问如何使txPanel仅在单击“enter pin ok”按钮后可见？

EN

public class ATMgui extends JFrame implements ActionListener {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    public static final int WIDTH = 500;
    public static final int HEIGHT = 200;
    private ATMbizlogic theBLU;// short for the Business Logic Unit
    public JLabel totalBalanceLabel;
    public JTextField withdrawTextField;
    public JTextField depositTextField;
    public JTextField pinTextField;

    /**
     * Creates a new instance of ATMgui
     */
    public ATMgui() {
        setTitle("ATM Transactions");
        setSize(WIDTH, HEIGHT);
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        Container contentPane = getContentPane();
        contentPane.setBackground(Color.BLACK);
        contentPane.setLayout(new BorderLayout());


        // Do the panel for the rest stop
        JLabel start = new JLabel("Welcome To Your Account", JLabel.CENTER);
        Font curFont = start.getFont();
        start.setFont(new Font(curFont.getFontName(), curFont.getStyle(), 25));
        start.setForeground(Color.BLUE);
        start.setOpaque(true);
        start.setBackground(Color.BLACK);


        pinTextField = new JTextField();
        JLabel pinLabel = new JLabel("Enter your PIN below:", JLabel.CENTER);
        pinLabel.setForeground(Color.RED);
        pinLabel.setOpaque(true);
        pinLabel.setBackground(Color.WHITE);



        JButton pinButton = new JButton("Enter Pin OK");
        pinButton.addActionListener(this);
        pinButton.setBackground(Color.red);

        JPanel pinPanel = new JPanel();
        pinPanel.setLayout(new GridLayout(3, 1, 100, 0));

        pinPanel.add(pinLabel);
        pinPanel.add(pinTextField);
        pinPanel.add(pinButton);

        contentPane.add(pinPanel, BorderLayout.WEST);


        JPanel headingPanel = new JPanel();
        headingPanel.setLayout(new GridLayout());
        headingPanel.add(start);

        contentPane.add(headingPanel, BorderLayout.NORTH);


        // Do the panel for the amount & type of transactions
        withdrawTextField = new JTextField();
        JLabel withdrawLabel = new JLabel("Withdraw (0.00)", JLabel.CENTER);
        withdrawLabel.setForeground(Color.RED);
        withdrawLabel.setOpaque(true);
        withdrawLabel.setBackground(Color.WHITE);



        depositTextField = new JTextField();
        JLabel depositLabel = new JLabel("Deposit (0.00)", JLabel.CENTER);
        depositLabel.setForeground(Color.RED);
        depositLabel.setOpaque(true);
        depositLabel.setBackground(Color.WHITE);



        JButton txButton = new JButton("Transactions OK");
        txButton.addActionListener(this);
        txButton.setBackground(Color.red);




        JPanel txPanel = new JPanel();
        txPanel.setLayout(new GridLayout(5, 1, 30, 0));

        txPanel.add(withdrawLabel);
        txPanel.add(withdrawTextField);
        txPanel.add(depositLabel);
        txPanel.add(depositTextField);
        txPanel.add(txButton);

        contentPane.add(txPanel, BorderLayout.EAST);
        txPanel.setVisible(true);


        totalBalanceLabel = new JLabel("Your balance after transactions: ", JLabel.CENTER);
        totalBalanceLabel.setForeground(Color.BLUE);
        totalBalanceLabel.setOpaque(true);
        totalBalanceLabel.setBackground(Color.BLACK);


        contentPane.add(totalBalanceLabel, BorderLayout.SOUTH);


        theBLU = new ATMbizlogic();
    }

    public void actionPerformed(ActionEvent e) {
        String actionCommand = e.getActionCommand();

        // Container contentPane = getContentPane();

        if (actionCommand.equals("Transactions OK")) {
            try {
                double deposit = Double.parseDouble(depositTextField.getText().trim());
                double withdraw = Double.parseDouble(withdrawTextField.getText().trim());
                theBLU.computeBalance(withdraw, deposit);
                totalBalanceLabel.setText("Your balance after transactions: " + theBLU.getBalance());

            } catch (ATMexception ex) {
                totalBalanceLabel.setText("Error: " + ex.getMessage());
            } catch (Exception ex) {
                totalBalanceLabel.setText("Error in deposit or withdraw amount: " + ex.getMessage());
            }
        } else if (actionCommand.equals("Enter Pin OK")) {

            try {

                double pin = Double.parseDouble(pinTextField.getText().trim());
                theBLU.checkPin(pin);

                totalBalanceLabel.setText("Your balance after transactions: " + theBLU.getBalance());



            } catch (ATMexception ex) {
                totalBalanceLabel.setText("Error: " + ex.getMessage());
            } catch (Exception ex) {
                totalBalanceLabel.setText("Error in pin: " + ex.getMessage());

            }
        } else {
            System.out.println("Error in button interface.");
        }
    }

    public static void main(String[] args) {
        ATMgui gui = new ATMgui();
        gui.setVisible(true);
    }
}