Swing addWindowFocusListener

Question

我有一个简单的Java应用程序。我想在关闭主窗口之前得到用户的确认。

这是我的密码：

package client_interface;

import java.awt.EventQueue;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Rectangle;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

public class MainWindow {

    private JFrame frame;

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

    public MainWindow() {
        initialize();
    }

    private void setFrameSize(JFrame frame) {
        GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
        int width = gd.getDisplayMode().getWidth();
        int height = gd.getDisplayMode().getHeight();
        frame.setBounds(new Rectangle(width/4, height/4, width/2, height/2));
        //frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
    }


    private void initialize() {
        frame = new JFrame("Test");
        setFrameSize(frame);
        frame.addWindowFocusListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                if (JOptionPane.showConfirmDialog(frame, 
                        "Are you sure to close this window?", "Really Closing?", 
                        JOptionPane.YES_NO_OPTION,
                        JOptionPane.QUESTION_MESSAGE) == JOptionPane.YES_OPTION){
                        System.exit(0);
                    }
            }
        });


    }

}

但似乎frame.addWindowFocusListener不起作用。

请告诉我添加事件windowClosing到我的帧的正确方法。

Answer 1

替换

frame.addWindowFocusListener(new WindowAdapter() {

使用

frame.addWindowListener(new WindowAdapter() {

第一个是WindowFocusListener，当窗口获得焦点或失去焦点时将调用它。