Question

我有几个课程，但我只发布了我的主课程。大部分代码都来自我教授的示例程序。我的问题是我要在窗口按钮关闭时运行检查。 'check'将查看另一个类中“已保存”的布尔变量是True还是False，并相应地执行操作。然后，关上窗户。到目前为止，我有这个，但我从JFrameL得到一个错误。如何使用其他类的WindowClosing方法？我看到我不应该自己打电话了吗？

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class Main {

public static JFrameL frame;

public static void main(String[] args) {
    // Create a window.
    frame  = new JFrameL("Checking Account Actions");

    // Set the size of the window.
    frame.setSize(450, 350);
    frame.setAlwaysOnTop(true);

    // Specify what happens when the close button is clicked.
    frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

    CheckingAccountActions panel = new CheckingAccountActions();
    frame.getContentPane().add(panel);
    frame.pack();

    // Display the window
    frame.setVisible(true);

}

public class JFrameL extends JFrame {

    public JFrameL(String title) {
        super(title);
        FrameListener listener = new FrameListener();
        addWindowListener(listener);
    }

    private class FrameListener extends WindowAdapter {

        public void windowClosing(WindowEvent e) {
            System.out.println("WindowListener method called: windowClosed.");
            if(!CheckingAccountActions.saved) {
                String  message = "The data in the application is not saved.\n"
                                + "Would you like to save it before exiting the application?";
                int confirm = JOptionPane.showConfirmDialog (null, message);

                if (confirm == JOptionPane.YES_OPTION)
                    CheckingAccountActions.chooseFile(2);
            }
            Main.frame.setVisible(false);
            System.exit(0);
        }
    }
}

 }

我在第2行从main（）收到的错误消息：

“不能访问Main类型的封闭实例。必须使用Main类型的封闭实例限定分配（例如x.new A（），其中x是Main的实例）。”

Answer 1

您似乎试图以静态方式调用实例方法。不要这样做。
我不会为你想要做的事扩展JFrame。
我将创建自己的WindowListener类，该类具有对该对象的有效引用，该对象知道是否需要文件保存以及是否已完成。

如，

class MyWindowAdapter extends WindowAdapter {
  private CheckingAccountActions checkActions;

  public MyWindowAdapter(CheckingAccountActions checkActions) {
    this.checkActions = checkActions;
  }

  // in your window closing method
  // check the state of checkActions first before doing anything
    public void windowClosing(WindowEvent e) {
        // note -- don't check for saved in a static way
        // use a method on the instance.
        if(!checkActions.getSaved()) {
            // etc...
        }

        JFrame frame = (JFrame)e.getSource();
        frame.setVisible(false);

        // Main.frame.setVisible(false);
        System.exit(0);
    }
}

然后在主要：

public static void main(String[] args) {
    frame  = new JFrame("Checking Account Actions");
    frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

    CheckingAccountActions panel = new CheckingAccountActions();

    MyWindowAdapter winAdapter = new MyWindowAdapter(panel);
    frame.addWindowListener(winAdapter);

    frame.getContentPane().add(panel);
    frame.pack();

    frame.setVisible(true);
}

修改

这种静态过度使用的气味：CheckingAccountActions.saved。

Answer 2

我怀疑你需要做的是移动panel以便以后可以访问它。

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class Main {

public static JFrameL frame;
public static CheckingAccountActions panel;

public static void main(String[] args) {
    // Create a window.
    frame  = new JFrameL("Checking Account Actions");

    // Set the size of the window.
    frame.setSize(450, 350);
    frame.setAlwaysOnTop(true);

    // Specify what happens when the close button is clicked.
    frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

    panel = new CheckingAccountActions();
    frame.getContentPane().add(panel);
    frame.pack();

    // Display the window
    frame.setVisible(true);

}

public class JFrameL extends JFrame {

    public JFrameL(String title) {
        super(title);
        FrameListener listener = new FrameListener();
        addWindowListener(listener);
    }

    private class FrameListener extends WindowAdapter {

        public void windowClosing(WindowEvent e) {
            System.out.println("WindowListener method called: windowClosed.");
            if(!panel.saved) {
                String  message = "The data in the application is not saved.\n"
                                + "Would you like to save it before exiting the application?";
                int confirm = JOptionPane.showConfirmDialog (null, message);

                if (confirm == JOptionPane.YES_OPTION)
                    panel.chooseFile(2);
            }
            Main.frame.setVisible(false);
            System.exit(0);
        }
    }
}

当用户尝试关闭窗口按钮时，如何检查文件是否已保存？

2 个答案: