I want to fetch jsonarray from a json api and show it in listview in android

Question

This is my code, we are using in MainActivity..I am using following code in MainActivity but it showing null pointer exception.

public class MainActivity extends ListActivity {

    // URL to get contacts JSON
    private static String url = "https://swastianalytics.herokuapp.com/api/v1/fw_f/?access_token=2xbvwsIlD5gQgoSsqqb3wKiW0soLrqUSVoBBOzcxED9A1D9WFP5M6HGBQlX5aroV";

    // JSON Node names
    private static final String TABLE_INFO = "fw_f";
    private static final String TAG_FIELDWORKER_ID = "fieldworkerid";
    private static final String TAG_FW_NAME = "fw_name";
    private static final String TAG_FACILITY_ID = "facility_id";
    private static final String TAG_FACILITY_NAME = "facility_name";
    private static final String TAG_FS_MENTOR_ID = "fs_mentor_id";
    private static final String TAG_FS_MENTOR_NAME = "fs_mentor_name";
    private static final String TAG_STATE_ID = "state_id";
    private static final String TAG_STATE_NAME = "state_name";
    private static final String TAG_REGION_ID = "region_id";
    private static final String TAG_REGION_NAME = "region_name";
    private static final String TAG_NATIONAL_ID = "national_id";
    private static final String TAG_NATIONAL_NAME = "national_name";
    private static final String TAG_TOTAL_MEMBERS = "total_members";
    private static final String TAG_POSITIVE_MEMBERS = "positive_members";
    private static final String TAG_ELIGIBLE_FOR_ART = "eligible_for_art";
    private static final String TAG_MEMBERS_ON_ART = "members_on_art";
    private static final String TAG_LOST_TO_FOLLOW_UP = "lost_to_follow_up";
    private static final String TAG_MEM_NOT_MET_COUNT = "mem_not_met_count";
    private static final String TAG_VULNERABLE_COUNT = "vulnerable_count";
    private static final String TAG_ID_ZERO = "id_zero";
    private static final String TAG_ID_ONE = "id_one";
    private static final String TAG_ID_TWO = "id_two";
    private static final String TAG_TOP_SCHEMES_ZERO = "top_schems_zero";
    private static final String TAG_TOP_SCHEMES_ONE = "top_schems_one";
    private static final String TAG_TOP_SCHEMES_TWO = "top_schems_two";
    private static final String TAG_SCHEMES_ZERO = "schems_zero";
    private static final String TAG_SCHEMES_ONE = "schems_one";
    private static final String TAG_SCHEMES_TWO = "schems_two";
    private static final String TAG_INCIDENTS_EXTREME = "incidents_extreme";
    private static final String TAG_INCIDENTS_FOLLOW = "incidents_follow";
    private static final String TAG_INCIDENTS_OPENED = "incidents_opened";
    private static final String TAG_INCIDENTS_SEVERITY = "incidents_severity";
    private static final String TAG_MEM_1_INCIDENT_WEEK = "mem_1_incident_week";
    private static final String TAG_MEM_FLS_NOT_COMPLETE = "mem_fls_not_complete";
    private static final String TAG_MEM_FPS_NOT_COMPLETE = "mem_fps_not_complete";
    private static final String TAG_MEM_NO_BANK_ACC_PO = "mem_no_bank_acc_po";
    private static final String TAG_MEM_NO_3MON_SAVINGS = "mem_no_3mon_savings";
    private static final String TAG_MEM_NO_SAVINGS = "mem_no_savings";
    private static final String TAG_MEM_NO_INSURANCE = "mem_no_insurance";
    private static final String TAG_MEM_NO_INVESTMENT = "mem_no_investment";
    private static final String TAG_MEM_DUE = "mem_due";
    private static final String TAG_MEM_CHAMPIONS = "mem_champions";
    private static final String TAG_DUE_COUNT = "due_count";
    private static final String TAG_OVERDUE_COUNT = "overdue_count";
    private static final String TAG_MEM_CHAMPIONS_PROPOSED = "mem_champions_proposed";
    private static final String TAG_MEM_CHAMPIONS_APPROVED = "mem_champions_approved";
    private static final String TAG_ID = "id";

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

        // Calling async task to get json
        new GetTable().execute();
    }

    /**
     * Async task class to get json by making HTTP call
     */
    private class GetTable extends AsyncTask<Void, Void, Void> {

        // Hashmap for ListView
        ArrayList<HashMap<String, String>> tableList;
        ProgressDialog pDialog;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
            pDialog = new ProgressDialog(MainActivity.this);
            pDialog.setMessage("Please wait...");
            pDialog.setCancelable(false);
            pDialog.show();
        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            WebRequest webreq = new WebRequest();

            // Making a request to url and getting response
            String jsonStr = webreq.makeWebServiceCall(url, WebRequest.GET);

