import javax.swing.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class MainFrame extends JFrame { private JPanel panelRoot; private JTextField txtUserId; private JPasswordField txtUserPw; private JButton btnSignUp; private JButton btnLogIn; public MainFrame() { setSize(800, 600); add(panelRoot); setDefaultCloseOperation(EXIT_ON_CLOSE); setLocationRelativeTo(n..