Put common listeners inside MainActivity class

Issue

Im interested if i can to set some common listeners inside main activity class? For my project i use FirebaseAuth, so i would like to init it in MainActivity onCreate(), setup needed listeners in onStart() and onStop(), and then inherit that class in every other activity class.

Some code to please you :]

MainActivity class [parent]:

    public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    protected FirebaseAuthentication firebaseAuthentication;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        firebaseAuthentication = new FirebaseAuthentication(FirebaseAuth.getInstance(), FirebaseDatabase.getInstance());
    }

    @Override
    protected void onStart() {
        super.onStart();
        firebaseAuthentication.addAuthStateListener();
    }

    @Override
    public void onStop() {
        super.onStop();
        firebaseAuthentication.removeAuthStateListener();
    }
}

AuthActivity class [child]:

public class AuthActivity extends MainActivity implements FirebaseAuthentication.OnUserAuthListener {
    @BindView(R.id.viewPager) LockableViewPager viewPager;

    private String userUID;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_market);
        ButterKnife.bind(this);

        firebaseAuthentication.setOnUserAuthListener(this);
        firebaseAuthentication.isSingedIn(); // check if user is singed in
    }

    @Override
    // response for firebaseAuthentication.isSingedIn() above
    public void onAuthSuccess(String userUID) {
        this.userUID = userUID;
    }

    @Override
    // response for firebaseAuthentication.isSingedIn() above
    public void onAuthFailure(String message) {
        snackbar(message);
        Intent intent = new Intent(this, AuthActivity.class);
        startActivity(intent);
        finish(); // TODO mb should to delete it
    }
}

Can this implementations bring me errors (maybe NullPointerExeption or what unexpectedly in future)? Would be great if you provide me some sources to read/watch. Thank you.

Solution

Perfect example of abstraction, but not really a question.

You will not get any nullpointers or other errors by implementing it like this.

Answered By - Stefan