From 10ce91ef631f03afe588bef9845158840d126dbf Mon Sep 17 00:00:00 2001
From: 206530118 <3046257660@qq.com>
Date: Wed, 23 Jun 2021 08:26:28 +0800
Subject: [PATCH] ..

---
 alien_bullet.py | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 alien_bullet.py

diff --git a/alien_bullet.py b/alien_bullet.py
new file mode 100644
index 0000000..65c18ab
--- /dev/null
+++ b/alien_bullet.py
@@ -0,0 +1,33 @@
+import pygame
+from pygame.sprite import Sprite
+
+class AlienBullet(Sprite):
+    """一个对外星人发射的子弹进行管理的类"""
+
+    def __init__(self, ai_settings, screen, alien):
+        """在飞船所处的位置创建一个子弹对象"""
+        super().__init__()
+        self.screen = screen
+
+        # 在(0,0)处创建一个表示子弹的矩形，再设置正确的位置
+        self.rect = pygame.Rect(0, 0, ai_settings.bullet_width, ai_settings.bullet_height)
+        self.rect.centerx = alien.rect.centerx
+        self.rect.top = alien.rect.bottom
+
+        # 存储用小数表示的子弹位置
+        self.y = float(self.rect.y)
+
+        # 设置子弹颜色及速度(从ai_settings中读取)
+        self.color = ai_settings.alien_bullet_color
+        self.speed_factor = ai_settings.bullet_speed_factor
+
+
+    def update(self):
+        """向下移动子弹"""
+        self.y += self.speed_factor
+        self.rect.y = self.y
+
+
+    def draw_alien_bullet(self):
+        """在屏幕上绘制子弹"""
+        pygame.draw.rect(self.screen, self.color, self.rect)