在 KivyMD 上的小部件之间添加数值

Posted 2023-04-14

【中文标题】在 KivyMD 上的小部件之间添加数值

【英文标题】：Adding numerical values among widgets on KivyMD

【发布时间】：2021-01-18 07:56:32

【问题描述】：

我正在构建一个作为差旅费用经理的应用程序。我目前正在尝试构建一个系统，您可以在其中将请求的金额插入 MDTextField 并按下按钮以确认请求。同时，在其他小部件上，我想将请求的总金额加起来。

即如果我在 TextField 上写 1000 并单击按钮“Ingresar Gasto”，则标签“MONTO TOTAL SOLICITADO”下方的值应该会更新，并且目标 MDTextField 和具有原始编号的 MDTextField 都应该具有正确格式的 $1,000.00。

对于我拥有相同小部件的所有扩展面板来说，同样的需要也是如此。

我尝试了以下方法：

扩展面板的Kivy代码：

<MyContentAliment>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_aliment_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            required: True
            on_text:
                root.limit_currency()

        MDRaisedButton:
            id: boton_aliment_viaje
            pos_hint: "x":0, "top":0.5
            text:'Ingresar Gasto'
            on_release:
                root.sumar_gasto()

MDCard 的 Kivy 代码（包含目标小部件）：

<TravelManagerWindow>:
    BoxLayout:
        size_hint:1,0.85
        pos_hint: "center_x": 0.5, "center_y":0.37
        adaptive_height:True
        height: self.minimum_height

        ScrollView:
            adaptive_height:True

            GridLayout:
                id: container
                size_hint_y: None
                cols: 1
                row_default_height: root.height*0.10
                height: self.minimum_height 

                MDBoxLayout:
                    adaptive_height: True
                    orientation: 'horizontal'
                    GridLayout:
                        id: panel_container
                        size_hint_x: 0.6
                        cols: 1
                        adaptive_height: True
            
                    MDBoxLayout:
                        size_hint_x: 0.05       
                    MDCard:
                        id: resumen_solicitud
                        size_hint: None, None
                        size: "250dp", "300dp"
                        pos_hint: "top": 0.9, "center_x": .5
                        elevation: 0.1

                        MDBoxLayout:
                            orientation: 'vertical'
                            canvas.before:
                                Color:
                                    rgba: 0.8, 0.8, 0.8, 1
                                Rectangle:
                                    pos: self.pos
                                    size: self.size
                            MDLabel:
                                text: 'Monto Total Solicitado'
                                font_style: 'Button'
                                halign: 'center'
                                font_size: (root.width**2 + root.height**2) / 15.5**4
                                size_hint_y: 0.2
                            MDSeparator:
                                height: "1dp"
                            MDTextField:
                                id: suma_solic_viaje
                                text: "$ 0.00"
                                bold: True
                                line_color_normal: app.theme_cls.primary_color
                                halign: "center"
                                size_hint_x: 0.8

最后但同样重要的是，Python 代码：

class TravelManagerWindow(Screen):
    viajeInicio = ObjectProperty(None)
    panel_container = ObjectProperty(None)
    travel_list = ObjectProperty(None)
    DateMDTextField = ObjectProperty(None)
    menu = ObjectProperty()

    # EXPANSION PANEL PARA SOLICITAR GV
    def set_expansion_panel(self):
        #FOOD PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food.png", 
                                     content=MyContentAliment(),
                                     panel_cls=MDExpansionPanelOneLine(
                                                 text="Alimentacion")))
        # CASETAS PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(
                               icon="casetas.png", 
                                     content=MyContentCasetas(),
                                           panel_cls=MDExpansionPanelOneLine(
                                                         text="Casetas")))
        # GAS PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="gas.png", 
                          content=MyContentGasolina(),
                                panel_cls=MDExpansionPanelOneLine(
                                                         text="Gasolina")))
        # HOSPEDAJE PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(
                 icon="hospedaje.png", content=MyContentHosped(),                                                         
                                 panel_cls=MDExpansionPanelOneLine(
                                                         text="Hospedaje")))
        # VARios PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(
                icon="varios.png", content=MyContentVarios(),                                                  
                        panel_cls=MDExpansionPanelOneLine(
                                                         text="Varios")))

