关闭 DatePicker（多屏）时出现 Kivy 错误

Question

我正在努力学习 Kivy。大多数东西在我单独编码时都能正常工作。但是当我像 MultiScreen 一样与其他代码结合时，我总是很挣扎。

这里我希望在关闭 DatePicker 后更改文本（id：date_label。相同的代码在没有 MultiScreen

的情况下工作

错误：第 31 行，在 on_cancel self.root.ids.date_label.text = "取消" AttributeError: 'CreateScreen' 对象没有属性 'root'

from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.uix.screenmanager import Screen, ScreenManager
from kivymd.uix.picker import MDDatePicker

Window.size = (350, 600)



class MenuScreen(Screen):
    def input_user(self):
        global username_1
        username_1 = self.userinput.text
        print(username_1)


class MainScreen(Screen):
    def user_name(self):
        print(username_1)


class CreateScreen(Screen):

    # Click Ok
    def on_save(self, instance, value, date_range):
        print(instance, value, date_range)

    
    # Click Close
    def on_cancel(self, instance, value): # HERE IS THE ERROR
        self.root.ids.date_label.text = "Cancel"

    def show_date_picker(self):
        date_dialog = MDDatePicker()
        date_dialog.bind(on_save=self.on_save, on_cancel=self.on_cancel)
        date_dialog.open()


sm = ScreenManager()
sm.add_widget(MenuScreen(name="menu"))
sm.add_widget(MainScreen(name="main-screen"))
sm.add_widget(CreateScreen(name="create-screen"))


class MyApp(MDApp):
    def build(self):

        screen = (Builder.load_file("kvfile.kv"))
        return screen


if __name__ == '__main__':
    MyApp().run()

KV 文件

ScreenManager:
    MenuScreen:
    MainScreen:
    CreateScreen:


<MenuScreen>:
    userinput: input
    name: "menu"
    BoxLayout:
        padding: "50dp"
        MDTextField:
            id: input
            padding: "10dp"
            hint_text: "Enter Username"
            pos_hint: {"center_x": 0.5, "center_y": 0.6}
    MDRectangleFlatButton:
        text: "Continue"
        pos_hint: {"center_x": 0.5, "center_y":0.5}
        on_release: root.manager.current = "main_screen" 
        on_press: root.input_user()


<MainScreen>:
    name: "main_screen"
    MDLabel:
        text: "Welcome"
        halign: "center"
        pos_hint: {"center_x": 0.5, "center_y": 0.9}
    MDRectangleFlatButton:
        text: "Back"
        pos_hint: {"center_x": 0.5, "center_y":0.2}
        on_press: root.manager.current = "menu"
    MDRectangleFlatButton:
        text: "Print"
        pos_hint: {"center_x": 0.5, "center_y":0.6}
        on_release: root.manager.current = "create_screen"
    MDRectangleFlatButton:
        text: "Empty"
        pos_hint: {"center_x": 0.5, "center_y":0.4}
        on_press: root.manager.current = "menu"


<CreateScreen>
    name: "create_screen"
    MDRaisedButton:
        text: "Date"
        pos_hint: {"center_x": 0.5, "center_y" : 0.5}
        on_release: root.show_date_picker()

    MDLabel:
        id: date_label
        text: "Select Date"
        pos_hint: {"center_x": 1, "center_y" : 0.4}

谢谢

Answer 1

错误告诉您'CreateScreen' object has no attribute 'root'。您正试图在行中引用 root：

self.root.ids.date_label.text = "Cancel"

在那一行中，self 是 CreateScreen 的实例，因此 self.root 正在尝试访问 self 的 root 属性（CreateScreen).如果您尝试访问 CreateScreen 的 ids，则只需使用：

self.ids.date_label.text = "Cancel"

关闭 DatePicker（多屏）时出现 Kivy 错误

Kivy Error when I close the DatePicker (MultiScreen)

python

kivy

kivymd