python - 外星人入侵 - Pygame - 外星人离开屏幕

Question

我正在制作 Python Crash Course 书中的 Alien Invasion 游戏项目，但遇到了外星人舰队应该向右移动直到到达屏幕右边缘、改变方向并向左移动等等的部分。
问题是我的外星人确实改变了方向，但只有当块中的第一个外星人(第一个一直在左边)碰到屏幕的右边缘时。他右边的所有外星人都经过了右边。
似乎它不能识别右侧外星人的矩形，它应该首先击中右边缘，而只能识别左侧第一个外星人的矩形......
1. Starting Position Image
2. The Problem Image
我严格按照书中的说明进行操作，现在我检查了 3 次可能出现问题的地方。你能帮我找出问题吗？
外星人入侵.py

import sys
import pygame
from settings import Settings
from ship import Ship
from bullet import Bullet
from alien import Alien

class AlienInvasion:
    """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((0, 0), pygame.FULLSCREEN)
        self.settings.screen_width = self.screen.get_rect().width
        self.settings.screen_height = self.screen.get_rect().height
        pygame.display.set_caption("Alien Invasion")
        self.ship = Ship(self)
        self.bullets = pygame.sprite.Group()
        self.aliens = pygame.sprite.Group()

        self._create_fleet()

        # Set the background color.
        self.bg_color = (230, 230, 230)

    def run_game(self):
        """Start the main loop for the game."""
        while True:
            self._check_events()
            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_RIGHT:
            # Move the ship to the right.
            self.ship.moving_right = True
        elif event.key == pygame.K_LEFT:
            # Move the ship to the left.
            self.ship.moving_left = True
        elif event.key == pygame.K_q:
            # Exit the game after pressing Q:
            sys.exit()
        elif event.key == pygame.K_SPACE:
            self._fire_bullet()

    def _check_keyup_events(self, event):
        """Respond to keypresses."""
        if event.key == pygame.K_RIGHT:
            # Stop moving the ship to the right.
            self.ship.moving_right = False
        elif event.key == pygame.K_LEFT:
            # Stop moving the ship to the left.
            self.ship.moving_left = False

    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 bullets positions.
        self.bullets.update()

        # Get rid of bullets that have dissapeared.
        for bullet in self.bullets.copy():
            if bullet.rect.bottom <= 0:
                self.bullets.remove(bullet)

    def _update_aliens(self):
        """Check if the fleet is at an edge, then update the positions of all aliens in the fleet."""
        self._check_fleet_edges()
        """Update the positios of all aliens in the fleet."""
        self.aliens.update()

    def _create_fleet(self):
        """Create a fleet of aliens."""
        # Create an alien and find the number of aliens in a row.
        # Spacing between each alien is equal to one alien width.
        alien = Alien(self)
        alien_width, alien_height = alien.rect.size
        available_space_x = self.settings.screen_width - (2 * alien_width)
        number_aliens_x = available_space_x // (2 * alien_width)

        # Determine the number of rows of aliens that fit on the screen.
        ship_height = self.ship.rect.height
        available_space_y = (self.settings.screen_height - (3 * alien_height) - ship_height)
        number_rows = available_space_y // (4 * alien_height)

        # Create the full fleet of aliens.
        for row_number in range(number_rows):
            for alien_number in range(number_aliens_x):
                self._create_alien(alien_number, row_number)
            
    def _create_alien(self, alien_number, row_number):
        # Create an alien and place it in the row.
        alien = Alien(self)
        alien_width, alien_height = alien.rect.size
        alien.x = alien_width + 4 * alien_width * alien_number
        alien.rect.x = alien.x
        alien.rect.y = alien.rect.height + 3 * alien.rect.height * 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 the fleet's direction."""
        for alien in self.aliens.sprites():
            alien.rect.y += self.settings.fleet_drop_speed
        self.settings.fleet_direction *= -1

    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()

if __name__ == '__main__':
    # Make a game instance, and run the game.
    ai = AlienInvasion()
    ai.run_game()

设置.py

class Settings:
    """A class to store all settings for Alien Invasion."""

    def __init__(self):
        """Initialize the game's settings."""
        # Screen settings
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230, 230, 230)
        self.ship_speed = 1.5

        # Bullet settings
        self.bullet_speed = 1.0
        self.bullet_width = 3
        self.bullet_height = 15
        self.bullet_color = (60, 60, 60)
        self.bullets_allowed = 3

        # Alien settings
        self.alien_speed = 1.0
        self.fleet_drop_speed = 10
        # fleet_direction of 1 represents right; -1 represents left.
        self.fleet_direction = 1

外星人.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """A class to represent a single alien in the fleet."""

    def __init__(self, ai_game):
        """Initialize the alien and set its starting postion."""
        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 left of the screen.
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        # Store the alien's exact horizontal position.
        self.x = float(self.rect.x)

    def check_edges(self):
        """Return True if an alien is at edge of screen."""
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right or self.rect.left <= 0:
            return True

    def update(self):
        """Move the alien right or left."""
        self.x += self.settings.alien_speed * self.settings.fleet_direction
        self.rect.x = self.x

Answer 1

这是Indentation的问题.你需要找到第一个碰到边缘的外星人，然后打破循环。实际上，您总是在列表中的第一个敌人之后中断循环:

class AlienInvasion:
    # [...]

    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()

                #-->| INDENTATION
                break
            
            # break <-- DELETE