把击球和重置写成方法

Coddy 用 Pygame 制作游戏课程的第 39 课，共 41 课。

球还有另外两项任务：从挡板上弹开，以及回到中间。把它们写成方法后，主循环读起来就像游戏规则。

def reset(self):
    self.rect.center = (300, 200)
    self.vx = -self.vx

两次挡板检测的区别只在于球离开的方向：从左侧挡板弹开后向右，从右侧挡板弹开后向左。把这个方向作为数字 way 传入，取 1 或 -1，这样一个方法就能处理两种情况：

ball.hit(left, 1)
ball.hit(right, -1)

在方法内部，self.vx = way * abs(self.vx) 会让球无论原本朝哪个方向运动，都朝指定方向移动，同时保持原来的发射角度。

挑战

困难

将球拍碰撞处理和重置操作移入 Ball 类。

编写 hit(paddle, way)：发生碰撞时，执行 self.vx = way * abs(self.vx)，并计算击球角度。
编写 reset()：将中心设为 (300, 200)，并反转 self.vx。
在循环中调用 ball.hit(left, 1)、ball.hit(right, -1)，并在每次得分后调用 ball.reset()。

按“开始”：游戏仍会以相同的方式运行。然后点击“检查”。

亲手试试

import pygame


class Ball:
    def __init__(self):
        self.rect = pygame.Rect(293, 193, 14, 14)
        self.vx = 5
        self.vy = 4

    def move(self):
        self.rect.x += self.vx
        self.rect.y += self.vy
        if self.rect.top <= 0 or self.rect.bottom >= 400:
            self.vy = -self.vy

    def draw(self, surface):
        pygame.draw.rect(surface, (255, 196, 0), self.rect)


pygame.init()
screen = pygame.display.set_mode((600, 400))
pygame.display.set_caption("Pong")
clock = pygame.time.Clock()
font = pygame.font.Font(None, 36)

ball = Ball()
left = pygame.Rect(20, 160, 12, 80)
right = pygame.Rect(568, 160, 12, 80)
left_score = 0
right_score = 0
waiting = False
winner = None

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN and event.key == pygame.K_SPACE:
            if winner is None:
                waiting = False

    keys = pygame.key.get_pressed()
    if keys[pygame.K_w]:
        left.y -= 6
    if keys[pygame.K_s]:
        left.y += 6
    if keys[pygame.K_UP]:
        right.y -= 6
    if keys[pygame.K_DOWN]:
        right.y += 6
    left.clamp_ip(screen.get_rect())
    right.clamp_ip(screen.get_rect())

    if not waiting:
        ball.move()
        if ball.rect.colliderect(left):
            ball.vx = abs(ball.vx)
            ball.vy = (ball.rect.centery - left.centery) // 6
        if ball.rect.colliderect(right):
            ball.vx = -abs(ball.vx)
            ball.vy = (ball.rect.centery - right.centery) // 6
        if ball.rect.left > 600:
            left_score += 1
            ball.rect.center = (300, 200)
            ball.vx = -ball.vx
            waiting = True
        if ball.rect.right < 0:
            right_score += 1
            ball.rect.center = (300, 200)
            ball.vx = -ball.vx
            waiting = True
        if left_score == 5:
            winner = "Left player wins!"
        elif right_score == 5:
            winner = "Right player wins!"

    screen.fill((30, 30, 46))
    pygame.draw.rect(screen, (80, 160, 255), left)
    pygame.draw.rect(screen, (235, 80, 80), right)
    ball.draw(screen)
    score = font.render(f"{left_score} : {right_score}", True, (240, 240, 240))
    screen.blit(score, score.get_rect(center=(300, 30)))
    if winner is not None:
        message = font.render(winner, True, (240, 240, 240))
        screen.blit(message, message.get_rect(center=(300, 120)))
    elif waiting:
        message = font.render("Press Space to serve", True, (240, 240, 240))
        screen.blit(message, message.get_rect(center=(300, 360)))
    pygame.display.flip()
    clock.tick(60)

pygame.quit()