            Log.d("Response: ", "> " + jsonStr);

            tableList = ParseJSON(jsonStr);
           // JSONArray jsonArray=jsonStr.makeWebSer(url);

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
            if (pDialog.isShowing())
                pDialog.dismiss();
            /**
             * Updating parsed JSON data into ListView
             * */
            ListAdapter adapter = new SimpleAdapter(
                    MainActivity.this, tableList,
                    R.layout.list_item, new String[]{TAG_FIELDWORKER_ID,
                    TAG_FW_NAME,TAG_FACILITY_ID,TAG_FACILITY_NAME}, new int[]{
                    R.id.fieldworkerid, R.id.fw_name,R.id.facility_id,
                    R.id.facility_name});

                     setListAdapter(adapter);
        }

    }

    private ArrayList<HashMap<String, String>> ParseJSON(String json) {
        if (json != null) {
            try {
                // Hashmap for ListView
                ArrayList<HashMap<String, String>> tableList = new ArrayList<HashMap<String, String>>();

               // JSONObject jsonObj = new JSONObject(json);

                // Getting JSON Array node
                JSONArray tableFields = new JSONArray(TABLE_INFO);

                // looping through All tableFields
                for (int i = 0; i < tableFields.length(); i++) {
                     //c=new JSONObject();
                    JSONObject c = tableFields.getJSONObject(i);
                    //JSONObject c=(JSONObject)tableFields.get(i);
                    String fieldworkerid = c.getString(TAG_FIELDWORKER_ID);
                    String fw_name = c.getString(TAG_FW_NAME);
                    String facility_id = c.getString(TAG_FACILITY_ID);
                    String facility_name = c.getString(TAG_FACILITY_NAME);
                    Log.d(TAG_FIELDWORKER_ID,fieldworkerid);
                    Log.d(TAG_FW_NAME,fw_name);
                    Log.d(TAG_FACILITY_ID,facility_id);
                    Log.d(TAG_FACILITY_NAME,facility_name);
                  /*  String fs_mentor_id = c.getString(TAG_FS_MENTOR_ID);
                    String fs_mentor_name = c.getString(TAG_FS_MENTOR_NAME);
                    String state_id = c.getString(TAG_STATE_ID);
                    String state_name = c.getString(TAG_STATE_NAME);
                    String region_id = c.getString(TAG_REGION_ID);
                    String region_name = c.getString(TAG_REGION_NAME);
                    String national_id = c.getString(TAG_NATIONAL_ID);
                    String national_name = c.getString(TAG_NATIONAL_NAME);
                    String total_members = c.getString(TAG_TOTAL_MEMBERS);
                    String positive_members = c.getString(TAG_POSITIVE_MEMBERS);
                    String eligible_for_art = c.getString(TAG_ELIGIBLE_FOR_ART);
                    String members_on_art = c.getString(TAG_MEMBERS_ON_ART);
                    String lost_to_follow_up = c.getString(TAG_LOST_TO_FOLLOW_UP);
                    String mem_not_met_count = c.getString(TAG_MEM_NOT_MET_COUNT);
                    String vulnerable_count = c.getString(TAG_VULNERABLE_COUNT);
                    String id_zero = c.getString(TAG_ID_ZERO);
                    String id_one = c.getString(TAG_ID_ONE);
                    String id_two = c.getString(TAG_ID_TWO);
                    String top_schems_zero = c.getString(TAG_TOP_SCHEMES_ZERO);
                    String top_schems_one = c.getString(TAG_TOP_SCHEMES_ONE);
                    String top_schems_two = c.getString(TAG_TOP_SCHEMES_TWO);
                    String schems_zero = c.getString(TAG_SCHEMES_ZERO);
                    String schschems_one = c.getString(TAG_SCHEMES_ONE);
                    String schems_two = c.getString(TAG_SCHEMES_TWO);
                    String incidents_extreme = c.getString(TAG_INCIDENTS_EXTREME);
                    String incidents_follow = c.getString(TAG_INCIDENTS_FOLLOW);
                    String incidents_opened = c.getString(TAG_INCIDENTS_OPENED);
                    String incidents_severity = c.getString(TAG_INCIDENTS_SEVERITY);
                    String mem_1_incident_week = c.getString(TAG_MEM_1_INCIDENT_WEEK);
                    String mem_fls_not_complete = c.getString(TAG_MEM_FLS_NOT_COMPLETE);
                    String mem_fps_not_complete = c.getString(TAG_MEM_FPS_NOT_COMPLETE);
                    String mem_no_bank_acc_po = c.getString(TAG_MEM_NO_BANK_ACC_PO);
                    String mem_no_3mon_savings = c.getString(TAG_MEM_NO_3MON_SAVINGS);
                    String mem_no_savings = c.getString(TAG_MEM_NO_SAVINGS);
                    String mem_no_insurance = c.getString(TAG_MEM_NO_INSURANCE);
                    String mem_no_investment = c.getString(TAG_MEM_NO_INVESTMENT);
                    String mem_due = c.getString(TAG_MEM_DUE);
                    String mem_champions = c.getString(TAG_MEM_CHAMPIONS);
                    String due_count = c.getString(TAG_DUE_COUNT);
                    String overdue_count = c.getString(TAG_OVERDUE_COUNT);
                    String mem_champions_proposed = c.getString(TAG_MEM_CHAMPIONS_PROPOSED);
                    String mem_champions_approved = c.getString(TAG_MEM_CHAMPIONS_APPROVED);
                    String id = c.getString(TAG_ID);*/

