Helper class for integrating Google sign in on Android

GoogleSignInManager.java

//
// GoogleSignInManager
// Created by Ben De La Haye on 24/03/2016.
//
public class GoogleSignInManager implements GoogleApiClient.OnConnectionFailedListener {

    public interface Listener {
        void onUserSignedIn(GoogleSignInAccount account);
        void onUserSignInFailed(int errorCode, String errorMessage);
        void onUserDataRetrieved(@Nullable Person person);
        void onUserSignedOut();
    }

    private static final boolean DEBUG = true;
    private static final int RC_SIGN_IN = 123;

    private GoogleSignInOptions _signInOptions;
    private GoogleApiClient _googleApiClient;
    private GoogleApiClient _googlePlusApiClient;

    private ProgressDialog _progressDialog;

    private final FragmentActivity _activity;
    private final Listener _listener;

    public GoogleSignInManager(FragmentActivity activity, Listener listener) {
        _activity = activity;
        _listener = listener;

        // Configure sign-in to request the user's ID, email address, and basic
        // profile. ID and basic profile are included in DEFAULT_SIGN_IN.
        _signInOptions = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .requestIdToken(Constants.WEB_CLIENT_ID)
                .build();

        // Build a GoogleApiClient with access to the Google Sign-In API and the
        // options specified by gso.
        _googleApiClient = new GoogleApiClient.Builder(_activity)
                .addApi(Auth.GOOGLE_SIGN_IN_API, _signInOptions)
                .build();

        // Build a GoogleApiClient with access to the Google Sign-In API and the
        // options specified by gso.
        _googlePlusApiClient = new GoogleApiClient.Builder(_activity)
                .addApi(Plus.API)
                .addScope(Plus.SCOPE_PLUS_LOGIN)
                .build();
    }

    public void attemptSilentSignIn() {

        if (DEBUG) Logger.debug(this, "attemptSilentSignIn()");

        ensureClientsAreConnected();

        OptionalPendingResult<GoogleSignInResult> opr = Auth.GoogleSignInApi.silentSignIn(_googleApiClient);
        if (opr.isDone()) {

            // If the user's cached credentials are valid, the OptionalPendingResult will be "done"
            // and the GoogleSignInResult will be available instantly.
            GoogleSignInResult result = opr.get();
            handleSignInResult(result);

        } else {

            // If the user has not previously signed in on this device or the sign-in has expired,
            // this asynchronous branch will attempt to sign in the user silently.  Cross-device
            // single sign-on will occur in this branch.
            showProgressDialog();
            opr.setResultCallback(new ResultCallback<GoogleSignInResult>() {
                @Override
                public void onResult(@NonNull GoogleSignInResult googleSignInResult) {
                    handleSignInResult(googleSignInResult);
                }
            });
        }
    }

    public void signIn(Activity activity) {
        if (DEBUG) Logger.debug(this, "signIn()");

        ensureClientsAreConnected();

        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(_googleApiClient);
        activity.startActivityForResult(signInIntent, RC_SIGN_IN);
    }

    private void signOut() {
        if (DEBUG) Logger.debug(this, "signOut()");

        ensureClientsAreConnected();

        Auth.GoogleSignInApi.signOut(_googleApiClient).setResultCallback(
                new ResultCallback<Status>() {
                    @Override
                    public void onResult(Status status) {
                        _listener.onUserSignedOut();
                    }
                });
    }

    private void ensureClientsAreConnected() {
        if (!_googleApiClient.isConnected()) _googleApiClient.connect();
        if (!_googlePlusApiClient.isConnected()) _googlePlusApiClient.connect();
    }

    public void handleActivityResult(int requestCode, int resultCode, Intent data) {

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (resultCode == Activity.RESULT_OK && requestCode == RC_SIGN_IN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            handleSignInResult(result);
        }
    }

    private void handleSignInResult(final GoogleSignInResult result) {
        Logger.debug(this, "handleSignInResult:" + result.isSuccess());

        hideProgressDialog();
        if (result.isSuccess() && result.getSignInAccount() != null) {

            _listener.onUserSignedIn(result.getSignInAccount());

        } else {

            // Signed out, show unauthenticated UI.
            _listener.onUserSignInFailed(result.getStatus().getStatusCode(), result.getStatus().getStatusMessage());
        }
    }

    public void getUserData(GoogleSignInAccount account) {

        // TODO Not working
        Plus.PeopleApi.load(_googlePlusApiClient, account.getId()).setResultCallback(new ResultCallback<People.LoadPeopleResult>() {
            @Override
            public void onResult(@NonNull People.LoadPeopleResult loadPeopleResult) {

                if (loadPeopleResult.getPersonBuffer() != null) {

                    Person person = loadPeopleResult.getPersonBuffer().get(0);
                    _listener.onUserDataRetrieved(person);

                } else {
                    _listener.onUserSignInFailed(-1, loadPeopleResult.getStatus().getStatusMessage());
                }
            }
        });
    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        if (DEBUG) Logger.debug(this, "onConnectionFailed()" + connectionResult);

        _listener.onUserSignInFailed(connectionResult.getErrorCode(), connectionResult.getErrorMessage());
    }

    private void showProgressDialog() {
        if (_progressDialog == null) {
            _progressDialog = new ProgressDialog(_activity);
            _progressDialog.setMessage("Signing you in...");
            _progressDialog.setIndeterminate(true);
        }

        _progressDialog.show();
    }

    private void hideProgressDialog() {
        if (_progressDialog != null && _progressDialog.isShowing()) {
            _progressDialog.hide();
        }
    }
}