为什么我无法访问 Screen.ids?

Why can#39;t I access the Screen.ids?(为什么我无法访问 Screen.ids?)

问题描述

更新:

Ryan P 的回答提供了解决方案.但是，我采用了该解决方案并对其进行了一些更改，丢弃了所有不存在的数据正确初始化为 RootWidget 的 on_enter 方法屏幕.这效果很好.

Ryan P's answer provided the solution. However, I took that solution and changed it up a bit, throwing all of the data that wasn't being properly initialised into the on_enter method of the RootWidget Screen. This has worked nicely.

直到今天，我的 RootWidget 类都是 Widget 的子类，我可以毫无问题地访问它的 id 来获取grid"的值.然而，我只是改变了它是Screen的子类，现在它说由于某种原因ID是空的……Screen确实有一个ID和所有这些，但由于某种原因，它没有注册那个我在 kv 文件中为 id ''grid'' 分配了一个 GridLayout.谁能告诉我为什么?

My RootWidget class was subclassing Widget until today, and I had no problem accessing it's ids to get the value of "grid". However, I just changed it to subclass Screen, and now it says the ids is empty for some reason... Screen does have an ids and all that, but for some reason, it isn't registering that I assigned a GridLayout to the id ''grid'' in the kv file. Can anyone tell me why?

回溯:

[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 文件:

#: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'

ma​​in.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()

推荐答案

在原始 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 - 它反过来创建其他小部件，包括 RootWidget.这意味着您的 RootWidget.__init__ 中的 ids 尚未填充！它们将在 Manager 完成实例化后立即出现 - 所以最好的方法是延迟其余的初始化，如下所示:

kv rules are not applied until the original Widget has finished instantiating. In this case, your Manager widget is the initial widget - it, in turn, creates the other widgets including RootWidget. This means that in your RootWidget.__init__ the ids are not yet populated! They will be as soon as Manager finishes instantiating - so the best approach is to just delay the rest of your initialization, like so:

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

这篇关于为什么我无法访问 Screen.ids?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编程学习网！