java - 更改 MouseRelease 事件上的 JLabel 背景

Question

我正在尝试编写一个Java程序，当您单击JFrame中的某个元素时，JLabel的背景就会改变。事件处理方法调用来更改背景的函数在从事件调用时不起作用，但是只要您在独立于任何事件的地方调用该方法，它就会起作用。有谁知道如何更改 MouseRelease 事件的背景，因为使用这样的事件处理方法不起作用？

private void MouseReleaseEvent(java.awt.event.MouseEvent evt) {                                             
    // Do some random stuff, like a println.
    // This println works as a normal println statement should.
    System.out.println("Hello World!");
    // Now let's try the method that changes the background.
    // This method will not work within this event handler, but trying it outside
    // of it does work.
    changeBackground();
}   

• 注意:上面的代码只是为了展示我的问题。它实际上不是我的代码的一部分。我不发布代码是因为我正在和一个 friend 一起开发这个程序，而他不想发布代码，即使它只是其中的一小部分，无法做任何有值(value)的事情。

编辑:根据所有试图帮助我的人的请求，我已将 NetBeans 项目工作区以 zip 文件形式上传到 FileDropper，您可以下载该文件 here 。您会注意到，当我从主类调用该方法时，它确实会闪烁另一张图像并按我想要的方式返回到当前图像，但是当您单击“播放”释放鼠标时，它不会调用它，即使它应该。请随意尝试您想要的代码。

编辑2:由于还要求我为那些不想下载工作区的人发布代码，因此这里是:

西蒙.java

package simon;

public class Simon {
    public static void main(String[] args) {
        // Load all of the other class files into this main class.
        SimonGUI SimonGUI = new SimonGUI();
        // For some reason, setting the background color doesn't work when we
        // try doing it within the GUI development environment, but it works
        // here, so that's what we are going to do.
        SimonGUI.getContentPane().setBackground(new java.awt.Color(0, 0, 0));
        // Make the form visible to the user. It is now ready for use.
        SimonGUI.setVisible(true);
        SimonGUI.playBackPattern();
    }
}

SimonGUI.java*

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package simon;

import java.awt.Component;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

/**
 *
 * @author Administrator
 */
public class SimonGUI extends javax.swing.JFrame {
    // Declare class level variables.
    boolean aboutTextVisible = false;
    boolean mainMenuVisible = true;
    boolean userResponseAllowed = false;
    private Component frame;

    /**
     * Creates new form SimonGUI
     */
    public SimonGUI() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        lblPlayButton1 = new javax.swing.JLabel();
        lblPlayButton = new javax.swing.JLabel();
        lblSimonBoard = new javax.swing.JLabel();

        lblPlayButton1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/MenuPlay.png"))); // NOI18N
        lblPlayButton1.setName("lblPlayButton"); // NOI18N

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Simon");
        setBackground(new java.awt.Color(0, 0, 0));
        setMaximumSize(new java.awt.Dimension(600, 600));
        setMinimumSize(new java.awt.Dimension(600, 600));
        setName("frmSimon"); // NOI18N
        setPreferredSize(new java.awt.Dimension(600, 600));
        setResizable(false);
        getContentPane().setLayout(null);

        lblPlayButton.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/MenuPlay.png"))); // NOI18N
        lblPlayButton.setCursor(new java.awt.Cursor(java.awt.Cursor.HAND_CURSOR));
        lblPlayButton.setName("lblPlayButton"); // NOI18N
        lblPlayButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                lblPlayButtonMouseReleased(evt);
            }
        });
        getContentPane().add(lblPlayButton);
        lblPlayButton.setBounds(150, 20, 317, 58);
        lblPlayButton.getAccessibleContext().setAccessibleName("lblPlayerButton");

        lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Original.PNG"))); // NOI18N
        lblSimonBoard.setToolTipText("");
        lblSimonBoard.setFocusable(false);
        lblSimonBoard.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
        lblSimonBoard.setName("lblSimon"); // NOI18N
        getContentPane().add(lblSimonBoard);
        lblSimonBoard.setBounds(-1, 93, 600, 497);
        lblSimonBoard.getAccessibleContext().setAccessibleName("lblSimon");

        getAccessibleContext().setAccessibleName("frmSimon");
        getAccessibleContext().setAccessibleDescription("");

        pack();
    }// </editor-fold>                        

    private void lblPlayButtonMouseReleased(java.awt.event.MouseEvent evt) {                                            
        // This handles the start of Simon gameplay.
        toggleBoard();
        playBackPattern();
    }                                           

    public void toggleBoard() {
        // Handles toggling between the main menu and the simon board.
        if (mainMenuVisible == true)
        {
            // Board is visible, let's toggle it off.
            lblPlayButton.setBounds(700, 700, 317, 58);
            mainMenuVisible = false;
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Original.PNG")));
        }
        else
        {
            // Board is not visible, let's toggle it on.
            lblPlayButton.setBounds(120, 140, 317, 58);
            mainMenuVisible = true;
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/SimonBackground.PNG")));
        }
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * Set the Nimbus look and feel
         */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the
         * default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(SimonGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(SimonGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(SimonGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(SimonGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new SimonGUI().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JLabel lblPlayButton;
    private javax.swing.JLabel lblPlayButton1;
    public javax.swing.JLabel lblSimonBoard;
    // End of variables declaration                   

    public void flashColor(int colorID) {
        // Flash one of the colors. The value of the color that we are going to
        // flash is passed here, and the color is flashed.
        // Pause for a fraction of a second before blinking the color. In case
        // something goes wrong during the pause, we have an error which we hope
        // to never use that will catch the program's weakness.
        try {
            Thread.sleep(250);
        } catch (InterruptedException ex) {
            JOptionPane.showMessageDialog(frame,"A fatal error has caused Simon to stop working.","Simon • Fatal Error",JOptionPane.ERROR_MESSAGE);
            System.exit(0);
        }
        // Flash the respective color.
        if(colorID == 1) {
            // Flash Red
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Red.PNG")));
        }
        else if(colorID == 2){
            // Flash Green
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Green.PNG")));
        }
        else if (colorID == 3) {
            // Flash Yellow
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Yellow.PNG")));
        }
        else {
            // Flash Blue
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Blue.PNG")));
        }
        // Wait for a fraction of a second before we return to the regular
        // board. In case something bad happens here while we pause, we have an
        // error message that we hope will never be used.
        try {
            Thread.sleep(250);
            lblSimonBoard.setIcon(new javax.swing.ImageIcon(getClass().getResource("/simon/resources/Original.PNG")));
        } catch (InterruptedException ex) {
            JOptionPane.showMessageDialog(frame,"A fatal error has caused Simon to stop working.","Simon • Fatal Error",JOptionPane.ERROR_MESSAGE);
            System.exit(0);
        }
    }
    public void userResponseEnabled(boolean responsePermitted) {
        // Toggles the class-level variable "userResponseAllowed", which
        // controls if the user can click on the buttons on the Simon board and
        // give a response.

        // Pass the value to the class-level variable.
        userResponseAllowed = responsePermitted;
    }

    // "Actual Game Code"
    int score = 0;
    ArrayList pattern = new ArrayList();
    int playerColor = 0;
    int y = 0;
    boolean correct = true;
    private SimonGUI SimonGUI;

    int certainColor = 1;
    int numberOfColors = 0;

    public void playBackPattern() {
        // Normally, the playBackPattern() method has more than just this line,
        // but for demo purposes, this line is all that is needed.
        flashColor(4);
    }
}

*部分代码是使用 NetBeans 的 Swing GUI 设计器插件自动生成的。

Answer 1

1. JLabel默认是透明的，必须更改setOpaque()

2. 我不知道什么方法MouseReleaseEvent是，不要重定向 Swing 事件(在某些情况下是可能且必需的，但不适用于 newbee)，

3. 在 MouseListener 中实现的标准事件是mousePressed, mouseReleased, mouseEntered, mouseExited, mouseClicked

4. 阅读 Oracle 教程 How to Write a Mouse Listener用于工作示例和各种不同的事件类型