG, list.toString());

                return LIST; //I also need to return the list2 here

        }

        @Override
        protected void onPostExecute(List<String> result) {
            cities = result; //lost in this part hahaha!
            showCities();
        }

    }

now you can use your both LIST & LIST1 when you want it. you also may not need to return arraylist in DoInBackground.

Hope it will Help you.

Answer 2

Create a new class with two Lists. Use that class as the return type.