python - 如何让方 block 在pygame中来回移动

Question

我正在尝试制作一个移动平台，因此当平台到达窗帘点时，它应该反转方向并返回，但从我所看到的来看，它看起来像是在前后振动程序链接:https://drive.google.com/file/d/0BzvvQCByWwmAQThfdkEtSlRKa1k/view?usp=sharing

这是我的代码:

class lbuild(pygame.sprite.Sprite):
#This class represents alevel builder. It derives from the "Sprite" class in Pygame.

def __init__(self, color, width, height,x,y):
    # Call the parent class (Sprite) constructor
    super().__init__()

    self.image = pygame.Surface([width, height])
    self.image.fill(WHITE)
    self.image.set_colorkey(WHITE)

    # Draw the car (a rectangle!)
    pygame.draw.rect(self.image, color, [0, 0, width, height])

     # Fetch the rectangle object that has the dimensions of the image.
    self.rect = self.image.get_rect()
    self.rect.x=x
    self.rect.y=y
all_sprites_list = pygame.sprite.Group()
movblock=pygame.sprite.Group()#sprite group
def level1():
     global all_sprites_list
     global movblock
     xpos=0

     for x in range(50):

        all_sprites_list.add(lbuild(GREY,20,20,xpos,680))
        xpos =xpos+20
    ypos=660
    xpos2 =40

    for x in range(2):
        all_sprites_list.add(lbuild(black,60,20,xpos2,ypos))
        ypos=ypos-20
    mblk=lbuild(RED,100,20,120,600)#draws the block
    movblock.add(mblk)#adds it to the sprite group





   clock=pygame.time.Clock()

   while True:
            for event in pygame.event.get():
                if event.type==QUIT:
                    pygame.quit()
                    sys.exit()
            #Game Logic
            all_sprites_list.update()


            #Drawing on Screen
            screen.fill(WHITE)
           #Draw The Road
           spd=5

           if mblk.rect.x>200:#supposed to cheak if the block x postion a has reached 200 and the reverse its direction but instead it looks like it is vibrating
               spd= -spd
           if mblk.rect.x<100:
               spd= -spd
           mblk.rect.x+=spd

           #Now let's draw all the sprites in one go. (For now we only have 1 sprite!)
           all_sprites_list.draw(screen)
           movblock.draw(screen)

        #Refresh Screen
            pygame.display.flip()

       #Number of frames per secong e.g. 60
       clock.tick(60)

Answer 1

您的问题是 spd = 5 在 while True 中。

你改变方向使用

spd = -spd

但在那之后你用

覆盖它

spd = 5

你必须在 while True 之前使用 spd = 5

---

具有其他修改的完整版本。

import pygame
import sys

# --- constants --- (UPPER_CASE names)

WHITE  = (255, 255, 255)
GREEN  = (20, 255, 140)
GREY   = (210, 210 ,210)
WHITE  = (255, 255, 255)
RED    = (255, 0, 0)
PURPLE = (255, 0, 255)
BLACK  = (0,0,0)

SCREEN_WIDTH=1000
SCREEN_HEIGHT=700

# --- classes --- (CamelCase names)

class LBuild(pygame.sprite.Sprite):

    def __init__(self, color, width, height, x, y):
        super().__init__()

        self.image = pygame.Surface([width, height])
        self.image.fill(WHITE)
        self.image.set_colorkey(WHITE)

        # Draw the car (a rectangle!)
        pygame.draw.rect(self.image, color, [0, 0, width, height])

        # Fetch the rectangle object that has the dimensions of the image.
        self.rect = self.image.get_rect()
        self.rect.x = x
        self.rect.y = y

# --- functions --- (lower_case names)

def level_1(screen, all_sprites_list, movblock):

    x = 0

    for _ in range(50):
        all_sprites_list.add(LBuild(GREY, 20, 20, x, 680))
        x += 20

    y = 660
    x2 = 40

    for _ in range(2):
        all_sprites_list.add(LBuild(BLACK, 60, 20, x2, y))
        y -= 20

    mblk = LBuild(RED, 100, 20, 120, 600)
    movblock.add(mblk)

    spd = 5

    # - mainloop -

    clock = pygame.time.Clock()

    #current_time = pygame.time.get_ticks()
    # change something after 2s
    #change_time = current_time + 2000 # 2000ms = 2s

    while True:

        # - events -

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                # False = exit game
                return False
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_ESCAPE:
                    # True = go to next level
                    return True

        # - updates (without draws) -

        #current_time = pygame.time.get_ticks()

        #if current_time >= change_time:
        #    TODO: change something
        #    # change something again after 2s
        #    change_time = current_time + 2000

        all_sprites_list.update()

        if mblk.rect.x > 200:
            spd = -spd

        if mblk.rect.x < 100:
            spd = -spd

        mblk.rect.x += spd

        # - draws (without updates) -

        screen.fill(WHITE)

        all_sprites_list.draw(screen)
        movblock.draw(screen)

        pygame.display.flip()

        # - FPS -

        clock.tick(60)

# --- main ---

# - init -
pygame.init()

screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
pygame.display.set_caption("Car Racing")

# - game -

all_sprites_list = pygame.sprite.Group()
movblock = pygame.sprite.Group()

goto_next_level = level_1(screen, all_sprites_list, movblock)

#if goto_next_level:
#    goto_next_level = level_2(screen, all_sprites_list, movblock) 

#if goto_next_level:
#    goto_next_level = level_3(screen, all_sprites_list, movblock) 

# - exit -

pygame.quit()
sys.exit()