Question

I know that ProgressDialog with Threads questions have been asked many times but none of the solutions seem to work for my project. Basically what I want to do is this:
1) when a user clicks a button the Activity sends an auth request to the server
2) while this is being done a ProgressDialog is shown
3) when the reponse comes I want to dismiss the ProgressDialog and the return object to be read and interpreted by the Activity

If I:
1) set the Thread to update the Application field with the reponse, the next method (which is outside of the Thread) throws an NPE when accessing the field
2) if I include the next method in the Thread, the second method throws a ‘java.lang.RuntimeException: Can’t create handler inside thread that has not called Looper.prepare()’

Sorry for a long text, but I am totally losing it over this… My code is sth like this:

public class XXX extends Activity implements OnClickListener {

// (...)
private SoapObject returnObject;
private String response;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    // (...)
        authProgressDialog = ProgressDialog.show(XXX.this, "", "Authenticating...", true, false);
        new Thread(new Runnable() {
            @Override
            public void run() {
                authenticate(); // method that calls the API via SOAP
                authenticateReal(); // method that handles the response
            }
        }).start();

        mHandler = new Handler() {
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                switch (msg.what) {
                    case 10:
                        authProgressDialog.dismiss();
                        break;
                }
            }
        };
    }
}

public void authenticate() {
    // API stuff (...)
    AndroidHttpTransport aht = new AndroidHttpTransport(URL);
    try {
        aht.call(SOAP_ACTION, soapEnvelope);
        returnObject = (SoapObject) soapEnvelope.getResponse();
        response = returnObject.getProperty("ResponseStatus").toString();
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    finally {
        mHandler.sendEmptyMessage(10);
    }
}

// Method that needs to access returnObject and reponse objects and
// it is here where the NPE's or other exceptions are thrown
public void authenticateReal() {
// (...)
}

Answer 1

You better use AsyncTask (which is the Android way):

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    new TheTask().execute();
}

private class TheTask extends AsyncTask<Void, Void, Void>{

    @Override
    protected void onPreExecute() {
        authProgressDialog = ProgressDialog.show(XXX.this, "", "Authenticating...", true, false);
    }

    @Override
    protected Void doInBackground(Void... params) {
        authenticate(); // method that calls the API via SOAP
        authenticateReal(); // method that handles the response
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        authProgressDialog.dismiss();
    }
}

By the way… I have found this presentation to be very useful (it talks about REST apps, but you can apply the same concept for different kind of apps): Developing Android REST client applications