KivyMD如何从MDToolbar的left_action_items返回上一界面？
How to go back to the previous screen from left_action_items of MDToolbar in KivyMD?
我按照 KivyMD 文档中的步骤创建了一个 NavigationDrawer，因此，我创建了它并且一切正常，但问题是 return 到第一个屏幕。当我单击 MDToolbar 中的左箭头时，我想返回到第一个屏幕（名称为 'main' 的屏幕），但我没有做任何工作。
KV 文件：
<ItemDrawer>:
theme_text_color: 'Custom'
on_release: self.parent.set_color_item(self)
IconLeftWidget:
id: icon
icon: root.icon
theme_text_color: 'Custom'
text_color: root.text_color
<ContentNavigationDrawer>:
orientation: 'vertical'
padding: '8dp'
spacing: '8dp'
AnchorLayout:
anchor_x: 'left'
size_hint_y: .3
ScrollView:
MDList:
OneLineIconListItem:
text: 'Reminders'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'RemindersWindow'
IconLeftWidget:
icon: 'bookmark-outline'
OneLineIconListItem:
text: 'To Do'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'ToDoWindow'
IconLeftWidget:
icon: 'check-outline'
OneLineIconListItem:
text: 'Settings'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'SettingsWindow'
IconLeftWidget:
icon: 'cog-outline'
OneLineIconListItem:
text: 'About'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'AboutWindow'
IconLeftWidget:
icon: 'information-outline'
Screen:
MDNavigationLayout:
ScreenManager:
id: screen_manager
Screen:
name: 'main'
MDToolbar:
title: 'Remindy'
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["menu", lambda x: nav_drawer.set_state('open')]]
MainScreen:
Screen:
name: 'SettingsWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
title: 'Settings'
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
OneLineIconListItem:
text: 'Themes'
pos_hint: {'center_x': .5, 'y': .8}
on_release: app.picker_theme()
IconLeftWidget
icon: 'palette-outline'
OneLineIconListItem:
text: 'Language'
pos_hint: {'center_x': .5, 'y': .7}
on_release:
IconLeftWidget:
icon: 'earth'
Screen:
name: 'RemindersWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'My Reminders'
halign: 'center'
Screen:
name: 'AboutWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'About'
halign: 'center'
Screen:
name: 'ToDoWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'To-Do'
halign: 'center'
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
<MainScreen@FloatLayout>:
name: 'MainScreen'
FloatLayout:
orientation: 'vertical'
MDFloatingActionButton:
icon: 'pencil-plus-outline'
pos_hint: {'x': .8, 'y': .1/2}
on_release: root.datacard()
<CardScreen>:
FloatLayout:
orientation: 'vertical'
MDCard:
size_hint: .8, .1
MDLabel:
id: base_label
text: 'New Reminder'
<CardBox>:
orientation: 'vertical'
size_hint: .7, .5
pos_hint: {'center_x': .5, 'center_y': .5}
MDBoxLayout:
size_hint_y: .5
md_bg_color: app.theme_cls.primary_color
MDLabel:
text: 'Add a Reminder'
font_style: 'H6'
theme_text_color: 'Custom'
text_color: 1, 1, 1, 1
halign: 'center'
MDIconButton:
icon: 'window-close'
on_release: root.closecard()
MDFloatLayout:
MDTextField:
id: title_id
hint_text: 'Title'
max_text_length: 15
required: True
helper_text_mode: 'on_error'
helper_text: 'This Field is Required.'
size_hint_x: .8
pos_hint: {'center_x': .5, 'y': .1}
MDFloatLayout:
orientation: 'horizontal'
MDRectangleFlatIconButton:
icon: 'clock-time-four-outline'
text: 'Hour'
pos_hint: {'x': .1, 'y': .3}
on_release: root.picker_hora()
MDRectangleFlatIconButton:
icon: 'calendar-outline'
text: 'Date'
pos_hint: {'x': .6, 'y': .3}
on_release: root.picker_data()
MDFloatLayout:
MDRectangleFlatButton:
text: 'Add'
size_hint_x: .8
pos_hint: {'center_x': .5, 'y': .2}
Python 文件：
import pickle
from kivy.app import App
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.uix.boxlayout import BoxLayout
from kivymd.uix.toolbar import MDToolbar
from kivy.properties import ObjectProperty
from kivymd.uix.list import StringProperty
from kivymd.theming import ThemableBehavior
from kivymd.uix.list import OneLineIconListItem
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.uix.floatlayout import FloatLayout
from kivymd.uix.picker import MDThemePicker
from kivymd.uix.picker import MDTimePicker
from kivymd.uix.picker import MDDatePicker
from kivymd.uix.list import MDList
from kivymd.uix.card import MDCard
class ItemDrawer(OneLineIconListItem):
icon = StringProperty()
class ContentNavigationDrawer(BoxLayout):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class MainScreen(FloatLayout):
def datacard(self):
self.add_widget(CardBox())
class CardBox(MDCard):
def closecard(self):
self.parent.remove_widget(self)
def picker_hora(self):
time_dialog = MDTimePicker()
time_dialog.open()
def picker_data(self):
date_dialog = MDDatePicker()
date_dialog.open()
def new_card(self):
# Remove and Create a New Card
self.parent.remove_widget(self)
title = self.ids.title_input.text
self.add_widget(CardScreen())
App.get_running_app().root.ids.base_label.text = title
class CardScreen(FloatLayout):
pass
class ReminderApp(MDApp):
Window.size = (400, 600)
def picker_theme(self):
theme_dialog = MDThemePicker()
theme_dialog.open()
def build(self):
return Builder.load_string(KV)
ReminderApp().run()
您需要从与 MDToolbar 关联的按钮触发一些操作才能切换到另一个屏幕。
为了简单使用，您可以使用默认函数 setattr 作为，
left_action_items: [["arrow-left", lambda *args : setattr(screen_manager, "current", "main")]]
或者对于高级用法，您可以参考一些相关 class 的函数，比如应用程序的子class，如
left_action_items: [["arrow-left", app.go_home]]
现在在那个方法中，
def go_home(self, *args):
# Access the `ScreenManager` and change the screen.
self.root.ids.screen_manager.current = "main"
# Some other actions.
另请注意，您应该将 kvlang 中的行 <MainScreen@FloatLayout> 更改为 <MainScreen>，因为您已经在 .py 中定义了它。否则可能会在日志中发出警告。
我按照 KivyMD 文档中的步骤创建了一个 NavigationDrawer，因此，我创建了它并且一切正常，但问题是 return 到第一个屏幕。当我单击 MDToolbar 中的左箭头时，我想返回到第一个屏幕（名称为 'main' 的屏幕），但我没有做任何工作。
KV 文件：
<ItemDrawer>:
theme_text_color: 'Custom'
on_release: self.parent.set_color_item(self)
IconLeftWidget:
id: icon
icon: root.icon
theme_text_color: 'Custom'
text_color: root.text_color
<ContentNavigationDrawer>:
orientation: 'vertical'
padding: '8dp'
spacing: '8dp'
AnchorLayout:
anchor_x: 'left'
size_hint_y: .3
ScrollView:
MDList:
OneLineIconListItem:
text: 'Reminders'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'RemindersWindow'
IconLeftWidget:
icon: 'bookmark-outline'
OneLineIconListItem:
text: 'To Do'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'ToDoWindow'
IconLeftWidget:
icon: 'check-outline'
OneLineIconListItem:
text: 'Settings'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'SettingsWindow'
IconLeftWidget:
icon: 'cog-outline'
OneLineIconListItem:
text: 'About'
on_press:
root.nav_drawer.set_state('close')
root.screen_manager.current = 'AboutWindow'
IconLeftWidget:
icon: 'information-outline'
Screen:
MDNavigationLayout:
ScreenManager:
id: screen_manager
Screen:
name: 'main'
MDToolbar:
title: 'Remindy'
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["menu", lambda x: nav_drawer.set_state('open')]]
MainScreen:
Screen:
name: 'SettingsWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
title: 'Settings'
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
OneLineIconListItem:
text: 'Themes'
