Android Duplicate list view due to onResume

Issue

Hello I'm new at android. There is a arrayList and a ListView. I used AsyncTask class to invoke the database from MYSQL DB. This AsyncTask class sets mArrayList(this is the arrayList). To update the list view when I return from another activity, I used onResume(). This is the part.

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_mold_breakage_history);

        brokenMoldListView = findViewById(R.id.brokenMoldListView);

        mArrayList = new ArrayList<>();
        GetData task = new GetData();
        task.execute("http://www.cafe24.com/aaa.php");

    }

    @Override
    protected void onResume() {
        super.onResume();

        mArrayList = new ArrayList<>();
        GetData task = new GetData();
        task.execute("http://www.cafe24.com/aaa.php");

In onResume(), I initialized the mArrayList and invoke AsyncTask again to update ListView. The problem is when this activity was first executed, the ListView was duplicated. But, when I back from next page of this Activity, the problem is disappeared. I hope that this issue is not present when activity is first executed. Please help. This is code of AsyncTask class.

@SuppressLint("StaticFieldLeak")
    private class GetData extends AsyncTask<String, Void, String> {
        ProgressDialog progressDialog;
        String errorString = null;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            progressDialog = ProgressDialog.show(MoldBreakageHistoryActivity.this,
                    "Please Wait", null, true, true);
        }


        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);

            progressDialog.dismiss();
            Log.d(TAG, "response  - " + result);

            mJsonString = result;
            showResult();
        }


        @Override
        protected String doInBackground(String... params) {

            String serverURL = params[0];


            try {

                URL url = new URL(serverURL);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();


                httpURLConnection.setReadTimeout(5000);
                httpURLConnection.setConnectTimeout(5000);
                httpURLConnection.connect();


                int responseStatusCode = httpURLConnection.getResponseCode();
                Log.d(TAG, "response code - " + responseStatusCode);

                InputStream inputStream;
                if (responseStatusCode == HttpURLConnection.HTTP_OK) {
                    inputStream = httpURLConnection.getInputStream();
                } else {
                    inputStream = httpURLConnection.getErrorStream();
                }


                InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

                StringBuilder sb = new StringBuilder();
                String line;

                while ((line = bufferedReader.readLine()) != null) {
                    sb.append(line);
                }


                bufferedReader.close();


                return sb.toString().trim();


            } catch (Exception e) {

                Log.d(TAG, "InsertData: Error ", e);
                errorString = e.toString();

                return null;
            }

        }
    }


    private void showResult() {
        try {
            JSONObject jsonObject = new JSONObject(mJsonString);
            JSONArray jsonArray = jsonObject.getJSONArray(TAG_JSON);

            for (int i = 0; i < jsonArray.length(); i++) {

                JSONObject item = jsonArray.getJSONObject(i);

                String brokenDate = item.getString(TAG_BROKEN_DATE);
                String moldCode = item.getString(TAG_MOLD_CODE);
                String finalHitting = item.getString(TAG_FINAL_HITTING_TIMES);


                HashMap<String, String> hashMap = new HashMap<>();

                hashMap.put(TAG_BROKEN_DATE, brokenDate);
                hashMap.put(TAG_MOLD_CODE, moldCode);
                hashMap.put(TAG_FINAL_HITTING_TIMES, finalHitting);


                mArrayList.add(hashMap);
            }

            ListAdapter adapter = new SimpleAdapter(
                    MoldBreakageHistoryActivity.this, mArrayList, R.layout.list_item_broken_mold,
                    new String[]{TAG_BROKEN_DATE, TAG_MOLD_CODE, TAG_FINAL_HITTING_TIMES},
                    new int[]{R.id.brokenDateListItem, R.id.brokenMoldListItem, R.id.finalHittingTimesListItem}
            );

            brokenMoldListView.setAdapter(adapter);

        } catch (JSONException e) {

            Log.d(TAG, "showResult : ", e);
        }
    }

Solution

Remove this:

 mArrayList = new ArrayList<>();
 GetData task = new GetData();
 task.execute("http://www.cafe24.com/aaa.php");

from onCreate. onResume is executed right after onCreate and your async task was executing twice, that's why it was duplicated in the first place. When you hit the back only the onResume was executed, so the problem would happen then.

Answered By - Levi Moreira