将 ScreenManager 与每个屏幕的单独 py 和 kv 文件一起使用

Question

I'm making a calculator app and I want to be able to use separate kv and py files for each screen, I haven't found any documentation or tutorial about this and the only answer I have found doesn't give a code example so I'm not sure how to implement it. Also the buttons on calc.kv send a callback to calc.py by referencing it in root so that could probably cause a problem because the root is screenmanager

If you try to open the calculator from the toolbar it will return this error message:

 screen = self.get_screen(value)
   File "C:\Python38\lib\site-packages\kivy\uix\screenmanager.py", line 1071, in get_screen
     raise ScreenManagerException('No Screen with name "%s".' % name)
 kivy.uix.screenmanager.ScreenManagerException: No Screen with name "calc".

here is the code:

calc.py

from logging import root
from kivymd.app import MDApp
from kivy.uix.widget import Widget
from kivy.core.window import Window
from kivy.properties import StringProperty
from kivy.lang import Builder


prev = ""
expression = "" 
prox = "" 
class calc(Widget):
    pass
    out = StringProperty('')
    Window.size = (420, 200)
    Window.minimum_width, Window.minimum_height = Window.size
    
    
    
    def my_callback(self, inpt):
        global prev
        global expression
        global prox
        
            
        if inpt == "=":
            prox = str(eval(expression))
            self.out = prox
            expression = ""
            prev = prox
            
            
        elif inpt == "ac":
            expression = ""
            prev = ""
            prox = ""
            self.out = expression
        
        
            
        else:
            expression = prev + inpt
            prev = expression
            self.out = expression
        
         
        
                    
class calcApp(MDApp):  
    def build(self):
        def press(text):
            print("called: ", text)
    
        return calc()


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

calc.kv

#:kivy 1.0.9

   

<calc>:
    BoxLayout:
        orientation: 'vertical'
        
        cols: 2
        size: root.width, root.height

        MDLabel:
            id: 'output'
            text: str(root.out)
            size_hint: 1, 0.2
            halign: 'center'

        GridLayout:
                       
            cols: 5
            MDFlatButton:
                
                text: '1'
                on_press: root.my_callback(self.text)
                
            MDFlatButton:
                
                text: '2' 
                on_press: root.my_callback(self.text)
            
            MDFlatButton:
                
                text: '3'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '-'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: 'ac'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '4'  
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '5' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '6'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '+' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: '('
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '7' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '8' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '9' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '*'
                on_press: root.my_callback(self.text)
            
            MDFlatButton:
                text: ')'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '0' 
                on_press: root.my_callback(self.text)
            MDFlatButton:
                
                text: '.'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: '/'
                on_press: root.my_callback(self.text)

            
            MDFlatButton:
                
                text: '**'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '='
                on_press: root.my_callback(self.text)            
            

main.kv

#:kivy 1.0.9

#: include calc.kv

NavigationLayout:
    id: nav_layout

    ScreenManager:

        Screen:

            BoxLayout:
                orientation: 'vertical'

                MDToolbar:
                    title: app.title
                    elevation: 10
                    left_action_items: [['menu', lambda x: nav_drawer.set_state()]]

                ScreenManager:
                    id: screen_manager
                    calculator:
                        
                    

    MDNavigationDrawer:
        id: nav_drawer

        BoxLayout:
            orientation: 'vertical'
            padding: '8dp'
            spacing: '8dp'

            Image:
                size_hint: None, None
                size: '280dp', "200dp"
                source: "logo.png"
            
            ScrollView:
            
                MDList:

                    OneLineIconListItem:
                        text: "calculadora"
                        on_release:
                            screen_manager.current = 'calc'
                            nav_drawer.set_state()
                        IconLeftWidget:
                            icon: 'view-dashboard'

main.py

import calc
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager

class ScreenManager(ScreenManager):
    pass

class MyApp(MDApp):
    def build(self):
        self.title = "calculadora"
        self.theme_cls.primary_palette = "Green"
        return Builder.load_file("main.kv")


MyApp().run()

thanks in advance.

