Android Studio สอบถามการทำ loading.. ระหว่างรอ call api หน่อยครับ

...} else if (id == R.id.nav_help) {

            FragmentTransaction ft  = getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.ftMain, new HelpFragment() );
            ft.commit();
}

public class HelpFragment extends Fragment {

    private String base_url = "https://domain.com/api";
    private String token_api = "xxxxx";


    public HelpFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view =  inflater.inflate(R.layout.fragment_help, container, false);

        final TextView btnBackToMenu = (TextView)view.findViewById(R.id.btnBackToMenu);
        btnBackToMenu.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                fragmentTransaction.replace(R.id.ftMain, new AccountFragment() );
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }
        });

        /* Send API */

        String url2 = base_url+"/help.php";
        HttpClient client2 = new DefaultHttpClient();
        HttpPost httpPost2 = new HttpPost(url2);

        List<NameValuePair> params2 = new ArrayList<NameValuePair>();
        params2.add(new BasicNameValuePair("action", "getHelp"));
         params2.add(new BasicNameValuePair("token_api", token_api));
        String resultServer  = getHttpPost(url2,params2);

        try {
            JSONObject dbarr = new JSONObject(resultServer);
            final TextView titleHelp = (TextView)view.findViewById(R.id.titleHelp);
            titleHelp.setText( dbarr.getString("title"));

            String textAccount = dbarr.getString("description");
            final TextView textHelp = (TextView)view.findViewById(R.id.textHelp);
            textHelp.setText(HtmlCompat.fromHtml(textAccount, 0));

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


       
        final ProgressBar loader = (ProgressBar)view.findViewById(R.id.loader);
        loader.setVisibility(View.INVISIBLE);
        return view;
    }

    public String getHttpPost(String url, List<NameValuePair> params) {
        StringBuilder str = new StringBuilder();
        HttpClient client = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        try {
            httpPost.setEntity(new UrlEncodedFormEntity(params));
            HttpResponse response = client.execute(httpPost);
            StatusLine statusLine = response.getStatusLine();
            int statusCode = statusLine.getStatusCode();
            if (statusCode == 200) { // Status OK
                HttpEntity entity = response.getEntity();
                InputStream content = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(content));
                String line;
                while ((line = reader.readLine()) != null) {
                    str.append(line);
                }
            } else {
                Log.e("Log", "Failed to download result..");
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return str.toString();
    }

}