多个子弹在添加到Pygame精灵组并更新时不显示
我正在做我的第一个Python/Pygame项目，这是一个射击风格的游戏。不过，当我创建多个子弹的实例并把它们添加到精灵组时，屏幕上只显示最新创建的那一个实例。也就是说，任何时候只会显示一颗子弹。
我觉得第175到180行，或者在Bullet类里面的代码可能出了问题。
我的代码：
import pygame, random , sys , time
from pygame.locals import *
# Screen dimensions
SCREEN_WIDTH = 640
SCREEN_HEIGHT = 480
# Global constants
WHITE = (255, 255, 255)
BLACK = ( 0, 0, 0)
LIGHTBLUE = ( 0, 0, 155)
FPS = 60
class Player(pygame.sprite.Sprite):
# set speed vector of the player
change_x = 0
change_y = 0
moverate = 5
# Constructor. Pass in x and y position
def __init__(self, x, y):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
# Create player image
self.image = pygame.image.load('player.png')
self.image.set_colorkey(WHITE)
# Set a referance to the image rect.
self.rect = self.image.get_rect()
self.rect.centerx = x
self.rect.y = y
def changespeed(self, x, y):
""" Change the speed of the player"""
self.change_x += x
self.change_y += y
def update(self):
""" Move the player. """
# Move left/right
self.rect.x += self.change_x
# Move up/down
self.rect.y += self.change_y
def stop(self):
""" Called when the user lets off the keyboard."""
self.change_x = 0
self.change_y = 0
self.image = pygame.image.load('player.png')
self.image.set_colorkey(WHITE)
class Enemy(pygame.sprite.Sprite):
""" This class represents the enemy sprites."""
minmoverate = 1
maxmoverate = 8
def __init__(self):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load('enemyShip.png')
self.image = pygame.transform.scale(self.image, (50, 50))
self.image.set_colorkey(WHITE)
self.rect = self.image.get_rect()
def reset_pos(self):
""" Reset position to the top of the screen, at a random x location.
Called by update() or the main program loop if there is a collision."""
self.rect.y = - ( SCREEN_HEIGHT / 4)
self.rect.x = random.randrange(SCREEN_WIDTH)
def update(self):
""" Move the enemies. """
# Move down, at some speed
self.rect.y += 2
# Move left and right, at some speed
self.rect.x += 0
# If enemy is too far down, reset to top of screen
if self.rect.y > SCREEN_HEIGHT:
self.reset_pos()
class Bullet(pygame.sprite.Sprite):
""" This class represents the bullet. """
def __init__(self):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface([8, 20])
self.image.fill(LIGHTBLUE)
self.rect = self.image.get_rect()
def update(self):
""" Move the bullet. """
self.rect.y -= 10
class Game(object):
""" This class represents an instance of the game. If we need to
rest the game we'd just need to create a new instance of this class."""
# --- Class attributes.
# Sprite lists
enemy_list = None
bullet_list = None
all_sprites_list = None
# --- Class methods
# Set up the game
def __init__(self):
self.score = 0
self.game_over = False
# Create sprite lists
self.enemy_list = pygame.sprite.Group()
self.bullet_list = pygame.sprite.Group()
self.all_sprites_list = pygame.sprite.Group()
# Create the starting enemy ships
for i in range(15):
enemy = Enemy()
enemy.rect.x = random.randrange(SCREEN_WIDTH)
enemy.rect.y = random.randrange(-300, 20)
self.enemy_list.add(enemy)
self.all_sprites_list.add(enemy)
# Create the player
self.player = Player(SCREEN_WIDTH / 2, SCREEN_HEIGHT - (SCREEN_HEIGHT / 6))
self.all_sprites_list.add(self.player)
def process_events(self):
""" Process all of the events. Return "True" if we need to close the window."""
for event in pygame.event.get():
if event.type == pygame.QUIT:
return True
elif event.type == KEYDOWN:
if event.key == K_ESCAPE:
return True
elif event.key == K_RETURN:
if self.game_over:
self.__init__()
elif event.key in (K_RIGHT ,K_d):
self.player.changespeed( self.moverate ,0)
elif event.key in (K_LEFT ,K_a):
self.player.changespeed( -self.moverate ,0)
elif event.key in (K_UP , K_w):
self.player.changespeed(0, -self.moverate)
elif event.key in (K_DOWN , K_s):
self.player.changespeed(0, self.moverate)
elif event.key == K_SPACE: # Fire bullet
bullet = Bullet(0
# Set bullet so it is where the player is
bullet.rect.centerx = self.player.rect.centerx
bullet.rect.y = self.player.rect.y
# Add bullet to lists
self.all_sprites_list.add(bullet)
self.bullet_list.add(bullet)
elif event.type == KEYUP:
if event.key in (K_RIGHT ,K_d):
self.player.changespeed( -self.moverate ,0)
elif event.key in (K_LEFT ,K_a):
self.player.changespeed( self.moverate ,0)
elif event.key in (K_UP , K_w):
self.player.changespeed(0, self.moverate)
elif event.key in (K_DOWN , K_s):
self.player.changespeed(0, -self.moverate)
def run_logic(self):
""" This method is run each time through the frame.
