为什么球的行为方式如此? [英] Why do the balls behave the way they do?

问题描述

我希望每个球都能独立移动.我认为问题与它们都具有相同的速度有关，但我不知道它们为什么会这样，或者这是否是问题所在.另外，为什么屏幕的右侧部分会以这种方式运行?我希望球能够在整个屏幕上正确移动.

I want each ball to move independently. I think the problem has something to do with them all having the same velocity, but I don't know why they do or if that's even the problem. Also, why does the right portion of the screen behave the way it does? I want the balls to be able to move all over the screen properly.

import sys
import pygame
import random

screen_size = (screen_x, screen_y) = (640, 480)
screen = pygame.display.set_mode(screen_size)

size = {"width": 10, "height": 10}
velocity = {"x": {"mag": random.randint(3,7), "dir": random.randrange(-1,2,2)}, "y": {"mag": random.randint(3,7), "dir": random.randrange(-1,2,2)}}


class Ball(object):
    def __init__(self, size, position, velocity):
        self.size = size
        self.position = position
        self.velocity = velocity
        self.color = (255, 255, 255)

    def update(self):
        self.position["x"] += (self.velocity["x"]["mag"] * self.velocity["x"]["dir"])
        self.position["y"] += (self.velocity["y"]["mag"] * self.velocity["y"]["dir"])

        if self.position["x"] <= 0 or self.position["x"] >= screen_y:
            self.velocity["x"]["dir"] *= -1

        if self.position["y"] <= 0 or self.position["y"] >= screen_y:
            self.velocity["y"]["dir"] *= -1

        self.rect = pygame.Rect(self.position["x"], self.position["y"], size["width"], size["height"])

    def display(self):
        pygame.draw.rect(screen, self.color, self.rect)


def main():
    pygame.init()
    fps = 30
    clock = pygame.time.Clock()
    balls = []

    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                sys.exit()
            elif event.type == pygame.MOUSEBUTTONDOWN:
                (x, y) = event.pos
                position = {"x": x, "y": y}
                new_ball = Ball(size, position, velocity)
                balls.append(new_ball)

        for ball in balls:
            ball.update()

        screen.fill((0,0,0))

        for ball in balls:
            ball.display()

        pygame.display.update()
        clock.tick(fps)

if __name__ == "__main__":
    main()

推荐答案

您的屏幕右侧问题是由于 update() 中这一行的拼写错误造成的:

Your problem with the right of the screen is due to a typo in this line in update():

if self.position["x"] <= 0 or self.position["x"] >= screen_y:
                                                         # ^ should be x

这可以防止您的 Ball 进入 screen 最右边的 640 - 480 == 160 像素.

This prevents your Balls from entering the rightmost 640 - 480 == 160 pixels of screen.

球的行为都是一样的，因为当你第一次创建 velocity 时，你只调用 randint 来获得一次随机值.尝试将 randint 调用移动到 __init__ 中，例如

The balls all behave the same because you only call randint to get random values once, when you first create velocity. Try moving the randint call into __init__, e.g.

def __init__(self, size, position, velocity=None):
    if velocity is None:
        velocity = {"x": {"mag": random.randint(3,7), 
                          "dir": random.randrange(-1,2,2)}, 
                    "y": {"mag": random.randint(3,7), 
                          "dir": random.randrange(-1,2,2)}}
    self.size = size
    self.position = position
    self.velocity = velocity
    self.color = (255, 255, 255)

这允许您提供 velocity 或随机分配一个.在 main() 中，你可以调用:

This allows you to provide a velocity or be assigned a random one. In main(), you can then call:

balls.append(Ball(size, position))

以随机速度在鼠标position处添加一个新的Ball.

to add a new Ball at the mouse position with random velocity.

顺便说一句，您可以将 position 和 velocity 属性简化为 (x, y) 元组，如 pygame，而不是你的 dict 结构，即:

On a side-note, you could simplify your position and velocity attributes to (x, y) tuples, as used in pygame, rather than your dict structures, i.e.:

velocity == (velocity['x']['mag'] * velocity['x']['dir'],
             velocity['y']['mag'] * velocity['y']['dir'])

position == (position['x'], position['y'])

那么你在 main() 中的调用可能是:

Then your call in main() could be:

balls.append(Ball(size, event.pos))

这篇关于为什么球的行为方式如此?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！