Python 速成班 - 13-5 Sideways Shooter Pt 2，添加外星人
Python Crash Course - 13-5 Sideways Shooter Pt 2, Adding the aliens
我在第 12 章完成了这个练习的第一部分，没有任何问题，但现在我试图将外星人加入其中，我 运行 遇到了麻烦。
我无法让他们在屏幕右上角画画，他们总是从左上角开始；而且他们根本不动。
其他一切似乎都正常，包括船舶移动和子弹碰撞。
那么，如何让外星人从右上角开始，按列开始绘制，并让它们上下移动？
sideways_shooter.py
import sys
from time import sleep
import pygame
from settings import Settings
from game_stats import GameStats
from ship import Ship
from bullet import Bullet
from alien import Alien
class SidewaysShooter:
"""Overall class to manage game assets and behavior"""
def __init__(self):
"""Initialize the game and create game resources."""
pygame.init()
self.settings = Settings()
self.screen = pygame.display.set_mode(
(self.settings.screen_width, self.settings.screen_height))
pygame.display.set_caption("Sideways Shooter")
self.stats = GameStats(self)
self.ship = Ship(self)
self.bullets = pygame.sprite.Group()
self.aliens = pygame.sprite.Group()
self._create_fleet()
def run_game(self):
"""Start the main loop for the game"""
while True:
self._check_events()
if self.stats.game_active:
self.ship.update()
self._update_bullets()
#self._update_aliens()
self._update_screen()
def _check_events(self):
#Respond to keypresses and mouse events
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
elif event.type == pygame.KEYDOWN:
self._check_keydown_events(event)
elif event.type == pygame.KEYUP:
self._check_keyup_events(event)
def _check_keydown_events(self, event):
#Respond to keypresses
if event.key == pygame.K_UP:
self.ship.moving_up = True
elif event.key == pygame.K_DOWN:
self.ship.moving_down = True
elif event.key == pygame.K_q:
sys.exit()
elif event.key == pygame.K_SPACE:
self._fire_bullet()
def _check_keyup_events(self, event):
#Respond to key releases
if event.key == pygame.K_UP:
self.ship.moving_up = False
elif event.key == pygame.K_DOWN:
self.ship.moving_down = False
def _update_aliens(self):
#Check if the fleet is at an edge, update the position of all the aliens
self._check_fleet_edges()
self.aliens.update()
#Check for alien-ship collisions
if pygame.sprite.spritecollideany(self.ship, self.aliens):
self._ship_hit()
#Look for aliens hitting the bottom
self._check_aliens_bottom()
def _fire_bullet(self):
#Create a new bullet and add it to the bullets group
if len(self.bullets) < self.settings.bullets_allowed:
new_bullet = Bullet(self)
self.bullets.add(new_bullet)
def _update_bullets(self):
#Update position of bullets and get rid of old bullets
#Update bullet positions
self.bullets.update()
#Get rid of bullets that have left the screen
for bullet in self.bullets.copy():
if bullet.rect.left >= self.settings.screen_width:
self.bullets.remove(bullet)
self._check_bullet_alien_collisions()
def _check_bullet_alien_collisions(self):
#Respond to alien bullet collsions
#Remove any bullets and aliens that have collided
collisions = pygame.sprite.groupcollide(
self.bullets, self.aliens, True, True)
if not self.aliens:
#Destroy existing bullets and create new fleet
self.bullets.empty()
self._create_fleet()
def _update_screen(self):
#Update images on the screen, and flip to the new screen
self.screen.fill(self.settings.bg_color)
self.ship.blitme()
for bullet in self.bullets.sprites():
bullet.draw_bullet()
self.aliens.draw(self.screen)
pygame.display.flip()
def _create_fleet(self):
#Create the fleet of aliens
#Make an alien and find the number of aliens in a column
#Spacing between each alien should be equal to one alien height
alien = Alien(self)
alien_width, alien_height = alien.rect.size
available_space_y = self.settings.screen_height - (2 * alien_height)
number_aliens_y = available_space_y // (2 * alien_height)
#Determine the number of columns that can fit on the screen
ship_width = self.ship.rect.width
available_space_x = (self.settings.screen_width -
(4 * alien_width) - ship_width)
number_rows = available_space_x // (2 * alien_width)
#Create the full fleet of aliens
for row_number in range(number_rows):
for alien_number in range(number_aliens_y):
self._create_alien(alien_number, row_number)
def _create_alien(self, alien_number, row_number):
#Create an alien and place it in the column
alien = Alien(self)
alien_width, alien_height = alien.rect.size
alien.y = alien_height + 2 * alien_height * alien_number
alien.rect.y = alien.y
alien.rect.x = alien.rect.width + 2 * alien.rect.width * row_number
self.aliens.add(alien)
