Python入門 Junior-做個小遊戲-做個彈珠小遊戲吧(6)

書接上回，還有下面的問題沒解決：

* 下面有一個紅色的小條，會隨著鼠標移動。小條就是個能移動的擋板，只能隨著鼠標水平移動，不能上下移動。

* 小球碰到紅色小條會反彈，沒碰到就消失了,死掉了 :(

先說第一個問題。是不是感覺和以前創建小球差不多？這就對了。

不過這次是畫個矩形，而且在遊戲一開始就畫好。

矩形的移動是隨著鼠標的X分量進行移動。

那就開始。

先定義紅色，檔板的長、寬和移動速度。

Red = (255, 0, 0) 
lines = []
Line_length = 100 
Line_weigh = 10 
Line_color = Red 
Line_speed = 2

為了給以後留擴展空間（比如人機對戰），我們像處理多個小球一樣，把檔板定義成一個列表變量。這樣，以後需要的時候就可以方便的創建多個檔板。

然後，需要定義幾個函數

create_line()

line_move()

line_redraw()

函數作用就不用多說了，從名字上就看得出來。

代碼如下：

def create_line(window):
 # 在指定的位置畫線
 # 保存線的信息
 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)
 # 畫線
 pygame.draw.line(window, Line_color, line_start_point, line_end_point, Line_weigh)

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

有了函數，在哪調用呢？

肯定在main_game()。但是要想一想。

• create_line()需要在窗口初始化時就調用，因為要顯示出檔板。所以放到while循環之前。
• line_move()和line_redraw()需要不停的循環調用，所以放到while循環內。

RUN一下試試，效果如下：

問題來了：檔板是有了，但沒起作用。 :(

下節解決這個問題。

以下為全部代碼：

import pygame
import random

WINDOW_WIDTH = 600 # 屏幕寬度
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)用於生成X,Y方向，如果其中一個是0，或者全是0
# 會造成生成的球垂直或水平或原地不動，不妥
# 故做以下函數
def my_randint(start, end):
 while True:
 x = random.randint(start, end) 

 if x != 0:
 break
 return x


def create_line(window):
 # 在指定的位置畫線
 # 保存線的信息
 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)
 # 畫線
 pygame.draw.line(window, Line_color, line_start_point, line_end_point, Line_weigh)

 pygame.display.update() # 第一次flip後面用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):
 # 畫球
 temp_ball = {
 'ball_center': pos,
 'ball_radius': Ball_radius,
 'ball_xspeed': my_randint(-5,5),
 'ball_yspeed': my_randint(-5,5)
 }
 balls.append(temp_ball)
 # print(balls)
 # 畫球 

 pygame.draw.circle(window, White, pos, Ball_radius, Ball_radius)

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


def ball_move():
 # 計算每個球的新座標
 for ball in balls:
 # 獲取球的新的原點
 ball_x, ball_y = ball['ball_center']
 new_x = ball_x + ball['ball_xspeed']
 new_y = ball_y + ball['ball_yspeed']

 # 檢測兩邊的邊界
 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

 # 檢測上下邊界
 if new_y < ball['ball_radius']: # 上邊界
 new_y = ball['ball_radius']
 ball['ball_yspeed'] *= -1
 elif new_y > WINDOW_HIGH - ball['ball_radius']: # 下邊界
 new_y = WINDOW_HIGH - ball['ball_radius']
 ball['ball_yspeed'] *= -1

 # 修改圓心座標
 ball['ball_center'] = new_x, new_y

 # 檢測球碰撞，每個球是否和其他的球的圓心距小於等於兩個半徑
 # 把球碰撞當做完全彈性碰撞
 # 球碰撞後如何處理
 # 如果像碰壁一樣處理（X,Y SPEED* -1），效果完成不符合物理規則
 # 可以兩個球互相交換速度
 for other in balls: 

 if ball == other:
 continue
 # 判斷兩個球是否相撞
 other_x, other_y = other['ball_center']
 # 算兩個球的圓心距
 center_distance = ((ball_x-other_x)**2 + (ball_y-other_y)**2)**0.5
 # 相撞後
 if center_distance <= Ball_radius*2:

 # 對心碰撞後,兩個球互換方向
 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，球就沒了
 for ball in balls:
 pygame.draw.circle(window, White, ball['ball_center'],ball['ball_radius'])

 pygame.display.update()
 # 每10毫秒刷新一次
 pygame.time.delay(10)


def main_game():
 # 初始化遊戲
 pygame.init()
 # 定義窗體，指定大小
 window = pygame.display.set_mode((WINDOW_WIDTH, WINDOW_HIGH))
 # 指定窗體的標題
 pygame.display.set_caption("PingPang")
 # 指定窗體底色
 window.fill(Black)
 # 顯示窗體 

 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()

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