icepick | treating frozen JavaScript objects as persistent | Functional Programming library

    public class LoginActivity extends AppCompatActivity {

    private static final int RC_SIGN_IN = 1;

    @BindView(R.id.activity_login_google_button)
    SignInButton googleButton;
    @BindView(R.id.activity_login_progress)
    ProgressBar progress;

    private GoogleApiClient mGoogleApiClient;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private FirebaseAuth mAuth;

    @State
    boolean isLoading;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        ButterKnife.bind(this);
        Icepick.restoreInstanceState(this, savedInstanceState);

        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .requestIdToken(getString(R.string.default_web_client_id))
                .build();

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build();

        mAuth = FirebaseAuth.getInstance();

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d("@@@@", "onAuthStateChanged:signed_in:" + user.getUid());
                    Intent home = new Intent(LoginActivity.this, MainActivity.class);
                    startActivity(home);
                    finish();
                } else {
                    // User is signed out
                    Log.d("@@@@", "onAuthStateChanged:signed_out");
                }
            }
        };

        displayLoadingState();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        Icepick.saveInstanceState(this, outState);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
            mAuth.removeAuthStateListener(mAuthListener);
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        if (mAuthListener != null) {
            mAuth.addAuthStateListener(mAuthListener);
        }
    }

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

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            hideProgress();
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            handleGoogleSignInResult(result);
        }
    }

    private void hideProgress() {
        isLoading = false;
        displayLoadingState();
    }

    private void displayLoadingState() {
        progress.setVisibility(isLoading ? VISIBLE : GONE);
        googleButton.setVisibility(!isLoading ? VISIBLE : GONE);
    }

    private void showProgress() {
        isLoading = true;
        displayLoadingState();
    }

    private void handleGoogleSignInResult(GoogleSignInResult result) {
        if (result.isSuccess()) {
            // Google Sign In was successful, authenticate with Firebase
            GoogleSignInAccount account = result.getSignInAccount();
            firebaseAuthWithGoogle(account);
        } else {
            Toast.makeText(this, R.string.error_google_sign_in, Toast.LENGTH_SHORT).show();
        }
    }

    private void firebaseAuthWithGoogle(GoogleSignInAccount acct) {
        Log.d("@@@@", "firebaseAuthWithGoogle:" + acct.getId());

        AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(), null);
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener() {
                    @Override
                    public void onComplete(@NonNull Task task) {
                        Log.d("@@@@", "firebaseAuthWithGoogleComplete:" + task.isSuccessful());

                        Needle.onBackgroundThread().execute(new Runnable() {
                            @Override
                            public void run() {
                                try {
                                    FirebaseInstanceId.getInstance().deleteInstanceId();
                                } catch (IOException e) {
                                    Log.d("@@@@", "deleteInstanceIdCatch: " + e.getMessage());
                                }
                            }
                        });

                        if (!task.isSuccessful()) {
                            Log.w("@@@@", "firebaseAuthWithGoogleFailed", task.getException());
                            Toast.makeText(LoginActivity.this, R.string.error_google_sign_in, Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }

    @OnClick(R.id.activity_login_google_button)
    public void attemptGoogleSignIn() {
        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
        startActivityForResult(signInIntent, RC_SIGN_IN);
        showProgress();
    }
}