It updates positions and checks for collisions."""
enemy = Enemy()
if not self.game_over:
# Move all the sprites
self.all_sprites_list.update()
if len(self.all_sprites_list) < 17:
self.enemy_list.add(enemy)
self.all_sprites_list.add(enemy)
enemy.rect.x = random.randrange(SCREEN_WIDTH)
enemy.rect.y = random.randrange(-100, -50)
# Bullet Mechanics
for bullet in self.bullet_list:
# See if the bullets has collided with anything.
self.enemy_hit_list = pygame.sprite.spritecollide(bullet, self.enemy_list, True)
# For each enemy hit, remove bullet and enemy and add to score
for enemy in self.enemy_hit_list:
self.bullet_list.remove(bullet)
self.all_sprites_list.remove(bullet)
self.score += 1
# Remove the bullet if it flies up off the screen
if bullet.rect.y < -10:
self.bullet_list.remove(bullet)
self.all_sprites_list.remove(bullet)
# Player Mechanics
for enemy in self.enemy_list:
# See if player has collided with anything.
self.player_hit_list = pygame.sprite.spritecollide(self.player, self.enemy_list, True)
if len(self.player_hit_list) == 1:
# If player is hit, show game over.
self.game_over = True
def display_frame(self, screen):
""" Display everything to the screen for the game. """
screen.fill(BLACK)
if self.game_over:
# font = pygame.font.Font("Serif:, 25)
font = pygame.font.SysFont("serif", 25)
text = font.render("Game Over! You scored " + str(self.score) +" points, press Enter to restart", True, WHITE)
center_x = (SCREEN_WIDTH // 2) - (text.get_width() // 2)
center_y = (SCREEN_HEIGHT // 2) - (text.get_height() // 2)
screen.blit(text, [center_x, center_y])
if not self.game_over:
self.all_sprites_list.draw(screen)
pygame.display.flip()
def main():
""" Main program function. """
# Initialize Pygame and set up the window
pygame.init()
size = [SCREEN_WIDTH, SCREEN_HEIGHT]
screen = pygame.display.set_mode(size)
screen_rect = screen.get_rect()
pygame.display.set_caption("My Game")
pygame.mouse.set_visible(False)
# Create our objects and set the data
done = False
clock = pygame.time.Clock()
# Create an instance of the Game class
game = Game()
# Main game loop
while not done:
# Process events (keystrokes, mouse clicks, etc)
done = game.process_events()
# Update object positions, check for collisions
game.run_logic()
# Draw the current frame
game.display_frame(screen)
# Pause for the next frame
clock.tick(FPS)
# Close window and exit
pygame.quit()
# Call the main function, start up the game
if __name__ == "__main__":
main()
1 个回答
0
问题在于你只创建了一个 Bullet 实例，并把它存储在 Game.bullet 这个类变量里。每次你开火时，代码只是把这个唯一的子弹移动到玩家的位置，然后从那里更新。
你可能想要为每一次射击创建一个新的子弹。在 process_events 中使用类似下面的代码：
elif event.key == K_SPACE: # Fire bullet
bullet = Bullet()
bullet.rect.centerx = self.player.rect.centerx
bullet.rect.y = self.player.rect.y
# Add bullet to lists
all_sprites_list.add(self.bullet)
bullet_list.add(self.bullet)
这样每次按下空格键时就会创建一个新的子弹。如果你的游戏设计规定了同时“活动”的子弹数量上限，你可能需要一些更复杂的逻辑（或者如果创建和销毁很多实例的性能开销太大，你可以写一些对象缓存的代码），但这应该能让你走上正轨。
不过，上面的代码并没有处理后续删除子弹的事情，所以你可能还需要处理这个问题，否则你的游戏会因为计算屏幕外子弹而变得很卡。我建议在 Bullet.update() 中加入一些逻辑，如果子弹在屏幕外，就调用 self.kill()（或者在适合你游戏的情况下）。当没有更多引用指向这个实例时，它会被自动回收。
我还建议你去掉 Game 类中的所有类变量，因为它们要么是多余的（被在 __init__ 中创建的实例变量遮蔽了），要么是有问题的（比如 bullet）。