贪 吃 蛇

简介

简易贪吃蛇，使用 javax.swing 组件构建游戏界面，通过监听键盘按键实现游戏操纵。

功能设计

• 按1 - 开始游戏
• 按2 - 重新开始
• 按3 - 暂停/继续
• 按Esc-退出游戏
• 统计吃到的苹果个数（得分）
• 难度控制，得分超过阈值时难度增加（蛇身移动速度加快）

实现

定义 SnakeGame 类：
继承 JPanel 类， 重写其由 JComponent 类中继承的 paintComponent 方法，在此方法中进行图像的绘制。
实现 ActionListener 类， 实现其 actionPerformed 方法， 通过监听在 SnakeGame 类中的Timer 计时器步长内按键的输入完成对图像的操作。

public class SnakeGame extends JPanel implements ActionListener {//(timer = new Timer(delay, this)).start();public void paintComponent(Graphics g) {//在这里操作图像的绘制，蛇身和苹果等}public void actionPerformed(ActionEvent e) {//在这里通过对定时器的监听完成对图像的操作}}

自定义按键适配器， 将键盘输入转换为程序识别的方向值，同时记录键盘输入。

/*** 定义方向*/
public interface Direction {char LEFT = 'L';char RIGHT = 'R';char UP = 'U';char DOWN = 'D';}/*** 按键适配器，用于监听输入按键*/
public class MyKeyAdapter extends KeyAdapter {public void keyPressed(KeyEvent e) {int keyCode = e.getKeyCode();eventKeyCode = e.getKeyCode();if ((keyCode == KeyEvent.VK_LEFT || keyCode == KeyEvent.VK_A) && direction != Direction.RIGHT) {direction = Direction.LEFT;} else if ((keyCode == KeyEvent.VK_RIGHT || keyCode == KeyEvent.VK_D) && direction != Direction.LEFT) {direction = Direction.RIGHT;} else if ((keyCode == KeyEvent.VK_UP || keyCode == KeyEvent.VK_W) && direction != Direction.DOWN) {direction = Direction.UP;} else if ((keyCode == KeyEvent.VK_DOWN || keyCode == KeyEvent.VK_S) && direction != Direction.UP) {direction = Direction.DOWN;}}
}

在 paintComponent 和 actionPerformed 方法中实现游戏逻辑。

注意：

• 对可用像素点的处理：可用像素点个数 = 屏幕长 * 屏幕宽 / 单位大小（苹果大小）。
• 对蛇身初始坐标的处理： 存储蛇身的初始坐标须在可用像素点中。
• 对苹果坐标的处理：需判断新的苹果坐标是否在蛇身内。
• 对游戏是否存活的处理：蛇头撞到蛇身或者蛇头撞到边缘都应视为结束。
• 对接收到的按键值的处理：除方向按键外，其余按键值使用完之后需做清除。

完整实现代码如下

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.Arrays;
import java.util.Random;public class SnakeGame extends JPanel implements ActionListener {public interface Direction {char LEFT = 'L';char RIGHT = 'R';char UP = 'U';char DOWN = 'D';}public interface RunStatus {char READY = '0'; // 就绪char RUN = '1'; // 运行char OVER = '2'; // 失败char PAUSE = '3'; // 暂停/继续}final Random random = new Random();volatile int eventKeyCode;//记时步长volatile int delay = 150;Timer timer = null;//屏幕大小static final int SCREEN_WIDTH = 600;static final int SCREEN_HEIGHT = 600;//可用像素点static final int UNIT_SIZE = 25;static final int GAME_UNITS = (SCREEN_WIDTH * SCREEN_HEIGHT) / UNIT_SIZE;//蛇身volatile int bodyParts;int snakeBodyX[];int snakeBodyY[];//目标int appleX;int appleY;//得分volatile int applesEaten;volatile char direction;volatile char runStatus;SnakeGame() {this.setPreferredSize(new Dimension(SCREEN_WIDTH, SCREEN_HEIGHT));this.setFocusable(true);this.addKeyListener(new MyKeyAdapter());(timer = new Timer(delay, this)).start();init();}public void init() {bodyParts = 1;snakeBodyX = new int[GAME_UNITS];Arrays.fill(snakeBodyX, -1);snakeBodyX[0] = 0;snakeBodyY = new int[GAME_UNITS];Arrays.fill(snakeBodyY, -1);snakeBodyY[0] = 0;appleX = nextCoordinate(SCREEN_WIDTH, snakeBodyX);appleY = nextCoordinate(SCREEN_HEIGHT, snakeBodyY);applesEaten = 0;direction = Direction.RIGHT;runStatus = RunStatus.READY;timer.setDelay(delay);}public void paintComponent(Graphics g) {super.paintComponent(g);String tip = "" + applesEaten;int y = SCREEN_HEIGHT / 2 - 120;switch (runStatus) {case RunStatus.READY:drawing(g);g.setColor(Color.BLUE);g.setFont(new Font(null, Font.ITALIC, 20));g.drawString("按1-开始游戏", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));g.drawString("按2-重新开始", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));g.drawString("按3-暂停/继续", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));g.drawString("按Esc-退出游戏", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));break;case RunStatus.PAUSE:drawing(g);g.setColor(Color.BLUE);g.setFont(new Font(null, Font.ITALIC, 20));y = y + 80;g.drawString("按3-继续", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));g.drawString("按Esc-退出游戏", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));break;case RunStatus.RUN:drawing(g);g.setColor(Color.blue);g.setFont(new Font(null, Font.BOLD, 20));g.drawString(tip, (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, g.getFont().getSize());break;case RunStatus.OVER:g.setColor(Color.RED);g.setFont(new Font("Ink Free", Font.BOLD, 40));g.drawString("Game Over", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, y - 120);g.setFont(new Font(null, Font.ITALIC, 20));g.drawString("得分：" + applesEaten, (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, y - 60);g.setColor(Color.BLUE);g.drawString("按2-重新开始", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));g.drawString("按Esc-退出游戏", (SCREEN_WIDTH - getFontMetrics(g.getFont()).stringWidth(tip)) / 2, (y = y + 40));break;default:break;}}/*** 绘制蛇身和苹果** @param g*/public void drawing(Graphics g) {//苹果颜色g.setColor(Color.PINK);//画苹果g.fillOval(appleX, appleY, UNIT_SIZE, UNIT_SIZE);//蛇身颜色g.setColor(Color.RED);//填充蛇身for (int i = 0; i < bodyParts; i++) {g.fillRect(snakeBodyX[i], snakeBodyY[i], UNIT_SIZE, UNIT_SIZE);}}/*** 执行的动作* 会定时执行此方法** @param e*/public void actionPerformed(ActionEvent e) {//前置事件doSomeThing();if (runStatus == RunStatus.RUN) {move();//撞到边缘if (snakeBodyX[0] < 0 || snakeBodyX[0] > SCREEN_WIDTH || snakeBodyY[0] < 0 || snakeBodyY[0] > SCREEN_HEIGHT) {runStatus = RunStatus.OVER;}//蛇身相撞for (int i = bodyParts; i > 0; i--) {if ((snakeBodyX[0] == snakeBodyX[i]) && (snakeBodyY[0] == snakeBodyY[i])) {runStatus = RunStatus.OVER;}}//得分if ((snakeBodyX[0] == appleX) && (snakeBodyY[0] == appleY)) {applesEaten++;bodyParts++;//重新生成苹果appleX = nextCoordinate(SCREEN_WIDTH, snakeBodyX);appleY = nextCoordinate(SCREEN_HEIGHT, snakeBodyY);//预留难度设置的方法difficultySettings();}}//重新绘图, 执行 paintComponent 方法repaint();}/*** 蛇身移动*/private void move() {for (int i = bodyParts; i > 0; i--) {snakeBodyX[i] = snakeBodyX[(i - 1)];snakeBodyY[i] = snakeBodyY[(i - 1)];}switch (direction) {case Direction.UP:snakeBodyY[0] -= UNIT_SIZE;break;case Direction.DOWN:snakeBodyY[0] += UNIT_SIZE;break;case Direction.LEFT:snakeBodyX[0] -= UNIT_SIZE;break;case Direction.RIGHT:snakeBodyX[0] += UNIT_SIZE;break;default:break;}}private void doSomeThing() {if (KeyEvent.VK_ESCAPE == eventKeyCode) {System.out.println("退出程序");System.exit(0);return;}if (KeyEvent.VK_1 == eventKeyCode) {System.out.println("开始游戏");runStatus = RunStatus.RUN;}if (KeyEvent.VK_2 == eventKeyCode) {if (runStatus != RunStatus.RUN) {System.out.println("重新开始");init();}runStatus = RunStatus.RUN;}if (KeyEvent.VK_3 == eventKeyCode) {if (runStatus == RunStatus.RUN) {System.out.println("暂停");runStatus = RunStatus.PAUSE;eventKeyCode = -1;return;}if (runStatus == RunStatus.PAUSE) {System.out.println("继续");runStatus = RunStatus.RUN;eventKeyCode = -1;return;}}eventKeyCode = -1;}/*** 难度设置， 默认得分超过16的倍数时速度提升1/4*/private void difficultySettings() {//难度增加， 速度加快if (applesEaten % 16 == 0 && applesEaten != 0) {timer.setDelay(timer.getDelay() - timer.getDelay() / 4);}}/*** 下一个苹果坐标** @param randomFactorint* @param arr* @return*/synchronized private int nextCoordinate(int randomFactorint, int[] arr) {int coordinate = random.nextInt(randomFactorint / UNIT_SIZE) * UNIT_SIZE;for (int i = 0; i < arr.length; i++) {if (arr[i] == -1) {break;}if (coordinate == arr[i]) {nextCoordinate(randomFactorint, arr);}}return coordinate;}/*** 按键适配器，用于监听输入按键*/public class MyKeyAdapter extends KeyAdapter {public void keyPressed(KeyEvent e) {int keyCode = e.getKeyCode();eventKeyCode = e.getKeyCode();if ((keyCode == KeyEvent.VK_LEFT || keyCode == KeyEvent.VK_A) && direction != Direction.RIGHT) {direction = Direction.LEFT;} else if ((keyCode == KeyEvent.VK_RIGHT || keyCode == KeyEvent.VK_D) && direction != Direction.LEFT) {direction = Direction.RIGHT;} else if ((keyCode == KeyEvent.VK_UP || keyCode == KeyEvent.VK_W) && direction != Direction.DOWN) {direction = Direction.UP;} else if ((keyCode == KeyEvent.VK_DOWN || keyCode == KeyEvent.VK_S) && direction != Direction.UP) {direction = Direction.DOWN;}}}public static void main(String[] args) {JFrame frame = new JFrame();frame.setTitle("贪吃蛇");SnakeGame snake = new SnakeGame();frame.add(snake);frame.setResizable(false);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.pack();frame.setVisible(true);}
}

效果展示

游戏启动

游戏暂停