                   /* // Phone node is JSON Object
                    JSONObject phone = c.getJSONObject(TAG_PHONE);
                    String mobile = phone.getString(TAG_PHONE_MOBILE);
                    String home = phone.getString(TAG_PHONE_HOME);*/

                    // tmp hashmap for single table
                    HashMap<String, String> table = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    table.put(TAG_FIELDWORKER_ID, fieldworkerid);
                    table.put(TAG_FW_NAME, fw_name);
                    table.put(TAG_FACILITY_ID, facility_id);
                    table.put(TAG_FACILITY_NAME, facility_name);

                    // adding table to tablelist
                    tableList.add(table);
                }
                return tableList;
            } catch (JSONException e) {
                e.printStackTrace();
                return null;
            }
        } else {
            Log.e("ServiceHandler", "Couldn't get any data from the url");
            return null;
        }
    }

}

This is http code...

public class WebRequest {

    static String response = null;
    public final static int GET = 1;
    public final static int POST = 2;

    //Constructor with no parameter
    public WebRequest() {

    }

    /**
    * Making web service call
    *
    * @url - url to make request
    * @requestmethod - http request method
    */
    public String makeWebServiceCall(String url, int requestmethod) {
        return this.makeWebServiceCall(url, requestmethod, null);
    }

    /**
    * Making service call
    *
    * @url - url to make request
    * @requestmethod - http request method
    * @params - http request params
    */
    public String makeWebServiceCall(String urladdress, int requestmethod, HashMap<String, String> params) {
        URL url;
        String response = "";
        try {
            url = new URL(urladdress);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(15000);
            conn.setConnectTimeout(15000);
            conn.setDoInput(true);
            conn.setDoOutput(true);

            if (requestmethod == POST) {
                conn.setRequestMethod("POST");
            } else if (requestmethod == GET) {
                conn.setRequestMethod("GET");
            }

            if (params != null) {
                OutputStream os = conn.getOutputStream();
                BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));

                StringBuilder result = new StringBuilder();
                boolean first = true;
                for (Map.Entry<String, String> entry : params.entrySet()) {
                    if (first)
                        first = false;
                    else
                        result.append("&");

                    result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
                    result.append("=");
                    result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
                }

                writer.write(result.toString());

                writer.flush();
                writer.close();
                os.close();
            }

            int responseCode = conn.getResponseCode();

            if (responseCode == HttpsURLConnection.HTTP_OK) {
                String line;
                BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                while ((line = br.readLine()) != null) {
                    response += line;
                }

            } else {
                response = "";
            }

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

        return response;
    }

}

This is the error that showing in logcat....

04-26 05:54:40.534 5884-5884/com.example.converbiz.apidemo E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPointerException at android.widget.SimpleAdapter.getCount(SimpleAdapter.java:93) at android.widget.ListView.setAdapter(ListView.java:462) at android.app.ListActivity.setListAdapter(ListActivity.java:265) at com.example.converbiz.apidemo.MainActivity$GetTable.onPostExecute(MainActivity.java:134) at com.example.converbiz.apidemo.MainActivity$GetTable.onPostExecute(MainActivity.java:86) at android.os.AsyncTask.finish(AsyncTask.java:631) at android.os.AsyncTask.access$600(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method)

Answer 1

I think problem in setListAdapter().

You calling setListAdapter(adapter); from GetTable class.

So try to call setListAdapter() from onCreate() of MainActivity class.

Answer 2

Can you replace below code and check

// Hashmap for ListView
    ArrayList<HashMap<String, String>> tableList;
    ProgressDialog pDialog;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        tableList= new ArrayList<HashMap<String, String>> ;
        // Showing progress dialog
        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();
    }

    @Override
    protected Void doInBackground(Void... arg0) {
        // Creating service handler class instance
        WebRequest webreq = new WebRequest();

        // Making a request to url and getting response
        String jsonStr = webreq.makeWebServiceCall(url, WebRequest.GET);

        Log.d("Response: ", "> " + jsonStr);

        tableList = ParseJSON(jsonStr);
       // JSONArray jsonArray=jsonStr.makeWebSer(url);

        return null;
    }