调试示例 Pygame 代码？

Question

一个简单的问题：为什么第一个代码可以工作，但看似相同的第二个代码在 pygame 窗口出现时冻结了？

# Moving Pan
# Demonstrates mouse input

from livewires import games

games.init(screen_width = 640, screen_height = 480, fps = 50)

class Pan(games.Sprite):
    """ A pan controlled by the mouse. """
    def update(self):
        """ Move to mouse coordinates. """
        self.x = games.mouse.x
        self.y = games.mouse.y

def main():
    wall_image = games.load_image("wall.jpg", transparent = False)
    games.screen.background = wall_image

    pan_image = games.load_image("pan.bmp")
    the_pan = Pan(image = pan_image,
                  x = games.mouse.x,
                  y = games.mouse.y)
    games.screen.add(the_pan)

    games.mouse.is_visible = False

    games.screen.event_grab = True

    games.screen.mainloop()

# kick it off!
main()

故障的第二个：

from livewires import games,color
games.init (screen_width = 640, screen_height = 480, fps = 50)

#Creating a moving object tied to the cursor. This includes one method with two
#lines of code.
class Pan (games.Sprite):
    def moved (self):
    #Receives mouse position
        self.x = games.mouse.x
    #Changes mouse position to new x,y values.
        self.y = games.mouse.y

#The Main
myscr = games.screen
myscr.set_background (games.load_image ("wall.jpg", transparent = False))
pan_image = games.load_image ("pan.bmp")
le_pan = Pan (image = pan_image,
              x = games.mouse.x,
              y = games.mouse.y)

games.mouse.is_visible = False
myscr.add (le_pan)
myscr.event_grab = True
myscr.mainloop()

Answer 1

我从未使用过 livewires，但在游戏中，您通常需要 - 或多或少 - 无休止的游戏循环。

游戏循环背后的意义在于，您总是想知道鼠标在哪里或按下了哪些键，而不仅仅是一次！所以你必须一遍又一遍地问Where is the mouse?。为了实现这一点，您可以使用一个循环，在每次执行时检查您想要的所有内容。

在第一个例子中，游戏循环是函数main。申请流程是这样的：

1. 导入需要的库

   from livewires import games
   

2. 初始化游戏画面

   games.init(screen_width = 640, screen_height = 480, fps = 50)
   

3. 声明一个可以在屏幕上显示的精灵

   class Pan(games.Sprite):
       """ A pan controlled by the mouse. """
       def update(self):
           """ Move to mouse coordinates. """
           self.x = games.mouse.x
           self.y = games.mouse.y
   

4. 声明main方法并设置游戏画面背景

   def main():
       wall_image = games.load_image("wall.jpg", transparent = False)
       games.screen.background = wall_image
   

5. 将上面定义的精灵添加到屏幕上，并将其移动到鼠标光标的位置

       pan_image = games.load_image("pan.bmp")
       the_pan = Pan(image = pan_image,
                     x = games.mouse.x,
                     y = games.mouse.y)
       games.screen.add(the_pan)
   

6. 使鼠标光标不可见并激活事件

       games.mouse.is_visible = False
       games.screen.event_grab = True
   

7. 运行主循环。这个方法的调用说：Run me( functionmain)over and over!

       games.screen.mainloop()
   

8. 第一次调用main

   main()
   

在第二个示例中，没有游戏循环。应用程序的流程（更紧凑）是这样的：

1. 导入库，初始化游戏画面，声明精灵

   from livewires import games,color
   games.init (screen_width = 640, screen_height = 480, fps = 50)
   
   class Pan (games.Sprite):
       def moved (self):
           self.x = games.mouse.x
           self.y = games.mouse.y
   

2. 设置游戏画面背景并添加精灵

   myscr = games.screen
   myscr.set_background (games.load_image ("wall.jpg", transparent = False))
   pan_image = games.load_image ("pan.bmp")
   le_pan = Pan (image = pan_image,
                 x = games.mouse.x,
                 y = games.mouse.y)
   myscr.add(le_pan)
   

3. 停用鼠标光标，启用事件

   games.mouse.is_visible = False
   myscr.event_grab = True
   

4. 运行主循环。这个方法的调用说：Run me( functionundefined)over and over!

   myscr.mainloop()
   

这是症结所在！ 您不能调用 Python 文件根目录中的代码！mainloop 函数不知道从哪里返回或从哪里开始。呼叫丢失，您的程序冻结。游戏画面无法更新，因为没有告诉它应该如何更新。

结论：您必须拥有一个用于您的游戏循环的函数！