How to implement onBackPressed() in Fragments?

I solved in this way override onBackPressed in the Activity. All the FragmentTransaction are addToBackStack before commit:

@Override
public void onBackPressed() {

    int count = getSupportFragmentManager().getBackStackEntryCount();

    if (count == 0) {
        super.onBackPressed();
        //additional code
    } else {
        getSupportFragmentManager().popBackStack();
    }

}