Eclipse Window Builder开发Swing程序：标签不更新问题求助

Hey there! Let's figure out why your Start panel labels aren't updating when you select a Key or Level. I've looked through your code, and here's what's going on:

The Root Problems #

• You only set the text of lblSelectkeylabel, lblSelectlevellabel, and lblChoicedone once when initializing the window. When you click Key/Level buttons to change the key and level variables, the labels never get told to refresh their display.
• The if-else check for whether the user has selected both options only runs during initialization. It doesn't re-run when you switch back to the Start panel, so the "Choose done" message stays stuck.

How to Fix It #

Let's adjust your code with these steps:

1. Move the Start panel's label variables to be class members so we can access them from any ActionListener.
2. Create a dedicated method to update the Start panel's labels and status message whenever needed.
3. Call this update method whenever you select a Key/Level, and when switching to the Start panel.

Modified Complete Code #

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JLabel;
import java.awt.Font;

public class Test {
    private JFrame frame;
    int key = 0;
    int level = 0;
    
    // Make these labels class members so we can update them later
    private JLabel lblSelectkeylabel;
    private JLabel lblSelectlevellabel;
    private JLabel lblChoicedone;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Test window = new Test();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Test() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JPanel Home = new JPanel();
        Home.setBounds(6, 6, 438, 266);
        frame.getContentPane().add(Home);

        JPanel SelectKey = new JPanel();
        SelectKey.setBounds(6, 6, 438, 266);
        frame.getContentPane().add(SelectKey);

        JPanel SelectLevel = new JPanel();
        SelectLevel.setBounds(6, 6, 438, 266);
        frame.getContentPane().add(SelectLevel);
        SelectLevel.setLayout(null);

        JPanel Start = new JPanel();
        Start.setBounds(6, 6, 438, 266);
        frame.getContentPane().add(Start);
        Start.setLayout(null);

        // Home Panel Components
        JButton btnHome = new JButton("Home");
        btnHome.setBounds(169, 141, 100, 29);
        btnHome.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.setVisible(true);
                SelectKey.setVisible(false);
                SelectLevel.setVisible(false);
                Start.setVisible(false);
            }
        });
        Home.setLayout(null);
        Home.add(btnHome);

        JButton btnSelectKey = new JButton("Select Key");
        btnSelectKey.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.setVisible(false);
                SelectKey.setVisible(true);
                SelectLevel.setVisible(false);
                Start.setVisible(false);
            }
        });
        btnSelectKey.setBounds(159, 67, 117, 29);
        Home.add(btnSelectKey);

        JButton btnSelectLevel = new JButton("Select Level");
        btnSelectLevel.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                SelectKey.setVisible(false);
                SelectLevel.setVisible(true);
                Home.setVisible(false);
                Start.setVisible(false);
            }
        });
        btnSelectLevel.setBounds(159, 37, 117, 29);
        Home.add(btnSelectLevel);

        JButton btnStart = new JButton("Start");
        btnStart.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                SelectKey.setVisible(false);
                SelectLevel.setVisible(false);
                Home.setVisible(false);
                Start.setVisible(true);
                // Update Start panel when switching to it
                updateStartPanel();
            }
        });
        btnStart.setBounds(159, 92, 117, 29);
        Home.add(btnStart);

        JLabel lblHome = new JLabel("Home");
        lblHome.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblHome.setBounds(197, 18, 61, 16);
        Home.add(lblHome);

        // SelectKey Panel Components
        JButton btnNewButton = new JButton("Home");
        btnNewButton.setBounds(169, 185, 100, 29);
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.setVisible(true);
                SelectKey.setVisible(false);
                SelectLevel.setVisible(false);
                Start.setVisible(false);
            }
        });
        SelectKey.setLayout(null);
        SelectKey.add(btnNewButton);

        JButton btnKeyA = new JButton("Key A");
        btnKeyA.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                key = 1;
                System.out.print(key);
                // Update Start panel when key is selected
                updateStartPanel();
            }
        });
        btnKeyA.setBounds(157, 44, 117, 29);
        SelectKey.add(btnKeyA);

        JButton btnKeyB = new JButton("Key B");
        btnKeyB.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                key = 2;
                System.out.print(key);
                updateStartPanel();
            }
        });
        btnKeyB.setBounds(157, 90, 117, 29);
        SelectKey.add(btnKeyB);

        JButton btnKeyC = new JButton("Key C");
        btnKeyC.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                key = 3;
                System.out.print(key);
                updateStartPanel();
            }
        });
        btnKeyC.setBounds(157, 129, 117, 29);
        SelectKey.add(btnKeyC);

