按钮未出现在Swing GUI中

Question

For my second programming assignment in my Java class, we have to create a Pizza Shop menu GUI. Everything appears on my GUI (including choices, boxes, radio buttons, etc.) except for the button ("Process Selection") you are supposed to click for calculating the total cost. The following is my code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class PizzaShop extends JFrame {

    private Topping t;
    private PizzaSize ps;
    private PizzaType pt;
    private JPanel buttonPanel;
    private JButton ProcessSelection;

    public PizzaShop() {
        super("Welcome To Home Pizza Shop");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
        t = new Topping();
        ps = new PizzaSize();
        pt = new PizzaType();
        createPanel();
        add(t, BorderLayout.NORTH);
        add(ps, BorderLayout.WEST);
        add(pt, BorderLayout.CENTER);
        setVisible(true);
    }

    private void createPanel() {
        buttonPanel = new JPanel();
        ProcessSelection = new JButton("Process Selection");
        ProcessSelection.addActionListener(new calButton());
        buttonPanel.add(ProcessSelection);
    }

    private class calButton implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            double subtotal;
            subtotal = t.getTopping() + ps.getPizzaSize();
            JOptionPane.showMessageDialog(null, "Your Order \n" + "Pizza Type" + pt.getPizzaType() + "\n" + "Amount Due" + subtotal);
        }
    }

    private class ExitButtonListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            System.exit(0);
        }
    }
}

Did I forget to do add some code somewhere? I'm boggled.

Answer 1

You are not adding the buttonPanel to the main view

UPDATE : you should do this:

private void createPanel() {
    buttonPanel = new JPanel();
    ProcessSelection = new JButton("Process Selection");
    ProcessSelection.addActionListener(new calButton());
    buttonPanel.add(ProcessSelection);
    add(buttonPanel, BorderLayout.SOUTH);
}

Answer 2

您需要将按钮面板添加到框架：

add(buttonPanel, BorderLayout.SOUTH);

Answer 3

Change your createPanel() to this:

private JPanel createPanel() {
    buttonPanel = new JPanel();
    ProcessSelection = new JButton("Process Selection");
    ProcessSelection.addActionListener(new calButton());
    buttonPanel.add(ProcessSelection);
    return buttonPanel;
 }

And add the code below to your PizzaShop() method:

add(createPanel(), BorderLayout.SOUTH);

Or you can just follow what Adel Boutros said.