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Kivy: How can I connect TextInput in .KV file to a variable in Python?

I'm trying to create a simple login page for this app using Kivy.
I'm new to this, and I'm wondering how I can connect the Email TextInput to a variable (email_catch) in my python code, similar to a normal .get() function.
Python Code
from kivy.app import App
from kivy.uix.anchorlayout import AnchorLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.image import Image
from kivy.uix.button import Button
from kivy.uix.textinput import TextInput
from kivy.uix.widget import Widget
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty, StringProperty
class Login_Window(Screen):
def verify(self):
email_catch = self.root.ids.email.text
print(email_catch)
class MyApp(App):
def build(self):
return Login_Window()
if __name__ == "__main__":
MyApp().run()
.KV File
#:kivy 2.0.0
<Login_Window>:
GridLayout:
cols:1
size: root.width, root.height
GridLayout:
cols:2
Label:
text: 'Email'
TextInput:
multiline: False
id: email
Button:
text: 'Log In'
on_press: root.verify()

Since you are calling root in verify method of Login_Window class (where it (root) hasn't been defined yet) and not in the build method of the App class you are supposed to get an AttributeError .
In order to access an id within that class you should use self.ids. So the change you need:
def verify(self):
email_catch = self.ids.email.text
print(email_catch)

kivy._event.EventDispatcher.__init__ is raising the error "TypeError: object.__init__() takes exactly one argument (the instance to initialize)"

I'm relatively new to programming, little over 8 months or so, but I am learning kivy and python3 and I am attempting to create a password managing application and I would like for it to open a new screen when a button is pressed. but I am getting a Type Error.
import kivy
from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
class LoginScreen(Widget):
pass
class PasswordScreen(Widget):
pass
class PasswordApp(App):
def build(self):
sm = ScreenManager()
sm.add_widget(LoginScreen(name='login'))
sm.add_widget(PasswordScreen(name='passwords'))
return sm
if __name__ == '__main__':
PasswordApp().run()
heres the .kv code
<LoginScreen>:
GridLayout:
Button:
text: 'Goto passwords'
on_press: root.manager.current = 'passwords'
Button:
text: 'Quit'
<PasswordScreen>:
GridLayout:
Button:
text: 'My settings button'
Button:
text: 'logout'
on_press: root.manager.current = 'login'

Your LoginScreen and PasswordScreen extend Widget, and the Widget __init__() does not support a name property. Both those classes should extend Screen instead of Widget.

ScreenManager accepts only Screen widget. is raised while run a basic code

I am just learning some styles and designs of kivymd, but for some reason when the code runs
kv = Builder.load_file(MainLayout.kv), it raises the Exception(
kivy.uix.screenmanager.ScreenManagerException: ScreenManager accepts only Screen widget.
).
I just can't get it to run and any further. It has been raising this Exception no matter what changes I make.
And Just for Reference, this is the Code for the Main.py
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager
from kivymd.app import MDApp
from kivy.uix.boxlayout import BoxLayout
from kivymd.uix.list import MDList
from kivymd.theming import ThemableBehavior
from kivy.core.window import Window
class Login(Screen):
pass
class Settings(Screen):
pass
sm = ScreenManager()
sm.add_widget(Login(name='login'))
sm.add_widget(Settings(name='settings'))
sm.current = "login"
class DemoApp(MDApp):
class ContentNavigationDrawer(BoxLayout):
pass
class DrawerList(ThemableBehavior, MDList):
pass
def build(self):
self.theme_cls.primary_palette = "Teal"
Window.size = (412, 732)
#The Error Occurs when the KV file is loaded
kv = Builder.load_file("MainLayout.kv")
return kv
if __name__ == '__main__':
DemoApp().run()
This the Kivy File and in Login File I just have ( )
#: include Login.kv
#: include Settings.kv.
NavigationLayout:
id:nav_layout
ScreenManager:
Screen:
BoxLayout:
orientation: 'vertical'
MDToolbar:
title: "Kivy Demo App"
Widget:
ScreenManager:
id: screen_manager
Login:
id: login1
name: "login"
Settings:
id: settings1
name:"settings"
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
orientation: 'vertical'
padding: "8dp"
spacing: "8dp"
MDLabel:
text: 'Username'
MDLabel:
text: 'Captions'

Okay, it was not too hard to fix this. I just Changed the name of the class/page from settings to just setting and it fixed the problem. Not really sure how it affected the code but would love to know about the bug if anyone might know.

