alien.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """创建单个外星人的类"""
    def __init__(self ,ai_settings ,screen):
        """初始化外星人并设置其起始位置"""
        super().__init__()
        self.ai_settings = ai_settings
        self.screen = screen

        #加载外星人并设置其rect属性
        self.image = pygame.image.load('images/alien00.png')
        self.rect = self.image.get_rect()
        self.screen_rect = self.screen.get_rect()

        #设置外星人的位置
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        #存储外星人的准确位置
        self.x = float(self.rect.x)

    def blitme(self):
        self.screen.blit(self.image, self.rect)

    
    def check_edges(self):
        """如果外星人撞到了屏幕，返回Ture"""
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right:
            return True
        elif self.rect.left <= 0:
            return True

    def update(self):
        self.x += (self.ai_settings.alien_speed_factor *
                   self.ai_settings.fleet_direction)
        self.rect.x = self.x