Kivy ScreenManager 的当前属性未找到具有所述名称属性的屏幕

问题描述 投票：0回答：1

我希望应用程序在一秒钟后将屏幕从 EntryWindow 屏幕更改为主屏幕。由于我在实际切换屏幕时已经遇到了 ScreenManager 当前属性的问题，因此我什至没有尝试使用 Clock 在 EntryWindow 一秒后触发切换。有人可以帮我解决这个问题吗？ 我有 python 版本 3.12、kivy 版本 2.3.0 和 kivymd 版本 1.2.0。 这是我的 .py 文件：

from kivymd.app import MDApp
from kivy.lang.builder import Builder
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.metrics import dp
from kivy.core.window import Window
from kivy.clock import Clock
import random as rd

Window.size = (360,640)

class MainApp(MDApp):
    
    def build(self):
        screen = Builder.load_file("myKv.kv")
        self.theme_cls.primary_palette ="Orange"
        self.theme_cls.primary_hue = "A700"
        self.theme_cls.theme_style="Dark"
        return screen
    
class EntryWindow(Screen):
    def on_enter(self):
        sm.current = "home"       


class Home(Screen):
    pass
class Exercises(Screen):
    pass     

class Gender(Screen):
    
    def on_enter(self):
        self.ids.extractedWord.color = (1,1,1,1)
        f = open(".venv/genderWordDatabase.txt")
        red = f.readlines()
        stripped = [elem.strip() for elem in red]
        separato = [elem.split() for elem in stripped]
        dizWords = {}
        for i in separato:
            dizWords[i[1]] = (i[0],i[2])
        print(dizWords)
        extracted = list(dizWords.keys())[rd.randint(0,len(dizWords)-1)]
        self.ids.extractedWord.font_style = "H6"
        self.ids.extractedWord.text = extracted
    
    def recordUpdate(self,extractedWord,operand):
        f = open(".venv/genderWordDatabase.txt", "r")
        red = f.readlines()
        f.close()
        for i in range(0,len(red)):
            if extractedWord in red[i]:
                red[i] = " ".join(red[i].strip("\n").split()[:-1]) + " " + str(int(red[i].strip("\n").split()[2])+operand)+"\n"
        g = open(".venv/genderWordDatabase.txt", "w")
        g.writelines(red)
        
    def wordExtraction(self):
        self.ids.extractedWord.color = (1,1,1,1)
        f = open(".venv/genderWordDatabase.txt")
        red = f.readlines()
        f.close()
        stripped = [elem.strip() for elem in red]
        separato = [elem.split() for elem in stripped]
        dizWords = {}
        for i in separato:
            dizWords[i[1]] = (i[0],i[2])
        extracted = list(dizWords.keys())[rd.randint(0,len(dizWords)-1)]
        self.ids.extractedWord.font_style = "H6"
        self.ids.extractedWord.text = extracted
    
    def check(self, answer):
        f = open(".venv/genderWordDatabase.txt")
        red = f.readlines()
        f.close()
        stripped = [elem.strip("\n").strip() for elem in red]
        separato = [elem.split() for elem in stripped]
        dizWords = {}
        for i in separato:
            dizWords[i[1]] = (i[0],i[2])
        print(dizWords)
        parola  = self.ids.extractedWord.text
        if dizWords[parola][0] == answer:
            self.ids.extractedWord.color = (0,1,0,1)
            self.ids.extractedWord.font_style = "H6"
            self.ids.extractedWord.text = "Right +1"
            #Chiamo la funzione che aggiorna il record di ciascuna parola
            self.recordUpdate(dizWords[parola][0],1)
            Clock.schedule_once(lambda dt: self.wordExtraction(), 1)
        else:
            self.ids.extractedWord.color = (1,0,0,1)
            self.ids.extractedWord.font_style = "Body1"
            self.ids.extractedWord.text = "Wrong -1, the correct one was: " + dizWords[self.ids.extractedWord.text][0]
            self.recordUpdate(dizWords[parola][0],-1)
            Clock.schedule_once(lambda dt: self.wordExtraction(), 2)

sm =  ScreenManager()
sm.add_widget(EntryWindow(name="starting"))
sm.add_widget(Home(name="home"))
sm.add_widget(Exercises(name="exercises"))
sm.add_widget(Gender(name="gender"))

MainApp().run()

这是我的 .kv 文件：

ScreenManager:
    EntryWindow:
    Home:
    Exercises:
    