所有面板容器都有相同的代码，仅引用不同的 小部件（为简单起见未添加）

class MyContentAliment(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_aliment_viaje.text) <= 3 and 
                (self.ids.monto_aliment_viaje.text).isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_aliment_viaje.text) == 4 and 
                (self.ids.monto_aliment_viaje.text).isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text[0] + "," + \
                                            self.ids.monto_aliment_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_aliment_viaje.text) == 5 and 
                (self.ids.monto_aliment_viaje.text).isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text[:2] + "," + \
                                            self.ids.monto_aliment_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_aliment_viaje.text) > 5 and 
                self.ids.monto_aliment_viaje.text.startswith('$') == False:
            self.ids.monto_aliment_viaje.text = self.ids.monto_aliment_viaje.text[:-1]

    def sumar_gasto(self):
        if self.ids.monto_aliment_viaje.text == "":
            pass
        else:
            travel_manager = TravelManagerWindow()
            monto_total = float(travel_manager.ids.suma_solic_viaje.text[2:])
            monto_total += float(self.ids.monto_aliment_viaje.text)
            travel_manager.ids.suma_solic_viaje.text= "$ " + str(monto_total)
            self.apply_currency_format()

### WINDOW MANAGER ################################

class WindowManager(ScreenManager):
    pass

ScreenManager().add_widget(LoginWindow(name='login'))
ScreenManager().add_widget(CreateAccountWindow(name='create'))
ScreenManager().add_widget(MainWindow(name='main'))
ScreenManager().add_widget(IngActivWindow(name='ingActiv'))
ScreenManager().add_widget(CronogramaWindow(name='cronograma'))
ScreenManager().add_widget(TravelManagerWindow(name='travelManager'))
ScreenManager().add_widget(SoporteTecnicoWindow(name='soporteTecnico'))

class powerApp2(MDApp):
    pass

if __name__ == "__main__":
    powerApp2().run()

由于 apply_currency_format 函数，目前我得到了正确的格式。然而，当我按下按钮时，目标文本字段的值保持不变。

非常感谢。

最小可重复示例的代码：

Python 代码：

from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
from kivymd.app import MDApp
from kivymd.uix.expansionpanel import MDExpansionPanel, MDExpansionPanelOneLine
from kivy.uix.boxlayout import BoxLayout


class MyContentAliment(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_aliment_viaje.text) <= 3 and self.ids.monto_aliment_viaje.text.isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_aliment_viaje.text) == 4 and self.ids.monto_aliment_viaje.text.isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text[0] + "," + \
                                        self.ids.monto_aliment_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_aliment_viaje.text) == 5 and self.ids.monto_aliment_viaje.text.isnumeric():
            self.ids.monto_aliment_viaje.text = "$" + self.ids.monto_aliment_viaje.text[:2] + "," + \
                                        self.ids.monto_aliment_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_aliment_viaje.text) > 5 and self.ids.monto_aliment_viaje.text.startswith('$') == False:
            self.ids.monto_aliment_viaje.text = self.ids.monto_aliment_viaje.text[:-1]

    def sumar_gasto(self):
        if self.ids.monto_aliment_viaje.text == "":
            pass
        else:
            travel_manager = TravelManagerWindow()
            monto_total = float(travel_manager.ids.suma_solic_viaje.text[2:])
            monto_total += float(self.ids.monto_aliment_viaje.text)
            travel_manager.ids.suma_solic_viaje.text = "$ " + str(monto_total)
            self.apply_currency_format()


