game_functions.py

import sys
from time import sleep
import pygame
from bullet import Bullet
from alien import Alien


def check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # 像飞船被撞到一样进行处理
            ship_hit(ai_settings, stats, screen, ship, aliens, bullets)
            break


def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edge():  # 如果到达边缘
            change_fleet_direction(ai_settings, aliens)
            break


def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移,并改变他们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1


def ship_hit(ai_settings, stats, screen, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0:
        # 将ships_left减1
        stats.ships_left -= 1
        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人,并将飞船放到屏幕底端中央
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

        # 暂停
        sleep(0.5)
    else:
        stats.game_active = False


def update_aliens(ai_settings, stats, screen, ship, aliens, bullets):
    """
    检查是否有外星人位于屏幕边缘,
        然后更新整群外星人的位置
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update()

    # 检测外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, stats, screen, ship, aliens, bullets)

    # 检查是否有外星人到达屏幕底端
    check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets)


def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    avaliable_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
    number_rows = int(avaliable_space_y / (2 * alien_height))
    return number_rows


def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))  # 一共要创建多少个外星人
    return number_aliens_x


def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人,并将其放在当前行"""
    alien = Alien(ai_settings, screen)  # 创建一个外星人,用于测定尺寸,此外星人不显示在屏幕上
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    # 创建一个外星人,并计算每行可容纳多少外星人
    alien = Alien(ai_settings, screen)
    number_alien_x = get_number_aliens_x(ai_settings, alien.rect.width)  # 计算一行一共要创建多少个外星人
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)  # 计算创建多少行外星人

    # 创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_alien_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)  # 传入的是外星人的行号和列号


def check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets):
    """相应子弹和外星人的碰撞"""
    # 删除发生碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, False, True)

    if len(aliens) == 0:
        # 删除现有的子弹并新建一群外星人
        bullets.empty()
        create_fleet(ai_settings, screen, ship, aliens)


def update_bullets(ai_settings, screen, ship, aliens, bullets):
    """更新子弹的位置,并删除已消失的子弹"""
    # 更新子弹的位置
    bullets.update()
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    # 检查是否有子弹击中了外星人,如果击中外星人,就删除相应的子弹和外星人
    check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets)


def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有达到限制,就发射一颗子弹"""
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)  # 加入编组


def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按键"""
    if event.key == pygame.K_RIGHT:  # 右键按压事件监测
        ship.moving_right = True  # 开启右移开关
    elif event.key == pygame.K_LEFT:  # 左键按压事件监测
        ship.moving_left = True  # 开启左移开关
    elif event.key == pygame.K_SPACE:  # 空格按压事件监测
        fire_bullet(ai_settings, screen, ship, bullets)  # 监测是否允许发射子弹,如果允许,就发射一颗子弹
    elif event.key == pygame.K_q:
        sys.exit()


def check_keyup_events(event, ai_settings, screen, ship, bullets):
    """响应松开"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False


def check_events(ai_settings, screen, ship, bullets):
    """相应案件和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:  # 关闭游戏的事件
            sys.exit()

        elif event.type == pygame.KEYDOWN:  # 按键按下事件
            check_keydown_events(event, ai_settings, screen, ship, bullets)

        elif event.type == pygame.KEYUP:  # 按键松开事件
            check_keyup_events(event, ai_settings, screen, ship, bullets)


def update_screen(ai_settings, screen, ship, aliens, bullets):
    """更新屏幕上的图像,并切换到新屏幕"""
    # 每次循环时都重绘屏幕
    screen.fill(ai_settings.bg_color)  # 显示屏幕
    ship.blitme()  # 显示飞船
    aliens.draw(screen)  # 显示外星人群

    # 在飞船和外星人后面重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()

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