def _check_fleet_edges(self):
#Respond appropriately if any aliens have reached an edge
for alien in self.aliens.sprites():
if alien.check_edges():
self._change_fleet_direction()
break
def _change_fleet_direction(self):
#Drop the entire fleet and change direction
for alien in self.aliens.sprites():
alien.rect.x += self.settings.fleet_drop_speed
self.settings.fleet_direction *= -1
def _check_aliens_bottom(self):
#Check if any aliens have reached the left of the screen
screen_rect = self.screen.get_rect()
for alien in self.aliens.sprites():
if alien.rect.left >= screen_rect.left:
#Treat this the same as if the ship was hit
self._ship_hit()
break
def _ship_hit(self):
#Respond to the ship being hit by an alien
if self.stats.ships_left > 0:
#Decrement ships_left
self.stats.ships_left -= 1
#Get rid of any remaining aliens and bullets
self.aliens.empty()
self.bullets.empty()
#Create a new fleet and center the ship
self._create_fleet()
self.ship.center_ship()
#Pause
sleep(0.5)
else:
self.stats.game_active = False
if __name__ == '__main__':
#Make a game instance, and run the game
ai = SidewaysShooter()
ai.run_game()
alien.py
import pygame
from pygame.sprite import Sprite
class Alien(Sprite):
#A class to represent an alien
def __init__(self, ai_game):
#Initialize the alien and set its starting position
super().__init__()
self.screen = ai_game.screen
self.settings = ai_game.settings
#Load the alien image and set its rect attribute
self.image = pygame.image.load('images/alien.bmp')
self.rect = self.image.get_rect()
#Start each new alien near the top right of the screen
self.rect.x = self.settings.screen_width - self.rect.width
self.rect.y = self.rect.height
#Store the alien's exact vertical position
self.y = float(self.rect.y)
def check_edges(self):
#Return True if alien is at the edge of screen
screen_rect = self.screen.get_rect()
if self.rect.bottom >= screen_rect.bottom or self.rect.top <= 0:
return True
def update(self):
#Move the alien up or down
self.y += (self.settings.alien_speed *
self.settings.fleet_direction)
self.rect.y = self.y
我相信你的外星人出现在屏幕左侧是因为这条线：
alien.rect.x = alien.rect.width + 2 * alien.rect.width * row_number
当行号为0时，这里的第二项为0，外星人的x位置将等于它的宽度。
如果你想让它们开始出现在屏幕的右侧，你可以让它的初始位置等于屏幕宽度减去一定量，就像外星人宽度的倍数。
我在第 12 章完成了这个练习的第一部分，没有任何问题，但现在我试图将外星人加入其中，我 运行 遇到了麻烦。
我无法让他们在屏幕右上角画画，他们总是从左上角开始；而且他们根本不动。
其他一切似乎都正常，包括船舶移动和子弹碰撞。
那么，如何让外星人从右上角开始，按列开始绘制，并让它们上下移动？
sideways_shooter.py
import sys
from time import sleep
import pygame
from settings import Settings
from game_stats import GameStats
from ship import Ship
from bullet import Bullet
from alien import Alien
class SidewaysShooter:
"""Overall class to manage game assets and behavior"""
def __init__(self):
"""Initialize the game and create game resources."""
pygame.init()
self.settings = Settings()
self.screen = pygame.display.set_mode(
(self.settings.screen_width, self.settings.screen_height))
pygame.display.set_caption("Sideways Shooter")
self.stats = GameStats(self)
self.ship = Ship(self)
self.bullets = pygame.sprite.Group()
self.aliens = pygame.sprite.Group()
self._create_fleet()
def run_game(self):
"""Start the main loop for the game"""
while True:
self._check_events()
if self.stats.game_active:
self.ship.update()
self._update_bullets()
#self._update_aliens()
self._update_screen()
def _check_events(self):
#Respond to keypresses and mouse events
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
elif event.type == pygame.KEYDOWN:
self._check_keydown_events(event)
elif event.type == pygame.KEYUP:
self._check_keyup_events(event)
def _check_keydown_events(self, event):
#Respond to keypresses
if event.key == pygame.K_UP:
self.ship.moving_up = True
elif event.key == pygame.K_DOWN:
self.ship.moving_down = True
elif event.key == pygame.K_q:
sys.exit()
elif event.key == pygame.K_SPACE:
self._fire_bullet()
def _check_keyup_events(self, event):
#Respond to key releases
if event.key == pygame.K_UP:
self.ship.moving_up = False
elif event.key == pygame.K_DOWN:
self.ship.moving_down = False
def _update_aliens(self):
#Check if the fleet is at an edge, update the position of all the aliens
self._check_fleet_edges()
self.aliens.update()
#Check for alien-ship collisions
if pygame.sprite.spritecollideany(self.ship, self.aliens):
self._ship_hit()
#Look for aliens hitting the bottom
self._check_aliens_bottom()
def _fire_bullet(self):
