为什么在里面碰撞模块不生效啊

import pygame
import sys,random
from pygame.locals import *
pygame.init()
screen = pygame.display.set_mode((700,750),0,32)
#飞机
class plane(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
#位置
self.x = 350
self.y = 600
#图片
self.image = pygame.image.load('飞机.png').convert_alpha()
self.rect = self.image.get_rect()
#移动
def move(self):
self.x,self.y = pygame.mouse.get_pos()
self.x = self.x - self.image.get_width()/2
self.y = self.y - self.image.get_height()/2
#子弹
class bullet(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
#位置
self.x,self.y = 0,-1
self.active = False
#图片
self.image = pygame.image.load('子弹.png').convert_alpha()
self.rect = self.image.get_rect()
#重置子弹位置
def restart(self):
self.x,self.y = pygame.mouse.get_pos()
self.active = True
#移动
def move(self):
if self.active:
self.y-=30
if self.y<0:
self.active = False
#敌机
class enemy(pygame.sprite.Sprite):
#位置
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.x = random.randint(100,600)
self.y = random.randint(-1000,0)
#图片
self.image = pygame.image.load('敌人.png').convert_alpha()
self.rect = self.image.get_rect()
#运动
def move(self):
self.y+=1
if self.y > 750:
self.y = random.randint(-2000,0)
self.x = random.randint(100,600)
bullets = []
enem = []
plane1 = plane()
for i in range(5):
bullets.append(bullet())
enem.append(enemy())
background = pygame.image.load('背景.jpg').convert_alpha()
moving = False
time = 0
number = 0
count = len(bullets)
bulletsimg = pygame.sprite.Group()
enemyimg = pygame.sprite.Group()
for i in bullets :
bulletsimg.add(i)
for i in enem:
enemyimg.add(i)
#主循环
while True:
screen.blit(background,(0,0))
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
sys.exit()
if event.type == pygame.MOUSEBUTTONDOWN:
if event.button == 1:
moving = True
if event.type == pygame.MOUSEBUTTONUP:
if event.button == 1:
moving = False
if moving:
plane1.move()
screen.blit(plane1.image,(plane1.x,plane1.y))
time-=1
if time<0 and moving == True:
bullets[number].restart()
time = 10
number = (number + 1)%count
for b in bullets:
if b.active:
b.move()
screen.blit(b.image,(b.x,b.y))
for n in enem:
n.move()
for ene in enem:
screen.blit(ene.image,(ene.x,ene.y))
pygame.sprite.groupcollide(enemyimg,bulletsimg,True,True)
pygame.sprite.spritecollide(plane1,enemyimg,True)
clock = pygame.time.Clock()
pygame.display.flip()
clock.tick(30)