Pygame滚动背景消失？

Question

我在Pygame上做游戏，背景是滚动。但它不断消失！它滚动两次，然后消失。我该如何解决？？下面是代码：

#Scrolling background 

    background = "foxhabitat.jpg" 
    back = pygame.image.load(background).convert() 
    back2 = pygame.image.load(background).convert() 

    screenWidth = 900 
    back=pygame.transform.scale(back, (1000,600)) 
    back2=pygame.transform.scale(back, (1000,600)) 

    screenscroll.blit(back, (xx,0)) 
    screenscroll.blit(back2,(xx+screenWidth,0)) 
    print xx 
    xx = xx - 12 
    if xx >= screenWidth: 
     xx = 0 

    msElapsed = clock.tick(100) # changes speed of scrolling 

Answer 1

我觉得

if xx >= screenWidth: 
    xx = 0 

应在0

if xx + screenWidth <= 0: 
    xx = 0 

xx开始，那么你每次。减去时间12从它。结果是xx始终是<= 0，所以xx >= screenWidth将始终为假。

xx + screenWidth是秒图像的位置，并且当该值小于零，则时间复位xx位置让滚动再次开始。

Answer 2

如果你减去那么你不能screenWidth比较但0（零）

xx = xx - 12 
if xx <= 0: 
    xx = screenWidth 

，或者你可以做

xx = xx - 12 
if xx <= 0: 
    xx = xx + screenWidth