python - Pygame 角色不会向左或向右移动

Question

在我使用 PyGame 的下面的代码中，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。它可以在没有带有按钮概念的整个开始菜单的情况下工作，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

the character won't move

玩家的移动player_change在主应用程序循环中连续设置为0。此外，玩家的位置是不断初始化的:

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
        # [...]

---

the bullet won't shoot

如果你想发射子弹，那么你必须设置子弹的初始位置bulletX,bulletY = playerX,playerY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'

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，因此不同范围内的完全不同的变量，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):
    # [...]