如何在JPanel中正确地重绘JFrame

Question

stackoverflow社区!我正在用JAVA制作一个基于GUI的小游戏。我现在遇到了一些麻烦。为了让你对我的程序有一个基本的了解，

我有一个窗口，首先显示菜单(JPanel)。当我点击"开始游戏"按钮时。它继续到另一个我可以玩游戏的JPanel。! [menu_window] [1]

我有一个计时器，用于定时移动的小子弹。每次计时器工作，小组就会重新粉刷子弹。我可以看到重绘方法工作，但它不能删除以前的痕迹。

![2]

这是我的主类

import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Main {
    private final int window_x_size = 500;
    private final int window_y_size = 500;
    private JFrame frame;
    private JPanel Menu;
    private Game myGame = new Game();//extends from JPanel

    private JButton startButton = new JButton("Game Start");
    private JButton exitButton = new JButton("Game Exit");
    private JButton showRank = new JButton("Rank");
    private JButton OneOnOne = new JButton("One on One");

    private ActionListener MyButtonListener = new MyButtonListener();
    public class MyButtonListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if (source == startButton) {
                frame.remove(Menu);
                frame.setContentPane(myGame);
                frame.validate();
                frame.repaint(); // prefer to write this always.
            } else if (source == exitButton) {
                System.exit(1);
            } else if (source == showRank) {
            } else {// one on one
            }
        }
    }

    public Main() {
        frame = new JFrame();
        frame.setBackground(Color.white);
        frame.setSize(window_x_size, window_y_size);
        frame.setTitle("My First GUI Game");
        frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
        Menu = new JPanel();
        startButton.addActionListener(MyButtonListener);
        exitButton.addActionListener(MyButtonListener);
        showRank.addActionListener(MyButtonListener);
        OneOnOne.addActionListener(MyButtonListener);
        Menu.setLayout(new GridLayout(4, 1));
        Menu.add(startButton);
        Menu.add(OneOnOne);
        Menu.add(showRank);
        Menu.add(exitButton);
        frame.setContentPane(Menu);
        frame.setVisible(true);
    }
    public static void main(String[] args) {
        /*
         * This is the most important part of your GUI app, never forget 
         * to schedule a job for your event dispatcher thread : 
         * by calling the function, method or constructor, responsible
         * for creating and displaying your GUI.
         */
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {  
                new Main();
            }
        });

    }
}

这是我的Game类

import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Random;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;
public class Game extends JPanel {
    private Random rnd = new Random();
    private ActionListener MyBulletListener = new BulletListener();
    public KeyListener myKeyListen = new MyKeyListener();
    Timer bullet_timer;
    private boolean IsExplosion = false;
    private ImageIcon spacecraftImg = new ImageIcon("spacecraft.png");
    private Rectangle spacecraftBox = new Rectangle(5, 10,
            spacecraftImg.getIconWidth(), spacecraftImg.getIconHeight());
    private ImageIcon explosionImg = new ImageIcon("explosion.png");
    private ImageIcon bulletImg = new ImageIcon("bullet.png");
    private Rectangle bulletBox = new Rectangle(70, 200,
            bulletImg.getIconWidth(), bulletImg.getIconHeight());
    private MySound explosion_sound = new MySound();
    public Game() {
        addKeyListener(myKeyListen);
        bullet_timer = new Timer(500, MyBulletListener);
        bullet_timer.start();
    }
    public class MyKeyListener implements KeyListener {
        private int x;
        private int y;
        @Override
        public void keyPressed(KeyEvent e) {
            // TODO Auto-generated method stub
            int keyCode = e.getKeyCode();
            if (keyCode == 37) {
                x = -10;
                y = 0;
            } else if (keyCode == 38) {
                x = 0;
                y = -10;
            } else if (keyCode == 39) {
                x = 10;
                y = 0;
            } else {
                x = 0;
                y = 10;
            }
            if (spacecraftBox.x + x < 0
                    || spacecraftBox.x + x > 500
                    || spacecraftBox.y + y < 0
                    || spacecraftBox.y + y > 500) {
            } else {
                move_plane(x, y);
                repaint();
            }
        }
        @Override
        public void keyReleased(KeyEvent e) {
            // TODO Auto-generated method stub
        }
        @Override
        public void keyTyped(KeyEvent e) {
            // TODO Auto-generated method stub
        }
    }
    public class BulletListener implements ActionListener {
        private int x;
        private int y;
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            Object source = e.getSource();
            if (source == bullet_timer) {
                int dir = rnd.nextInt(4);
                if (dir == 0) {// move left
                    x = -10;
                    y = 0;
                } else if (dir == 1) {// move right
                    x = 10;
                    y = 0;
                } else if (dir == 2) {// move up
                    x = 0;
                    y = -10;
                } else {// move down
                    x = 0;
                    y = 10;
                }
                if (bulletBox.x + x < 0
                        || bulletBox.x + x > 500
                        || bulletBox.y + y < 0
                        || bulletBox.y + y > 500) {
                } else {
                    move_bullets(x, y);
                    repaint();
                }
            }
        }
    }

    @Override
    public void paint(Graphics g) {
        g.drawImage(bulletImg.getImage(), (int) bulletBox.getX(),
                (int) bulletBox.getY(), null);
        g.drawImage(spacecraftImg.getImage(), (int) spacecraftBox.getX(),
                (int) spacecraftBox.getY(), null);
        if (IsExplosion) {
            g.drawImage(explosionImg.getImage(), (int) bulletBox.getX(),
                    (int) bulletBox.getY(), null);
            MySound.play();
            IsExplosion = false;
        }
    }
    public void move_plane(int x, int y) {
        spacecraftBox.translate(x, y);
        if (spacecraftBox.intersects(bulletBox)) {
            IsExplosion = true;
        }
    }
    public void move_bullets(int x, int y) {
        bulletBox.translate(x, y);
        if (spacecraftBox.intersects(bulletBox)) {
            IsExplosion = true;
        }
    }
}

加上我添加了KeyListener，但它不起作用。我不知道如何解决这个问题。

我试着在谷歌上搜索这个问题。我尝试了游戏面板聚焦在主要类，但它没有工作。

我真的很感激你的帮助。

最诚挚的问候,

Dongseop

Answer 1

这几乎总是由于你的绘画方法没有调用super的绘画方法来清理脏的像素。由于要重写paint，因此需要调用super.paint(g);作为paint override中的第一个方法调用。

其他问题:

• 接下来我将建议你而不是覆盖油漆，而是paintComponent(Graphics g)，因为这将给你的动画自动双重缓冲，使动画更平滑。再次，在你的方法override中调用super.paintComponent(g);。
• 最简单的方法是使用CardLayout。
• 最好使用KeyBindings而不是KeyListener，因为这将帮助您绕过KeyListener的焦点问题，这个问题可能会阻止您的KeyListener工作。它还允许您使用可重用的action。请在KeyListeners上搜索这个站点，了解我的意思，并查看键绑定的示例(其中一些是我的)。也谷歌Java Key Bindings Tutorial看到如何使用这些官方教程。