python - Pygame 显示在 If 条件下不工作

Question

我试图让我的代码在一个正方形超过 500 像素后在屏幕中间显示一个文本，但它似乎确实在我的 If 条件下显示。我不知道我做错了什么。

import pygame
pygame.init()
displaywidth=500
displayheight=500

gameDisplay = pygame.display.set_mode((displaywidth, displayheight))
pygame.display.set_caption("First Game")

red = (0,255,0)

font=pygame.font.Font(None, 20)

#Class
def Message(msg, color):
    screen_text=font.render(msg,True,color)
    gameDisplay.blit(screen_text,[displaywidth/2,displayheight/2])

win = pygame.display.set_mode((displaywidth, displayheight))
x = 50
y = 50
width = 40
height = 40
vel = 5

x1 = 0
y1 = 0
width1 = 40
height1 = 40
vel2 = 100
vel3=100

x2 = 100
y2 = 100
pygame.draw.rect(win, (0, 255, 0), (x, y, width, height))
run = True
while run:
    pygame.time.delay(100)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        x -= vel2
    elif keys[pygame.K_RIGHT]:
        x += vel2
    elif keys[pygame.K_UP]:
        y1-=vel3
    elif keys[pygame.K_DOWN]:
        y1+=vel3
    if x > 500:
        Message("meow", red)
        pygame.display.update()
        print("pew")
    elif x < 0:
        x = 50
    elif y1 > 500:
        y1 = 450
    elif y1 < 0:
        y1 = 50

    print(x)
    print(y)
    win.fill((0, 0, 0))
    meow = pygame.draw.rect(win, (0, 255, 0), (x, y1, width, height))
    pygame.draw.rect(win, (160, 0, 0), (x1, y1, width1, height1))
    pygame.display.update()

pygame.quit()

我的打印命令似乎可以工作，但我不知道为什么不显示。

Answer 1

问题是您在代码中对 pygame.display.update() 进行了 2 次调用，但显示在第一次调用后立即被清除:

if x > 500:
   Message("meow", red)
   pygame.display.update()  # <----
   print("pew")
# [...]

win.fill((0, 0, 0))         # <----

在绘制任何内容之前清除显示并在主应用程序循环结束时执行单个 pygame.display.update():

run = True
while run:
    pygame.time.delay(100)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        x -= vel2
    elif keys[pygame.K_RIGHT]:
        x += vel2
    elif keys[pygame.K_UP]:
        y1-=vel3
    elif keys[pygame.K_DOWN]:
        y1+=vel3

    if x < 0:
        x = 50
    elif y1 > 500:
        y1 = 450
    elif y1 < 0:
        y1 = 50

    # clear dispaly
    win.fill((0, 0, 0)) 

    # draw scene
    if x > 500:
        Message("meow", red)
        print("pew")
    meow = pygame.draw.rect(win, (0, 255, 0), (x, y1, width, height))
    pygame.draw.rect(win, (160, 0, 0), (x1, y1, width1, height1))

    # update display
    pygame.display.update()