#Create a new bullet and add it to the bullets group
if len(self.bullets) < self.settings.bullets_allowed:
new_bullet = Bullet(self)
self.bullets.add(new_bullet)
def _update_bullets(self):
#Update position of bullets and get rid of old bullets
#Update bullet positions
self.bullets.update()
#Get rid of bullets that have left the screen
for bullet in self.bullets.copy():
if bullet.rect.left >= self.settings.screen_width:
self.bullets.remove(bullet)
self._check_bullet_alien_collisions()
def _check_bullet_alien_collisions(self):
#Respond to alien bullet collsions
#Remove any bullets and aliens that have collided
collisions = pygame.sprite.groupcollide(
self.bullets, self.aliens, True, True)
if not self.aliens:
#Destroy existing bullets and create new fleet
self.bullets.empty()
self._create_fleet()
def _update_screen(self):
#Update images on the screen, and flip to the new screen
self.screen.fill(self.settings.bg_color)
self.ship.blitme()
for bullet in self.bullets.sprites():
bullet.draw_bullet()
self.aliens.draw(self.screen)
pygame.display.flip()
def _create_fleet(self):
#Create the fleet of aliens
#Make an alien and find the number of aliens in a column
#Spacing between each alien should be equal to one alien height
alien = Alien(self)
alien_width, alien_height = alien.rect.size
available_space_y = self.settings.screen_height - (2 * alien_height)
number_aliens_y = available_space_y // (2 * alien_height)
#Determine the number of columns that can fit on the screen
ship_width = self.ship.rect.width
available_space_x = (self.settings.screen_width -
(4 * alien_width) - ship_width)
number_rows = available_space_x // (2 * alien_width)
#Create the full fleet of aliens
for row_number in range(number_rows):
for alien_number in range(number_aliens_y):
self._create_alien(alien_number, row_number)
def _create_alien(self, alien_number, row_number):
#Create an alien and place it in the column
alien = Alien(self)
alien_width, alien_height = alien.rect.size
alien.y = alien_height + 2 * alien_height * alien_number
alien.rect.y = alien.y
alien.rect.x = alien.rect.width + 2 * alien.rect.width * row_number
self.aliens.add(alien)
def _check_fleet_edges(self):
#Respond appropriately if any aliens have reached an edge
for alien in self.aliens.sprites():
if alien.check_edges():
self._change_fleet_direction()
break
def _change_fleet_direction(self):
#Drop the entire fleet and change direction
for alien in self.aliens.sprites():
alien.rect.x += self.settings.fleet_drop_speed
self.settings.fleet_direction *= -1
def _check_aliens_bottom(self):
#Check if any aliens have reached the left of the screen
screen_rect = self.screen.get_rect()
for alien in self.aliens.sprites():
if alien.rect.left >= screen_rect.left:
#Treat this the same as if the ship was hit
self._ship_hit()
break
def _ship_hit(self):
#Respond to the ship being hit by an alien
if self.stats.ships_left > 0:
#Decrement ships_left
self.stats.ships_left -= 1
#Get rid of any remaining aliens and bullets
self.aliens.empty()
self.bullets.empty()
#Create a new fleet and center the ship
self._create_fleet()
self.ship.center_ship()
#Pause
sleep(0.5)
else:
self.stats.game_active = False
if __name__ == '__main__':
#Make a game instance, and run the game
ai = SidewaysShooter()
ai.run_game()
alien.py
import pygame
from pygame.sprite import Sprite
class Alien(Sprite):
#A class to represent an alien
def __init__(self, ai_game):
#Initialize the alien and set its starting position
super().__init__()
self.screen = ai_game.screen
self.settings = ai_game.settings
#Load the alien image and set its rect attribute
self.image = pygame.image.load('images/alien.bmp')
self.rect = self.image.get_rect()
#Start each new alien near the top right of the screen
self.rect.x = self.settings.screen_width - self.rect.width
self.rect.y = self.rect.height
#Store the alien's exact vertical position
self.y = float(self.rect.y)
def check_edges(self):
#Return True if alien is at the edge of screen
screen_rect = self.screen.get_rect()
if self.rect.bottom >= screen_rect.bottom or self.rect.top <= 0:
return True
def update(self):
#Move the alien up or down
self.y += (self.settings.alien_speed *
self.settings.fleet_direction)
self.rect.y = self.y
我相信你的外星人出现在屏幕左侧是因为这条线：
alien.rect.x = alien.rect.width + 2 * alien.rect.width * row_number
当行号为0时，这里的第二项为0，外星人的x位置将等于它的宽度。
如果你想让它们开始出现在屏幕的右侧，你可以让它的初始位置等于屏幕宽度减去一定量，就像外星人宽度的倍数。