di4.java

public class LoginFragment extends Fragment {
  
  private LoginListener listener;
  
  @Override public void onAttach(Activity activity) {
    super.onAttach(activity);
    loginListener = (LoginListener) activity;
  }
  
  void onLoginClicked() {
    listener.onLogin();
  }
  
  void onRegisterClicked() {
    listener.onRegister();
  }
  
  public interface LoginListener {
    void onLogin();
    void onRegister();
  }
}