Python入门 Junior-做个小游戏-做个弹珠小游戏吧(7)

书接上回，还有个问题没解决：

* 小球在向下运动时，碰到档板会反弹，没碰到就消失了,死掉了 :(

想想，反弹这事我们做过。在窗口的上下左右边界上用if做了判断。

现在的目标是下边界，在做判断的时候增加上档板。

原先的在 ball_move() 函数中的相关代码如下：

 # 检测上下边界
 if new_y < ball['ball_radius']: # 上边界
 new_y = ball['ball_radius']
 ball['ball_yspeed'] *= -1
 elif new_y > WINDOW_HIGH - ball['ball_radius']-Line_weigh: # 下边界
 new_y = WINDOW_HIGH - ball['ball_radius']-Line_weigh
 # 检测是否碰到线（拍子）
 if new_x > lines[0]['line_start_point'][0] and new_x < lines[0]['line_end_point'][0]:
 ball['ball_yspeed'] *= -1
 else:
 ball['ball_alive'] = False

我们需要修改下边界这部分的代码。

先不着急开始修改，还需要解决一个问题：小球在向下运动时，如果没有碰到档板，就会消失,死掉了。

怎么表达小球死掉这件事呢？我们新还记得用于表示小球的列表变量吧 balls = []，里面用字典类型保存了多个小球的信息，现在可以在增加一项 ball_alive，如果小球活着就是True, 如果死了就是False。然后，在 ball_redraw 函数里进行判读，如果是True就重画, 如果是False就从balls 列表中移除这一项。

想明白方法就可以开始干活了，要改动的地方比较多。顺着刚才的思路，一个一个地修改。

1、修改 creat_ball 函数，如下：

def creat_ball(window, pos):
 # 画球
 temp_ball = {
 'ball_center': pos,
 'ball_radius': Ball_radius,
 'ball_xspeed': my_randint(-5,5),
 'ball_yspeed': my_randint(-5,5),
 'ball_alive': True
 }
 balls.append(temp_ball)
 # print(balls)
 # 画球
 pygame.draw.circle(window, White, pos, Ball_radius, Ball_radius)

 pygame.display.update() # flip后面用update

2、修改ball_move 函数，代码片断如下

 # 检测上下边界
 if new_y < ball['ball_radius']: # 上边界
 new_y = ball['ball_radius']
 ball['ball_yspeed'] *= -1
 elif new_y > WINDOW_HIGH - ball['ball_radius']-Line_weigh: # 下边界
 new_y = WINDOW_HIGH - ball['ball_radius']-Line_weigh
 # 检测是否碰到线（拍子）
 if new_x > lines[0]['line_start_point'][0] and new_x < lines[0]['line_end_point'][0]:
 ball['ball_yspeed'] *= -1
 else:
 ball['ball_alive'] = False

3、修改ball_redraw函数，代码如下

def ball_redraw(window):
 window.fill(Black) # 窗口背景色重新置成黑色，球就没了 

 for ball in balls:
 if ball['ball_alive']:
 pygame.draw.circle(window, White, ball['ball_center'],ball['ball_radius'])
 else:
 balls.remove(ball)
 pygame.display.update()
 # 每10毫秒刷新一次
 pygame.time.delay(10)

RUN一下，没问题，搞定！

完整代码如下，共182行，包括空白行。

import pygame
import random

WINDOW_WIDTH = 600 # 屏幕宽度
WINDOW_HIGH = 400 # 屏幕高度

Black = (0, 0, 0)
White = (255, 255, 255)
Red = (255, 0, 0)

lines = []
Line_length = 100
Line_weigh = 10
Line_color = Red
Line_speed = 2

balls = []
Ball_radius = 20
Ball_xspeed = 1
Ball_yspeed = 4


# random.randint(-5,5)用于生成X,Y方向，如果其中一个是0，或者全是0
# 会造成生成的球垂直或水平或原地不动，不妥
# 故做以下函数
def my_randint(start, end): 

 while True:
 x = random.randint(start, end)
 if x != 0:
 break
 return x


def create_line(window):
 # 在指定的位置画线
 # 保存线的信息
 line_start_point = (WINDOW_WIDTH/2-Line_length/2, WINDOW_HIGH-Line_weigh)
 line_end_point = (WINDOW_WIDTH/2+Line_length/2, WINDOW_HIGH-Line_weigh)
 temp_line = {
 'line_start_point': line_start_point,
 'line_end_point': line_end_point,
 'line_length': Line_length
 }
 lines.append(temp_line)
 # 画线
 pygame.draw.line(window, Line_color, line_start_point, line_end_point, Line_weigh)

