Question

我正在读一本名为“为绝对初学者编写更多Python编程”的书，我正在尝试编写第27页（动画矩形）的代码，当然还有改进。

我清楚地告诉pygame改变形状的x值，但它没有移动。我希望形状在屏幕上水平移动，当它到达另一端时转向，反之亦然。

这是代码：

# Animated Rectangle
#
# Demonstrating the basics of ANIMATION!!!
#
# ---------------------------------------------------

import pygame, sys
from pygame.locals import *

WHITE = 255, 255, 255
GREEN = 0, 255, 255

# rectangle properties
COLOUR = GREEN
POS_X = 400 # position
POS_Y = 200
THICKNESS = 0

VELOCITY = 1

pygame.init()

SURFACE = pygame.display.set_mode((600, 500))
SURFACE.fill(WHITE)
pygame.display.set_caption("Animationing")

if POS_X > 400 or POS_X < 100:
    VELOCITY = -VELOCITY

def draw(POS_X, VELOCITY):
    pygame.draw.rect(SURFACE, COLOUR, (POS_X, POS_Y, 100, 100), THICKNESS)
    POS_X -= VELOCITY # HERE IS THE SOURCE OF MY PROBLEM
    pygame.display.update()

while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            sys.exit()

    draw(POS_X, VELOCITY)

这就是问题所在;

def draw(POS_X, VELOCITY):
    pygame.draw.rect(SURFACE, COLOUR, (POS_X, POS_Y, 100, 100), THICKNESS)
    POS_X -= VELOCITY # HERE IS THE SOURCE OF MY PROBLEM
    pygame.display.update()

编辑：有人试图修复我的语法。我喜欢这样，至少你可以理解它。

编辑2：我的问题因为偏离主题而被搁置，所以我试图修复它。

Answer 1

您遇到问题，因为您对全局变量和局部变量POS_X

使用相同的名称

这创建局部变量POS_X

def draw(POS_X, VELOCITY):

并在此函数中更改本地POS_X

使用global访问全局POS_X（在此功能之外创建）

def draw(VELOCITY):
     global POS_X

然后调用它

draw(VELOCITY)

BTW：有规则（PEP8）：仅对常量值使用大写变量，如颜色WHITE，GREEN。

修改

您的代码可能如下所示

import pygame, sys from pygame.locals import * #--------------------- # constants WHITE = (255, 255, 255) GREEN = ( 0, 255, 255) #--------------------- # rectangle properties color = GREEN pos_x = 400 # position pos_y = 200 thickness = 0 velocity = 1 #--------------------- # classes and functions def move_player(): global pos_x, velocity pos_x -= velocity if pos_x > 400 or pos_x < 100: velocity = -velocity def draw_player(): pygame.draw.rect(screen, color, (pos_x, pos_y, 100, 100), thickness) #--------------------- # GAME pygame.init() screen = pygame.display.set_mode((600, 500)) pygame.display.set_caption("Animationing") # mainloop running = True while running: # events for event in pygame.event.get(): if event.type == QUIT: running = False if event.type == KEYDOWN: if event.key == K_ESCAPE: running = False # moves move_player() # move_enemy() # collision detection - nothing yet # draws screen.fill(WHITE) draw_player() # draw_enemy() pygame.display.update() # clock - to keep constant speed - nothing yet # quit pygame.quit()

Pygame - 为什么我的形状不动？

1 个答案: