当用户按下底部的图标时，我试图提出一种逻辑来更改屏幕。我可以使用“测试”按钮来更改它的屏幕，但是底部工具栏图标有困难。下面是我的代码。当我按下第二个图标时，其打印的“ Hello”表示代码似乎可以正常工作，但我感觉缺少连接到不同屏幕的kivy功能。请让我知道我在做什么错。
from kivymd.app import MDApp
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.lang import Builder
from kivymd.uix.floatlayout import FloatLayout
from kivymd.uix.textfield import MDTextField
# Builder String
allLayout = '''
ScreenManager:
MainPage:
#List:
#History:
StudentName:
#Support:
#FAQ:
#TermsAndConditions:
#MyAccount:
<Button@MdButton>:
font_size: 20
background_color: 144/235,252/255,144/255,1
size_hint: 0.32, 0.07
<Ticker@MDTextField>:
font_size: 20
hint_text: "Enter student Name"
icon_right: 'database-search'
helper_text: "From the list (2nd icon in bottom bar)"
helper_text_mode: 'on_focus'
size_hint_x : None
width:200
<MainPage>:
name: 'mainpage1'
NavigationLayout:
ScreenManager:
Screen:
BoxLayout:
orientation:'vertical'
MDToolbar:
title: 'Main Page'
elevation: 10
right_action_items: [["dots-vertical", lambda x: x]]
# on_action_button: app.callback(self.icon)
Widget: #if you delete this line... you will spend hours figuring out like before
MDBottomAppBar:
MDToolbar:
icon: "history"
text_color: 0,0,0,0
icon_size: 0.5
type: "bottom"
mode: "end"
left_action_items: [["home", lambda x: x], ["view-list", lambda x: app.listScreen()], ["watch", lambda x: x], ["help", lambda x: x]]
Button:
text:"Class 1"
pos_hint: {'x': 0.025, 'y':.8}
Button:
text:"Class 2"
pos_hint: {'x': 0.345, 'y':.8}
Button:
text:"Class 3"
pos_hint: {'x': 0.665, 'y':.8}
Ticker:
pos_hint: {'x':0.025, 'y': .7}
Button:
text:"Test"
pos_hint: {'x': 0.665, 'y':.6}
on_release:
root.manager.current = 'student'
<StudentName>:
name: 'student'
MDLabel:
text: "Hi"
'''''
class MainPage(Screen):
pass
class StudentName(Screen):
pass
sm = ScreenManager()
sm.add_widget(MainPage(name = 'mainpage1'))
sm.add_widget(StudentName(name = 'student'))
class DemoApp(MDApp):
def listScreen(self):
self.current = StudentName()
print("Hello")
# root.manager.transition.direction = 'left'
def build(self):
self.theme_cls.primary_palette = 'Lime'
self.theme_cls.primary_hue = 'A700'
screen = Screen()
main_code = Builder.load_string(allLayout)
screen.add_widget(main_code)
return screen
DemoApp().run()
代码中发生了几件奇怪的事情。一种是代码：
sm = ScreenManager()
sm.add_widget(MainPage(name = 'mainpage1'))
sm.add_widget(StudentName(name = 'student'))
正在创建ScreenManager并添加Screens到其中。但是，然后不使用created ScreenManager（sm）。可以删除这些行。
另一个是build()方法代码：
screen = Screen()
main_code = Builder.load_string(allLayout)
screen.add_widget(main_code)
return screen
这段代码使用来构建整个显示器Builder.load_string()。该显示ScreenManager的根为（如字符串所定义allLayout）。然后将ScreenManager其添加到Screen（screen.add_widget(main_code)），然后将Screen其返回到App根窗口。我怀疑这不是您想要的，但这完全是法律法规。我怀疑该build()方法实际上应该是：
def build(self):
self.theme_cls.primary_palette = 'Lime'
self.theme_cls.primary_hue = 'A700'
main_code = Builder.load_string(allLayout)
return main_code
上面的代码使ScreenManagerApp的根目录显示出来。
最后一个问题是listScreen()方法。该行：
self.current = StudentName()
正在创建的新实例，Student然后将其赋值给一个名为变量current的DemoApp类。我怀疑您实际上想这样更改Screens：
def listScreen(self):
self.root.current = 'student'
print("Hello")
此代码将current应用程序根目录（即ScreenManager）的属性设置为StudentName该类的现有实例。
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