java - setDefaultCloseOperation 改为显示 JFrame

Question

我正在制作一个文字处理器应用程序以练习 Java，我希望这样当用户尝试关闭应用程序时，会出现一个 JFrame，要求保存更改。

我正在考虑 setDefaultCloseOperation() 但到目前为止我运气不佳。如果可能的话，我还希望它在用户单击窗口右上角的“X”时出现。

Answer 1

您可以将 JFrame DefaultCloseOperation 设置为 DO_NOTHING，然后设置一个 WindowsListener 来获取关闭事件并执行您想要的操作。我会在几分钟后发布一个例子。

编辑：这是示例：

public static void main(String[] args) {
        final JFrame frame = new JFrame("Test Frame");

        frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

        frame.setSize(800, 600);

        frame.addWindowListener(new WindowAdapter() {
            //I skipped unused callbacks for readability

            @Override
            public void windowClosing(WindowEvent e) {
                if(JOptionPane.showConfirmDialog(frame, "Are you sure ?") == JOptionPane.OK_OPTION){
                    frame.setVisible(false);
                    frame.dispose();
                }
            }
        });

        frame.setVisible(true);
    }

Answer 2

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

public class QuickGuiTest {

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                final JFrame frame = new JFrame("Test Frame");

                frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
                frame.setSize(600, 400);
                frame.addWindowListener(new WindowAdapter() {
                    @Override
                    public void windowClosing(WindowEvent e) {
                        int result = JOptionPane.showConfirmDialog(
                                frame, "Are you sure?");
                        if( result==JOptionPane.OK_OPTION){
                            // NOW we change it to dispose on close..
                            frame.setDefaultCloseOperation(
                                    JFrame.DISPOSE_ON_CLOSE);
                            frame.setVisible(false);
                            frame.dispose();
                        }
                    }
                });
                frame.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

Answer 3

• 您必须WindowListener在JFrame.

• 在windowClosing方法内部，您可以提供所需的代码。

例如：

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

public class ClosingFrame extends JFrame {

    private JMenuBar MenuBar = new JMenuBar();
    private JFrame frame = new JFrame();
    private static final long serialVersionUID = 1L;
    private JMenu File = new JMenu("File");
    private JMenuItem Exit = new JMenuItem("Exit");

    public ClosingFrame() {
        File.add(Exit);
        MenuBar.add(File);
        Exit.addActionListener(new ExitListener());
        WindowListener exitListener = new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent e) {
                int confirm = JOptionPane.showOptionDialog(frame,
                        "Are You Sure to Close this Application?",
                        "Exit Confirmation", JOptionPane.YES_NO_OPTION,
                        JOptionPane.QUESTION_MESSAGE, null, null, null);
                if (confirm == JOptionPane.OK_OPTION) {
                    System.exit(0);
                }
            }
        };
        frame.addWindowListener(exitListener);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setJMenuBar(MenuBar);
        frame.setPreferredSize(new Dimension(400, 300));
        frame.setLocation(100, 100);
        frame.pack();
        frame.setVisible(true);
    }

    private class ExitListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            int confirm = JOptionPane.showOptionDialog(frame,
                    "Are You Sure to Close this Application?",
                    "Exit Confirmation", JOptionPane.YES_NO_OPTION,
                    JOptionPane.QUESTION_MESSAGE, null, null, null);
            if (confirm == JOptionPane.OK_OPTION) {
                System.exit(0);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ClosingFrame cf = new ClosingFrame();
            }
        });
    }
}