class MyContentCasetas(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_casetas_viaje.text) <= 3 and self.ids.monto_casetas_viaje.text.isnumeric():
            self.ids.monto_casetas_viaje.text = "$" + self.ids.monto_casetas_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_casetas_viaje.text) == 4 and self.ids.monto_casetas_viaje.text.isnumeric():
            self.ids.monto_casetas_viaje.text = "$" + self.ids.monto_casetas_viaje.text[0] + "," + \
                                            self.ids.monto_casetas_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_casetas_viaje.text) == 5 and self.ids.monto_casetas_viaje.text.isnumeric():
            self.ids.monto_casetas_viaje.text = "$" + self.ids.monto_casetas_viaje.text[:2] + "," + \
                                            self.ids.monto_casetas_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_casetas_viaje.text) > 5 and self.ids.monto_casetas_viaje.text.startswith('$') == False:
            self.ids.monto_casetas_viaje.text = self.ids.monto_casetas_viaje.text[:-1]


class MyContentGasolina(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_gas_viaje.text) <= 3 and self.ids.monto_gas_viaje.text.isnumeric():
            self.ids.monto_gas_viaje.text = "$" + self.ids.monto_gas_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_gas_viaje.text) == 4 and self.ids.monto_gas_viaje.text.isnumeric():
            self.ids.monto_gas_viaje.text = "$" + self.ids.monto_gas_viaje.text[0] + "," + \
                                        self.ids.monto_gas_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_gas_viaje.text) == 5 and self.ids.monto_gas_viaje.text.isnumeric():
            self.ids.monto_gas_viaje.text = "$" + self.ids.monto_gas_viaje.text[:2] + "," + \
                                        self.ids.monto_gas_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_gas_viaje.text) > 5 and self.ids.monto_gas_viaje.text.startswith('$') == False:
            self.ids.monto_gas_viaje.text = self.ids.monto_gas_viaje.text[:-1]


class MyContentHosped(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_hosped_viaje.text) <= 3 and self.ids.monto_hosped_viaje.text.isnumeric():
            self.ids.monto_hosped_viaje.text = "$" + self.ids.monto_hosped_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_hosped_viaje.text) == 4 and self.ids.monto_hosped_viaje.text.isnumeric():
            self.ids.monto_hosped_viaje.text = "$" + self.ids.monto_hosped_viaje.text[0] + "," + \
                                           self.ids.monto_hosped_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_hosped_viaje.text) == 5 and self.ids.monto_hosped_viaje.text.isnumeric():
            self.ids.monto_hosped_viaje.text = "$" + self.ids.monto_hosped_viaje.text[:2] + "," + \
                                           self.ids.monto_hosped_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_hosped_viaje.text) > 5 and self.ids.monto_hosped_viaje.text.startswith('$') == False:
            self.ids.monto_hosped_viaje.text = self.ids.monto_hosped_viaje.text[:-1]


class MyContentVarios(BoxLayout):
    def apply_currency_format(self):
        # if len <= 3
        if len(self.ids.monto_varios_viaje.text) <= 3 and self.ids.monto_varios_viaje.text.isnumeric():
            self.ids.monto_varios_viaje.text = "$" + self.ids.monto_varios_viaje.text + '.00'
        # n,nnn
        elif len(self.ids.monto_varios_viaje.text) == 4 and self.ids.monto_varios_viaje.text.isnumeric():
            self.ids.monto_varios_viaje.text = "$" + self.ids.monto_varios_viaje.text[0] + "," + \
                                           self.ids.monto_varios_viaje.text[1:] + '.00'
        # nn,nnn
        elif len(self.ids.monto_varios_viaje.text) == 5 and self.ids.monto_varios_viaje.text.isnumeric():
            self.ids.monto_varios_viaje.text = "$" + self.ids.monto_varios_viaje.text[:2] + "," + \
                                           self.ids.monto_varios_viaje.text[2:] + '.00'

    def limit_currency(self):
        if len(self.ids.monto_varios_viaje.text) > 5 and self.ids.monto_varios_viaje.text.startswith('$') == False:
            self.ids.monto_varios_viaje.text = self.ids.monto_varios_viaje.text[:-1]


class LoginWindow(Screen):
    pass

class TravelManagerWindow(Screen):
    panel_container = ObjectProperty(None)

    # EXPANSION PANEL PARA SOLICITAR GV
    def set_expansion_panel(self):
        # FOOD PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food", content=MyContentAliment(),
                                                         panel_cls=MDExpansionPanelOneLine(text="Alimentacion")))
        # CASETAS PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food", content=MyContentCasetas(),
                                                         panel_cls=MDExpansionPanelOneLine(text="Casetas")))
        # GAS PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food", content=MyContentGasolina(),
                                                         panel_cls=MDExpansionPanelOneLine(text="Gasolina")))
        # HOSPEDAJE PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food", content=MyContentHosped(),
                                                         panel_cls=MDExpansionPanelOneLine(text="Hospedaje")))
        # VARIOS PANEL
        self.ids.panel_container.add_widget(MDExpansionPanel(icon="food", content=MyContentVarios(),
                                                         panel_cls=MDExpansionPanelOneLine(text="Varios")))

### WINDOW MANAGER ################################


class WindowManager(ScreenManager):
    pass

ScreenManager().add_widget(LoginWindow(name='login'))
ScreenManager().add_widget(TravelManagerWindow(name='travelManager'))


class reprodExample(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "Teal"
        return WindowManager()


if __name__ == "__main__":
    reprodExample().run()

KV 文件代码：

<WindowManager>:
    LoginWindow:
    TravelManagerWindow:

<LoginWindow>:
    MDRaisedButton:
        text: 'Enter'
        pos_hint: 'center_x': 0.5, 'center_y': 0.5
        size_hint: None, None
        on_release:
            root.manager.transition.direction = 'up'
            root.manager.current = 'travelManager'

<TravelManagerWindow>:
    name:'travelManager'
    on_pre_enter: root.set_expansion_panel()

    BoxLayout:
        orientation: 'vertical'
        size_hint:1,0.85
        pos_hint: "center_x": 0.5, "center_y":0.37
        adaptive_height:True
        height: self.minimum_height

        ScrollView:
            adaptive_height:True

            GridLayout:
                size_hint_y: None
                cols: 1
                row_default_height: root.height*0.10
                height: self.minimum_height

                BoxLayout:
                    adaptive_height: True
                    orientation: 'horizontal'

                    GridLayout:
                        id: panel_container
                        size_hint_x: 0.6
                        cols: 1
                        adaptive_height: True

                    BoxLayout:
                        size_hint_x: 0.05
                    MDCard:
                        id: resumen_solicitud
                        size_hint: None, None
                        size: "250dp", "300dp"
                        pos_hint: "top": 0.9, "center_x": .5
                        elevation: 0.1

                        MDBoxLayout:
                            orientation: 'vertical'
                            canvas.before:
                                Color:
                                    rgba: 0.8, 0.8, 0.8, 1
                                Rectangle:
                                    pos: self.pos
                                    size: self.size
                            MDLabel:
                                text: 'Monto Total Solicitado'
                                font_style: 'Button'
                                halign: 'center'
                                font_size: (root.width**2 + root.height**2) / 15.5**4
                                size_hint_y: 0.2
                            MDSeparator:
                                height: "1dp"
                            MDTextField:
                                id: suma_solic_viaje
                                text: "$ 0.00"
                                bold: True
                                line_color_normal: app.theme_cls.primary_color
                                halign: "center"
                                size_hint_x: 0.8
                                pos_hint: 'center_x': 0.5, 'center_y': 0.5
                            MDSeparator:
                                height: "1dp"
                            BoxLayout:
                                id: expense_graph
                                halign: 'center'

<MyContentAliment>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_aliment_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            required: True
            on_text:
                root.limit_currency()

        MDRaisedButton:
            id: boton_aliment_viaje
            pos_hint: "x":0, "top":0.5
            text:'Ingresar Gasto'
            on_release:
                root.sumar_gasto()

### CASETAS
<MyContentCasetas>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_casetas_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            #input_filter: 'float'
            required: True
            on_text:
                root.limit_currency()

        MDRaisedButton:
            id: boton_casetas_viaje
            pos_hint: "x":0, "top":0.5
            text:'Ingresar Gasto'
            on_release:
                root.apply_currency_format()

