Pygame角色不会向左或向右移动

Question

在我下面使用 PyGame 的代码中，角色不会向左或向右移动，子弹也不会射击。我不确定是什么原因造成的。它没有带有按钮概念的整个开始菜单，所以我想知道这是否是问题所在？

import pygame
from pygame import mixer
import math
import random
import time
# Initialize pygame module
pygame.init()
# Create the screen
screen = pygame.display.set_mode((800, 600))
display_width = 800
display_height = 600
# Background
background = pygame.image.load('space1.jpg')
# Background Sound
mixer.music.load('background.wav')
mixer.music.play(-1)
# Title and Icon
pygame.display.set_caption('Space Invaders')
icon = pygame.image.load('ufo.png')
pygame.display.set_icon(icon)
# Player
playerImg = pygame.image.load('space-invaders.png')
playerX = 370
playerY = 480
player_change = 0
playerX += player_change
# Enemy
enemyImg = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_of_enemies = 6
# Colours
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (150, 0, 0)
GREEN = (0, 150, 0)
BRIGHT_RED = (255, 0,0)
BRIGHT_GREEN = (0, 255, 0)

for i in range(num_of_enemies):
enemyImg.append(pygame.image.load('alien.png'))
enemyX.append(random.randint(0, 736))
enemyY.append(random.randint(50, 150))
enemyX_change.append(2)
enemyY_change.append(40)
# Bullet
# Ready - You cant see the bullet on the screen
# Fire - The bullet is current moving
bulletImg = pygame.image.load('bullet.png')
bulletX = 0
bulletY = 480
bulletY_change = 10
bullet_state = 'ready'
# Score
score_value = 0
font = pygame.font.Font('freesansbold.ttf', 32)
textX = 10
textY = 10
# Game Over Text
over_font = pygame.font.Font('freesansbold.ttf', 64)
# Clock
clock = pygame.time.Clock()
def show_score(x, y):
score = font.render('score : ' + str(score_value), True, (0, 255, 0))
screen.blit(score, (x, y))
def game_over_text():
over_text = over_font.render('GAME OVER', True, (0, 255, 0))
screen.blit(over_text, (200, 250))
def player(x, y):
screen.blit(playerImg, (x, y))

def enemy(x, y, i):
screen.blit(enemyImg[i], (x, y))

