如何在卡片布局中使用 JButton

Question

我一直在尝试一个有趣的 UI，因为我对 Java 很陌生。我已经了解了卡片布局的工作原理，但是我遇到了 JButtons 没有在卡片布局中显示正确卡片的问题。我正在使用 ItemListeners 和 Actionlisteners 来更改卡片布局。这是我的代码...

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

public class LoginCards implements ItemListener, ActionListener
{
    JPanel cards; //a panel that uses CardLayout
    JButton login1;
    JButton login2;
    JButton login3;

    final static String STUDENTPANEL = "Student";
    final static String INSTRUCTORPANEL = "Instructor";
    final static String DEPTSTAFFPANEL = "Department Staff";
    final static String DEPTSTAFFOPTIONS = "";
    final static String INSTRUCTOROPTIONS = "";
    final static String STUDENTOPTIONS ="";

    public void addComponentToPane(Container pane) 
    {       
        login1 = new JButton("Login");
        login2 = new JButton("Login");
        login3 = new JButton("Login");      
        login1.addActionListener(new ActionListener() 
        {           
            public void actionPerformed(ActionEvent e)
            {
                CardLayout cl = (CardLayout) (cards.getLayout());

                cl.show(cards, STUDENTOPTIONS);
            }
        });

        login2.addActionListener(new ActionListener() 
        {           
            public void actionPerformed(ActionEvent e)
            {
                CardLayout cl = (CardLayout) (cards.getLayout());

                cl.show(cards, INSTRUCTOROPTIONS);
            }
        });

        login3.addActionListener(new ActionListener() 
        {           
            public void actionPerformed(ActionEvent e)
            {
                CardLayout cl = (CardLayout) (cards.getLayout());

                cl.show(cards, DEPTSTAFFOPTIONS);
            }
        });

        //Put the JComboBox in a JPanel to get a nicer look.
        JPanel comboBoxPane = new JPanel(); //use FlowLayout
        String comboBoxItems[] = { STUDENTPANEL, INSTRUCTORPANEL, DEPTSTAFFPANEL };
        JComboBox cb = new JComboBox(comboBoxItems);

        cb.setEditable(false);
        cb.addItemListener(this);
        comboBoxPane.add(cb);

        //Create the "cards".
        JPanel card1 = new JPanel();

        card1.add(new JLabel("UserName: "));
        card1.add(new JTextField("Student UserName", 20));
        card1.add(new JLabel("Password: "));
        card1.add(new JPasswordField(20));
        card1.add(login1);

        JPanel card2 = new JPanel();

        card2.add(new JLabel("UserName: "));
        card2.add(new JTextField("Instructor UserName", 20));
        card2.add(new JLabel("Password: "));
        card2.add(new JPasswordField(20));
        card2.add(login2);       

        JPanel card3 = new JPanel();

        card3.add(new JLabel("UserName: "));
        card3.add(new JTextField("Dept. Staff UserName", 20));
        card3.add(new JLabel("Password: "));
        card3.add(new JPasswordField(20));
        card3.add(login3);

        JPanel instructorViewCard = new JPanel();

        instructorViewCard.add(new JLabel("instructorViewCard"));

        JPanel deptStaffViewCard = new JPanel();

        deptStaffViewCard.add(new JLabel("deptStaffViewCard"));

        JPanel studentViewCard = new JPanel();

        studentViewCard.add(new JLabel("studentViewCard"));

        //Create the panel that contains the "cards".
        cards = new JPanel(new CardLayout());
        cards.add(card1, STUDENTPANEL);
        cards.add(card2, INSTRUCTORPANEL);
        cards.add(card3, DEPTSTAFFPANEL);
        cards.add(deptStaffViewCard, DEPTSTAFFOPTIONS);
        cards.add(studentViewCard, STUDENTOPTIONS);
        cards.add(instructorViewCard, INSTRUCTOROPTIONS);        
        pane.add(comboBoxPane, BorderLayout.PAGE_START);
        pane.add(cards, BorderLayout.CENTER);
    }

    public void itemStateChanged(ItemEvent evt) 
    {
        CardLayout cl = (CardLayout)(cards.getLayout());

        cl.show(cards, (String)evt.getItem());
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event dispatch thread.
     */
    private static void createAndShowGUI() 
    {
        //Create and set up the window.
        JFrame frame = new JFrame("OUR System");

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        LoginCards demo = new LoginCards();

        demo.addComponentToPane(frame.getContentPane());

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) 
    {
        /* Use an appropriate Look and Feel */
        try 
        {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
              UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } 
        catch (UnsupportedLookAndFeelException ex) 
        {
            ex.printStackTrace();
        } 
        catch (IllegalAccessException ex) 
        {
            ex.printStackTrace();
        } 
        catch (InstantiationException ex) 
        {
            ex.printStackTrace();
        } 
        catch (ClassNotFoundException ex) 
        {
            ex.printStackTrace();
        }

        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);

        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() 
        {
            public void run() 
            {
                createAndShowGUI();
            }
        });
    }

    @Override
    public void actionPerformed(ActionEvent e) 
    {
        // TODO Auto-generated method stub      
    }
}

如果您注意到无论您在哪个按钮上（1、2 或 3），您总是会看到带有“instructorViewCard”标签的相同卡片布局。我希望能够使用 login1 按钮等查看 studentViewCard。我只是不确定我错过了什么。有人看到答案吗？有没有更好的办法？

Answer 1

您没有为部门员工、教师和学生选项的卡标识符指定唯一名称...

final static String DEPTSTAFFOPTIONS = "";
final static String INSTRUCTOROPTIONS = "";
final static String STUDENTOPTIONS = "";

这基本上意味着它使用instructorViewCard 作为每个元素的相同视图（已添加的最后一个），因为卡片在内部由Map 管理...