更新：
Ryan P的回答提供了解决方案。但是，我采取了这个解决方案 然后把它改了一点，丢掉了所有不存在的数据 正确初始化为RootWidget的on_enter方法 屏幕。这很好用。
我的RootWidget类是Widget的子类，直到今天，我没有问题访问它的ID以获得＆＃34; grid＆＃34;的值。但是，我刚改变了 它是子类屏幕，现在它说ids因某种原因是空的...屏幕确实有一个ID和所有这些，但由于某种原因，它没有注册 我将一个GridLayout分配给了id＆＃39;＆＃39;＆＃39;＆＃39;＆＃39;在kv文件中。谁能告诉我为什么？
追溯：
[INFO ] [Logger ] Record log in /home/yerman/.kivy/logs/kivy_14-11-13_201.txt
[INFO ] Kivy v1.9.0-dev
[INFO ] [Python ] v2.7.6 (default, Mar 22 2014, 22:59:56)
[GCC 4.8.2]
[INFO ] [Factory ] 172 symbols loaded
[INFO ] [Image ] Providers: img_tex, img_dds, img_pygame, img_pil, img_gif (img_sdl2, img_ffpyplayer ignored)
[INFO ] [Window ] Provider: pygame(['window_egl_rpi'] ignored)
[WARNING] [WinPygame ] Video: failed (multisamples=2)
[WARNING] [WinPygame ] trying without antialiasing
[INFO ] [GL ] OpenGL version <2.1 Mesa 10.1.3>
[INFO ] [GL ] OpenGL vendor <Intel Open Source Technology Center>
[INFO ] [GL ] OpenGL renderer <Mesa DRI Intel(R) Ironlake Mobile >
[INFO ] [GL ] OpenGL parsed version: 2, 1
[INFO ] [GL ] Shading version <1.20>
[INFO ] [GL ] Texture max size <8192>
[INFO ] [GL ] Texture max units <16>
[INFO ] [Window ] virtual keyboard not allowed, single mode, not docked
[INFO ] [Text ] Provider: pygame(['text_sdl2'] ignored)
{} #<<< note the emtpy ids I printed out
Traceback (most recent call last):
File "main.py", line 169, in <module>
MineSweeperApp().run()
File "/usr/lib/python2.7/dist-packages/kivy/app.py", line 799, in run
root = self.build()
File "main.py", line 163, in build
return Manager()
File "/usr/lib/python2.7/dist-packages/kivy/uix/screenmanager.py", line 844, in __init__
super(ScreenManager, self).__init__(**kwargs)
File "/usr/lib/python2.7/dist-packages/kivy/uix/floatlayout.py", line 66, in __init__
super(FloatLayout, self).__init__(**kwargs)
File "/usr/lib/python2.7/dist-packages/kivy/uix/layout.py", line 66, in __init__
super(Layout, self).__init__(**kwargs)
File "/usr/lib/python2.7/dist-packages/kivy/uix/widget.py", line 269, in __init__
Builder.apply(self)
File "/usr/lib/python2.7/dist-packages/kivy/lang.py", line 1837, in apply
self._apply_rule(widget, rule, rule)
File "/usr/lib/python2.7/dist-packages/kivy/lang.py", line 1942, in _apply_rule
child = cls(__no_builder=True)
File "main.py", line 43, in __init__
self.grid = self.ids["grid"]
KeyError: 'grid'
kv档案：
#:kivy 1.8.0
<RootWidget>:
GridLayout:
id: grid
size: root.size
cols: root.sides
<Blank>:
background_color: 1, 1, 1, 1
background_disabled_down: "kivy_white_bg.png"
on_press: self.parent.parent.sweep(self)
<Mine>:
background_color: 1, 1, 1, 1
background_disabled_down: "kivy_white_bg.png"
on_press: self.parent.parent.sweep(self)
<TryAgain>:
anchor_x: 'center'
anchor_y: 'center'
BoxLayout:
size: root.size
orientation: 'vertical'
padding_bottom: '20dp'
Label:
font_size: '20dp'
text: root.text
BoxLayout:
size_hint: 1, .3
spacing: 10
padding: 10
Button:
size_hint: .4, 1
font_size: '20dp'
text: "yes"
on_press: app.stop(); app.run()
Button:
size_hint: .4, 1
font_size: '20dp'
text: "no"
on_press: root.quit()
<Menu>:
GridLayout:
rows: 2
Button:
text: "8x8"
on_press: root.manager.current = 'game_screen'
Button:
text: "16x16"
on_press: root.manager.current = 'game_screen'
Button:
text: "30x16"
on_press: root.manager.current = 'game_screen'
Button:
text: "custom"
on_press: root.manager.current = 'game_screen'
<Manager>:
id: _manager
menu: menu
game: game
current: menu_screen
Menu:
id: menu
manager: _manager
name: 'menu_screen'
RootWidget:
id: game
manager: _manager
name: 'game_screen'
main.py：
#!/usr/bin/env python
from random import sample
import sys
import kivy
kivy.require('1.8.0')
from kivy.app import App
from kivy.core.window import Window
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.properties import NumericProperty, ListProperty, StringProperty, ObjectProperty
