java - 向 main() 添加按键监听器不起作用

Question

我正在用Java制作一个游戏，其中球在没有用户控制的情况下不断向前移动，但用户可以使用向上和向下箭头键控制球的垂直运动，但是我坚持添加keylistener 类/无论它对我的 JFrame 是什么，通过我的 main 方法。基本上，我执行add(keylistener_class/method)，而Java(非常正确)提示我的类或方法不是组件。那么我的问题是我应该如何将按键监听器添加到我的 Jframe 中？

干杯， 马特

代码:

    package org.ultraluminous.vertiball;


import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game extends JPanel{
    static int x = 0;
    static int y = 0;
    static int ys = 0;

private static void shift(){
    x+=1;
    y+=ys;
    }

public static void event(KeyEvent e){
    if(e.getKeyCode() == KeyEvent.VK_UP){
        ys = 1;
    }
    if (e.getKeyCode() == KeyEvent.VK_DOWN){
        ys = -1;
    }
}

public class key{
public void Listen() {
    KeyListener listener = new KeyListener() {
        @Override
        public void keyTyped(KeyEvent e) {
        }

        @Override
        public void keyPressed(KeyEvent e) {
        }

        @Override
        public void keyReleased(KeyEvent e) {
        }
    };
    addKeyListener(listener);
    setFocusable(true);
}
}   
    @Override
    public void paint(Graphics g){
        super.paint(g);
        Graphics2D Graph = (Graphics2D) g;
        Graph.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
        RenderingHints.VALUE_ANTIALIAS_ON);
        Graph.setColor(Color.BLUE);
        Graph.drawOval(x, y, 50, 50);
        Graph.fillOval(x, y, 50, 50);
    }

    public static void main (String[] args){
        JFrame Win = new JFrame("Pong");
            Game game = new Game();
            Win.add(new Game());
            //Win.add... add what? I need to add the key listener here    
            //but seem to be unable to.
            Win.setResizable(false);
            Win.setSize(900, 600);
            Win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            Win.setVisible(true);
            while (true) {
                shift();
                Win.repaint();
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e){
                    e.printStackTrace();
                }
            }   
    }

Answer 1

我通过将 KeyListener 添加到您的 JFrame 来让它工作。或者，您可以为 KeyListener 创建一个单独的类并以这种方式添加它(而不是使用匿名内部类)。这是我添加的内容:

public static void main (String[] args){
        JFrame Win = new JFrame("Pong");
            Game game = new Game();
            Win.add(new Game());
            Win.addKeyListener(new KeyListener() {

                @Override
                public void keyTyped(KeyEvent e) {
                }

                @Override
                public void keyPressed(KeyEvent e) {
                    if(e.getKeyCode() == KeyEvent.VK_UP){
                        ys = -1;
                    }
                    if (e.getKeyCode() == KeyEvent.VK_DOWN){
                        ys = 1;
                    }
                }

                @Override
                public void keyReleased(KeyEvent e) {
                }

            });
            Win.setResizable(false);
            Win.setSize(900, 600);
            Win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            Win.setVisible(true);
            while (true) {
                shift();
                Win.repaint();
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e){
                    e.printStackTrace();
                }
            }   
      }
}