 pygame.display.update() # 第一次flip后面用update


def line_move():
 pos = pygame.mouse.get_pos()
 line_start_point = (pos[0]-Line_length/2, WINDOW_HIGH-Line_weigh)
 line_end_point = (pos[0] + Line_length / 2, WINDOW_HIGH-Line_weigh)

 lines[0]['line_start_point'] = line_start_point
 lines[0]['line_end_point'] = line_end_point


def line_redraw(window):
 pygame.draw.line(window, Line_color, lines[0]['line_start_point'], lines[0]['line_end_point'], Line_weigh)
 pygame.display.update()
 pygame.time.delay(50)


def creat_ball(window, pos):
 # 画球
 temp_ball = {
 'ball_center': pos,
 'ball_radius': Ball_radius,
 'ball_xspeed': my_randint(-5,5),
 'ball_yspeed': my_randint(-5,5),
 'ball_alive': True
 } 

 balls.append(temp_ball)
 # print(balls)
 # 画球
 pygame.draw.circle(window, White, pos, Ball_radius, Ball_radius)

 pygame.display.update() # flip后面用update


def ball_move():
 # 计算每个球的新坐标
 for ball in balls:
 # 获取球的新的原点
 ball_x, ball_y = ball['ball_center']
 new_x = ball_x + ball['ball_xspeed']
 new_y = ball_y + ball['ball_yspeed']

 # 检测两边的边界
 if new_x < ball['ball_radius']:
 new_x = ball['ball_radius']
 ball['ball_xspeed'] *= -1
 elif new_x > WINDOW_WIDTH - ball['ball_radius']:
 new_x = WINDOW_WIDTH - ball['ball_radius']
 ball['ball_xspeed'] *= -1

 # 检测上下边界
 if new_y < ball['ball_radius']: # 上边界
 new_y = ball['ball_radius']
 ball['ball_yspeed'] *= -1
 elif new_y > WINDOW_HIGH - ball['ball_radius']-Line_weigh: # 下边界
 new_y = WINDOW_HIGH - ball['ball_radius']-Line_weigh
 # 检测是否碰到线（拍子）
 if new_x > lines[0]['line_start_point'][0] and new_x < lines[0]['line_end_point'][0]:
 ball['ball_yspeed'] *= -1
 else:
 ball['ball_alive'] = False

 # 修改圆心坐标
 ball['ball_center'] = new_x, new_y

 # 检测球碰撞，每个球是否和其他的球的圆心距小于等于两个半径
 # 把球碰撞当做完全弹性碰撞 

 # 球碰撞后如何处理
 # 如果像碰壁一样处理（X,Y SPEED* -1），效果完成不符合物理规则
 # 可以两个球互相交换速度
 for other in balls:
 if ball == other or ball['ball_alive'] == False or other['ball_alive'] == False:
 continue
 # 判断两个球是否相撞
 other_x, other_y = other['ball_center']
 # 算两个球的圆心距
 center_distance = ((ball_x-other_x)**2 + (ball_y-other_y)**2)**0.5
 # 相撞后
 if center_distance <= Ball_radius*2:

 # 对心碰撞后,两个球互换方向
 ball['ball_xspeed'],other['ball_xspeed'] = other['ball_xspeed'],ball['ball_xspeed']
 ball['ball_yspeed'], other['ball_yspeed'] = other['ball_yspeed'], ball['ball_yspeed']

 new_x = ball_x + ball['ball_xspeed']
 new_y = ball_y + ball['ball_yspeed']
 ball['ball_center'] = new_x, new_y

 new_x = other_x + other['ball_xspeed']
 new_y = other_y + other['ball_yspeed']
 other['ball_center'] = new_x, new_y


def ball_redraw(window):
 window.fill(Black) # 窗口背景色重新置成黑色，球就没了
 for ball in balls:
 if ball['ball_alive']:
 pygame.draw.circle(window, White, ball['ball_center'],ball['ball_radius'])
 else:
 balls.remove(ball)
 pygame.display.update()
 # 每10毫秒刷新一次
 pygame.time.delay(10)


def main_game():
 # 初始化游戏 

 pygame.init()
 # 定义窗体，指定大小
 window = pygame.display.set_mode((WINDOW_WIDTH, WINDOW_HIGH))
 # 指定窗体的标题
 pygame.display.set_caption("PingPang")
 # 指定窗体底色
 window.fill(Black)
 # 显示窗体
 pygame.display.flip()

 create_line(window)

 while True:
 for event in pygame.event.get():
 if event.type == pygame.QUIT:
 exit()
 if event.type == pygame.MOUSEBUTTONDOWN:
 creat_ball(window, event.pos)
 ball_move()
 ball_redraw(window)

 line_move()
 line_redraw(window)


if __name__ == '__main__':
 main_game()

到现在，我们开始设想的功能都实现了，就是看起来比较粗糙。

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