“if”命令只运行一次，不重复

Question

我对 python 和 Pygame 非常陌生，正在尝试创建一个游戏。 我希望在设定的时间后出现“加电”，然后在每次计时器达到这么多秒时重复。

代码中出现“powerup”并在5秒后掉屏，定时器复位，但下次定时器达到5秒时，继续计数，没有产生“powerup”。

我花了几个小时试图弄清楚为什么这不起作用。

import pygame
import random

WIDTH = 480
HEIGHT = 600
FPS = 60

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
GREEN = (0, 255, 0)

pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
clock = pygame.time.Clock()

time_difference = 0

font_name = pygame.font.match_font('arial')
def draw_text(surf, text, size, x, y):
    font = pygame.font.Font(font_name, size)
    text_surface = font.render(text, True, WHITE)
    text_rect = text_surface.get_rect()
    text_rect.midtop = (x, y)
    surf.blit(text_surface, text_rect)

class HealthPack(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 40))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.radius = 50
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.y = random.randrange(-150, -100)
        self.speedy = 6
        self.speedx = 0

    def update(self):
        self.rect.y += self.speedy
        if self.rect.top > HEIGHT:
            self.kill()

all_sprites = pygame.sprite.Group()

healthpack = HealthPack()

running = True
while running:
    clock.tick(FPS)
    time_difference = pygame.time.get_ticks()
    if time_difference >= 5000:
        all_sprites.add(healthpack)
        time_difference -= 5000
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    all_sprites.update()

    screen.fill(BLACK)
    all_sprites.draw(screen)
    draw_text(screen, str(time_difference), 18, WIDTH / 2, 55)

    pygame.display.flip()

pygame.quit()

Answer 1

您没有计算自上一个powerup 以来的时间差。 time_difference 始终是游戏开始后的时间。每次要重置计时器时，您都需要保存刻度，并与之进行比较。

prev_time = pygame.time.get_ticks() #initialize tick counter
while running:
    clock.tick(FPS)
    time_difference = pygame.time.get_ticks() - prev_time
    if time_difference >= 5000:
        all_sprites.add(healthpack)
        prev_time = pygame.time.get_ticks() # reset counter
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    all_sprites.update()

    screen.fill(BLACK)
    all_sprites.draw(screen)
    draw_text(screen, str(time_difference), 18, WIDTH / 2, 55)

    pygame.display.flip()

Answer 2

@Barmar 给出了部分答案。他对time_difference 的修复是正确的，但您的代码也存在另一个问题。

另一个问题是healthpack。你正在这样做all_sprites.add(healthpack)，它只是将旧的healthpack 放回all_sprites 列表中。该精灵离开屏幕并下降。您需要一个HealthPack 的新实例。所以你需要像这样修改@Barmar的解决方案：

prev_time = pygame.time.get_ticks() #initialize tick counter
while running:
    clock.tick(FPS)
    time_difference = pygame.time.get_ticks() - prev_time
    if time_difference >= 5000:
        healthpack = HealthPack()      # <-----------------   add this line
        all_sprites.add(healthpack)
        prev_time = pygame.time.get_ticks() # reset counter