NullPointerException for ListView using CustomAdapter

Question

CustomAdapter File included...

1.Initializing ArrayList.

2.Initializing ListView.

3.Grapping the Data from URL and storing in ArrayList

4.Setting ListView with CustomAdapter

5.Please check the CustomAdapter code which below the MainActivity..

public class Screen2 extends AppCompatActivity {     

ProgressDialog pDialog;
        ArrayList<Information> record_list;
        ListView list_view;
        CustomAdapter listAdapter;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.screen2);
            record_list=new ArrayList<Information>();
            list_view=(ListView) findViewById(R.id.list_view);
            new Test().execute();
        }

        public class Test extends AsyncTask<String, Void, ArrayList<Information>> {
            @Override
            protected void onPreExecute() {

                super.onPreExecute();

                // Showing progress dialog
                pDialog = new ProgressDialog(Screen2.this);
                pDialog.setMessage("Please wait...");
                pDialog.setCancelable(false);
                pDialog.show();
            }

            @Override
            protected ArrayList<Information> doInBackground(String... params) {

                String jsonStr = makeServiceCall();
                try {
                    JSONArray jsonArray=new JSONArray(jsonStr);
                    for(int i=0;i<jsonArray.length();i++){
                        JSONObject jsonObject=jsonArray.getJSONObject(i);
                        String id=jsonObject.getString("id");
                        String name=jsonObject.getString("label");
                        String email=jsonObject.getString("email");
                        Information information=new Information(id,name,email);
                        record_list.add(information);
                        return record_list;
                    }
                    System.out.println(jsonStr);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

                return null;
            }

            @Override
            protected void onPostExecute(ArrayList<Information> s) {
                super.onPostExecute(s);
                // Dismiss the progress dialog
                //listAdapter=new CustomAdapter(Screen2.this,record_list);
                listAdapter=new CustomAdapter(Screen2.this,record_list);
                list_view.setAdapter(listAdapter);
                if (pDialog.isShowing())
                    pDialog.dismiss();

                /**
                 * Updating parsed JSON data into ListView
                 * */
            }

            public String makeServiceCall(){
                String response = null;
                try {
                    URL url = new URL("http://192.168.1.109:9000/tasks2");
                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                    conn.setRequestMethod("GET");
                    // read the response
                    InputStream in = new BufferedInputStream(conn.getInputStream());
                    response = convertStreamToString(in);
                } catch (MalformedURLException e) {
                    System.out.println("MalformedURLException: " + e.getMessage());
                } catch (ProtocolException e) {
                    System.out.println("MalformedURLException: " + e.getMessage());
                } catch (IOException e) {
                    System.out.println("MalformedURLException: " + e.getMessage());
                } catch (Exception e) {
                    System.out.println("MalformedURLException: " + 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();
                    }
                }
                System.out.println(sb);
                return sb.toString();
            }
        }

}

CustomAdapter.java:(Here is my CustomAdapter File) I don't see any error in this file too...

public class CustomAdapter extends ArrayAdapter<Information> {

        public CustomAdapter(Context c, ArrayList<Information> record) {
            super(c, R.layout.custom_row, record);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            // Get the data item for this position

            Information information = getItem(position);

            //LayoutInflater inflater=LayoutInflater.from(getContext());

            // Check if an existing view is being reused, otherwise inflate the view

            convertView = LayoutInflater.from(getContext()).inflate(R.layout.custom_row, parent, false);

            // Lookup view for data population

            TextView record_id = (TextView) convertView.findViewById(R.id.record_id);

            TextView record_name = (TextView) convertView.findViewById(R.id.record_name);

            TextView record_email = (TextView) convertView.findViewById(R.id.record_email);