def fire_bullet(x, y):
global bullet_state
bullet_state = 'fire'
screen.blit(bulletImg, (x + 16, y + 10))
def isCollision(enemyX, enemyY, bulletX, bulletY):
distance = math.sqrt((math.pow(enemyX - bulletX, 2)) + (math.pow(enemyY - bulletY, 2)))
if distance < 27:
return True
else:
return False
def text_objects(text, font):
textSurface = font.render(text, True, WHITE)
return textSurface, textSurface.get_rect()
def game_intro():
intro = True
while intro:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
quit()
screen.fill(BLACK)
largeText = pygame.font.Font('freesansbold.ttf', 105)
TextSurf, TextRect = text_objects('Space Invaders', largeText)
TextRect.center = ((display_width/2), 200)
screen.blit(TextSurf, TextRect)
button('Start Invasion', 325, 350, 150, 50, GREEN, BRIGHT_GREEN, 'play')
button('Quit Mission', 325, 450, 150, 50, RED, BRIGHT_RED, 'quit')
pygame.display.update()
clock.tick(15)
#Game Loop
def game_loop(playerX, playerY, player_change, bulletX, bulletY, bulletX_change, bulletY_change, bullet_state, bulletImg):
running = True
while running:
playerX = 370
playerY = 480
player_change = 0
playerX += player_change
# RGB         R    G    B
screen.fill((0, 0, 0))
# Background Image
screen.blit(background, (0, 0))
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
# If keystroke is pressed check whether its left or right
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
player_change = -5
if event.key == pygame.K_RIGHT:
player_change = 5
if event.key == pygame.K_SPACE:
if bullet_state is 'ready':
bullet_sound = mixer.Sound('laser.wav')
bullet_sound.play()
# Get the current x coordinate of the spaceship
bulletX = playerX
fire_bullet(bulletX, bulletY)
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
player_change = 0
# boundary for spaceship
if playerX <= 0:
playerX = 0
elif playerX >= 736:
playerX = 736
# Enemy movement
for i in range(num_of_enemies):
# Game Over
if enemyY[i] > 440:
for j in range(num_of_enemies):
enemyY[j] = 2000
game_over_text()
break
enemyX[i] += enemyX_change[i]
if enemyX[i] <= 0:
enemyX_change[i] = 2
enemyY[i] += enemyY_change[i]
elif enemyX[i] >= 736:
enemyX_change[i] = -2
enemyY[i] += enemyY_change[i]
# Collision
collision = isCollision(enemyX[i], enemyY[i], bulletX, bulletY)
if collision:
explosion_sound = mixer.Sound('explosion.wav')
explosion_sound.play()
bulletY = 480
bullet_state = "ready"
score_value += 1
enemyX[i] = random.randint(0, 736)
enemyY[i] = random.randint(50, 150)
enemy(enemyX[i], enemyY[i], i)
# Bullet movement
if bulletY <= 0:
bulletY = 480
bullet_state = 'ready'
if bullet_state is 'fire':
fire_bullet(bulletX, bulletY)
bulletY -= bulletY_change
player(playerX, playerY)
show_score(textX, textY)
pygame.display.update()
def button(msg, x, y, w, h, inactivecolour, activecolour, action=None):
mouse = pygame.mouse.get_pos()
click = pygame.mouse.get_pressed()
if x + w > mouse[0] > x and y + h > mouse[1] > y:
pygame.draw.rect(screen, activecolour, (x, y, w, h))
if click[0] == 1 and action != None:
if action == 'play':
game_loop(370, 480, 0, 0, 480, 0, 10, 'ready', pygame.image.load('bullet.png'))
if action == 'quit':
pygame.quit()
quit()
else:
pygame.draw.rect(screen, inactivecolour, (x, y, w, h))
smallText = pygame.font.Font('freesansbold.ttf', 20)
textSurf, textRect = text_objects(msg, smallText)
textRect.center = ((x + (w / 2)), (y + (h / 2)))
screen.blit(textSurf, textRect)
game_intro()

Answer 1

字符不会移动

在主应用程序循环中，播放器player_change的移动连续设置为 0。此外，玩家的位置是连续初始化的：

def game_loop(playerX, playerY, player_change, bulletX, bulletY, bulletX_change, >bulletY_change, bullet_state, bulletImg):
running = True
while running:
playerX = 370
playerY = 480
player_change = 0

在循环之前初始化playerX、playerY和player_change：

def game_loop(playerX, playerY, player_change, bulletX, bulletY, bulletX_change, bulletY_change, bullet_state, bulletImg):
running = True
player_change = 0
playerX = 370
playerY = 480
while running:    
playerX += player_change
# [...]

---

子弹不会射

如果要发射子弹，则必须设置子弹bulletX, bulletY = playerX, playerY的初始位置并设置bullet_state = 'fire'：

def game_loop(playerX, playerY, player_change, bulletX, bulletY, bulletX_change, bulletY_change, bullet_state, bulletImg):
# [...]    
while running:    
playerX += player_change
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
# If keystroke is pressed check whether its left or right
if event.type == pygame.KEYDOWN:
# [...]               
if event.key == pygame.K_SPACE:
if bullet_state is 'ready':
#bullet_sound = mixer.Sound('laser.wav')
#bullet_sound.play()
# Get the current x coordinate of the spaceship
bulletX, bulletY = playerX, playerY
bullet_state = 'fire'

请注意，global变量bullet_state

def fire_bullet(x, y):
global bullet_state
bullet_state = 'fire'

与game_loop中的局部变量bullet_state不同，因为bullet_state是game_loop的参数，因此是不同作用域中完全不同的变量，其名称随意相同：

def game_loop(playerX, playerY, player_change, bulletX, bulletY, 
bulletX_change, bulletY_change, 
bullet_state, # <--- that is a new variable in local scope
#      and not the "global" bullet_state
bulletImg):
# [...]

Answer 2

player_change = 0
playerX += player_change

尝试交换这两行的顺序。否则，更新 X 位置时，更改将始终为零。