KeyListener不听

Question

我有以下代码。当我按向右箭头时，需要打印一条消息。但是当我按下VK_RIGHT时，键监听器不会触发。它不会打印它应该打印的消息。你知道为什么吗？

public class AutoClicker implements KeyListener{

       public static int rate = 0;
       static boolean  keep = true;

   public static void main(String[] args) {
       AutoClicker clicker = new AutoClicker();
      JFrame frame = new JFrame();
      frame.setLocationRelativeTo(null);
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setSize(new Dimension(200,300));
       frame.setVisible(true);

       frame.setFocusable(true);
       frame.requestFocus();
   }

    @Override
    public void keyTyped(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
;
    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
            keep = false;
            System.out.println(keep);

            //System.out.println("Right key typed");
        }
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            System.out.println("Left key typed");
        }

        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void keyReleased(KeyEvent e) {
       // throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Answer 1

首先，您不应该将KeyListeners用于Swing应用程序。请看一下How to Use Key Bindings。现在来看看你的主要问题：

您没有在框架中添加KeyListener，这就是它不起作用的原因。因此，添加frame.addKeyListener(this); (或者理想情况下，添加到您想要拥有键侦听器的面板中)，它就可以工作了--但是您不能在静态上下文中执行此操作，因此我建议在构造函数中创建框架。(并且在main方法中仅调用new AutoClicker() )。你也可以在另一个答案中使用解决方案，但我更喜欢这样:P

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;

public class AutoClicker implements KeyListener {

    public static int rate = 0;
    static boolean keep = true;

    public AutoClicker() {

        JFrame frame = new JFrame();
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(200, 300));
        frame.setFocusable(true);
        frame.addKeyListener(this);
        frame.requestFocus();
        frame.setVisible(true);

    }

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                new AutoClicker();
            }
        });

    }

    @Override
    public void keyTyped(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet.");
    };

    @Override
    public void keyPressed(KeyEvent e) {

        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
            keep = false;
            System.out.println(keep);

            System.out.println("Right key typed");
        }
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            System.out.println("Left key typed");
        }

        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void keyReleased(KeyEvent e) {
        // throw new UnsupportedOperationException("Not supported yet."); //To
        // change body of generated methods, choose Tools | Templates.
    }

}

Answer 2

您必须将keylistener添加到帧中。只需根据以下代码更新你的main方法。

   AutoClicker clicker = new AutoClicker();
   JFrame frame = new JFrame();
   frame.addKeyListener(clicker);
   frame.setLocationRelativeTo(null);
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   frame.setSize(new Dimension(200,300));
   frame.setVisible(true);

   frame.setFocusable(true);
   frame.requestFocus();