Android Null pointer exception while using Async Task method

Question

While executing Async Task in android and getting Json response and while converting response into JSONArray,i am getting NUll pointer Exception. I am trying fron two days Please help me. Here is the code to get the Json String. error is at task.get().

DownloadTask task=new DownloadTask();
        task.execute(new String[]{"URL"});
        try {
            jsonArr=new JSONArray(task.get());
                Toast.makeText(getApplicationContext(), jsonArr.toString(), Toast.LENGTH_LONG).show();
                for (int i = 0; i < jsonArr.length(); i++) {
                    obj = jsonArr.getJSONObject(i);
                    name = obj.getString("name");
                    phno = obj.getString("phone");
                    dcount = obj.getString("count");
                }
        } catch (JSONException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

Here Is the Async task code.

class DownloadTask extends AsyncTask<String,Void,String>{

        private ProgressDialog mProgressDialog=new ProgressDialog(MainActivity.this);

        @Override
        protected void onPreExecute(){
            mProgressDialog.setMessage("Processing");
            mProgressDialog.show();
        }

        @Override
        protected String doInBackground(String... targetURL) {
            URL url;
            HttpURLConnection connection = null;
            try {

                url = new URL(targetURL[0]);
                connection = (HttpURLConnection)url.openConnection();

                connection.setRequestMethod("GET");
                connection.setRequestProperty("Content-Type",
                        "application/json");

                connection.setUseCaches (false);
                connection.setDoInput(true);
                connection.setDoOutput(true);

             /*   //Send request
                DataOutputStream wr = new DataOutputStream (
                        connection.getOutputStream ());
                wr.writeBytes("BID1");
                wr.flush();
                wr.close();*/

                //Get Response
                InputStream is = connection.getInputStream();
                BufferedReader rd = new BufferedReader(new InputStreamReader(is));
                String line;
                StringBuffer response = new StringBuffer();
                while((line = rd.readLine()) != null) {
                    response.append(line);
                    response.append('\r');
                }
                rd.close();
                return response.toString();

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

            } finally {

                if(connection != null) {
                    connection.disconnect();
                }
            }
        }
        @Override
        protected void onPostExecute(String result) {

            Toast.makeText(getApplicationContext(),result, Toast.LENGTH_SHORT);
            mProgressDialog.dismiss();

        }
    }

Answer 1

You are forgot to call the super method of the onPostExecute

It should be like this

@Override
protected void onPostExecute(String result) {

    Toast.makeText(getApplicationContext(),result, Toast.LENGTH_SHORT);
    mProgressDialog.dismiss();
    super.onPostExecute(result);
}

Other Solution

You can use an interface for your callback

ICallback.java

public interface ICallback {
    void onResult(String result);
}

DownloadTask

class DownloadTask extends AsyncTask<String, Void, String> {
    private ProgressDialog mProgressDialog = new ProgressDialog(MainActivity.this);
    private ICallback callback;

    public DownloadTask(ICallback callback) {
        this.callback = callback;
    }

    @Override
    protected void onPreExecute() {
        //Your Codes Here
    }

    @Override
    protected String doInBackground(String... targetURL) {
        //Your Codes Here
    }

    @Override
    protected void onPostExecute(String result) {
        //Your Codes Here
        callback.onResult(result)
    }
}

How to use it

DownloadTask task = new DownloadTask(new ICallback() {
    @Override
    public void onResult(String result) {
        try {
            jsonArr=new JSONArray(result);
            Toast.makeText(getApplicationContext(), jsonArr.toString(), Toast.LENGTH_LONG).show();
            for (int i = 0; i < jsonArr.length(); i++) {
                obj = jsonArr.getJSONObject(i);
                name = obj.getString("name");
                phno = obj.getString("phone");
                dcount = obj.getString("count");
            }
        } catch (JSONException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
}); 

task.execute(new String[]{"URL"});