在《Pygame中Sprite实现逃亡游戏3》中实现了玩家跳跃飞火的效果，接下来通过精灵类的碰撞检测来判断飞火是否击中玩家、飞火是否击中飞龙以及飞龙是否抓住玩家。

1 飞火是否击中玩家的判断

判断飞火是否击中玩家的代码如图1所示。

图1 判断飞火是否击中玩家的代码

第137行代码使用精灵类的collide_rect()方法判断飞火是否击中玩家，该方法的参数arrow表示飞火，参数player表示玩家，当飞火击中玩家时，collide_rect()方法返回True，第138代码在屏幕的右侧重置飞火，第139行代码将玩家的横坐标向左移动（玩家被飞火击中后要退后）。

相关链接1 reset_arrow()方法以及player.X属性请参考《Pygame中Sprite实现逃亡游戏2》

注意1 判断飞火是否击中玩家、飞火是否击中飞龙以及飞龙是否抓住玩家的代码均在while True循环中。

2 飞火是否击中飞龙的判断

判断飞火是否击中飞龙的代码如图2所示。

图2 判断飞火是否击中飞龙的代码

从图2中可知，当飞火是否击中飞龙后，需要重置飞火并且将飞龙的横坐标向左移动。

3 飞龙是否抓住玩家

判断飞龙是否抓住玩家的代码如图3所示。

图3 判断飞龙是否抓住玩家的代码

从图3中可以看出，当飞龙抓住玩家，此时游戏结束，game_over标志设置为True。

4 程序运行效果

程序运行效果如图4所示。

图4 程序运行效果

5 完整代码

import pygame
import os
import time
import random
from pygame.locals import *

class MySprite(pygame.sprite.Sprite):
    def __init__(self, target):
        pygame.sprite.Sprite.__init__(self) #extend the base Sprite class
        self.master_image = None
        self.frame = 0
        self.old_frame = -1
        self.frame_width = 1
        self.frame_height = 1
        self.first_frame = 0
        self.last_frame = 0
        self.columns = 1
        self.last_time = 0
    #X property
    def _getx(self):
        return self.rect.x
    def _setx(self,value):
        self.rect.x = value
    X = property(_getx,_setx)

    #Y property
    def _gety(self):
        return self.rect.y
    def _sety(self,value):
        self.rect.y = value
    Y = property(_gety,_sety)

    #position property
    def _getpos(self):
        return self.rect.topleft
    def _setpos(self,pos):
        self.rect.topleft = pos
    position = property(_getpos,_setpos)
    
    def load(self, filename, width, height, columns):
        self.master_image = pygame.image.load(filename).convert_alpha()
        self.frame_width = width
        self.frame_height = height
        self.rect = Rect(0,0,width,height)
        self.columns = columns
        #try to auto-calculate total frames
        rect = self.master_image.get_rect()
        self.last_frame = (rect.width // width) * (rect.height // height) - 1

    def update(self, current_time, rate=30):
        #update animation frame number
        if current_time > self.last_time + rate:
            self.frame += 1
            if self.frame > self.last_frame:
                self.frame = self.first_frame
            self.last_time = current_time

        #build current frame only if it changed
        if self.frame != self.old_frame:
            frame_x = (self.frame % self.columns) * self.frame_width
            frame_y = (self.frame // self.columns) * self.frame_height
            rect = Rect(frame_x, frame_y, self.frame_width, self.frame_height)
            self.image = self.master_image.subsurface(rect)
            self.old_frame = self.frame

    def __str__(self):
        return str(self.frame) + "," + str(self.first_frame) + \
               "," + str(self.last_frame) + "," + str(self.frame_width) + \
               "," + str(self.frame_height) + "," + str(self.columns) + \
               "," + str(self.rect)
    
def reset_arrow():
    y = random.randint(250,350)
    arrow.position = 800,y
    
pygame.init()
screen = pygame.display.set_mode((800,600))
pygame.display.set_caption('Escape The Dragon Game')
font = pygame.font.Font('1.ttf', 18)
framerate = pygame.time.Clock()

group = pygame.sprite.Group()
player = MySprite(screen)
player.load('caveman.png', 50, 64, 8)
player.first_frame = 1
player.last_frame = 7
player.position = 400, 303
group.add(player)

bg = pygame.image.load('background.png').convert_alpha()

#create the dragon sprite
dragon = MySprite(screen)
dragon.load("dragon.png", 260, 150, 3)
dragon.position = 100, 230
group.add(dragon)

#create the arrow sprite
arrow = MySprite(screen)
arrow.load("flame.png", 40, 16, 1)
arrow.position = 800,320
group.add(arrow)

game_over = False
arrow_vel = 8.0
player_jumping = False
jump_vel = 0.0
player_start_y = player.Y
while True:
    framerate.tick(30)
    ticks = pygame.time.get_ticks()
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            os.sys.exit()
        keys = pygame.key.get_pressed()
        if keys[K_ESCAPE]:
            pygame.quit()
            os.sys.exit()
        elif keys[K_SPACE]:
            if not player_jumping:
                player_jumping = True
                jump_vel = -8.0
    #update the arrow
    if not game_over:
        arrow.X -= arrow_vel
        if arrow.X < 0:
            reset_arrow()
    if player_jumping:
        player.Y += jump_vel
        jump_vel += 0.5
        if player.Y > player_start_y:
            player.Y = player_start_y
            player_jumping = False
            jump_vel = 0.0

    if pygame.sprite.collide_rect(arrow, player):
        reset_arrow()
        player.X -= 10

    
    if pygame.sprite.collide_rect(arrow, dragon):
        reset_arrow()
        dragon.X -= 10

    if pygame.sprite.collide_rect(player, dragon):
        game_over = True
        
    screen.blit(bg, (0,0))
    group.update(ticks, 50)
    group.draw(screen)
    pygame.display.update()