A basic implementation of the GoogleSignInManager

BaseAuthActivity.java

//
// BaseAuthActivity
// Created by Ben De La Haye on 28/04/2016.
//
public abstract class BaseAuthActivity extends BaseActivity implements GoogleSignInManager.Listener, Callback<LoginResponse> {

    private GoogleSignInManager _googleSignInManager;
    private AuthenticatedUser authenticatedUser;

    public abstract void onUserLoggedIn();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        _googleSignInManager = new GoogleSignInManager(this, this);
        authenticatedUser = AuthenticatedUser.getInstance();
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {

        if (AuthenticatedUser.getInstance().isLoggedIn()) {
            menu.findItem(R.id.action_log_in).setVisible(false);
            menu.findItem(R.id.action_user_profile).setVisible(true);
        } else {
            menu.findItem(R.id.action_log_in).setVisible(true);
            menu.findItem(R.id.action_user_profile).setVisible(false);
        }
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_log_in:
                if (AuthenticatedUser.getInstance().isAuthenticated()) {
                    loginToBackend();
                } else {
                    _googleSignInManager.signIn(this);
                }
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onStart() {
        super.onStart();

        if (!authenticatedUser.isLoggedIn()) {
            if (authenticatedUser.getSocialToken() != null && authenticatedUser.getAuthPlatform() == AuthenticatedUser.AUTH_GOOGLE) {

                // Authenticate with Google
                Toaster.makeShort("attemptSilentSignIn()");
                _googleSignInManager.attemptSilentSignIn();

            } else {
                Toaster.makeShort("User isn't logged in");
            }
        } else {
            Toaster.makeShort("User is already logged in");
        }
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        _googleSignInManager.handleActivityResult(requestCode, resultCode, data);
    }

    @Override
    public void onUserSignedIn(GoogleSignInAccount account) {

        Toaster.makeShort("onUserSignedIn()");
        authenticatedUser.onUserAuthenticated(account.getDisplayName(), account.getEmail(), account.getIdToken());
        if (account.getPhotoUrl() != null) authenticatedUser.setAvatarUrl(account.getPhotoUrl().toString());

        _googleSignInManager.getUserData(account);
        loginToBackend();
    }

    private void loginToBackend() {
        RequestManager.getInstance().loginGoogle(new GoogleLoginBundle(authenticatedUser.getSocialToken(), authenticatedUser.getUser().getName(),
                                                    authenticatedUser.getEmail()), this);
    }

    @Override
    public void onUserSignInFailed(int errorCode, String errorMessage) {
        Toaster.makeShort("onUserSignInFailed() + errorCode = " + errorCode + ", message = " + errorMessage);
        invalidateOptionsMenu();
    }

    @Override
    public void onUserDataRetrieved(@Nullable Person person) {
        AuthenticatedUser authUser = AuthenticatedUser.getInstance();
        if (person != null) {
            authUser.setUserData(person);
        }
    }

    @Override
    public void onUserSignedOut() {
        Toaster.makeShort("onUserSignedOut()");
    }

    @Override
    public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {
        if (response.isSuccess()) {

            Toaster.makeShort("User is logged in!");
            LoginResponse loginResponse = response.body();
            authenticatedUser.onUserLoggedIn(loginResponse);
            invalidateOptionsMenu();

            onUserLoggedIn();
            updateUserData();

        } else {
            Toaster.makeShort("Login failed");
        }
    }

    @Override
    public void onFailure(Call<LoginResponse> call, Throwable t) {
        Toaster.makeShort("Login failed");
    }
}