[FIXED] Kivy - ScreenManager saying it does not recognize another screen name despite it being there?

Issue

So, I wanted to create an app that created tasks/habits in kivy. Basically, there would be a screen that shows you your tasks/habits, and you could click on a button to take you to another screen to create a new task/habit. You would input information about the task/habit in that screen, and click the submit button. The submit button would add the task/habit to the first screen. However, when I run my code, it works the first time. I can go to the second screen, add my habit/code and then go back to the first screen. However, when I click the button on the first screen, it gives me an error.

The error being: kivy.uix.screenmanager.ScreenManagerException: No Screen with name "second".

Here is my code:

main.py:

from kivy.lang import Builder
from kivy.properties import ObjectProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.widget import Widget
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.image import Image
from PIL import Image
import numpy as np

class FirstWindow(Screen):
    def add_label(self, name, time, date):
        label = Label(text= f' {name}, {time}, {date}')
        self.ids.boxlayout.add_widget(label)


class SecondWindow(Screen):
    a_task = False
    a_habit = False
    name = ""
    time = ""
    date = ""

    def task_button(self):
        self.a_task = True
        self.a_habit = False


    def habit_button(self):
        self.a_habit = True
        self.a_task = False


    def submit_button(self):
        self.name = self.ids.the_name.text
        self.time = f'{self.ids.time_spinner_1.text}:{self.ids.time_spinner_2.text}'
        self.date = f'{self.ids.date_spinner_1.text}/{self.ids.date_spinner_2.text}'


    def get_name(self):
        return self.name

    def get_time(self):
        return self.time

    def get_date(self):
        return self.date


kv = Builder.load_file('Button.kv')


class ButtonApp(App):
    def build(self):
        sm = ScreenManager()
        sm.add_widget(FirstWindow())
        sm.add_widget(SecondWindow())
        return sm

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

Button.kv:

<FirstWindow>:
    name: "first"
    BoxLayout:
        id: boxlayout
        orientation: "vertical"
        canvas.before:
            Color:
                rgba: (0.3,0.33,0.3,1)
            Rectangle:
                pos: self.pos
                size: self.size
        FloatLayout:
            Label:
                text: "To Do List"
                font_size: 32
                pos_hint: { 'right': 0.65, 'top': 1.4 }
        Button:
            text: "add a task"
            on_release: root.manager.current = "second"

<SecondWindow>:
    name: "second"
    BoxLayout:
        orientation: "vertical"
        spacing: "10dp"
        canvas.before:
            Color:
                rgba: (0.3,0.33,0.3,1)
            Rectangle:
                pos: self.pos
                size: self.size
        FloatLayout:
            Label:
                text: "Add A Task"
                font_size: 32
                pos_hint: { 'right': 0.65, 'top': 1.2 }
        BoxLayout:
            orientation: "horizontal"
            Button:
                text: "task"
                on_press: root.task_button()
            Button:
                text: "habit"
                on_press: root.habit_button()

        TextInput:
            id: the_name
            text: "Name"

        Label:
            text: "alert"

        BoxLayout:
            orientation: "horizontal"
            Spinner:
                id: time_spinner_1
                text: "00"
                values: ['1','2','3','4','5','6','7','8','9','10','11', '12']

            Spinner:
                id: time_spinner_2
                text: "00"
                values: ['01','02','03','04','05','06','07','08','09','10','11', '12', '13','14','15','16','17','18','19','20','21','22','23','24','25','26','27','28','29','30','31','32','33','34','35','36','37','38','39','40','41','42','43','44','45','46','47','48','49','50','51','52','53','54','55','56','57','58','59']

        BoxLayout:
            orientation: "horizontal"
            Spinner:
                id: date_spinner_1
                text: "00"
                values: ['1','2','3','4','5','6','7','8','9','10','11', '12']

            Spinner:
                id: date_spinner_2
                text: "00"
                values: ['01','02','03','04','05','06','07','08','09','10','11', '12', '13','14','15','16','17','18','19','20','21','22','23','24','25','26','27','28','29','30','31']



        Button:
            text: "submit"
            on_press: root.submit_button()
            on_release:
                root.manager.current = "first"
                root.manager.get_screen("first").add_label(root.get_name(), root.get_time(), root.get_date())

Solution

Your code:

def submit_button(self):
    self.name = self.ids.the_name.text
    self.time = f'{self.ids.time_spinner_1.text}:{self.ids.time_spinner_2.text}'
    self.date = f'{self.ids.date_spinner_1.text}/{self.ids.date_spinner_2.text}'

changes the name property of the SecondWindow Screen, so trying to change Screen to the second will no longer work. It looks like you are trying to use name for some other purpose. I suggest you use a variable with a different name.

Answered By - John Anderson
Answer Checked By - Pedro (JavaFixing Volunteer)