在 pygame 中执行 for 循环后图像不会保留在屏幕上

Question

我一直在尝试修改此 Tutorial 的代码，以便在子弹击中敌人后 player.png 图像显示在位置 x = 60 和 y = 48。但是图像 并没有保持固定 ，它只是出现和消失。我不知道代码中错误或缺失元素的确切位置，但我怀疑原因之一是我在 draw_reaction 函数中滥用 for 循环部分。

我的player.png图片

我的MWE代码：

import pygame
import random

# Define some colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)
BLUE = (0, 0, 255)

# --- Classes


class Block(pygame.sprite.Sprite):
    """ This class represents the block. """
    def __init__(self, color):
        # Call the parent class (Sprite) constructor
        super().__init__()

        self.image = pygame.Surface([20, 15])
        self.image.fill(color)

        self.rect = self.image.get_rect()


class Player(pygame.sprite.Sprite):
    """ This class represents the Player. """

    def __init__(self):
        """ Set up the player on creation. """
        # Call the parent class (Sprite) constructor
        super().__init__()

        self.image = pygame.Surface([20, 20])
        self.image.fill(RED)

        self.rect = self.image.get_rect()

    def update(self):
        """ Update the player's position. """
        # Get the current mouse position. This returns the position
        # as a list of two numbers.
        pos = pygame.mouse.get_pos()

        # Set the player x position to the mouse x position
        self.rect.x = pos[0]


class Bullet(pygame.sprite.Sprite):
    """ This class represents the bullet . """
    def __init__(self):
        # Call the parent class (Sprite) constructor
        super().__init__()

        self.image = pygame.Surface([4, 10])
        self.image.fill(BLACK)

        self.rect = self.image.get_rect()

    def update(self):
        """ Move the bullet. """
        self.rect.y -= 3


# --- Create the window

# Initialize Pygame
pygame.init()

# Set the height and width of the screen
screen_width = 700
screen_height = 400
screen = pygame.display.set_mode([screen_width, screen_height])

# --- Sprite lists

# This is a list of every sprite. All blocks and the player block as well.
all_sprites_list = pygame.sprite.Group()

# List of each block in the game
block_list = pygame.sprite.Group()

# List of each bullet
bullet_list = pygame.sprite.Group()

# --- Create the sprites

for i in range(0,1,2):
    # This represents a block
    block = Block(BLUE)

    # Set a random location for the block
    block.rect.x = random.randrange(screen_width)
    block.rect.y = random.randrange(350)

    # Add the block to the list of objects
    block_list.add(block)
    all_sprites_list.add(block)

# Create a red player block
player = Player()
all_sprites_list.add(player)
player_image = pygame.image.load("player.png").convert() 
# Loop until the user clicks the close button.
done = False

# Used to manage how fast the screen updates
clock = pygame.time.Clock()

score = 0
player.rect.y = 370

# -------- Main Program Loop -----------
while not done:
    # --- Event Processing
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

        elif event.type == pygame.MOUSEBUTTONDOWN:
            # Fire a bullet if the user clicks the mouse button
            bullet = Bullet()
            # Set the bullet so it is where the player is
            bullet.rect.x = player.rect.x
            bullet.rect.y = player.rect.y
            # Add the bullet to the lists
            all_sprites_list.add(bullet)
            bullet_list.add(bullet)

    # --- Game logic

    # Call the update() method on all the sprites


    # Calculate mechanics for each bullet
    for bullet in bullet_list:

        # See if it hit a block
        block_hit_list = pygame.sprite.spritecollide(bullet, block_list, True)

        # For each block hit, remove the bullet and add to the score
        for block in block_hit_list:
            bullet_list.remove(bullet)
            all_sprites_list.remove(bullet)
            score += 1
            print(score)

        # Remove the bullet if it flies up off the screen
        if bullet.rect.y < -10:
            bullet_list.remove(bullet)
            all_sprites_list.remove(bullet)
    def draw_reaction():
        for bullet in bullet_list:
            block_hit_list = pygame.sprite.spritecollide(bullet, block_list, True)
            for block in block_hit_list:
                screen.blit(player_image, [60, 48]) 
    all_sprites_list.update() 
    # --- Draw a frame

    # Clear the screen
    screen.fill(WHITE)
    draw_reaction()
    # Draw all the spites
    all_sprites_list.draw(screen)

    # Go ahead and update the screen with what we've drawn.
    pygame.display.flip()

    # --- Limit to 20 frames per second
    clock.tick(60)

pygame.quit()

编辑更新：每次游戏重新开始时，游戏只有一个随机出现的敌人。

编辑更新 2： 我知道在大多数游戏中，碰撞后敌人会从屏幕上消失。这也发生在我的代码中。但是出于我的特殊需要，我需要一个图像 (player.png) 在与敌人发生子弹碰撞后始终保持固定状态。

Answer 1

问题是由 draw_reaction() 函数仅在子弹与方块碰撞的绝对时间内绘制 player_image 引起的。所以它只显示一帧图像（60 分之一秒），但在下一个循环中不再发生碰撞（子弹被移除），所以它永远不会被绘制。

有很多解决方法，但我不确定显示此位图的目的，所以它们可能没有应有的帮助.

最简单的解决方法可能是将玩家图像变成精灵，并在子弹击中触发时将其简单地添加到现有的 all_sprites_list 中，然后在一段时间后（或以任何方式）将其移除它应该工作）。

class PlayerShip( pygame.sprite.Sprite ):
    def __init__(self):
        super().__init__()
        self.image = pygame.image.load( "player.png" ) #.convert() 
        self.rect  = self.image.get_rect()
        self.rect.topleft = ( 60, 48 )

然后：

player_sprite = PlayerShip()

和

def draw_reaction():
    for bullet in bullet_list:
        block_hit_list = pygame.sprite.spritecollide(bullet, block_list, True)
        for block in block_hit_list:
            # TODO: ensure it's not showing already
            all_sprites_list.add( player_sprite )      # add the player sprite 
            break                                      # only add once

编辑：根据评论更新了代码片段

在 pygame 中执行 for 循环后图像不会保留在屏幕上

Image does not remain on screen after executing for loop in pygame

python

loops

pygame

class

draw