java如何修复KeyListener

Question

为什么这不起作用 JFrame已经制作好，油漆也在使用，但我无法让keylistener正常工作。我试图在keylistener中打印一些内容，但当按下左箭头时，它没有显示出来

import java.awt.event.KeyEvent;


public class movingsquare extends runpaintgui{
    public void key(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_LEFT){

            x = x - 5;
            repaint(); 
            System.out.println( x);
        }

    }
}

其他类

import java.awt.Graphics;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;

public class runpaintgui extends JFrame{    
int x = 30;
    public static void main(String[] args){
        runpaintgui frame = new runpaintgui();
        frame.setSize(1275, 775);
        frame.setResizable(false);
        frame.setTitle("game");
        frame.setVisible(true);    

    }
     public void paint(Graphics g){
            super.paint(g);

            g.fill3DRect(x, 30, 60, 60, true);


        }    


        }

Answer 1

通过以下方式更改代码：

package de.swisslife.muellerj.test;

import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;

    public class runpaintgui  extends JFrame implements KeyListener{

      public runpaintgui(){

        this.setSize(1275, 775);
        this.setResizable(false);
        this.setTitle("game");
        this.setVisible(true);    
        this.addKeyListener(this);
        this.setVisible(true);;
      }
        int x = 30;
        public static void main(String[] args){
          runpaintgui runpaintgui = new runpaintgui();

        }
         public void paint(Graphics g){
                super.paint(g);

                g.fill3DRect(x, 30, 60, 60, true);


            }    

        public void keyTyped(KeyEvent e) {
          // TODO Auto-generated method stub

        }
        public void keyPressed(KeyEvent e) {
          if (e.getKeyCode() == KeyEvent.VK_LEFT){

            x = x - 5;
            repaint(); 
            System.out.println( x);
        }

        }
        public void keyReleased(KeyEvent e) {
          // TODO Auto-generated method stub

        }
    }

Answer 2

首先，我不会从你的主程序中得到一个子类实现

我不确定你想在程序中做什么，但你可能只需要实现一个键侦听器，如下所示：

public class Test extends JFrame {

    static int x = 30;

    public static void main(String[] args) {


        final Test frame = new Test();
        frame.setSize(1275, 775);
        frame.setResizable(false);
        frame.setTitle("game");
        frame.setVisible(true);
        frame.addKeyListener(new KeyListener() {

            @Override
            public void keyTyped(KeyEvent arg0) {
                if (arg0.getKeyCode() == KeyEvent.VK_LEFT){
                    x = x - 5;
                    frame.repaint(); 
                    System.out.println( x);
                }

            }

            @Override
            public void keyReleased(KeyEvent arg0) {}

            @Override
            public void keyPressed(KeyEvent arg0) {}
        });
    }

    public void paint(Graphics g) {
        super.paint(g);

        g.fill3DRect(x, 30, 60, 60, true);
    }
}