python kivy, why my "enter" button with "on_keyboard_down" not working - python-3.x

Question

I am working on the same issue from my previous post. Now I added screen manager, and I can switch to different pages.
why is my kivy program not calling the function from another class?
I am still confused about OOP with GUIs, however I tried the following, and none of them worked.
I tried to add an instance of Screen 1() in the main app(), and it did nothing. Then, I tried to add the contractor method init into Screen_1() and it says I don't have a build method. And few other ideas that didn't work at all.
Then I realized that there is no link between Screen_Manager() and Screen_1() because all of my methods are in Screen_1(), but the build method is returning Screen_Manager(). On my kv file, there is this code:
<Screen_Manager>:
Screen_1:
Screen_2:
isn't this is where the program "links" between the Screen_Manager() class to other classes?
if someone can help me understand what I am not understanding and help me correct my problem, it would help me to learn about kivy. I understand, <> is like apply to rules, which has 2 widgets screen 1 and screen 2, and also have their own rules.
here is my main.py
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.lang.builder import Builder
from kivy.properties import ObjectProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.textinput import TextInput
from kivy.modules import keybinding
from kivy.core.window import Window
from kivy.uix.screenmanager import ScreenManager, Screen
class Screen_Manager(ScreenManager):
pass
class Screen_1(Screen):
main_display = ObjectProperty()
text_input = ObjectProperty()
def plus_1(self):
self.value = int(self.main_display.text)
self.main_display.text = str(self.value + 1)
def minus_1(self):
self.value = int(self.main_display.text)
self.main_display.text = str(self.value - 1)
def up(self):
self.main_display.text = self.text_input.text
self.text_input.text = ''
class Keyboard(Widget):
def __init__(self, instance):
super().__init__()
self.a = instance
self.keyboard = Window.request_keyboard(None, self)
self.keyboard.bind(on_key_down=self.on_keyboard_down)
def on_keyboard_down(self, keyboard, keycode, text, modifiers):
if keycode[1] == 'enter':
self.a.up()
return True
class Screen_2(Screen):
pass
class MainApp(App):
def build(self):
self.title = "Number Control App"
self.sm = Screen_Manager()
key = Keyboard(self.sm)
return self.sm
if __name__=="__main__":
MainApp().run()
my kv file
<Screen_Manager>:
Screen_1:
Screen_2:
<Screen_1>:
name: "first"
main_display: display_1
text_input: text_input_1
#------inherenting from BoxLayout
BoxLayout:
orientation: "vertical"
#------begining of conent--
BoxLayout:
size_hint_y: 1
#-nexted content------
Label:
id: display_1
text: "0"
font_size: "150sp"
background_color: 0.1, 0.5, 0.6,
#--------
BoxLayout:
size_hint_y: .35
orientation: "horizontal"
#-nexted content------
Button:
text: "-"
font_size : "60sp"
on_press: root.minus_1()
#-nexted content------
Button:
text: "+"
font_size : "35sp"
background_color: (0, 1, 0, 1)
on_press: root.plus_1()
#--------
BoxLayout:
size_hint_y: .15
orientation: "horizontal"
#-nexted content-------
Button:
text: "Config"
size_hint_x: .25
on_release:
root.manager.current = "second"
root.manager.transition.direction = "left"
#-nexted content-------
TextInput:
id: text_input_1
size_hint_x: 1
hint_text: "Enter your initial # here"
multiline: False
#-nexted content-------
Button:
text: "Up"
size_hint_x: .25
on_press: root.up()
<Screen_2>:
name: "second"
Button:
text: "Go Back"
on_press:
app.root.current = "first"
root.manager.transition.direction = "right"enter code here
thanks again for taking the time to help.

Answer 1

Not sure I understand your question, but pressing Enter in your TextInput executed your code:
self.a.up()
but a in your KeyBoard is the Screen_Manager as set at the line:
self.sm = Screen_Manager()
key = Keyboard(self.sm)
and Screen_Manager has no up method. You can fix that by changing the code in your KeyBoard code to:
self.a.current_screen.up()
Note that this will only work when the current screen is Screen_1.