@Python编程从入门到实践 Python项目练习
四、创建Ship类
建立ship.py,创建Ship类，管理飞船行为。
# ship.py
import pygame
class Ship():
def __init__(self, ai_settings, screen):
"""初始化飞船并设置其初始位置"""
self.screen = screen
self.ai_settings = ai_settings
# 加载飞船图像
self.image = pygame.image.load('images/ship.bmp')
self.image = pygame.transform.scale(self.image, (37*2, 34*2))
# 获取其外接矩形（rect为surface矩形属性）
self.rect = self.image.get_rect()
self.screen_rect = screen.get_rect()
# 将每艘新飞船放在屏幕底部中央
self.rect.centerx = self.screen_rect.centerx
self.rect.bottom = self.screen_rect.bottom
# 在飞船的属性center中存储小数值
self.center_x = float(self.rect.centerx)
self.center_y = float(self.rect.centery)
# 移动标志
self.moving_right = False
self.moving_left = False
self.moving_up = False
self.moving_down = False
def update(self):
"""根据移动标志调整飞船到位置"""
# 更新飞船的center值， 而不是rect
if self.moving_right and self.rect.right < self.screen_rect.right:
self.center_x += self.ai_settings.ship_speed_factor
if self.moving_left and self.rect.left > 0:
self.center_x -= self.ai_settings.ship_speed_factor
if self.moving_down and self.rect.bottom < self.screen_rect.bottom:
self.center_y += self.ai_settings.ship_speed_factor
if self.moving_up and self.rect.top > self.screen_rect.top:
self.center_y -= self.ai_settings.ship_speed_factor
# 根据self.center更新rect对象
self.rect.centerx = self.center_x
self.rect.centery = self.center_y
def blitme(self):
"""在指定位置绘制飞船"""
self.screen.blit(self.image, self.rect)
def center_ship(self):
"""让飞船在屏幕上居中"""
self.center_x = self.screen_rect.centerx
ship_half_width = self.rect.bottom - self.center_y
self.center_y = self.screen_rect.bottom - ship_half_width
五、创建Bullet类
建立bullet.py，创建Bullet类，继承pygame.sprite中的Sprite类，作为游戏中的子弹元素。
# settings.py
import pygame
from pygame.sprite import Sprite
class Bullet(Sprite):
"""一个对子弹发射进行管理的类"""
def __init__(self, ai_settings, screen, ship):
super(Bullet, self).__init__()
self.screen = screen
# 在(0, 0)处创建一个表示子弹的矩形，将初始位置放在（0，0）
self.rect = pygame.Rect(0, 0, ai_settings.bullet_width,
ai_settings.bullet_height)
# 重设子弹位置
self.rect.centerx = ship.rect.centerx
# self.rect.centery = ship.rect.centery
self.rect.top = ship.rect.top
# 存储用小数表示的子弹位置
self.y = float(self.rect.y)
self.color = ai_settings.bullet_color
self.speed_factor = ai_settings.bullet_speed_factor
def update(self):
"""向上移动子弹"""
# 更新表示子弹的小数值
self.y -= self.speed_factor
# 更新表示子弹的rect的位置
self.rect.y = self.y
def draw_bullet(self):
"""在屏幕上绘制子弹"""
pygame.draw.rect(self.screen, self.color, self.rect)
六、创建game_functions模块
创建game_functions.py 模块，存储函数，让alien_invasion中主代码更易懂。
#game_functions.py
import sys
import pygame
from bullet import Bullet
from passenger import Passenger
from time import sleep
def check_keydown_events(event, ai_settings, screen, ship, bullet_group):
"""响应按键"""
if event.key == pygame.K_RIGHT:
ship.moving_right = True
elif event.key == pygame.K_LEFT:
ship.moving_left = True
elif event.key == pygame.K_UP:
ship.moving_up = True
elif event.key == pygame.K_DOWN:
ship.moving_down = True
elif event.key == pygame.K_SPACE:
fire_bullet(ai_settings, screen, ship, bullet_group)
elif event.key == pygame.K_ESCAPE:
sys.exit()
def fire_bullet(ai_settings, screen, ship, bullet_group):
"""如果没有到达限制，就发射一颗子弹"""
# 创建一颗子弹，并将其加入到编组bullets中
if len(bullet_group) < ai_settings.bullet_group_allowed:
new_bullet = Bullet(ai_settings, screen, ship)
bullet_group.add(new_bullet)
def check_keyup_events(event, ship):
"""松开按键"""
if event.key == pygame.K_RIGHT:
ship.moving_right = False
elif event.key == pygame.K_LEFT:
ship.moving_left = False
elif event.key == pygame.K_UP:
ship.moving_up = False
elif event.key == pygame.K_DOWN:
ship.moving_down = False
def check_events(ai_settings, screen, ship, bullet_group):
"""响应按键和鼠标事件"""
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
# 按下
elif event.type == pygame.KEYDOWN:
check_keydown_events(event, ai_settings, screen, ship, bullet_group)
# 松开
elif event.type == pygame.KEYUP:
check_keyup_events(event, ship)
def update_screen(ai_settings, screen, ship, passenger_group, bullet_group):