from kivy.uix.gridlayout import GridLayout
from kivy.uix.modalview import ModalView
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.clock import Clock
class Blank(Button):
index = ListProperty([0, 0])
count = NumericProperty(0)
def __init__(self, **kwargs):
super(Blank, self).__init__(**kwargs)
class Mine(Button):
index = ListProperty([0, 0])
count = NumericProperty(0) # not really necessary
def __init__(self, **kwargs):
super(Mine, self).__init__(**kwargs)
class RootWidget(Screen):
sides = NumericProperty(10)
mine_count = NumericProperty(20)
def __init__(self, **kwargs):
super(RootWidget, self).__init__(**kwargs)
self.grid = self.ids["grid"]
# generate random mine indices
mines = sample(xrange(self.sides**2), self.mine_count)
x, y = -1, 0
for i in xrange(self.sides**2):
if x == self.sides - 1:
x = 0
y += 1
else:
x += 1
if i not in mines:
b = Blank(index=[x, y])
else:
b = Mine(index=[x, y])
self.grid.add_widget(b)
# record mine, blank and safe blank indices
self.all_btns = [c.index for c in self.grid.children]
self.mines = [c.index for c in self.grid.children if isinstance(c, Mine)]
self.blanks = [c.index for c in self.grid.children if isinstance(c, Blank)]
# a safe blank has no adjacent mines
self.safe_blanks = [c.index for c in self.grid.children if self.is_safe(c)]
# give each btn an 'adjacent mines count'
for x, y in self.all_btns:
btn = self.get_child_by_index([x, y])
for index in self.field(x, y):
if index in self.mines:
btn.count += 1
def field(self, x, y):
""" the minefield surrounding a btn """
field = [[x-1, y], [x+1, y], [x, y+1], [x, y-1],
[x+1, y+1], [x-1, y-1], [x+1, y-1], [x-1, y+1]]
get = self.get_child_by_index
return [i for i in field if i in self.all_btns and get(i).disabled == False]
def sweep(self, instance):
instance.disabled = True
if instance.index in self.mines:
print "Boom!" # It's a mine! You lose
instance.text = "Boom!"
self.game_over()
pressed = sum(1 for c in self.grid.children if c.disabled == True)
print pressed
if self.sides**2 - pressed == self.mine_count:
self.game_over(win=True)
if instance.count > 0:
instance.text = str(instance.count)
instance.disabled = True
return
else:
x, y = instance.index
for index in self.field(x, y):
if index not in self.mines:
blank = self.get_child_by_index(index)
blank.disable = True
if blank.count > 0:
blank.text = str(blank.count)
self.sweep(blank)
def is_safe(self, btn):
x, y = btn.index
for index in self.field(x, y):
if index in self.mines:
return False
return True
def get_child_by_index(self, index):
for child in self.grid.children:
if child.index == index:
return child
def game_over(self, q=False, win=False):
if q == True:
sys.exit()
if win == True:
result = "Win"
elif win == False:
result = "lost"
view = TryAgain(
size_hint = (None, None),
width = self.width/2,
height = self.height/2,
center = self.center,
text = "You {}! Try Again?".format(result))
view.open()
class TryAgain(ModalView):
text = StringProperty('')
def quit(self):
sys.exit()
class Menu(Screen):
pass
class Manager(ScreenManager):
menu = ObjectProperty(None)
game = ObjectProperty(None)
class MineSweeperApp(App):
def build(self):
return Manager()
if __name__ == "__main__":
MineSweeperApp().run()
答案 0 :(得分：8)
Widget完成实例化之前，不会应用 kv规则。在这种情况下，您的Manager小部件是初始小部件 - 它反过来会创建其他小部件，包括RootWidget。这意味着在您的RootWidget.__init__ ids尚未填充！它们将在Manager完成实例化后立即执行 - 所以最好的方法是延迟初始化的其余部分，如下所示：
class RootWidget(Screen):
def __init__(self, **kwargs):
super(RootWidget, self).__init__(**kwargs)
Clock.schedule_once(self._finish_init)
def _finish_init(self, dt):
self.grid = self.ids.grid
# etc
答案 1 :(得分：0)
Since Kivy 1.11.0，您可以使用on_kv_post事件：
与小部件关联的所有kv规则以及所有这些规则中的所有其他小部件都应用了所有kv规则后触发。 base_widget 是最基本的窗口小部件，其实例化触发了kv规则（即，从Python实例化的窗口小部件，例如
MyWidget()）。
class RootWidget(Screen):
def on_post_kv(self, base_widget):
# self.ids will be populated here