Java KeyListener:如何在按下两个键时执行操作？

Question

请查看以下代码

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

public class KeyCheck extends JFrame
{
    private JButton check;
    private JPanel panel;
    private FlowLayout flow;

    public KeyCheck()
    {
        check = new JButton("Check");
        check.addKeyListener(new KeyWork());

        panel = new JPanel();
        panel.setLayout(new FlowLayout());
        panel.add(check);

        getContentPane().add(panel);

    }

    private class KeyWork extends KeyAdapter
    {
        public void keyPressed(KeyEvent k)
        {
            if(k.getKeyCode()==KeyEvent.VK_CONTROL && KeyEvent.VK_A)
            {
                JOptionPane.showMessageDialog(null, "OK");
            }
        }
    }
    public static void main(String[]args)
    {
        KeyCheck k = new KeyCheck();
        k.setVisible(true);
        k.setSize(200,200);
        k.validate();
        k.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

在这种情况下,我在按钮上添加了一个keylister,当按住CTRL + A(控制键和"A"键)时,我需要它显示消息"OK".但上面的代码是错误的.所以,当两个键被按在一起时,请帮助我获取消息.

Answer 1

您正在混合关键代码和修饰符:

 if(k.getKeyCode()==KeyEvent.VK_A 
     && (k.getModifiers & KeyEvent.CTRL_MASK==KeyEvent.CTRL_MASK))

但更一般地说,最好使用KeyBindings而不是KeyListener.它将使您的生活更轻松,避免您必须进行这些测试.

1.创建这样的动作:

 public class MyAction extends AbstractAction {

     public void actionPerformed(ActionEvent e) {
          JOptionPane.showMessageDialog(null, "OK");
     }
 }

2.将动作绑定到击键:

check.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_A, InputEvent.CTRL_MASK), "doSomething");
check.getActionMap().put("doSomething", new MyAction());

注意事项:我没有测试过这段代码,所以可能需要修复一些小错误.