I ran into the same problem. The class name "Settings" causes the error "ScreenManager accepts only Screen widget". I changed the class name to "Setting" and the screen widget's id and name both to "setting" and everything works fine. Frustrating.

Kivy ScreenManager Errors

I'm a beginner with kivy language. I'm writing an app but I have some difficulties. My app is going to consist of a few screens so I decided to use the ScreenManager but each time I'm trying to launch the .py I get an error and this makes the python not responding. I have saved both the .py file and the .kv file in the same folder.
Traceback (most recent call last):
File "C:\Users\Eng. Aladdin Hammodi\Desktop\kivy\main.py", line 15, in <module>
presentation = Builder.load_file(Aladdin.kv)
NameError: name 'Aladdin' is not defined
Python file:
import kivy
kivy.require("1.9.1")
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.popup import Popup
from kivy.core.window import Window
from kivy.uix.textinput import TextInput
from kivy.properties import ObjectProperty
from kivy.uix.button import Button
from kivy.lang import Builder
presentation = Builder.load_file(Aladdin.kv)
class ScreenOne(Screen):
pass
class ScreenTwo(Screen):
pass
class ScreenManager(ScreenManager):
pass
class AladdinApp(App):
def build(self):
return presentation
sample_app = AladdinApp()
sample_app.run()
aladdin.kv
<ScreenOne>:
name:screen1
FloatLayout:
canvas:
source:'image1'
Label:
text:'Hello\n Welcome to my app\n'
font_size: 40
Button:
text: 'Next'
pos: 0,1
font_size:20
hint_size:0.1,0.05
on_press:root.manager.current='screen2'
<ScreenTwo>:
name:screen2
FloatLayout:
canvas:
source:'image1'
Label:
text:'Please insert your name'
text:'Please insert your Password'
font_size: 40
Button:
text: 'Next'
pos: 0,1
font_size:20
hint_size:0.1,0.05
on_press:root.manager.current='screen1'

The problem is in the line:
presentation = Builder.load_file(Aladdin.kv)
Aladdin is interpreted as the variable. If you want to pass a string to the method, call it like:
presentation = Builder.load_file("Aladdin.kv")

The files had a couple of issues:
#Artur R. Czechowski already pointed out missing quotation marks Builder.load_file('Aladdin.kv')
you did not define a root widget in the kv file or in your python code. I changed this by returning it in the build method def build(self): return ScreenManager()
it is not hint_size, correct is size_hint
I think you tried having an image as background. This is one way of doing it, do not forget the file ending e.g. .jpg
canvas.before:
Rectangle:
pos:self.pos
size: self.size
source:'image1.jpg'
As a side note: It makes sense to build your app step by step. Write as little code as possible which works and then check. Write some more code, check again. Happy coding with kivy :).
python code:
import kivy
kivy.require("1.9.1")
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.popup import Popup
from kivy.core.window import Window
from kivy.uix.textinput import TextInput
from kivy.properties import ObjectProperty
from kivy.uix.button import Button
from kivy.lang import Builder
#### in comment requested to also make cursor visible and not full screen ####
from kivy.config import Config
Config.set('graphics', 'fullscreen', '0')
Config.set('graphics','show_cursor','1')
####
Builder.load_file('Aladdin.kv')
class ScreenOne(Screen):
pass
class ScreenTwo(Screen):
pass
class ScreenManager(ScreenManager):
pass
class AladdinApp(App):
def build(self):
return ScreenManager()
AladdinApp().run()
revised kv file:
<ScreenManager>:
ScreenOne:
ScreenTwo:
<ScreenOne>:
name:'screen1'
FloatLayout:
canvas.before:
Rectangle:
pos:self.pos
size: self.size
source:'image1.jpg'
Label:
text:'Hello\n Welcome to my app\n'
font_size: 40
Button:
text: 'Next'
pos: 0,1
font_size:20
size_hint:0.1,0.05
on_press:root.manager.current='screen2'
<ScreenTwo>:
name:'screen2'
FloatLayout:
canvas.before:
Rectangle:
pos:self.pos
size: self.size
source:'image1.jpg'
Label:
text:'Please insert your name'
#text:'Please insert your Password'
font_size: 40
Button:
text: 'Next'
pos: 0,1
font_size:20
size_hint:0.1,0.05
on_press:root.manager.current='screen1'

Kivy's ScreenManager and Popups don't want to work together

as stated in the title - I'm stuck. I've been playing with the code around and everything works as long as I keep ScreenManager and Popup separate. Once combined - they refuse to cooperate. Anyway, here is the simple app that shows the problem I'm having.
from kivy.lang import Builder
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.popup import Popup
from kivy.uix.screenmanager import Screen, ScreenManager
class First(GridLayout,Screen):
def show_popup(self):
Popp().open()
pass
class Second(Screen):
pass
class Popp(Popup):
pass
class ScreenManagement(ScreenManager):
pass
app = Builder.load_file("main.kv")
class MainApp(App):
def build(self):
return app
if __name__ == "__main__":
MainApp().run()
And main.kv file
ScreenManagement:
First:
Second:
<First>:
name:"First"
rows: 2
Button:
text: "FirstButton"
on_release: app.root.current = "Second"
Button:
text: "Show popup"
on_release: root.show_popup()
<Second>:
name:"Second"
Button:
text: "BUTTON"
on_release: app.root.current = "First"
<Popp>:
title: "testing"
text: "Hello world"
size_hint: None,None
size: 400,400
auto_dismiss: False
Button:
text: "Okay"
on_press: root.dismiss()
App starts, first and second screen are working but when trying to get popup up I end up with:
kivy.uix.popup.PopupException: Popup can have only one widget as content
Somehow Screen is seen as a widget inside of Popp? Or am I terribly misinterpreting kivy docs?

It's a bug with loading kv file, it should throw an exception in this case.
What you are doing in the code is loading the kv file twice, what causes some weird behavior. Just delete the Builder.load_file(..) and it will work. The file is going to be loaded automatically.
Also, never do double subclassing of widgets like class First(GridLayout, Screen) as it might lead to some problems. Instead, create a grid layout inside the screen.

Put the elements in the Popup inside a layout, for example: Boxlayout.
Here's what I mean:
<Popp>:
title: "testing"
BoxLayout:
orientation: 'vertical'
size_hint: None,None
size: 400,400
Label:
text: "Hello world"
Button:
text: "Okay"
on_press: root.dismiss()

I have same problem with using kivy Builder.load_file and Popup, they dont work together.
the solution is simple, build popup in python code side. this is a loading popup example:
python:
from kivy.app import App
from kivy.uix.popup import Popup
from kivy.factory import Factory
from kivy.properties import ObjectProperty
from kivy.clock import Clock
from kivy.lang import Builder
from kivy.uix.popup import Popup
from kivy.uix.image import Image
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout
import time, threading
buildKV = Builder.load_file("example.kv")
class ExampleApp(App):
def show_popup(self):
content = BoxLayout(orientation= "vertical")
image=Image(source= 'files/loading.gif', anim_delay= 0)
label=Label(text= 'Model is Running.\nBe Patient Please.')
content.add_widget(image)
content.add_widget(label)
self.popup = Popup(title='Model is Running.',
size_hint=(.250, .785),
content=content, auto_dismiss=False)
self.popup.open()
def process_button_click(self):
# Open the pop up
self.show_popup()
# Call some method that may take a while to run.
# I'm using a thread to simulate this
mythread = threading.Thread(target=self.something_that_takes_5_seconds_to_run)
mythread.start()
def something_that_takes_5_seconds_to_run(self):
thistime = time.time()
while thistime + 10 > time.time(): # 5 seconds
time.sleep(1)
# Once the long running task is done, close the pop up.
self.pop_up.dismiss()
if __name__ == "__main__":
ExampleApp().run()
kivy:
BoxLayout:
Button:
height: 40
width: 100
size_hint: (None, None)
text: 'Click Me'
on_press: app.process_button_click()