我试图从我的.py文件中访问.kv文件中由其ID定义的按钮/标签，并更改其“text”值。 所以我在构建函数中写道：
#self.root.ids.button.text='newValue'
它说AttributeError: 'NoneType' object has no attribute 'ids'
我尝试过很多方法从我班上的其他地方访问'self.root'，但是没有一种方法可以工作。
我想知道为什么我班上没有自我根源？
这是我的kv档案：
<MyRun>:
BoxLayout:
id:bx1
orientation: 'vertical'
spacing: 10
padding: [20]
canvas:
Color:
rgba: .6, .6, .6, .3
Rectangle:
size: root.size
source: 'pic\germanFlag.png'
ActionBar:
ActionView:
id: av
ActionPrevious:
with_previous: False
title: 'DeutschLerne'
Label:
id:qtitle
text: 'Percentage of Question Answered:{}%'.format(int(7))
font_size: '30sp'
size_hint_y: None
height: '48dp'
Label:
id:qbody
text: 'The answer is '+('{}'.format(str("Richtig!")) if 1>0 else '{}'.format(str("Falsch!")))
color: [.3, 1, .5, 1] if 1>0 else [1, .2, .3, 1]
font_size: '30sp'
size_hint_y: None
height: '48dp'
Widget:
canvas:
Color:
rgba: .6 , .6 , .6 , .3
Rectangle:
source: "pic\questionCanvas.png"
size: [self.width,self.height*3]
pos: [self.x,self.y-300]
BoxLayout:
id:bx2
spacing: 10
padding: [10, 200 , 10 , 0]
Button:
id:selA
text: 'A'
size_hint_y: None
size_hint_x: .5
on_release: app.answer(self.text)
on_release: app.disableButton(self)
Button:
id:selB
text: 'B'
size_hint_y: None
size_hint_x: .5
on_release: app.answer(self.text)
on_release: app.disableButton(self)
Button:
id:selC
text: 'C'
size_hint_y: None
size_hint_x: .5
on_release: app.answer(self.text)
on_release: app.disableButton(self)
Button:
id:selD
text: 'D'
size_hint_y: None
size_hint_x: .5
on_release: app.answer(self.text)
on_release: app.disableButton(self)
#on_release: app.go_screen(0)
ProgressBar:
id: pb
size_hint_x: 1
size_hint_y: None
height: '48dp'
value: (app.time * 20) % 100.
这是我的主要课程，Desutsch.py
from time import time
from kivy.app import App
from os.path import dirname, join
from kivy.properties import NumericProperty, StringProperty, BooleanProperty,\
ListProperty,OptionProperty
from kivy.clock import Clock
from kivy.animation import Animation
from kivy.uix.screenmanager import Screen
from kivy.uix.gridlayout import GridLayout
from kivy.lang import Builder
from functools import partial
from kivy.uix.boxlayout import BoxLayout
from kivy.app import App
import random
NUM_OF_NOUN = 416 #constant . don't change its value
class MyRun(BoxLayout):
pass
class DeutschApp(App):
index = NumericProperty(-1)
challenges = NumericProperty(0)
time = NumericProperty(0)
wl = ListProperty([])
len = 0
ans = [] #.[0] => answer [1:3]
ansID=[] #.[0] => answer [1:3]
order=[] #random list(1~4)
def build(self):
Builder.load_file('Question.kv')
self.title = 'Destsch Lernen'
Clock.schedule_interval(self._update_clock, 1 / 60.)
self.screens = {}
self.available_screens = sorted([
'Menu','Question'])
len = self.loadWordList('default.txt')
self.question(len)
self.root.ids.selA.text='newValue'
return MyRun()
def go_screen(self, idx):
self.index = idx
self.root.ids.sm.switch_to(load_screen(idx), direction='left')
def load_screen(self, index):
if(0==index):
screen = Builder.load_file('Question.kv')
if(1==index):
screen = Builder.load_file('Menu.kv')
self.screens[index] = screen
return screen
#load question from local file
def loadWordList(self,WordList):
fd = open (WordList,'r')
fd.readline()
for line in fd:
#line.split("|"):id|german|translation|[sentence1^^sen2^^]|hisCount|dailyCount|percentage
line = line.rstrip("\n")
tmp = line.split('|')
tmp[3] = tmp[3].replace("[", "")
tmp[3] = tmp[3].replace("]", "")
sen = tmp[3].split('^^')
self.wl.append({'id': int(tmp[0]), 'german': tmp[1],'translation': tmp[2], 'sentences': sen, 'hisCount': int(tmp[4]), 'dailyCount': int(tmp[5]), 'percentage':int(tmp[-1]) })
#sentence encode not good
print tmp[0]
self.len = int(tmp[0]) #self.len = self.len+1
print self.len
self.question(self.len)
return self.len
def question(self,len):
x = random.randint(0,len)
ans = self.ans
ansID = self.ansID
#id0~416 =nouns #Nouns self.wl[x].get('german')
if x in range(0,NUM_OF_NOUN+1):
qType = 0 #0=def , 1=senten 2=pic qType= random.randint(0,2)
if (0==qType):
ans.append({'id':x , 'sel':self.wl[x].get('translation')})
ansID.append( int(x) )
for all in range(0,3):
y = random.randint(0,NUM_OF_NOUN+1)
while( (y in ansID) or (y not in range(0,NUM_OF_NOUN+1)) ):
y = random.randint(0,NUM_OF_NOUN+1)
ans.append({'id':y , 'sel':self.wl[y].get('translation')})
ansID.append( int(y) )
print ans
#elif:
#else:
#assign selections to buttons randomly
order = self.RandomSelList
print order
def RandomSelList(self):
a = random.sample(range(4), 4)
return a
def checkAnswer(self,ansList,choice):
right = 0
print "++"
print ansList
print choice
return right
def answer(self,choice):
#print self.order[0]
self.checkAnswer(self.ans,choice)
print 'answer(%s)'%choice
def Test(len):
print random.randint(0,len)
def _update_clock(self, dt):
self.time = time()
#modify screen
def selChange(self,button,sel):
print 'selChange()'
print self
print self.root
print super
#self.root.ids.button.text='sel'
def disableButton(self,button):
button.disabled = True
print super
#Clock.schedule_interval(Test(len), 1)
if __name__=='__main__':
DeutschApp().run()
我是新来的。对不起，丑陋的代码。我还在学习如何提出一个好问题。
答案 0 :(得分：1)
root属性设置为从构建方法返回的任何内容，因此当您尝试访问它时它不存在（或者具体地说，默认值为None）。
你不需要它，因为无论如何你都有对小部件的引用。您可以将构建方法的结尾更改为
root = MyRun()
root.ids.selA.text='newValue'
return root