Firebase link user authentication to another activity

Question

I have say a user who signs in to my app using one activity via Firebase, can I access the user's details in the next activity. Eg:

Login class:

public class LoginActivity extends AppCompatActivity {

    EditText editText;
    EditText editText2;
    Button button;
    public FirebaseAuth Auth = FirebaseAuth.getInstance();
    public FirebaseAuth.AuthStateListener authlistener;
    String email, pass;
    ProgressBar bar;

    public View.OnClickListener buttonListener = new View.OnClickListener() {
        public void onClick (View view){
            email = editText.getText().toString().trim();
            pass = editText2.getText().toString().trim();
            logInUser();

        }};


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editText = (EditText)findViewById(R.id.editText);
        editText2 = (EditText)findViewById(R.id.editText2);
        button = (Button)findViewById(R.id.button2);
        Auth = FirebaseAuth.getInstance();
        button.setOnClickListener(buttonListener);
        bar = (ProgressBar)findViewById(R.id.progressBar2);
        bar.setVisibility(View.INVISIBLE);

        authlistener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in

                } else {
                    // User is signed out

                }
                // ...
            }
        };
        // ...
    }

    @Override
    public void onStart() {
        super.onStart();
        Auth.addAuthStateListener(authlistener);
    }

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

    public void logInUser(){
        bar.setVisibility(View.VISIBLE);

        Auth.signInWithEmailAndPassword(email, pass)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if(task.isSuccessful()) {

                            Intent loggedInActivity = new Intent(getApplicationContext(), Loggedin.class);
                            startActivity(loggedInActivity);

                        }
                        else{

                            Toast.makeText(getApplicationContext(), "There was an error, try again", Toast.LENGTH_SHORT).show();
                        }


                    }
                });


    }
}

Logged in Activity:

public class Loggedin extends AppCompatActivity {

    Button changeMail, changePass;
    String oldPassword;
    String newPassword;
    EditText oldpass, newpass;
    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    public FirebaseAuth Auth = FirebaseAuth.getInstance();

    public void updatePassword(){
        oldPassword = oldpass.getText().toString();
        newPassword = newpass.getText().toString();



    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_loggedin);
        changeMail = (Button)findViewById(R.id.changeMail);
        changePass = (Button)findViewById(R.id.changePass);
        oldpass = (EditText)findViewById(R.id.oldPass);
        newpass = (EditText)findViewById(R.id.newPass);
        oldpass.setVisibility(View.INVISIBLE);
        newpass.setVisibility(View.VISIBLE);

    }
}

Say I want to change the password of the user in the loggedinClass. Do I have to uses the intent from the "login.class" and then use the sign in method in the loggedin class rather than the login.class.

but what if I had multiple activities, this would get tedious, signing in to every activity?

Answer 1

You don't need a listener for Firebase... its a singleton and available throughout your activities. Just add this to your base activity

public FirebaseUser getFirebaseUser() {
    return FirebaseAuth.getInstance().getCurrentUser();
}

or use if(FirebaseAuth.getInstance().getCurrentUser() != null) { ...} where you need it

Answer 2

If you put an AuthStateListener in the other classes, you can detect the sign-in state of the user without requiring them to sign in again.

authlistener = new FirebaseAuth.AuthStateListener() {
   @Override
   public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
       FirebaseUser user = firebaseAuth.getCurrentUser();
       if (user != null) {
            // User is signed in

        } else {
            // User is signed out

        }
        // ...
    }
};
FirebaseAuth.getInstance().addAuthStateListener(authListener);