//define constructor
public BackgroundTask (Context ctx){
    this.ctx = ctx;
    activity = (Activity)ctx;
}

@Override
protected void onPreExecute() {
    builder = new AlertDialog.Builder(activity);
    progressDialog = new ProgressDialog(ctx);
    progressDialog.setTitle("Please wait");
    progressDialog.setMessage("Connecting to server.....");
    progressDialog.setIndeterminate(true);
    progressDialog.setCancelable(false);
    progressDialog.show();
}

@Override
protected String doInBackground(String... params){
    String method = params[0];

    if (method.equals("register"))
    {
        try {
            URL url = new URL(register_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            OutputStream outputStream = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            String email = params[1];
            String username = params[2];
            String password = params[3];
            String data = URLEncoder.encode("email", "UTF-8")+"="+URLEncoder.encode(email,"UTF-8")+"&"+
                    URLEncoder.encode("username", "UTF-8")+"="+URLEncoder.encode(username,"UTF-8")+"&"+
                    URLEncoder.encode("password", "UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
            bufferedWriter.write(data);
            bufferedWriter.flush();
            bufferedWriter.close();
            outputStream.close();
            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder stringBuilder = new StringBuilder();
            String line = "";
            while ((line=bufferedReader.readLine())!=null);
            {
                stringBuilder.append(line+"n");
            }
            httpURLConnection.disconnect();
            Thread.sleep(5000);
            return stringBuilder.toString().trim();


        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    return null;
}

@Override
protected void onProgressUpdate(Void... values) {
    super.onProgressUpdate(values);
}

@Override
protected void onPostExecute(String json) {

    try{
        progressDialog.dismiss();

            JSONObject jsonObject = new JSONObject(json);
            JSONArray jsonArray = jsonObject.getJSONArray("server_response");
            JSONObject JO = jsonArray.getJSONObject(0);
            String code = JO.getString("code");
            String message = JO.getString("message");
        if (code.equals("reg_true")){
            showDialog("Registration Success",message,code);
        }
        else if(code.equals("reg_false")){
            showDialog("Registration Failed!",message,code);
        }

    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data:" + e.toString());
    }
}

public void showDialog(String title,String message,String code){
    builder.setTitle(title);
    if (code.equals("reg_true")||code.equals("reg_false")){
        builder.setMessage(message);
        builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                activity.finish();
            }
        });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }
}