How to add user to firebase database?

Question

Java

I have a firestore database, and in the application there are two ways to authorize using login and password and using google signIn. So when I register with a login and password, the user is added to the firestore database, and when I log in using google signIn, the user is not added to the database. How to solve it?

My LoginActivity code in which authorization takes place using a login and password as well as google signIn

public class LoginActivity extends AppCompatActivity {

    private static final String TAG = "GoogleActivity";
    private static final int RC_SIGN_IN = 9001;

    private FirebaseAuth mAuth;
    ProgressDialog dialog;

    private GoogleSignInClient mGoogleSignInClient;

    ImageView login_google_btn, login_phone_btn, login_facebook_btn;
    TextView create_account_btn, forgot_password;
    Button login_btn;
    EditText inputEmail, inputPassword;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        inputEmail = findViewById(R.id.inputEmail);
        inputPassword = findViewById(R.id.inputPassword);
        login_btn = findViewById(R.id.login_btn);

        login_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });

        // Configure Google Sign In
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_id))
                .requestEmail()
                .build();

        mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
        // Initialize Firebase Auth
        mAuth = FirebaseAuth.getInstance();

        dialog = new ProgressDialog(this);
        dialog.setMessage("Logging in...");

        create_account_btn = findViewById(R.id.create_account_btn);
        create_account_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(LoginActivity.this, SignUpActivity.class);
                startActivity(intent);
                finish();
            }
        });

        login_google_btn = findViewById(R.id.login_google_btn);
        login_google_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sign_google();
            }
        });

        if(mAuth.getCurrentUser() != null) {
            startActivity(new Intent(LoginActivity.this, MainActivity.class));
            finish();
        }

        login_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email, pass;
                email = inputEmail.getText().toString();
                pass = inputPassword.getText().toString();


                dialog.show();

                mAuth.signInWithEmailAndPassword(email, pass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        dialog.dismiss();
                        if(task.isSuccessful()) {
                            startActivity(new Intent(LoginActivity.this, MainActivity.class));
                            finish();
                        } else {
                            Toast.makeText(LoginActivity.this, task.getException().getLocalizedMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                });
            }
        });
    }

    private void sign_google() {
        Intent signInIntent = mGoogleSignInClient.getSignInIntent();
        startActivityForResult(signInIntent, RC_SIGN_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(...);
        if (requestCode == RC_SIGN_IN) {
            Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
            try {
                // Google Sign In was successful, authenticate with Firebase
                GoogleSignInAccount account = task.getResult(ApiException.class);
                Log.d(TAG, "firebaseAuthWithGoogle:" + account.getId());
                firebaseAuthWithGoogle(account.getIdToken());
            } catch (ApiException e) {
                // Google Sign In failed, update UI appropriately
                Log.w(TAG, "Google sign in failed", e);
            }
        }
    }

    private void firebaseAuthWithGoogle(String idToken) {
        AuthCredential credential = GoogleAuthProvider.getCredential(idToken, null);
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            // Sign in success, update UI with the signed-in user's information
                            Log.d(TAG, "signInWithCredential:success");
                            FirebaseUser user = mAuth.getCurrentUser();
                            updateUI(user);
                        } else {
                            // If sign in fails, display a message to the user.
                            Log.w(TAG, "signInWithCredential:failure", task.getException());
                            updateUI(null);
                        }
                    }
                });
    }

    private void updateUI(FirebaseUser user) {
        if(user != null){
            Intent intent = new Intent(LoginActivity.this, MainActivity.class);
            startActivity(intent);
            finish();
        } else{
            Toast.makeText(LoginActivity.this, "Something Error", Toast.LENGTH_SHORT).show();
        }
    }
}

The SignUpActivity code in which authorization takes place using a login and password

public class SignUpActivity extends AppCompatActivity {

    TextView have_account_btn;
    EditText inputName, inputEmail, inputPassword, inputConfirmPassword;
    Button signup_btn;

    FirebaseAuth auth;
    FirebaseFirestore database;
    ProgressDialog dialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sign_up);

        inputName = findViewById(R.id.inputName);
        inputEmail = findViewById(R.id.inputEmail);
        inputPassword = findViewById(R.id.inputPassword);
        inputConfirmPassword = findViewById(R.id.inputConfirmPassword);
        signup_btn = findViewById(R.id.signup_btn);
        have_account_btn = findViewById(R.id.have_account_btn);

        auth = FirebaseAuth.getInstance();
        database = FirebaseFirestore.getInstance();

        dialog = new ProgressDialog(this);
        dialog.setMessage("We're creating new account...");

        have_account_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(SignUpActivity.this, LoginActivity.class);
                startActivity(intent);
                finish();
            }
        });

        signup_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String email, pass, name, confPass;

                email = inputEmail.getText().toString();
                pass = inputPassword.getText().toString();
                name = inputName.getText().toString();
                confPass = inputConfirmPassword.getText().toString();

                final User user = new User(name, email, pass, confPass);

                dialog.show();
                auth.createUserWithEmailAndPassword(email, pass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if(task.isSuccessful()) {
                            String uid = task.getResult().getUser().getUid();

                            database
                                    .collection("users")
                                    .document(uid)
                                    .set(user).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    if(task.isSuccessful()) {
                                        dialog.dismiss();
                                        startActivity(new Intent(SignUpActivity.this, MainActivity.class));
                                        finish();
                                    } else {
                                        Toast.makeText(SignUpActivity.this, task.getException().getLocalizedMessage(), Toast.LENGTH_SHORT).show();
                                    }
                                }
                            });
                        } else {
                            dialog.dismiss();
                            Toast.makeText(SignUpActivity.this, task.getException().getLocalizedMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                });

            }
        });
    }
}