game_functions.py

import sys

import pygame

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


def check_keydown_events(event, ai_settings, screen, ship, bullets):
        """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_SPACE:
            fire_bullet(ai_settings, screen, ship, bullets)
        elif event.key == pygame.K_q:
            sys.exit()


def check_keyup_events(event, ship):
    """响应按键"""
    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):
    # 监听键盘和鼠标的事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ai_settings, screen, ship, bullets)

        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)


def update_screen(ai_settings, screen, ship, aliens, bullets):
    """更新屏幕上的图像，并切换到新屏幕"""
    # 每次循环都重绘屏幕
    screen.fill(ai_settings.bg_color)

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

    ship.blitme()
    aliens.draw(screen)

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


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()

    # 删除已经消失的子弹
    for bullet in bullets:
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets)


def check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets):
    # 检查是否有子弹击中了外星人
    # 如果时这样，就删除相应的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, 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 fire_bullet(ai_settings, screen, ship, bullets):
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)


def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    # 创建一个外星人，并计算一行可容纳多少个外星人
    # 外星人间距为外星人宽度
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    number_alien_x = get_number_aliens_x(ai_settings, alien_width)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)

    # 创建外星人群
    for row_number in range(number_rows):
        for alien_number in range(number_alien_x):
            # 创建一个外星人并将其加入当前行
            create_alien(ai_settings, screen, aliens, alien_number, row_number)


def create_alien(ai_settings, screen,  aliens, alien_number, row_number):
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien = Alien(ai_settings, screen)
    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 get_number_aliens_x(ai_settings, alien_width):
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_alien_x = int(available_space_x / (2 * alien_width))
    return number_alien_x


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


def update_aliens(ai_settings, stats, screen, ship, aliens, bullets):
    check_fleet_edges(ai_settings, aliens)
    aliens.update()

    # 检查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 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_edges():
            change_fleet_direction(ai_settings, aliens)
            break


def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变它们的方向"""
    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):
    """响应飞船被外星人撞到"""
    if stats.ships_left > 0:
        # 将ship_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 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:
            # 像飞船被撞到一样处理
            ship_hit(ai_settings, stats, screen, ship, aliens, bullets)
            break