"""更新屏幕上的图像，并切换到新屏幕"""
# 每次循环时(即打开游戏运行)重绘屏幕
screen.fill(ai_settings.bg_color)
# 绘制子弹
for bullet in bullet_group:
bullet.draw_bullet()
ship.blitme()
for i in passenger_group:
i.blitme()
#passenger_group.draw(screen)
# 更新屏幕（隐藏旧屏，更新新屏）
pygame.display.flip()
def update_bullet_group(ai_settings, screen, ship, passenger_group, bullet_group ):
"""更新子弹的位置，并删除已消失的子弹"""
# 更新子弹的位置
bullet_group.update()
# 删除已消失的子弹
for bullet in bullet_group.copy():
if bullet.rect.top <= 0:
bullet_group.remove(bullet)
check_bullet_passenger_collisions(ai_settings, screen, ship, passenger_group,
bullet_group)
def check_bullet_passenger_collisions(ai_settings,screen, ship, passenger_group,
bullet_group):
# 检查是否有子弹击中了乘客
# 如果是这样，就删除相应的子弹和乘客
# groupcollide（）返回字典，实参为True即删除发生碰撞的子弹或外星人
collisions = pygame.sprite.groupcollide(bullet_group, passenger_group, False, True)
if len(passenger_group) == 0:
# 删除现有子弹并新建一波新的乘客
bullet_group.empty()
create_fleet(ai_settings, screen, ship, passenger_group)
def get_number_passenger_x(ai_settings, passenger_width):
"""计算每行可以容纳多少个乘客"""
available_space_x = ai_settings.screen_width - 2 * passenger_width
number_passenger_x = int(available_space_x / (2 * passenger_width))
return number_passenger_x
def get_number_rows(ai_settings, ship_height, passenger_height):
"""计算屏幕可以容纳多少行的乘客"""
available_space_y = (ai_settings.screen_height - passenger_height - ship_height)
number_rows = int(available_space_y / (1.5 * passenger_height))
return number_rows
def create_passenger(ai_settings, screen, passenger_group, passenger_number, row_number):
"""创建一个乘客并将其放在当前行"""
passenger = Passenger(ai_settings, screen)
passenger_width = passenger.rect.width
passenger.x = passenger_width + 2 * passenger_width * passenger_number
passenger.rect.x = passenger.x
passenger.rect.y = 0.5 * passenger.rect.height + 1.5 * passenger.rect.height * row_number
passenger_group.add(passenger)
def create_fleet(ai_settings, screen, ship, passgener_group):
"""创建乘客群"""
# 创建一个乘客，并计算一行可以容纳多少人
passenger = Passenger(ai_settings, screen)
number_passenger_x = get_number_passenger_x(ai_settings, passenger.rect.width)
number_rows = get_number_rows(ai_settings, ship.rect.height, passenger.rect.height)
# 创建乘客群
for row_number in range(number_rows):
for passenger_number in range(number_passenger_x):
create_passenger(ai_settings, screen, passgener_group, passenger_number,
row_number)
def change_fleet_direction(ai_settings, passenger_group):
"""将整群乘客下移，并改变它们的方向"""
for passenger in passenger_group.sprites():
passenger.rect.y += ai_settings.fleet_drop_speed
ai_settings.fleet_direction *= -1
def check_fleet_edges(ai_settings, passenger_group):
"""有外星人到达边缘时采取相应的措施"""
for passenger in passenger_group.sprites():
if passenger.check_edges():
change_fleet_direction(ai_settings, passenger_group)
break
def ship_hit(ai_settings, stats, screen, ship, passenger_group, bullet_group):
"""响应被乘客撞到的飞船"""
if stats.ships_left > 0:
# 讲ship_left减一
stats.ships_left -= 1
# 清空乘客列表和子弹列表
passenger_group.empty()
bullet_group.empty()
# 创建一群新的外星人，并讲飞船放在屏幕底部中央
create_fleet(ai_settings, screen, ship, passenger_group)
ship.center_ship()
# 暂停
sleep(0.5)
else:
stats.game_active = False
def check_passenger_group_bottom(ai_settings, stats, screen, ship, passenger_group, bullet_group):
"""检查是否有外星人到达屏幕底端"""
screen_rect = screen.get_rect()
for passenger in passenger_group.sprites():
if passenger.rect.bottom >= screen_rect.bottom:
# 像飞船被撞到一样进行处理
ship_hit(ai_settings, stats, screen, ship, passenger_group, bullet_group)
break
def update_passenger_group(ai_settings, stats, screen, ship, passenger_group, bullet_group):
"""检查是否有乘客在边缘，并更新乘客群中所有乘客的位置"""
check_fleet_edges(ai_settings, passenger_group)
passenger_group.update()
# 检测外星人和飞船之间的碰撞
if pygame.sprite.spritecollideany(ship, passenger_group):
ship_hit(ai_settings, stats, screen, ship, passenger_group, bullet_group)
# 检查是否有外星让到达屏幕底端
check_passenger_group_bottom(ai_settings, stats, screen, ship, passenger_group, bullet_group)