gistfile1.txt

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        mAuth = FirebaseAuth.getInstance();

        databaseReference = FirebaseDatabase.getInstance().getReference();

        hRequestAdapter = new HRequestAdapter(hRequestsList);
        recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        recyclerView.setAdapter(helpRequestAdapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setItemAnimator(new DefaultItemAnimator());

        checkAuthState();

    }
    
    here's checkAuthState():
    
    public void checkAuthState() {
        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d("signedIn", "onAuthStateChanged:signed_in:" + user.getUid());

                    retrieveUserInfo();
                    retrieveHRequests();

                    
                } else {
                    // User is signed out
                    Log.d("signedOut", "onAuthStateChanged:signed_out");
                    Intent signUpActivityIntent = new Intent(MainActivity.this, SignupActivity.class);
                    signUpActivityIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    signUpActivityIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                    startActivity(signUpActivityIntent);
                }
                // ...
            }
        };
    }