pos_hint: {'center_x': .5, 'y': .8}
on_release: app.picker_theme()
IconLeftWidget
icon: 'palette-outline'
OneLineIconListItem:
text: 'Language'
pos_hint: {'center_x': .5, 'y': .7}
on_release:
IconLeftWidget:
icon: 'earth'
Screen:
name: 'RemindersWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'My Reminders'
halign: 'center'
Screen:
name: 'AboutWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'About'
halign: 'center'
Screen:
name: 'ToDoWindow'
FloatLayout:
orientation: 'vertical'
MDToolbar:
elevation: 10
pos_hint: {'top': 1}
left_action_items: [["arrow-left", lambda x: x]]
MDLabel:
text: 'To-Do'
halign: 'center'
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
<MainScreen@FloatLayout>:
name: 'MainScreen'
FloatLayout:
orientation: 'vertical'
MDFloatingActionButton:
icon: 'pencil-plus-outline'
pos_hint: {'x': .8, 'y': .1/2}
on_release: root.datacard()
<CardScreen>:
FloatLayout:
orientation: 'vertical'
MDCard:
size_hint: .8, .1
MDLabel:
id: base_label
text: 'New Reminder'
<CardBox>:
orientation: 'vertical'
size_hint: .7, .5
pos_hint: {'center_x': .5, 'center_y': .5}
MDBoxLayout:
size_hint_y: .5
md_bg_color: app.theme_cls.primary_color
MDLabel:
text: 'Add a Reminder'
font_style: 'H6'
theme_text_color: 'Custom'
text_color: 1, 1, 1, 1
halign: 'center'
MDIconButton:
icon: 'window-close'
on_release: root.closecard()
MDFloatLayout:
MDTextField:
id: title_id
hint_text: 'Title'
max_text_length: 15
required: True
helper_text_mode: 'on_error'
helper_text: 'This Field is Required.'
size_hint_x: .8
pos_hint: {'center_x': .5, 'y': .1}
MDFloatLayout:
orientation: 'horizontal'
MDRectangleFlatIconButton:
icon: 'clock-time-four-outline'
text: 'Hour'
pos_hint: {'x': .1, 'y': .3}
on_release: root.picker_hora()
MDRectangleFlatIconButton:
icon: 'calendar-outline'
text: 'Date'
pos_hint: {'x': .6, 'y': .3}
on_release: root.picker_data()
MDFloatLayout:
MDRectangleFlatButton:
text: 'Add'
size_hint_x: .8
pos_hint: {'center_x': .5, 'y': .2}
Python 文件：
import pickle
from kivy.app import App
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.uix.boxlayout import BoxLayout
from kivymd.uix.toolbar import MDToolbar
from kivy.properties import ObjectProperty
from kivymd.uix.list import StringProperty
from kivymd.theming import ThemableBehavior
from kivymd.uix.list import OneLineIconListItem
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.uix.floatlayout import FloatLayout
from kivymd.uix.picker import MDThemePicker
from kivymd.uix.picker import MDTimePicker
from kivymd.uix.picker import MDDatePicker
from kivymd.uix.list import MDList
from kivymd.uix.card import MDCard
class ItemDrawer(OneLineIconListItem):
icon = StringProperty()
class ContentNavigationDrawer(BoxLayout):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class MainScreen(FloatLayout):
def datacard(self):
self.add_widget(CardBox())
class CardBox(MDCard):
def closecard(self):
self.parent.remove_widget(self)
def picker_hora(self):
time_dialog = MDTimePicker()
time_dialog.open()
def picker_data(self):
date_dialog = MDDatePicker()
date_dialog.open()
def new_card(self):
# Remove and Create a New Card
self.parent.remove_widget(self)
title = self.ids.title_input.text
self.add_widget(CardScreen())
App.get_running_app().root.ids.base_label.text = title
class CardScreen(FloatLayout):
pass
class ReminderApp(MDApp):
Window.size = (400, 600)
def picker_theme(self):
theme_dialog = MDThemePicker()
theme_dialog.open()
def build(self):
return Builder.load_string(KV)
ReminderApp().run()
您需要从与 MDToolbar 关联的按钮触发一些操作才能切换到另一个屏幕。
为了简单使用，您可以使用默认函数 setattr 作为，
left_action_items: [["arrow-left", lambda *args : setattr(screen_manager, "current", "main")]]
或者对于高级用法，您可以参考一些相关 class 的函数，比如应用程序的子class，如
left_action_items: [["arrow-left", app.go_home]]
现在在那个方法中，
def go_home(self, *args):
# Access the `ScreenManager` and change the screen.
self.root.ids.screen_manager.current = "main"
# Some other actions.
另请注意，您应该将 kvlang 中的行 <MainScreen@FloatLayout> 更改为 <MainScreen>，因为您已经在 .py 中定义了它。否则可能会在日志中发出警告。