在具有卡片布局的JPanel中的两个JPanel之间交换

Question

我正试图通过那些特定面板上的按钮来交换两个jpanel，我不希望两个面板上都有常规按钮，就像普通的卡片布局一样，在两个面板都重复使用。我试着在主面板上有一个名为"添加"的按钮，可以引导到下一页，在下一页上有一个子按钮，名为"返回"，可以引导至主面板。然而，由于某种原因，它不起作用。我不希望JFrame上有两个JPanel，因为稍后我将把JPanel添加到选项卡式窗格中。以下是我已经掌握的：

控制器：

import java.awt.CardLayout;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Controller extends JPanel {
    private static Controller instance = new Controller();
    JPanel cards;
    Main mainPanel;
    NextPage nextPage;
    public Controller() {
        setLayout(new BorderLayout());
        setSize(810, 510);
        cards = new JPanel(new CardLayout());
        mainPanel = new Main();
        nextPage = new NextPage();
        cards.add(mainPanel, "Main");
        cards.add(nextPage, "Next");
        add(cards);
        setVisible(true);
    }
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("MainPanel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Controller con = new Controller();
        frame.getContentPane().add(con);
        frame.setSize(800, 600);
        frame.setVisible(true);
    }
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

    public void changeCard(String card) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, card);
    }
    public static Controller getInstance() {
        return instance;
    }
}

Main：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.*;
public class Main extends JPanel implements ActionListener {
    private JButton search, add, delete;
    private JTextField textField;
    public Main() {
        search = new JButton("Search");
        add = new JButton("Add");
        delete = new JButton("Delete");
        textField = new JTextField(20);
        add.addActionListener(this);
        delete.addActionListener(this);
        setLayout(new BorderLayout());
        JPanel top = new JPanel();
        top.add(search);
        add(top, BorderLayout.NORTH);
        JPanel bottom = new JPanel();
        bottom.add(add);
        bottom.add(delete);
        add(bottom, BorderLayout.SOUTH);
        setVisible(true);
        setSize(400, 500);
    }
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == add) {
            Controller.getInstance().changeCard("Next");
        } else if (e.getSource() == delete) {
           System.out.println("do something");
        }
    }
}

下一页：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.*;
public class NextPage extends JPanel implements ActionListener {
    private JButton back;
    private JTextField textField;
    public NextPage() {
        back = new JButton("Back");
        textField = new JTextField(20);
        back.addActionListener(this);
        setLayout(new BorderLayout());
        add(back);
        setVisible(true);
        setSize(400, 500);
    }
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == back) {
            Controller.getInstance().changeCard("Next");
        }
    }
}

Answer 1

这样更改Controller：

private static Controller instance;
...
private static void createAndShowGUI() {
    JFrame frame = new JFrame("MainPanel");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    instance = new Controller();
    frame.getContentPane().add(instance);
    frame.setSize(800, 600);
    frame.setVisible(true);
}

实际上，您在Controller的一个实例上创建了所有内容并进行了展示，但使用了另一个实例来管理事件。对Controller构造函数的多次调用应该敲响了警钟，因为您只需要一个Controller。