            // Populate the data into the template view using the data object

            record_id.setText(information.id);
            record_name.setText(information.name);
            record_email.setText(information.email);

            return convertView;
        }
}

Extracted JSON Response:I/System.out: id: 2name:Physiotherapyemailhariprasad.sala@gmail.com I/System.out: id: 3name:Cardiologyemailhariprasad.sala@gmail.com I/System.out: id:5name:FirstGooseDoesemailhariprasad.sala@gmail.com I/System.out: id: 9name:BestOneemailhariprasad.sala@gmail.com I/System.out: id: 17name:Overallemailhariprasad.sala@gmail.com I/System.out: id: 19name:Androidemailhariprasad.sala@gmail.com — Hari Prasad Sala, Dec 18 '17 at 02:43
Guy's Thanks a alot for your time...., that was a small confusion with layouts, Forgot to changes the ListView id for my Screen Size Layout. — Hari Prasad Sala, Dec 19 '17 at 07:35

score 0 · Accepted Answer · answered Dec 18 '17 at 02:15

0

There are logical errors in code:

The for loop has a return statement inside it while you have to iterate so do this for a good design define another variable for Arraylist lets say s and the code would look like this:

@Override
protected ArrayList<Information> doInBackground(String... params) {

    String jsonStr = makeServiceCall();
    ArrayList<Information> s = new ArrayList<Information>();
    try {
        JSONArray jsonArray=new JSONArray(jsonStr);
        for(int i=0;i<jsonArray.length();i++){
            JSONObject jsonObject=jsonArray.getJSONObject(i);
            String id=jsonObject.getString("id");
            String name=jsonObject.getString("label");
            String email=jsonObject.getString("email");
            Information information=new Information(id,name,email);
            s.add(information); 
        }
        System.out.println(jsonStr);
        return s;
    } catch (JSONException e) {
        e.printStackTrace();
    }

    return null;
}

Then on your onPostExecute make record_list be s like this:

@Override
protected void onPostExecute(ArrayList<Information> s) {
    super.onPostExecute(s);
    // Dismiss the progress dialog
    //listAdapter=new CustomAdapter(Screen2.this,record_list);
    record_list = s;
    listAdapter=new CustomAdapter(Screen2.this,record_list);
    list_view.setAdapter(listAdapter);
    if (pDialog.isShowing())
        pDialog.dismiss();

    /**
     * Updating parsed JSON data into ListView
     * */
}

answered Dec 18 '17 at 02:15

Xenolion

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Tried changing to above, still have the same Exception. – Hari Prasad Sala Dec 18 '17 at 02:23
Which line does the log say it has a problem? The line that appear in blue! – Xenolion Dec 18 '17 at 02:24
list_view.setAdapter(listAdapter); @ onPostExecute. – Hari Prasad Sala Dec 18 '17 at 02:29
What gets printed on logs by this line of code does this say `System.out.println(jsonStr);` – Xenolion Dec 18 '17 at 02:29
It prints JSON string which I've extracted from URL... – Hari Prasad Sala Dec 18 '17 at 02:31
I/System.out: [{"id":2,"label":"Physiotherapy","image":"/9j/7QAsUGhvd.....}] – Hari Prasad Sala Dec 18 '17 at 02:33
does `"email"` exist? – Xenolion Dec 18 '17 at 02:35
Yes, I've already extracted those value's from JSON data and displayed on to my screen. They are very much there... – Hari Prasad Sala Dec 18 '17 at 02:36
If you real updated the `onPostExecute` and `doBackground` code like I have shown you then there is no more problem there! I am doubting your `CustomAdapter` edit the question add it! – Xenolion Dec 18 '17 at 02:43
Guy's Thanks a alot for your time...., that was a small confusion with layouts, Forgot to changes the ListView id for my Screen Size Layout. – Hari Prasad Sala Dec 19 '17 at 07:36
@Hari I am glad you solved the problem **Happy Coding!**. – Xenolion Dec 19 '17 at 07:38
Thank You...Wish you the same. – Hari Prasad Sala Dec 19 '17 at 07:43

NullPointerException for ListView using CustomAdapter

1 Answers1