Python 速成课程 - 外星人入侵 - 船舶无法正常移动

Question

我正在逐步阅读这本书。屏幕出现，船.bmp 显示在它应该出现的位置。问题是它不会左右移动，大多数时候。当它移动时，它只会向右移动，从不向左移动。它飞到右下角并停留在那里。不确定代码有什么问题。提前致谢。

外星人入侵.py

import sys
import pygame
from settings import Settings
from ship import Ship
import game_functions as gf

def run_game():
    #Initialize game and create a screeen object.
    pygame.init()
    ai_settings = Settings()
    screen = pygame.display.set_mode((
        ai_settings.screen_width, ai_settings.screen_height))
    pygame.display.set_caption("Alien Invasion")

    # Make a ship.
    ship = Ship(ai_settings, screen)



#Start the main loop for the game.
while True:
    gf.check_events(ship)
    ship.update()
    gf.update_screen(ai_settings, screen, ship)
    #Redraw the screen during each pass through the loop.
    screen.fill(ai_settings.bg_color)
    ship.blitme()
    
    # Watch for keyboard and mouse events.
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
    
    # Make the most recently drawn screen visible.
    pygame.display.flip()
    
run_game()

settings.py

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

    def __init__(self):
        """Initialize the game's settings."""
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (0,0, 90)
        self.ship_speed_factor = 1.5

ship.py

import pygame

class Ship():

    def __init__(self, ai_settings, screen):
        """Initialize the ship and set its starting position."""
        self.screen = screen
    
        # Load the ship image and get its rect.
        self.image = pygame.image.load('images/ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()
        self.ai_settings = ai_settings
    
        # Start each new ship at the bottom center of the screen.
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
    
        # Store a decimal value for the ship's center.
        self.center = float(self.rect.centerx)
    
        # Movement flag
        self.moving_right = False 
        self.moving_left = False
    
    def update(self):
        """Update the ship's position based on movement flags."""
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left < 0:
            self.center -= self.ai_settings.ship_speed_factor
    
        # Update rect object from self.center.
        self.rect.centerx = self.center 
    def blitme(self):
        """Draw the ship at its current location."""
        self.screen.blit(self.image, self.rect)

game_functions.py

import sys

import pygame

def check_keydown_events(event, ship):
    """Respond to keypresses."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    
def check_keyup_events(event, ship):
    """Respond to key releases."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False
    
def check_events(ship):
    """Respond to keypresses and mouse events."""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
    
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ship)
        
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        
        
def update_screen(ai_settings, screen, ship):
    """Update images on the screen and flip to the new screen."""
    # Redraw the screen during each pass through the loop.
    screen.fill(ai_settings.bg_color)
    ship.blitme()

    # Make the most recently drawn screen visible.
    pygame.display.flip()

Answer 1

我发现了什么：

1. IndentationError: 应在 (settings.py) 中有一个缩进块。

一个错误（之前）：

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

def __init__(self):
    """Initialize the game's settings."""
    self.screen_width = 1200
    self.screen_height = 800
    self.bg_color = (0,0, 90)
    self.ship_speed_factor = 1.5

右边的（后）

class Settings():
    #"""A class to store all the settings for Alien Invasion."""
    def __init__(self):
        # """Initialize the game's settings."""
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (0,0, 90)
        self.ship_speed_factor = 1.5

Answer 2

在ship类的update方法中，你写了：

if self.moving_left and self.rect.left < 0:
    self.center -= self.ai_settings.ship_speed_factor

应该是：

if self.moving_left and self.rect.left > 0:
    self.center -= self.ai_settings.ship_speed_factor