大雨不停

Question

我一直试图在PythonPyGame中创建一个稳定的雨，但偶然发现了一个问题。当我没有输入运动代码的部分时，雨滴的网格在那里没有问题。然而，当我添加运动时，网格消失了，只剩下一行移动的雨滴。请参阅下面的代码：

import sys
import pygame
from pygame.sprite import Group
from settings import Settings
from raindrop import Raindrop
import game_functions as gf

def run_game():
    # Initialize game and create a screen object.
    pygame.init()
    settings = Settings()
    screen = pygame.display.set_mode((settings.screen_width, 
settings.screen_height))
    pygame.display.set_caption("13-3")

    # Make raindrop group.
    raindrops = Group()

    # Create the raindrops.
    gf.create_raindrops(settings, screen, raindrops)

    # Start the main loop for the game.
    while True:

        gf.update_raindrops(raindrops)
        gf.update_screen(settings, screen, raindrops)

        # Watch for keyboard and mouse events.
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()

run_game()

设置.py

class Settings():
    """A class to store all settings."""

    def __init__(self):
        """Initialize the game's settings."""
        # Screen settings
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (0, 0, 255)

        # Raindrop settings
        self.raindrop_speed_factor = 1

game_functions.py

import sys
import pygame
from raindrop import Raindrop

def update_screen(settings, screen, raindrops):
    """Update images on the screen and flip to the new screen."""
    # Redraw the screen during each pass through the loop.
    screen.fill(settings.bg_color)
    raindrops.draw(screen)

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

def get_number_raindrops_x(settings, raindrop_width):
    """Determine the number of raindrops that fit in a row."""
    available_space_x = settings.screen_width - 2 * raindrop_width
    number_raindrops_x = int(available_space_x / (2 * raindrop_width))
    return number_raindrops_x

def get_number_rows(settings, raindrop_height):
    """Determine the number of rows of raindrops that fit on the screen."""
    available_space_y = settings.screen_height - (2 * raindrop_height)
    number_rows = int(available_space_y / (2 * raindrop_height))
    return number_rows

def create_raindrop(settings, screen, raindrops, raindrop_number, row_number):
    """Create a raindrop and place it in the row."""
    raindrop = Raindrop(settings, screen)
    raindrop_width = raindrop.rect.width
    raindrop.x = raindrop_width + 2 * raindrop_width * raindrop_number
    raindrop.rect.x = raindrop.x
    raindrop.rect.y = raindrop.rect.height + 2 * raindrop.rect.height * row_number
    raindrops.add(raindrop)

def create_raindrops(settings, screen, raindrops):
    """Create a full sky of raindrops."""
    # Create a raindrop and find the number of raindrops in a row.
    raindrop = Raindrop(settings, screen)
    number_raindrops_x = get_number_raindrops_x(settings, raindrop.rect.width)
    number_rows = get_number_rows(settings, raindrop.rect.height)

    # Create the full sky of raindrops.
    for row_number in range(number_rows):
        for raindrop_number in range(number_raindrops_x):
            create_raindrop(settings, screen, raindrops, raindrop_number, row_number)

def update_raindrops(raindrops):
    """Update the positions of all raindrops in sky."""
    raindrops.update()

雨滴

import pygame
from pygame.sprite import Sprite

class Raindrop(Sprite):
    """A class to represent a single raindrop in the sky."""

    def __init__(self, settings, screen):
        """Initialize the raindrop and set its starting position."""
        super(Raindrop, self).__init__()
        self.screen = screen
        self.settings = settings

        # Load the raindrop image and set its rect attribute.
        self.image = pygame.image.load('images/raindrop.png')
        self.rect = self.image.get_rect()

        # Start each new raindrop near the top left of the screen.
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        self.y = float(self.rect.y)

    def update(self):
        """Move raindrop down."""
        self.y += self.settings.raindrop_speed_factor
        self.rect.y = self.y

    def blitme(self):
        """Draw the raindrop at its current location."""
        self.screen.blit(self.image, self.rect)

我知道解决这个问题的方法（从另一个线程-多亏了gammazero）是改变这一点：

raindrop.rect.y = raindrop.rect.height + 2 * raindrop.rect.height * row_number

致：

raindrop.y = raindrop.rect.height + 2 * raindrop.rect.height * row_number
raindrop.rect.y = raindrop.y

我想知道为什么，但我找不到答案。有谁能解释一下上面代码的改变实际上有什么不同，以及为什么它突然起作用

Answer 1

创建雨滴并将其rect的y设置为某个位置时，实际的raindrop.y设置为某个默认值Raindrop.update()使用Raindrop.y而不是Raindrop.rect.y来获取drop的当前位置。替换代码所做的就是为raindrop.y分配一个适当的值，然后使用该值设置raindrop.rect.y