【GUI】-- 12 贪吃蛇小游戏之让小蛇动起来

news2024/11/17 7:28:08

GUI编程

04 贪吃蛇小游戏

4.3 第三步：让小蛇动起来(键盘控制)

首先，在构造器中要获取焦点事件、键盘监听事件并加入定时器(定时器定义需要实现ActionListener接口并重写actionPerformed方法)：

//构造器
    public GamePanel() {
        init();

        this.setFocusable(true);  //获取焦点事件
        this.addKeyListener(this);  //获取键盘监听事件
        timer.start();  //游戏一开始，定时器就启动

    }

然后，在键盘监听事件中，通过定时器来实现监听(即通过固定的时间进行刷新)，并加入对上下左右按键的判断，以实现改变小蛇身体的对应走向：

//键盘监听事件
    @Override
    public void keyPressed(KeyEvent e) {
        int keyCode = e.getKeyCode();  //获取键盘按键
        if (keyCode == KeyEvent.VK_SPACE) {
            isStart = !isStart;
            repaint();
        }

        //键盘监听到按键后画上对应方向的蛇头
        if (keyCode == KeyEvent.VK_UP) {
            direction = "U";
        } else if (keyCode == KeyEvent.VK_DOWN) {
            direction = "D";
        } else if (keyCode == KeyEvent.VK_LEFT) {
            direction = "L";
        } else if (keyCode == KeyEvent.VK_RIGHT) {
            direction = "R";
        }
    }

下面对实现ActionListener接口的actionPerformed方法进行重写：

//事件监听需要定时器来实现，即通过固定的时间进行刷新(例如1s=10次)
    @Override
    public void actionPerformed(ActionEvent e) {
        if (isStart) {
            //小蛇身体右移
            for (int i = length - 1; i > 0; i--) {  //后一节身体移动至前一节 snakeX[1] = snakeX[0]
                snakeX[i] = snakeX[i - 1];
                snakeY[i] = snakeY[i - 1];
            }

            //判断蛇头走向
            switch (direction) {
                case "R":
                    snakeX[0] += 25;
                    //边界判断
                    if (snakeX[0] > 850) {
                        snakeX[0] = 25;
                    }
                    break;
                case "L":
                    snakeX[0] -= 25;
                    //边界判断
                    if (snakeX[0] < 25) {
                        snakeX[0] = 850;
                    }
                    break;
                case "U":
                    snakeY[0] -= 25;
                    //边界判断
                    if (snakeY[0] < 75) {
                        snakeY[0] = 650;
                    }
                    break;
                case "D":
                    snakeY[0] += 25;
                    //边界判断
                    if (snakeY[0] > 650) {
                        snakeY[0] = 75;
                    }
                    break;
            }


            repaint();
        }
        timer.start();
    }

综上，GamePanel类中代码如下：

package com.duo.snake;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Objects;

//游戏的面板
public class GamePanel extends JPanel implements KeyListener, ActionListener {
    //定义蛇的数据结构
    int length;  //小蛇总长
    int[] snakeX = new int[600];  //蛇的X坐标 25*25
    int[] snakeY = new int[500];  //蛇的Y坐标 25*25
    String direction;  //蛇头方向
    boolean isStart = false;  //默认未开始游戏
    //定时器
    Timer timer = new Timer(250, this);  //100ms执行一次
    //构造器
    public GamePanel() {
        init();
        this.setFocusable(true);  //获取焦点事件
        this.addKeyListener(this);  //获取键盘监听事件
        timer.start();  //游戏一开始，定时器就启动
    }
    //初始化方法
    public void init() {
        length = 3;
        snakeX[0] = 100; snakeY[0] = 100;  //脑袋的坐标
        snakeX[1] = 75; snakeY[1] = 100;  //第一节身体的坐标
        snakeX[2] = 50; snakeY[2] = 100;  //第二节身体的坐标
        direction = "R";  //蛇头初始向右
    }
    //绘制静态面板
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);  //起到清屏的作用
        Data.header.paintIcon(this, g, 25, 11);  //将广告栏画入面板
        g.fillRect(25, 75, 850, 600);  //默认的游戏界面(黑色区域)
        this.setBackground(Color.white);
        //将小蛇画入面板中的游戏区域，且蛇头部分需要判断方向
        switch (direction) {
            case "R":
                Data.right.paintIcon(this, g, snakeX[0], snakeY[0]);
                break;
            case "L":
                Data.left.paintIcon(this, g, snakeX[0], snakeY[0]);
                break;
            case "U":
                Data.up.paintIcon(this, g, snakeX[0], snakeY[0]);
                break;
            case "D":
                Data.down.paintIcon(this, g, snakeX[0], snakeY[0]);
                break;
        }
        //画小蛇的身体部分
        for (int i = 1; i < length; i++) {
            Data.body.paintIcon(this, g, snakeX[i], snakeY[i]);
        }
        //绘制当前游戏状态
        if (!isStart) {
            g.setColor(Color.white);
            g.setFont(new Font("宋体", Font.BOLD, 40));
            g.drawString("按下空格开始游戏", 300, 300);
        }
    }
    //键盘监听事件
    @Override
    public void keyPressed(KeyEvent e) {
        int keyCode = e.getKeyCode();  //获取键盘按键
        if (keyCode == KeyEvent.VK_SPACE) {
            isStart = !isStart;
            repaint();
        }
        //键盘监听到按键后画上对应方向的蛇头
        if (keyCode == KeyEvent.VK_UP) {
            direction = "U";
        } else if (keyCode == KeyEvent.VK_DOWN) {
            direction = "D";
        } else if (keyCode == KeyEvent.VK_LEFT) {
            direction = "L";
        } else if (keyCode == KeyEvent.VK_RIGHT) {
            direction = "R";
        }
    }
    //事件监听需要定时器来实现，即通过固定的时间进行刷新(例如1s=10次)
    @Override
    public void actionPerformed(ActionEvent e) {
        if (isStart) {
            //小蛇身体右移
            for (int i = length - 1; i > 0; i--) {  //后一节身体移动至前一节 snakeX[1] = snakeX[0]
                snakeX[i] = snakeX[i - 1];
                snakeY[i] = snakeY[i - 1];
            }
            //判断蛇头走向
            switch (direction) {
                case "R":
                    snakeX[0] += 25;
                    //边界判断
                    if (snakeX[0] > 850) {
                        snakeX[0] = 25;
                    }
                    break;
                case "L":
                    snakeX[0] -= 25;
                    //边界判断
                    if (snakeX[0] < 25) {
                        snakeX[0] = 850;
                    }
                    break;
                case "U":
                    snakeY[0] -= 25;
                    //边界判断
                    if (snakeY[0] < 75) {
                        snakeY[0] = 650;
                    }
                    break;
                case "D":
                    snakeY[0] += 25;
                    //边界判断
                    if (snakeY[0] > 650) {
                        snakeY[0] = 75;
                    }
                    break;
            }
            repaint();
        }
        timer.start();
    }
    @Override
    public void keyReleased(KeyEvent e) {}
    @Override
    public void keyTyped(KeyEvent e) {}
}