Replacing fragment on the fly

Android Studio 0.5.8

Hello,

I have one activity (MainActivity) that will host 2 fragments (ListAddressBookFragment, AddAddressBookFragment) (only one at a time). The initial fragment will be the ListAddressBookFragment and will be inflated when MainActivity onCreate gets called.

/* MainActivity.java */
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    /* Add and display fragment */
    FragmentManager fragmentManager = getSupportFragmentManager();
    Fragment fragment = fragmentManager.findFragmentById(R.id.flFragmentContainer);

    /* Create new fragment if this hasn't already been done */
    if(fragment == null) {
        fragment = new ListAddressBookFragment();
        fragmentManager.beginTransaction()
                .add(R.id.flFragmentContainer, fragment)
                .commit();
    }
}

In the ListAddressBookFragment I have a option menu to add a new addressbook item. So this will call call MainActivity. So I want to replace ListAddressBookFragment with AddAddressBookFragment. However, because the code above is hardcoded I am wondering is there anyway to do this on the fly?

/* ListAddressBookFragment.java */
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.new_addressbook) {
        Intent intent = new Intent(getActivity(), MainActivity.class);
        startActivity(intent);
        return true;
    }
    return super.onOptionsItemSelected(item);
}

Many thanks for any suggestions,