        BoxLayout:
            size_hint_x: 0.05

### GASOLINA
<MyContentGasolina>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_gas_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            #input_filter: 'float'
            required: True
            on_text:
                root.limit_currency()

        MDRaisedButton:
            id: boton_gas_viaje
            pos_hint: "x":0, "top":0.5
            text:'Ingresar Gasto'
            on_release:
                root.apply_currency_format()

        BoxLayout:
            size_hint_x: 0.05

 ### HOSPEDAJE
<MyContentHosped>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_hosped_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            #input_filter: 'float'
            required: True
            on_text:
                root.limit_currency()

    MDRaisedButton:
        id: boton_hosped_viaje
        pos_hint: "x":0, "top":0.5
        text:'Ingresar Gasto'
        on_release:
            root.apply_currency_format()

        BoxLayout:
            size_hint_x: 0.05

### VARIOS
<MyContentVarios>:
    adaptive_height: True
    MDBoxLayout:
        orientation:'horizontal'
        adaptive_height:True
        size_hint_x:self.width
        pos_hint: "center_x":0.5, "center_y":0.5
        spacing: dp(10)
        padding_horizontal: dp(10)
        MDLabel:
            text: 'Monto:'
            multiline: 'True'
            halign: 'center'
            pos_hint: "x":0, "top":0.5
            size_hint_x: 0.15
            font_style: 'Button'
            font_size: 19

        MDTextField:
            id: monto_varios_viaje
            hint_text: 'Monto a solicitar'
            pos_hint: "x":0, "top":0.5
            halign: 'left'
            size_hint_x: 0.3
            helper_text: 'Ingresar el monto a solicitar'
            helper_text_mode: 'on_focus'
            write_tab: False
            #input_filter: 'float'
            required: True
            on_text:
                root.limit_currency()

        MDRaisedButton:
            id: boton_varios_viaje
            pos_hint: "x":0, "top":0.5
            text:'Ingresar Gasto'
            on_release:
                root.apply_currency_format()

        BoxLayout:
            size_hint_x: 0.05

【问题讨论】：

请发minimal reproducible example。

【参考方案1】：

在您的 sumar_gasto() 方法中，该行：

travel_manager = TravelManagerWindow()

正在创建TravelManagerWindow 的新实例，该实例与您的 GUI 中显示的实例无关。因此，您对该实例所做的任何更改都不会影响您的 GUI。

如果没有看到更多您的代码，我无法猜测您如何访问实际在您的 GUI 中的 TravelManagerWindow 实例。

所以，您可以自己解决这个问题，也可以发帖 minimal, complete, verifiable example。

所以，随着附加代码的发布，我认为您可以替换：

travel_manager = TravelManagerWindow()

与：

travel_manager = MDApp.get_running_app().root.get_screen('travelManager')

这是因为MDApp 的root 小部件是WindowManager。

您还应该在kv 中为LoginWindow 添加name：

<LoginWindow>:
    name: 'login'
    MDRaisedButton:
        text: 'Enter'
        pos_hint: 'center_x': 0.5, 'center_y': 0.5
        size_hint: None, None
        on_release:
            root.manager.transition.direction = 'up'
            root.manager.current = 'travelManager'

我还注意到你有一些不必要的代码：

ScreenManager().add_widget(LoginWindow(name='login'))
ScreenManager().add_widget(TravelManagerWindow(name='travelManager'))

以上行没有任何效果，原因与travel_manager = TravelManagerWindow() 代码相同。调用ScreenManager() 会创建一个不在您的GUI 中的ScreenManager 的新实例，向该实例添加Widget 不会对您的GUI 产生任何影响。在kv 开头的WindowManager 规则将构建两个Screens，然后添加到WindowManager。

【讨论】：

感谢您的回复约翰，我编辑了我的帖子并添加了一个用于最小可重现示例的代码部分。非常感谢提前

约翰你能看看我最近发布的这个新问题吗？这是您帮助我解决的这个老问题的延续。我会分享链接。非常感谢。[***.com/questions/65583656/…