Android : How to implement kerberos authentication for Android

I have already implemented a restfull web service for Android. Now what i want to do is to implement the log-in authentication part using kerberos. I'm a completely newbee to kerberos (I do have the basic understanding as to what happens).

My login activity async task code is as follows.

protected class AsyncLogin extends AsyncTask {

        String userName=null;
        @Override
        protected Boolean doInBackground(String... params) {

              RestAPI api = new RestAPI();
              boolean userAuth = false;
              try {

                    // Call the User Authentication Method in API
                    JSONObject jsonObj = api.UserAuthentication(params[0],
                                params[1],params[2]);

                    //Parse the JSON Object to boolean
                    JSONParser parser = new JSONParser();
                    userAuth = parser.parseUserAuth(jsonObj);
                    userName=params[0];
              } catch (Exception e) {
                    // TODO Auto-generated catch block
                    Log.d("AsyncLogin", e.getMessage());

              }
              return userAuth;
        }

        @Override
        protected void onPreExecute() {

              super.onPreExecute();

              Toast.makeText(context, "Please Wait...",Toast.LENGTH_SHORT).show();
        }

        @Override
        protected void onPostExecute(Boolean result) {
              // TODO Auto-generated method stub

              //Check user validity
              if (result) {


                  Toast.makeText(context, " Valid username/password ",Toast.LENGTH_SHORT).show();

                 Intent i = new Intent(LoginActivity.this,
                         Connecting_interface.class);
                         i.putExtra("username",userName);
                         startActivity(i);

              }
              else
              {
                    Toast.makeText(context, "Not valid username/password ",Toast.LENGTH_SHORT).show();
              }

        }

  }

How can i implement kerberos into this ?? Please help me

Your valued help is much appreciated. Thanks & Regards