Question

我想要3种退出应用程序的方法

按键CTRL-Q
选择＆＃39;退出＆＃39;来自菜单栏
关闭＆＃39; x＆＃39; JFrame上的按钮

我到目前为止所做的是为前两个添加偶数听众，但我无法弄清楚如何让JFrame关闭＆＃39; x＆＃39;按钮做同样的事情。现在它只是在不提示确认的情况下退出应用程序，因为它不知道如何实现。在用户确认要退出之后，我基本上希望处理所有帧。在前两种情况下会发生这种情况，原因很简单，因为它们的动作侦听器调用确认退出的exit（）方法，然后继续处理所有帧。

public class MainWindow extends JFrame {
    ...
    this.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

    this.addWindowListener(new WindowListener() {
        @Override
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    }

    ...

    // this is part of the main menu bar (case #2)
    JMenuItem mntmExit = new JMenuItem("Exit");
    mntmExit.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            MainWindow.this.exit();
        }

    });

    // this is case #1
    KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(new KeyEventDispatcher() {

        @Override
        public boolean dispatchKeyEvent(KeyEvent e) {
            if(e.getKeyCode() == KeyEvent.VK_Q && e.getModifiers() == InputEvent.CTRL_MASK) {
                MainWindow.this.exit();
            }

            return false;
        }

    });
}

// the exit method
private void exit() {
    int confirmed = JOptionPane.showConfirmDialog(this, "Are you sure you want to quit?", "Confirm quit", JOptionPane.YES_NO_OPTION);

    if(confirmed == JOptionPane.YES_OPTION) {
        Frame[] frames = Frame.getFrames();

        for(Frame frame : frames) {
            frame.dispose();
        }
    }
}

是否可以为关闭按钮分配动作侦听器？如果没有，我还有另一种方法吗？

Answer 1

将JFrame的默认关闭操作保持为JFrame.DO_NOTHING_ON_CLOSE，但使用WindowListener（或更简洁的WindowAdapter）监听关闭尝试。

您可以对菜单项和按钮使用相同的AbstractAction，然后在WindowListener中调用action的方法。例如

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.*;

public class ClosingJFrame {
   public static void main(String[] args) {
      final JFrame frame = new JFrame("My Frame");
      frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

      final CloseAction closeAction = new CloseAction(frame);

      JPanel panel = new JPanel();
      panel.add(new JButton(closeAction));

      JMenuItem exitMenuItem = new JMenuItem(closeAction);
      JMenu menu = new JMenu("File");
      menu.setMnemonic(KeyEvent.VK_F);
      menu.add(exitMenuItem);
      JMenuBar menuBar = new JMenuBar();
      menuBar.add(menu);

      frame.setJMenuBar(menuBar);

      frame.addWindowListener(new WindowAdapter() {
         @Override
         public void windowClosing(WindowEvent e) {
            closeAction.confirmClosing();
         }
      });

      frame.add(panel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);


   }
}

class CloseAction extends AbstractAction {
   private JFrame mainFrame;

   public CloseAction(JFrame mainFrame) {
      super("Exit");
      putValue(MNEMONIC_KEY, KeyEvent.VK_X);
      this.mainFrame = mainFrame;
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      confirmClosing();
   }

   public void confirmClosing() {
      int confirmed = JOptionPane.showConfirmDialog(mainFrame,
            "Are you sure you want to quit?", "Confirm quit",
            JOptionPane.YES_NO_OPTION);
      if (confirmed == JOptionPane.YES_OPTION) {
         // clean up code
         System.exit(0);
      }
   }
}

修改
糟糕，我忘记了你的ctrl-Q击键位。对此使用相同的Action，并使用KeyBindings将其绑定到ctrl-q键。改进的代码：

import java.awt.event.ActionEvent; import java.awt.event.InputEvent; import java.awt.event.KeyEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.*; public class ClosingJFrame { public static void main(String[] args) { final JFrame frame = new JFrame("My Frame"); frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE); final CloseAction closeAction = new CloseAction(frame); JPanel panel = new JPanel(); panel.add(new JButton(closeAction)); JMenuItem exitMenuItem = new JMenuItem(closeAction); JMenu menu = new JMenu("File"); menu.setMnemonic(KeyEvent.VK_F); menu.add(exitMenuItem); JMenuBar menuBar = new JMenuBar(); menuBar.add(menu); frame.setJMenuBar(menuBar); frame.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { closeAction.confirmClosing(); } }); // also use the same Action in your ctrl-q key bindings int condition = JComponent.WHEN_IN_FOCUSED_WINDOW; InputMap inputMap = panel.getInputMap(condition); ActionMap actionMap = panel.getActionMap(); KeyStroke ctrlQKey = KeyStroke.getKeyStroke(KeyEvent.VK_Q, InputEvent.CTRL_DOWN_MASK); inputMap.put(ctrlQKey, ctrlQKey.toString()); actionMap.put(ctrlQKey.toString(), closeAction); frame.add(panel); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } } class CloseAction extends AbstractAction { private JFrame mainFrame; public CloseAction(JFrame mainFrame) { super("Exit"); putValue(MNEMONIC_KEY, KeyEvent.VK_X); this.mainFrame = mainFrame; } @Override public void actionPerformed(ActionEvent e) { confirmClosing(); } public void confirmClosing() { int confirmed = JOptionPane.showConfirmDialog(mainFrame, "Are you sure you want to quit?", "Confirm quit", JOptionPane.YES_NO_OPTION); if (confirmed == JOptionPane.YES_OPTION) { // clean up code System.exit(0); } } }

编辑2
这句话让我担心：


然后继续处理所有帧

因为它意味着你有多个JFrame。如果是这样，您应该阅读此链接，因为它将解释为什么通常不需要这样做：The Use of Multiple JFrames, Good/Bad Practice?

编辑3
根据Rob Camick的评论：


您也可以通过执行以下操作来为CloseAction设置加速器：

putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke("control Q"));


然后菜单项将为您执行键绑定。

这将进入CloseAction的构造函数，如下所示：

public CloseAction(JFrame mainFrame) { super("Exit"); putValue(MNEMONIC_KEY, KeyEvent.VK_X); putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke("control Q")); this.mainFrame = mainFrame; }

Answer 2

在windowClosing方法中，请在exit()之前调用System.exit()方法。

单击X时会自动关闭java程序。

如何覆盖JFrame关闭（＆＃39; x＆＃39;）按钮的默认侦听器？

2 个答案: