为什么当我按下退出键时框架没有关闭？

Question

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


public class displayFullScreen extends JFrame {
        private JLabel alarmMessage = new JLabel("Alarm !");
        private JPanel panel = new JPanel();
        public displayFullScreen() {
            setUndecorated(true);
            panel.setLayout(new FlowLayout(FlowLayout.CENTER));
            alarmMessage.setText("Alarm !");
            alarmMessage.setFont(new Font("Cambria",Font.BOLD,100));
            alarmMessage.setForeground(Color.CYAN);
            panel.add(alarmMessage);
            Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
            setBounds(0,0,screenSize.width,screenSize.height);
            panel.setBackground(Color.black);
            add(panel);

            addKeyListener(new KeyAdapter() {
               public void keyPressed(KeyEvent ke) {  // handler
        if(ke.getKeyCode() == ke.VK_ESCAPE) {
                       System.out.println("escaped ?");
                       setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); // trying to close
                    } else {
                       System.out.println("not escaped");
                     }
              } 
           });
        }

        public static void main(String args[]) {
    new displayFullScreen().setVisible(true);
    }

}

我已经为按键设置了监听器。每当我按下ESC按键时，为什么框架没有关闭？

Answer 1

调用setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
不会关闭框架，它将定义按下Windows装饰[X]关闭按钮时的行为（已禁用全屏显示）。您可以将其替换为setVisible(false);或退出程序。