on the activity

super.onViewCreated(view, savedInstanceState);
ButterKnife.inject(this, view);

callbackManager = CallbackManager.Factory.create();
facebookLoginButton.setFragment(this);
facebookLoginButton.registerCallback(callbackManager, presenter);

presenter.bindView(this);

on the presenter

@Override
public void onSuccess(LoginResult loginResult) {
     // do something with the facebook result and notify UI.
     // here you can store the FB UserID on a backend
}

@Override
public void onCancel() {
    view().showLoginError("canceled");
}

@Override
public void onError(FacebookException error) {
    view().showLoginError("error " + error);
}