关于python：pygame中没有pygame.display初始化错误无法转换

cannot convert without pygame.display initialized error in pygame

我正在使用pygame在我的大学为一个项目制作游戏。我现在想要做的就是创建一个可以控制的球，当用户按下向左和向右箭头键时，它可以在屏幕上来回移动。老实说，我真的不知道自己在做什么，所以我使用的是pygame文档中的代码，该文档曾将pong用作游戏的基础。我的代码在下面，如果有人知道为什么我得到标题中的错误，请告诉我。

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try:
import sys
import random
import math
import os
import getopt
import pygame
from socket import *
from pygame.locals import *
except ImportError, err:
print"couldn't load module. %s" % (err)
sys.exit(2)

def load_png(name):
""" Load image and return image object"""
fullname = name
try:
image = pygame.image.load(fullname)
if image.get_alpha() is None:
image = image.convert()
else:
image = image.convert_alpha()
except pygame.error, message:
print 'Cannot load image:', fullname
raise SystemExit, message
return image, image.get_rect()

class Ball(pygame.sprite.Sprite):
def __init__(self, (xy)):
pygame.sprite.Sprite.__init__(self)
self.image, self.rect = load_png('ball.png')
screen = pygame.display.get_surface()
self.area = screen.get_rect()
self.hit = 0
self.speed = 10
self.state ="still"

def reinit(self):
self.state ="still"
self.movepos = [0,0]
if self.side =="left":
self.rect.midleft = self.area.midleft

def update(self):
newpos = self.rect.move(self.movepos)
if self.area.contains(newpos):
self.rect = newpos
pygame.event.pump()

def moveleft(self):
self.movepos[1] = self.movepos[1] - (self.speed)
self.state ="moveleft"

def moveright(self):
self.movepos[1] = self.movepos[1] + (self.speed)
self.state ="moveright"

def main():
running = True
pygame.init()
(width, height) = (800, 600)
screen = pygame.display.set_mode((width, height))

# Fill background
background = pygame.Surface(screen.get_size())
background = background.convert()
background.fill((0, 0, 0))
screen.blit(background, (0, 0))
pygame.display.flip()

global player
player = Ball("left")
playersprite = pygame.sprite.RenderPlain(player)

playersprite.draw(screen)
player.update()
while running:

for event in pygame.event.get():
if event.type == KEYDOWN:
if event.key == K_q:
running = False
if event.key == K_LEFT:
player.moveleft()
if event.key == K_RIGHT:
player.moveright()
elif event.type == KEYUP:
if event.key == K_UP or event.key == K_DOWN:
player.movepos = [0,0]
player.state ="still"
#screen.blit(background, ball.rect, ball.rect)
screen.blit(background, player.rect, player.rect)
#screen.blit(background, player2.rect, player2.rect)
#ballsprite.update()
playersprite.update()
#ballsprite.draw(screen)
playersprite.draw(screen)

if __name__ == '__main__': main()

All I'm trying to get done right now is create a ball that can be
controlled to go back and forth on the screen when the user presses
the left and right arrow keys.

您已经非常复杂了，您不需要102条线就可以移动一个球。我写并评论了一个简单的示例，我认为它可以为您提供很多帮助。您真正需要做的就是检测按键，然后更新x和y变量，然后使用x和y变量绘制图像。

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import pygame

screen_width = 1280
screen_height = 720

pygame.init()
screen = pygame.display.set_mode((screen_width,screen_height))

BLACK = (0,0,0)

ballImg = pygame.image.load("ball.jpg")
ballPosition = [0,0]
speed = 1

def game_loop():
while 1:
for event in pygame.event.get():
if event.type == pygame.QUIT:
exit()

#get all the keys being pressed
keys = pygame.key.get_pressed()

#depending on what key the user presses, update ball x and y position accordingly
if keys[pygame.K_UP]:
ballPosition[1] -= speed
if keys[pygame.K_DOWN]:
ballPosition[1] += speed
if keys[pygame.K_LEFT]:
ballPosition[0] -= speed
if keys[pygame.K_RIGHT]:
ballPosition[0] += speed

screen.fill(BLACK) #fill the screen with black
screen.blit(ballImg, ballPosition) #draw the ball
pygame.display.update() #update the screen

game_loop()