Attempting to use the Built-in android LoginActivity with parse

/**
     * Represents an asynchronous login/registration task used to authenticate
     * the user.
     */
    public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
        @Override
        protected Boolean doInBackground(Void... params) {
            // TODO: attempt authentication against a network service.

            try {
                // Simulate network access.
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                return false;
            }

            ParseUser user = new ParseUser();
            ParseQuery<ParseObject> query = new ParseQuery<ParseObject>(ParseConstants.CLASS_USER);
            query.whereEqualTo(ParseConstants.KEY_EMAIL, mEmail);
            query.findInBackground(new FindCallback<ParseObject>() {
                @Override
                public void done(List<ParseObject> users, ParseException e) {
                    String[] emails = new String[users.size()];
                    int i = 0;
                    for(ParseObject user : users) {
                        emails[i] = user.getString(ParseConstants.KEY_EMAIL);
                        i++;
                    }
                }
            });

            for (String credential : DUMMY_CREDENTIALS) {
                String[] pieces = credential.split(":");
                if (pieces[0].equals(mEmail)) {
                    // Account exists, return true if the password matches.
                    return pieces[1].equals(mPassword);
                }
            }

            // TODO: register the new account here.
            user.setUsername(mEmail);
            user.setEmail(mEmail);
            user.setPassword(mPassword);

            user.signUpInBackground(new SignUpCallback() {
                public void done(ParseException e) {
                    if (e == null) {
                        // Success!
                    } else {
                        // Oops!
                        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
                    }
                }
            });

            return true;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            if (success) {
                Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                startActivity(intent);
            } else {
                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }