Python实现贪吃蛇三

上篇文章Python实现贪吃蛇一，实现了一个贪吃蛇的基础版本。后面第二篇文章Python实现贪吃蛇二修改了一些不足，但最近发现还有两点需要优化：

1、生成食物的时候有概率和记分牌重合

2、游戏缺少暂停功能

先看生成食物的时候有概率和记分牌重合的问题。在游戏过程中，有时吃掉一个食物后，发现"没有"生成新的食物。实际上是食物生成的位置和记分牌重合了，被挡住了。这种情况很影响游戏体验，并且尝试去吃掉记分牌下面的食物时很容易撞墙。针对上面问题，在生成新的食物的时候，增加是否与记分牌重合的校验，如果重合，重新生成食物，直到符合要求。修改后的代码片段如下：

python 复制代码

    def _check_food(self):
        """ 检查新生成的食物是否不与蛇身及记分牌重合 """
        food = self.food
        food.rect.x = round(
            random.randrange(20, self.settings.screen_width - self.settings.snake_width * 2) / 20.0) * 20.0
        food.rect.y = round(
            random.randrange(20, self.settings.screen_height - self.settings.snake_height * 2) / 20.0) * 20.0
        for snake in self.snakes:
            if snake.rect.colliderect(food.rect) or self.sb.score_rect.colliderect(food.rect):
                return False
        return True

再看游戏暂停功能。有时正在游戏过程中，尤其是得分比较高的时候，有事需要离开，这时候没有游戏暂停功能的话，只能结束游戏，体验不太好。如何增加暂停功能，思路其实比较简单：在游戏状态类里增加一个游戏暂停状态的属性，当按下"空格"键的时候，将这个属性值取反。同时游戏主循环里增加游戏暂停状态的判断，如果是暂停状态游戏不再刷新，如果不是暂停状态，游戏正常刷新。这样，就实现了游戏暂停功能。相关代码片段：

python 复制代码

class GameStats:
    """ 跟踪游戏的统计信息 """

    def __init__(self, ai_game):
        """ 初始化统计信息 """
        self.settings = ai_game.settings
        self.reset_stats()

        # 游戏刚启动时处于非活动状态
        self.game_active = False

        # 游戏暂停状态
        self.game_pause = False

    def reset_stats(self):
        """ 初始化在游戏运行期间可能变化的统计信息 """
        self.score = 0

    
def run_game(self):
    """ 开始游戏的主循环 """
    while True:
        self._check_events()
        if self.stats.game_active and not self.stats.game_pause:
            if self.settings.update_count > 500: #控制游戏速度
                self._update_snakes()
                self._check_edges()
                self.settings.update_count = 0
            self.settings.update_count += self.settings.game_speed
        self._update_screen()

修改后主程序类（gluttonous_snake.py）的完整代码：

python 复制代码

import sys
import time

import pygame
import random

from settings import Settings
from snake import Snake
from game_stats import GameStats
from button import Button
from food import Food
from scoreboard import Scoreboard
from game_sound import GameSound


class GluttonousSnake:
    """ 管理游戏资源和行为的类 """

    def __init__(self):
        """ 初始化游戏并创建游戏资源 """
        pygame.init()

        # 初始化音频混合器
        pygame.mixer.init()

        # 初始化游戏声音
        self.snake_eat_food_sound = GameSound('snake_eat_food.mp3')
        self.snake_game_over_sound = GameSound('snake_game_over.mp3')
        self.background_sound = GameSound('snake_background_sound.mp3')
        self.cheer_sound = GameSound('snake_cheer_sound.mp3')

        self.settings = Settings()

        self.screen = pygame.display.set_mode((self.settings.screen_width, self.settings.screen_height))

        pygame.display.set_caption("贪吃蛇")

        # 创建一个用于存储游戏统计信息的实例
        self.stats = GameStats(self)

        # 创建记分牌
        self.sb = Scoreboard(self)

        self.food = Food(self)

        self.snakes = []

        self._create_snakes()

        # 创建Play按钮
        self.play_button = Button(self, "Play")

    def _create_snakes(self):
        """ 初始化创建长度为3的蛇 """
        for snake_number in range(3):
            self._create_snake(snake_number)

    def _create_snake(self, snake_number):
        """ 创建一段蛇身 """
        snake = Snake(self)
        self.screen_rect = self.screen.get_rect()
        snake.x = self.settings.screen_width / 2
        snake.y = self.settings.screen_height / 2 + snake_number * self.settings.snake_height
        snake.rect.x = snake.x
        snake.rect.y = snake.y
        self.snakes.append(snake)

    def _check_events(self):
        # 监视键盘和鼠标的事件
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                self._check_keydown_events(event)
            elif event.type == pygame.MOUSEBUTTONDOWN:
                mouse_pos = pygame.mouse.get_pos()
                self._check_play_button(mouse_pos)

    def _check_play_button(self, mouse_pos):
        """ 在玩家单击Play按钮时开始新游戏 """
        button_clicked = self.play_button.rect.collidepoint(mouse_pos)
        if button_clicked and not self.stats.game_active:
            # 重置游戏设置
            self.stats.game_active = True

            # 播放背景音乐
            self.background_sound.play(0)

            # 隐藏鼠标光标
            pygame.mouse.set_visible(False)

            self.stats.score = 0
            self.sb.prep_score()
            self.settings.snake_direction = 'up'
            self.settings.update_count = 0
            self.settings.game_speed = 1

            # 清空余下的蛇身
            self.snakes.clear()

            # 重新创建蛇身
            self._create_snakes()

    def _check_keydown_events(self, event):
        # 响应按键
        if event.key == pygame.K_RIGHT:
            if self.settings.snake_direction == 'right':
                self._change_speed(1)
            elif self.settings.snake_direction == 'left':
                self._change_speed(-1)
            else:
                self.settings.snake_direction = 'right'
        elif event.key == pygame.K_LEFT:
            if self.settings.snake_direction == 'left':
                self._change_speed(1)
            elif self.settings.snake_direction == 'right':
                self._change_speed(-1)
            else:
                self.settings.snake_direction = 'left'
        elif event.key == pygame.K_UP:
            if self.settings.snake_direction == 'up':
                self._change_speed(1)
            elif self.settings.snake_direction == 'down':
                self._change_speed(-1)
            else:
                self.settings.snake_direction = 'up'
        elif event.key == pygame.K_DOWN:
            if self.settings.snake_direction == 'down':
                self._change_speed(1)
            elif self.settings.snake_direction == 'up':
                self._change_speed(-1)
            else:
                self.settings.snake_direction = 'down'
        elif event.key == pygame.K_SPACE:
            self.stats.game_pause = not self.stats.game_pause
        elif event.key == pygame.K_q:
            sys.exit()

    def _change_speed(self, add):
        # 改变蛇的移动速度
        if (self.settings.game_speed + add) > 0:
            self.settings.game_speed += add

    def _update_snakes(self):
        """ 更新蛇 """
        snake_head = self.snakes[0]
        self._create_snake_head(snake_head.rect.x, snake_head.rect.y)

        """ 检查是否吃到食物 """
        eat_food = self._check_eat_food()
        if not eat_food:
            self.snakes.pop()

    def _check_edges(self):
        """ 蛇碰到边缘时采取相应的措施 """
        snake_head = self.snakes[0]
        if snake_head.check_edges():
            self._game_over()

    def _check_eat_self(self, snake_head):
        """ 是否碰到自己 """
        for snake in self.snakes:
            if snake.rect.colliderect(snake_head.rect):
                self._game_over()
                break

    def _game_over(self):
        # 播放音乐
        self.snake_game_over_sound.play(1)
        self.stats.game_active = False
        # 显示鼠标光标
        pygame.mouse.set_visible(True)

    def _check_eat_food(self):
        """ 检测蛇吃到食物 """
        snake_head = self.snakes[0]
        food = self.food
        if snake_head.rect.colliderect(food.rect):
            self.stats.score += self.settings.food_score
            # 播放声音
            if self.stats.score % 100 == 0:
                self.cheer_sound.play(1)
            else:
                self.snake_eat_food_sound.play(1)
            self.sb.prep_score()
            self._update_food()
            return True
        else:
            return False

    def _update_food(self):
        """ 更新食物 """
        while True:
            if self._check_food():
                return

    def _check_food(self):
        """ 检查新生成的食物是否不与蛇身及记分牌重合 """
        food = self.food
        food.rect.x = round(
            random.randrange(20, self.settings.screen_width - self.settings.snake_width * 2) / 20.0) * 20.0
        food.rect.y = round(
            random.randrange(20, self.settings.screen_height - self.settings.snake_height * 2) / 20.0) * 20.0
        for snake in self.snakes:
            if snake.rect.colliderect(food.rect) or self.sb.score_rect.colliderect(food.rect):
                return False
        return True

    def _create_snake_head(self, x, y):
        """ 创建蛇头 """
        snake = Snake(self)
        if self.settings.snake_direction == 'up':
            snake.x = x
            snake.y = y - self.settings.snake_height
        elif self.settings.snake_direction == 'down':
            snake.x = x
            snake.y = y + self.settings.snake_height
        elif self.settings.snake_direction == 'right':
            snake.x = x + self.settings.snake_width
            snake.y = y
        elif self.settings.snake_direction == 'left':
            snake.x = x - self.settings.snake_width
            snake.y = y
        snake.rect.x = snake.x
        snake.rect.y = snake.y
        self._check_eat_self(snake)
        self.snakes.insert(0, snake)

    def run_game(self):
        """ 开始游戏的主循环 """
        while True:
            self._check_events()
            if self.stats.game_active and not self.stats.game_pause:
                if self.settings.update_count > 500: #控制游戏速度
                    self._update_snakes()
                    self._check_edges()
                    self.settings.update_count = 0
                self.settings.update_count += self.settings.game_speed
            self._update_screen()

    def _update_screen(self):
        # 每次循环时都会重绘屏幕
        self.screen.fill(self.settings.bg_color)
        self.food.draw_food()
        for snake in self.snakes:
            snake.draw_snake()

        # 如果游戏处于非活动状态，就绘制Play按钮
        if not self.stats.game_active:
            self.play_button.draw_button()

        # 显示得分
        self.sb.show_score()

        # 让最近绘制的屏幕可见
        pygame.display.flip()

if __name__ == '__main__':
    # 创建实例并运行游戏
    ai = GluttonousSnake()
    ai.run_game()