AsyncTask and SOAP webservices

I'm new to SOAP webservices and AsyncTask, I'm developing an app which is using SOAP webservices for login. I tried to do all work in onCreate method but I got android.os.NetworkOnMainThreadException.

So i tried to use AsyncTask, but I'm not able to get reference to emailText and passwordText in RetrieveFeedTask class.

Here is my code:

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {


    private static String SOAP_ACTION = "intentionally hided";
    private static String NAMESPACE = "intentionally hided";
    private static String METHOD_NAME = "intentionally hided";
    private static String URL = "intentionally hided";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        final EditText emailText = (EditText) findViewById(R.id.emailText);
        final EditText passwordText = (EditText) findViewById(R.id.passwordText);
        Button loginButton = (Button) findViewById(R.id.button_login);

        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                new RetrieveFeedTask().execute();

            }
        });
    }

    class RetrieveFeedTask extends AsyncTask<String, String, String> {



        protected String doInBackground(String... urls) {


            SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);

            request.addProperty("userName", emailText.getText().toString());
            request.addProperty("userPassword", passwordText.getText().toString());

            SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);

            envelope.setOutputSoapObject(request);
            envelope.dotNet = true;

            try {
                HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);

                androidHttpTransport.call(SOAP_ACTION, envelope);

                SoapObject result = (SoapObject) envelope.bodyIn;
                if (result != null) {
                    Toast.makeText(getApplicationContext(), "Login Successful!", Toast.LENGTH_LONG).show();
                } else {
                    Toast.makeText(getApplicationContext(), "Login Failed!", Toast.LENGTH_LONG).show();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }