Pygame开发Pie Game报event无key属性、图形不渲染问题求解

问题根因 #

你遇到的两个核心问题均由缩进错误导致：

1. event对象无key属性报错：判断数字键1-4的分支缩进错误，和event.type == KEYUP判断同级，没有嵌套在键盘事件的判断逻辑内。Pygame事件队列包含鼠标移动、窗口重绘等大量非键盘事件，这类事件本身没有key属性，触发对应事件时直接读取event.key就会抛出属性错误。
2. 黑屏、图形不渲染：清屏、绘制元素、刷新屏幕的所有渲染逻辑，全部写在了while True主循环的外部，程序启动后会无限循环遍历事件，永远执行不到渲染代码，自然无法显示画面。

另外你当前每个扇形的半径边绘制逻辑有误，四个块都固定画向上、向右的两条半径，除第一块外其余扇形的边都会错位，无法拼成完整披萨。

具体修改步骤 #

• 调整按键判断分支的缩进：将判断pygame.K_1到pygame.K_4的所有elif块向内缩进一层，放到elif event.type == KEYUP:的代码块内，和ESC键退出的判断同级。
• 调整渲染逻辑的缩进：将从screen.fill((0,0,200))开始，到pygame.display.update()结束的所有渲染、刷新代码，向内缩进一层，放到主循环内部、事件遍历for循环的后面，保证每帧都会执行绘制。
• 修正每个扇形对应的半径线段：
  • 第2块（左上90°-180°）：绘制向上半径、向左半径
  • 第3块（左下180°-270°）：绘制向左半径、向下半径
  • 第4块（右下270°-360°）：绘制向下半径、向右半径

修正后完整代码 #

# -*- coding = utf-8 -*-
# @File : piegame.py
# @Software:PyCharm

import math
import sys
import pygame
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((600,500))
pygame.display.set_caption("The Pie Game - Press 1,2,3,4")
myfont = pygame.font.Font(None,60)

color = 200,80,60
width = 4
x = 300
y = 250
radius = 200
position = x-radius,y-radius,radius*2,radius*2

piece1 = False
piece2 = False
piece3 = False
piece4 = False

while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            sys.exit()
        elif event.type == KEYUP:
            if event.key == pygame.K_ESCAPE:
                sys.exit()
            elif event.key == pygame.K_1:
                piece1 = True
            elif event.key == pygame.K_2:
                piece2 = True
            elif event.key == pygame.K_3:
                piece3 = True
            elif event.key == pygame.K_4:
                piece4 = True

    # clear the screen
    screen.fill((0,0,200))

    # draw the four numbers
    testImg1 = myfont.render("1",True,color)
    screen.blit(testImg1,(x+radius/2-20,y-radius/2))
    testImg2 = myfont.render("2",True,color)
    screen.blit(testImg2,(x-radius/2,y-radius/2))
    testImg3 = myfont.render("3",True,color)
    screen.blit(testImg3,(x-radius/2,y+radius/2-20))
    testImg4 = myfont.render("4",True,color)
    screen.blit(testImg4,(x+radius/2-20,y+radius/2-20))

    #should the pieces be drawn?
    if piece1:
        start_angle=math.radians(0)
        end_angle =math.radians(90)
        pygame.draw.arc(screen,color,position,start_angle,end_angle,width)
        pygame.draw.line(screen,color,(x,y),(x,y-radius),width)
        pygame.draw.line(screen,color,(x,y),(x+radius,y),width)
    if piece2:
        start_angle=math.radians(90)
        end_angle =math.radians(180)
        pygame.draw.arc(screen,color,position,start_angle,end_angle,width)
        pygame.draw.line(screen,color,(x,y),(x,y-radius),width)
        pygame.draw.line(screen,color,(x,y),(x-radius,y),width)
    if piece3:
        start_angle=math.radians(180)
        end_angle =math.radians(270)
        pygame.draw.arc(screen,color,position,start_angle,end_angle,width)
        pygame.draw.line(screen,color,(x,y),(x-radius,y),width)
        pygame.draw.line(screen,color,(x,y),(x,y+radius),width)
    if piece4:
        start_angle = math.radians(270)
        end_angle = math.radians(360)
        pygame.draw.arc(screen, color, position, start_angle, end_angle, width)
        pygame.draw.line(screen, color, (x, y), (x, y + radius), width)
        pygame.draw.line(screen, color, (x, y), (x + radius, y), width)

    #is the pie finished?
    if piece1 and piece2 and piece3 and piece4:
        color = 0,255,0

    pygame.display.update()

修正后运行程序，按1-4键会依次点亮对应扇形，四块全部点亮后线条会变成绿色，符合原教材的设计效果。

内容的提问来源于stack exchange，提问作者zhw054