使用KeyListener移动矩形 [英] Moving a Rectangle Using KeyListener

问题描述

我正在尝试使用KeyListener移动一个矩形。我见过其他人使用相同的代码但由于某种原因我不能让它移动。现在矩形确实出现了。如果有什么东西我不知道，我不确定我是否会遗忘某些东西。
这是我的代码：

I'm trying to get a rectangle to move using KeyListener. I have seen others use the same code but for some reason I can't get it to move. Right now the rectangle does show up. I'm not sure if I'm forgetting something if there is something I'm missing. Here's my code:

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();
    }

}

推荐答案

除了不尊重油漆链（并且调用 super.paintComponent ）之外，你的主要问题是使用 KeyListener 。

Apart from not honouring the paint chain (and calling super.paintComponent), you're primary issue is the use of KeyListener.

少量搜索会很快告诉你 KeyListener 因为没有回复而臭名昭着通常是不可靠的。

A short amount of searching will tell you quickly that KeyListener is notorious for not responding as is generally unreliable.

最常见的解决方案是使用键绑定API

The most common solution is to use the key bindings API

以下是将键绑定实现到当前代码库的非常简单的示例

The following is very simply example of implementing key bindings into your current code base

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;
        }

    }
}

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