<EntryWindow>:
    name: "starting"
    BoxLayout: 
        orientation: "vertical"
        Widget:
        MDLabel:
            text: "German"
            halign: "center"
            markup: True
            color: (1,1,1,1)
            font_style: "H3"
        MDLabel:
            text: "By Staffo"
            markup: True
            color: (1,1,1,1)
            halign: "center"
            font_style: "H6"
        Widget:
        Widget:
<Home>:
    name: "home"
    AnchorLayout:
        anchor_x: "center"
        anchor_y: "center"
        BoxLayout: 
            orientation: "vertical"
            spacing: 30
            Widget:
            MDFillRoundFlatButton:
                text: "exercises"
                pos_hint: {"center_x":0.5,"center_y":0.5}
                on_press:root.manager.current = "exercises"
            MDFillRoundFlatButton:
                text: "customize dictionary"
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press:root.manager.current = "customize"
            MDFillRoundFlatButton:
                text: "Settings"
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press:root.manager.current = "settings"
            MDFillRoundFlatButton:
                text: "Credits"
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press: root.manager.current = "credits"
            Widget:
<Exercises>:
    name: "exercises"
    AnchorLayout:
        anchor_x: "center"
        anchor_y: "center"
        BoxLayout: 
            orientation: "vertical"
            spacing: 30
            Widget:
            MDFillRoundFlatButton:
                text: "[b]M/F/N/P[/b]"
                markup: True
                pos_hint: {"center_x":0.5,"center_y":0.5}
                on_press:root.manager.current = "gender"
                text_color: (1,1,1,1)
                
            MDFillRoundFlatButton:
                text: "[b]Learn New Words[/b]"
                markup: True
                text_color: (1,1,1,1)
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press:root.manager.current = ""
            MDFillRoundFlatButton:
                text: "[b]Phrases[/b]"
                markup: True
                text_color: (1,1,1,1)
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press:root.manager.current = ""
            MDFillRoundFlatButton: 
                text: "[b]Listening[/b]"
                markup: True
                text_color: (1,1,1,1)
                pos_hint: {"center_x":0.5,"center_y":0.5}
                #on_press: root.manager.current = ""
            Widget:
<Gender>:
    name: "gender"
    AnchorLayout:
        anchor_x: "center"
        anchor_y: "center"
        BoxLayout:
            orientation: "vertical"
            Widget:
            Widget:
            Widget:
            MDCard:
                size_hint: .85, 2 
                pos_hint: {"center_x": .5, "center_y": .5}
                MDRelativeLayout:
                    MDLabel:
                        halign: "center"
                        id: extractedWord
                        markup: True
                        text: "extractedWord"
                        font_style: "H6"
                        color: (0,0,0,1)
            BoxLayout:
                spacing: 20
                Widget:
                MDFillRoundFlatButton:  
                    text: "[b]der[/b]"
                    markup: True
                    text_color: (1,1,1,1)
                    on_press: root.check("der")
                MDFillRoundFlatButton:  
                    text: "[b]die[/b]"
                    markup: True
                    text_color: (1,1,1,1)
                    on_press: root.check("die")
                MDFillRoundFlatButton:  
                    text: "[b]das[/b]"
                    markup: True
                    text_color: (1,1,1,1)
                    on_press: root.check("das") 
                Widget:
            Widget:
            Widget:
            Widget:
            Widget:

我收到以下错误：

kivy.uix.screenmanager.ScreenManagerException: No Screen with name "home".
python kivy kivy-language kivymd
1个回答
0
投票

问题出在你的 

on_enter()
EntryWindow
方法上。因为您的 
kv
创建了一个 
EntryWindow
作为第一个 
Screen
，并且其 
on_enter()
方法在创建其他 
Screens
之前就被触发了。一个简单的修复方法是使用 
screen
稍微延迟 
Clock.schedule_once()
的更改，如下所示：

class EntryWindow(Screen):
    def on_enter(self):
        # delay the Screen switch
        Clock.schedule_once(self.switch_screen)

    def switch_screen(self, _dt):
        self.manager.current = "home"

如您所见，在 

switch_screen()
方法中，我将 
sm
更改为 
self.manager
。您在代码中定义的 
sm
未使用，应删除：

# sm = ScreenManager()
# sm.add_widget(EntryWindow(name="starting"))
# sm.add_widget(Home(name="home"))
# sm.add_widget(Exercises(name="exercises"))
# sm.add_widget(Gender(name="gender"))
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