Swing addWindowFocusListener

Question

我有簡單的Java Swing應用程序。我想在關閉主窗口之前得到用戶的確認。

有我的代碼：

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); 
        } 
      } 
     }); 


    } 

} 

但目前看來，frame.addWindowFocusListener不起作用。

請告訴我正確的方法添加事件windowClosing到我的框架。

Answer 1

替換

frame.addWindowFocusListener(new WindowAdapter() { 

與

frame.addWindowListener(new WindowAdapter() { 

第一取WindowFocusListener其將被稱爲窗口任一增益時或失去焦點。