send user data from login page to main activity and logout from main activity as well

Question

I created two activites one LoginActivity and other MainActivity where I want to get user data to be shown like name and photos, then I want user to log out from MainActivity as well. I made a google sign in button from a tutorial where login, logout and userdata was shown in same activity. Now I know I have to put explicit intent on (if login is successful) but I don't know how do I carry userdata like emailID, name(at least), photo to next activity where I use them and update using updateUI method which updated the user details previously in the same Login activity.

My login activity

public class LoginActivity extends AppCompatActivity {

static final int GOOGLE_SIGN_IN = 123;
FirebaseAuth mAuth;
Button btn_login, btn_logout;
TextView text;
ImageView image;
ProgressBar progressBar;
GoogleSignInClient mGoogleSignInClient;

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

    btn_login = findViewById(R.id.login);
    btn_logout = findViewById(R.id.logout);
    text = findViewById(R.id.text);
    image = findViewById(R.id.image);
    progressBar = findViewById(R.id.progress_circular);

    mAuth = FirebaseAuth.getInstance();

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

    mGoogleSignInClient = GoogleSignIn.getClient(this, gso);

    btn_login.setOnClickListener(v -> SignInGoogle());
    btn_logout.setOnClickListener(v -> Logout());

    if (mAuth.getCurrentUser() != null) {
        FirebaseUser user = mAuth.getCurrentUser();
        updateUI(user);
    }
}

public void SignInGoogle() {
    progressBar.setVisibility(View.VISIBLE);
    Intent signInIntent = mGoogleSignInClient.getSignInIntent();
    startActivityForResult(signInIntent, GOOGLE_SIGN_IN);
}

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

    AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(), null);
    mAuth.signInWithCredential(credential)
            .addOnCompleteListener(this, task -> {
                if (task.isSuccessful()) {
                    progressBar.setVisibility(View.INVISIBLE);

                    Log.d("TAG", "signInWithCredential:success");

                    FirebaseUser user = mAuth.getCurrentUser();
                    updateUI(user);
                } else {
                    progressBar.setVisibility(View.INVISIBLE);

                    Log.w("TAG", "signInWithCredential:failure", task.getException());

                    Toast.makeText(LoginActivity.this, "Authentication failed.",
                            Toast.LENGTH_SHORT).show();
                    updateUI(null);
                }
            });
}

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

    if (requestCode == GOOGLE_SIGN_IN) {
        Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
        try {
            GoogleSignInAccount account = task.getResult(ApiException.class);
            if (account != null) firebaseAuthWithGoogle(account);
        } catch (ApiException e) {
            Log.w("TAG", "Google sign in failed", e);
        }
    }
}

private void updateUI(FirebaseUser user) {
    if (user != null)
    {
        String name = user.getDisplayName();
        String email = user.getEmail();
        String photo = String.valueOf(user.getPhotoUrl());
        for (UserInfo userInfo : user.getProviderData())
            if (name == null && userInfo.getDisplayName() != null)
                name = userInfo.getDisplayName();
        text.append("Info : \n");
        text.append(name + "\n");
        text.append(email);
        Picasso.get().load(photo).into(image);
        btn_logout.setVisibility(View.VISIBLE);
        btn_login.setVisibility(View.INVISIBLE);
    } else
    {
        text.setText("Distress Alert\n");
        btn_logout.setVisibility(View.INVISIBLE);
        btn_login.setVisibility(View.VISIBLE);
        Picasso.get().load(R.drawable.ic_firebase_logo).into(image);

    }
}


private void Logout()
{
    FirebaseAuth.getInstance().signOut();
    mGoogleSignInClient.signOut().addOnCompleteListener(this,
            task -> updateUI(null));
}

}

Answer 1

I do not have commenting privileges as of yet, but a simple google search for passing data between activities would have given you this.

How do I pass data between Activities in Android application?

Also, using Intent in this case would not be a good solution, as you're already using Firebase for authentication, you can get the current FirebaseUser in next Activity.

Declare an instance (class variable)

private FirebaseAuth mAuth;

In onCreate() initialize mAuth

mAuth = FirebaseAuth.getInstance();

In onStart() check if the user is signed in and check for null

@Override
public void onStart() {
    super.onStart();
    FirebaseUser currentUser = mAuth.getCurrentUser();
    if (currentUser == null) {
        // No user is signed in
    } else {
        // User logged in
    }
}

Using the second method you can get the complete FirebaseUser object in next activity if the user is signed in. Or, you can use Intent to pass data between activities.