使用KeyListener移动矩形

Question

我正在尝试使用keyListener移动矩形。我已经看到其他人使用相同的代码，但是由于某种原因，我无法移动它。现在，矩形确实出现了。我不确定如果我缺少某些东西，我是否会忘记一些东西。这是我的代码：

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.Graphics;
public class roomwars extends JPanel implements ActionListener, KeyListener {
    //public JPanel pane;
    public JFrame frame;
    public JButton start, help;
    public JTextField box;
    int x=0, y=0, velx =0, vely =0;
    Timer t = new Timer(5, this);
    public void run(){
        frame = new JFrame("ROOM WARS!");
        frame.setSize(700, 700);
        frame.setVisible(true);
        frame.add(this);
    }
    public void second (){
        t.start();
        addKeyListener(this);
        //setFocusalbe(true);
        //SETFocusTraversalKeyEnabled(false);
    }
    public void paintComponent(Graphics g) {
        Color mypurple = new Color(34, 0, 56);
        g.setColor(mypurple);
        g.fillRect(x, y, 30, 30);
        //g.setColor(Color.PINK);
        //g.fillRect(655,632,30,30);
    }
    public void actionPerformed(ActionEvent e){
        repaint();
        x+= velx;
        y+= vely;
    }
     public void keyPressed(KeyEvent e){
        int code = e.getKeyCode();
        if (code == KeyEvent.VK_UP){
            vely = -1;
            velx = 0;
        }
        else if (code == KeyEvent.VK_DOWN) {
            vely = 1;
            velx = 0;
        }
        else if (code == KeyEvent.VK_RIGHT) {
            velx = -1;
            vely = 0;
        }
        else if (code == KeyEvent.VK_LEFT) {
            velx = 1;
            vely = 0;
        }
    }
    public void keyTyped(KeyEvent e){}
    public void keyReleased(KeyEvent e) {}
    public static void main(String[] args) {
        new roomwars().run();
    }
}

Answer 1

除了不尊重油漆链(并致电super.paintComponent(外，您的主要问题是使用KeyListener。

少量搜索会很快告诉您KeyListener臭名昭著，因为不响应通常是不可靠的。

最常见的解决方案是使用键绑定API

以下是将密钥绑定在您当前的代码库中实现的示例

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.io.IOException;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
    public static void main(String[] args) throws IOException, InterruptedException {
        new Test();
    }
    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new RoomWars());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    public class RoomWars extends JPanel implements ActionListener {
        //public JPanel pane;
        int x = 0, y = 0, velx = 0, vely = 0;
        Timer t = new Timer(5, this);
        public RoomWars() {
            t.start();
            InputMap im = getInputMap(JPanel.WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), "up.pressed");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true), "up.released");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), "down.pressed");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "down.released");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false), "left.pressed");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true), "left.released");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false), "right.pressed");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true), "right.released");
            am.put("up.pressed", new MoveAction(-1, 0));
            am.put("up.released", new MoveAction(0, 0));
            am.put("down.pressed", new MoveAction(1, 0));
            am.put("down.released", new MoveAction(0, 0));
            am.put("left.pressed", new MoveAction(0, -1));
            am.put("left.released", new MoveAction(0, 0));
            am.put("right.pressed", new MoveAction(0, 1));
            am.put("right.released", new MoveAction(0, 0));
        }
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Color mypurple = new Color(34, 0, 56);
            g.setColor(mypurple);
            g.fillRect(x, y, 30, 30);
            //g.setColor(Color.PINK);
            //g.fillRect(655,632,30,30);
        }
        public class MoveAction extends AbstractAction {
            private int yDelta;
            private int xDelta;
            public MoveAction(int yDelta, int xDelta) {
                this.yDelta = yDelta;
                this.xDelta = xDelta;
            }
            @Override
            public void actionPerformed(ActionEvent e) {
                vely = yDelta;
                velx = xDelta;
            }
        }
        public void actionPerformed(ActionEvent e) {
            repaint();
            x += velx;
            y += vely;
        }
    }
}

Answer 2

请注意，在代码片段中，second()未调用，因此未注册键侦听器。您的面板还需要集中注意力才能接收关键新闻事件。您可能还需要在方法中首先致电super.paintComponent()。

有关详细信息：

请参阅此处

https://docs.oracle.com/javase/tutorial/uiswing/events/keylistener.html