Answer 1

You need to give a name to the <calc> in the calc.kv file and instead of inheriting from the Widget class, inherit from the Screen class in the calc.py file. After that you need to load the calc.kv file in main.py using Builder.load_file("calc.kv") and then add the calc() Screen in your.kv with a function like on_release

calc.py (just change inheritance from Widget to Screen over here)

from logging import root
from kivymd.app import MDApp
from kivy.uix.screenmanager import Screen
from kivy.core.window import Window
from kivy.properties import StringProperty
from kivy.lang import Builder


prev = ""
expression = "" 
prox = "" 
class calc(Screen):
    out = StringProperty('')
    Window.size = (420, 200)
    Window.minimum_width, Window.minimum_height = Window.size
    
    
    
    def my_callback(self, inpt):
        global prev
        global expression
        global prox
        
            
        if inpt == "=":
            prox = str(eval(expression))
            self.out = prox
            expression = ""
            prev = prox
            
            
        elif inpt == "ac":
            expression = ""
            prev = ""
            prox = ""
            self.out = expression
        
        
            
        else:
            expression = prev + inpt
            prev = expression
            self.out = expression
        
         
        
                    
class calcApp(MDApp):  
    def build(self):
        def press(text):
            print("called: ", text)
    
        return calc()


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

calc.kv (just give a name to the class for reference)

#:kivy 1.0.9

   

<calc>:
    name: 'calc'
    BoxLayout:
        orientation: 'vertical'
        
        cols: 2
        size: root.width, root.height

        MDLabel:
            id: 'output'
            text: str(root.out)
            size_hint: 1, 0.2
            halign: 'center'

        GridLayout:
                       
            cols: 5
            MDFlatButton:
                
                text: '1'
                on_press: root.my_callback(self.text)
                
            MDFlatButton:
                
                text: '2' 
                on_press: root.my_callback(self.text)
            
            MDFlatButton:
                
                text: '3'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '-'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: 'ac'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '4'  
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '5' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '6'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '+' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: '('
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '7' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '8' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '9' 
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '*'
                on_press: root.my_callback(self.text)
            
            MDFlatButton:
                text: ')'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '0' 
                on_press: root.my_callback(self.text)
            MDFlatButton:
                
                text: '.'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                text: '/'
                on_press: root.my_callback(self.text)

            
            MDFlatButton:
                
                text: '**'
                on_press: root.my_callback(self.text)

            MDFlatButton:
                
                text: '='
                on_press: root.my_callback(self.text)

main.py (just load calc.kv in the beginning)

import calc
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager

Builder.load_file("calc.kv")

class MyApp(MDApp):
    def build(self):
        self.title = "calculadora"
        self.theme_cls.primary_palette = "Green"
        return Builder.load_file("main.kv")


MyApp().run()

main.kv (just import the calc class, and add its object to the manager)

#:kivy 1.0.9
#:import calc calc.calc

NavigationLayout:
    id: nav_layout

    ScreenManager:

        Screen:

            BoxLayout:
                orientation: 'vertical'

                MDToolbar:
                    title: app.title
                    elevation: 10
                    left_action_items: [['menu', lambda x: nav_drawer.set_state()]]

                ScreenManager:
                    id: screen_manager
                    calculator:
                        
                    

    MDNavigationDrawer:
        id: nav_drawer

        BoxLayout:
            orientation: 'vertical'
            padding: '8dp'
            spacing: '8dp'

            Image:
                size_hint: None, None
                size: '280dp', "200dp"
                source: "logo.png"
            
            ScrollView:
            
                MDList:

                    OneLineIconListItem:
                        text: "calculadora"
                        on_release:
                            screen_manager.add_widget(calc())
                            screen_manager.current = 'calc'
                            nav_drawer.set_state()
                        IconLeftWidget:
                            icon: 'view-dashboard'