        JLabel lblSelectKey = new JLabel("Select Key");
        lblSelectKey.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblSelectKey.setBounds(168, 19, 117, 23);
        SelectKey.add(lblSelectKey);

        // SelectLevel Panel Components
        JButton btnBeginnner = new JButton("Beginnner");
        btnBeginnner.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                level = 1;
                System.out.print(level);
                updateStartPanel();
            }
        });
        btnBeginnner.setBounds(158, 67, 117, 29);
        SelectLevel.add(btnBeginnner);

        JButton btnIntermediate = new JButton("Intermediate");
        btnIntermediate.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                level = 2;
                System.out.print(level);
                updateStartPanel();
            }
        });
        btnIntermediate.setBounds(158, 113, 117, 29);
        SelectLevel.add(btnIntermediate);

        JButton btnAdvanced = new JButton("Advanced");
        btnAdvanced.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                level = 3;
                System.out.print(level);
                updateStartPanel();
            }
        });
        btnAdvanced.setBounds(158, 166, 117, 29);
        SelectLevel.add(btnAdvanced);

        JButton btnHome_1 = new JButton("Home");
        btnHome_1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.setVisible(true);
                SelectKey.setVisible(false);
                SelectLevel.setVisible(false);
                Start.setVisible(false);
            }
        });
        btnHome_1.setBounds(158, 207, 117, 29);
        SelectLevel.add(btnHome_1);

        JLabel lblSelectLevel = new JLabel("Select Level");
        lblSelectLevel.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblSelectLevel.setBounds(162, 19, 158, 36);
        SelectLevel.add(lblSelectLevel);

        // Start Panel Components
        JLabel lblStart = new JLabel("Start");
        lblStart.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblStart.setBounds(186, 25, 61, 16);
        Start.add(lblStart);

        JButton btnHome_2 = new JButton("Home");
        btnHome_2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.setVisible(true);
                SelectKey.setVisible(false);
                SelectLevel.setVisible(false);
                Start.setVisible(false);
            }
        });
        btnHome_2.setBounds(155, 216, 117, 29);
        Start.add(btnHome_2);

        lblSelectkeylabel = new JLabel("SelectKeyLabel");
        lblSelectkeylabel.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblSelectkeylabel.setBounds(175, 64, 97, 41);
        Start.add(lblSelectkeylabel);

        lblSelectlevellabel = new JLabel("Selectlevellabel");
        lblSelectlevellabel.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblSelectlevellabel.setBounds(169, 107, 146, 41);
        Start.add(lblSelectlevellabel);

        lblChoicedone = new JLabel("Choicedone");
        lblChoicedone.setFont(new Font("Comic Sans MS", Font.PLAIN, 16));
        lblChoicedone.setBounds(175, 147, 250, 16); // Widen bounds to fit longer text
        Start.add(lblChoicedone);

        JButton btnStart_1 = new JButton("Start");
        btnStart_1.setBounds(155, 185, 117, 29);
        Start.add(btnStart_1);

        // Initialize Start panel display
        updateStartPanel();
    }

    // Method to update Start panel labels and status
    private void updateStartPanel() {
        // Update key and level labels
        lblSelectkeylabel.setText(key == 0 ? "No Key Selected" : "Key: " + getKeyName(key));
        lblSelectlevellabel.setText(level == 0 ? "No Level Selected" : "Level: " + getLevelName(level));
        
        // Update status message
        if (key == 0 || level == 0) {
            lblChoicedone.setText("Please go back and choose a key and a level");
        } else {
            lblChoicedone.setText("Ready to Start!");
        }
    }

    // Helper to get friendly key name instead of number
    private String getKeyName(int keyNum) {
        switch(keyNum) {
            case 1: return "A";
            case 2: return "B";
            case 3: return "C";
            default: return "None";
        }
    }

    // Helper to get friendly level name instead of number
    private String getLevelName(int levelNum) {
        switch(levelNum) {
            case 1: return "Beginner";
            case 2: return "Intermediate";
            case 3: return "Advanced";
            default: return "None";
        }
    }
}

What Changed #

• Added class-level label variables so we can modify them anywhere in the class.
• Created updateStartPanel() method that handles updating all Start panel labels and the status message.
• Called updateStartPanel() every time a Key/Level is selected, and when switching to the Start panel.
• Added helper methods to convert key/level numbers to friendly names (makes the UI nicer!).
• Adjusted the lblChoicedone bounds to fit longer text without cutting off.

Now when you select a Key or Level, the Start panel will automatically reflect your choices, and the status message will update correctly when you switch to the Start screen.

内容的提问来源于stack exchange，提问作者A Stephens