在我的一个程序中，我希望在用户尝试退出应用程序时出现一个对话框。然后用户必须选择保存程序的某些状态，不保存或取消退出操作。

我写这篇文章是为了先找到解决方案，然后再实现它:

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

class WL implements WindowListener
{
    private boolean statussaved;
    private JFrame tframe;

    WL (JFrame frame)
    {
        statussaved = false;
        tframe = frame;
    }

    @Override public void windowActivated (WindowEvent w) { }
    @Override public void windowClosed (WindowEvent w) { }
    @Override public void windowDeactivated (WindowEvent w) { }
    @Override public void windowDeiconified (WindowEvent w) { }
    @Override public void windowIconified (WindowEvent w) { }
    @Override public void windowOpened (WindowEvent w) { }

    @Override public void windowClosing (WindowEvent w)
    {
        if (statussaved)
        {
            return;
        }

        final JDialog diag = new JDialog (tframe, "Save Progress", true);
        diag.setPreferredSize (new Dimension (500, 100));
        diag.setResizable (false);
        diag.setDefaultCloseOperation (JDialog.DISPOSE_ON_CLOSE);

        JPanel notifypanel = new JPanel ();
        notifypanel.add (new JLabel ("Do you want to save the current status ?"));

        JButton yesbutton = new JButton ("Yes");
        JButton nobutton = new JButton ("No");
        JButton cancelbutton = new JButton ("Cancel");

        yesbutton.addActionListener (new ActionListener ()
        {
            @Override public void actionPerformed (ActionEvent a)
            {
                //SAVE THE STATUS

                System.out.println ("Saving status...");
                statussaved = true;

                diag.dispose ();
                tframe.dispose ();
            }
        });

        nobutton.addActionListener (new ActionListener ()
        {
            @Override public void actionPerformed (ActionEvent a)
            {
                //just exit/close the application

                diag.dispose ();
                tframe.dispose ();
            }
        });

        cancelbutton.addActionListener (new ActionListener ()
        {
            @Override public void actionPerformed (ActionEvent a)
            {
                //DON'T EXIT !!!

                diag.dispose ();
            }
        });

        notifypanel.add (yesbutton);
        notifypanel.add (nobutton);
        notifypanel.add (cancelbutton);

        diag.setContentPane (notifypanel);

        diag.pack ();
        diag.setVisible (true);
    }
}

public class SaveTest
{
    public static void main (String[] args)
    {
        SwingUtilities.invokeLater (new Runnable ()
        {
            @Override public void run ()
            {
                JFrame frame = new JFrame ("Save Test");
                frame.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);
                frame.addWindowListener (new WL (frame));

                JLabel lab = new JLabel ("just some information");

                frame.setPreferredSize (new Dimension (400, 300));
                frame.setResizable (false);
                frame.add (lab);
                frame.pack ();
                frame.setVisible (true);
            }
        });
    }
}

它编译并运行没有任何变化，所以你可以测试它。

"is"和“否”选项按预期工作，但我完全不知道在“取消”按钮的 ActionListener 中写什么。我想要的是，当用户单击“取消”按钮时，对话框消失，但主窗口仍然可见(即程序继续运行)。

现在，由于所有这些都是在 windowClosing 方法中实现的，很明显发送了某种处理信号以销毁 JFrame。这意味着在当前设计中可能无法做到这一点。我不介意重新组织/重新设计这一切以使其发挥作用。只是……我不知道怎么办。

有什么想法吗？

最佳答案

替换

mainframe.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);

与

mainframe.setDefaultCloseOperation (JFrame.DO_NOTHING_ON_CLOSE);

如果用户取消关闭 - 什么都不做。如果同意 - 手动调用 dispose()。

关于Java:如何取消应用程序退出，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9249596/