I don't know what I am doing wrong. I follow the tutorial but button appears only if i use .kv file.If I want to add it directly in python code,it doesn't appear.
class StackLayoutExample(StackLayout):
def _init__(self,**kwargs):
super().__init__(**kwargs)
b = Button(text='Z')
self.add_widget(b)
TheLabApp().run()
`
I tried to google it but still it works only with .kv file
Related
I have 2 buttons, the first is created in a .py file and the second in a .kv file, how can I make it so that when you click on a button that is created in .py, the text of the button that is created in .kv changes! how can i change it?
class Start(MDFloatLayout):
def test1(self):
self.button.text = 'Hello'
btn1.bind(on_release = lambda x: Start().test1())
but when you click on the button, the text of the button in .kv does not change; if you write print('Hello') there, then 'Hello' will be displayed, but the text of the button will not change! how can i change it?
The easiest way I have found to do this is to:
create an id in the kv file for the button
in the test1 function change the value of the id.text by calling self.buttonid.text = 'hello'
Let me know if you need more details, if you provide an example of your kv file I can show you how to edit it
I'm new to programming and trying to use Kivy to create a simple game.
I am following a tutorial, and I'm using VSCode, but I can't understand why the code I write in the .kvfile doesn't is used by the main.pyfile.
I have two files in the directory.
main.py
from kivy.app import App
from kivy.uix.widget import Widget
class MainWidget(Widget):
pass
class TheLabApp(App):
pass
TheLabApp().run()
thelab.kv
MainWidget:
<MainWidget>:
Button:
text: 'Hello'
size: 400, 200
I have installed a Kivy extension, and of course the Kivy module. But when I run the code the only thing that appears is a black screen, without the button.
What is happening?
I found the solution. It is required to save the .kv file before running the code, it is just such a sily thing, but if it isn't saved it is read like if it was empty, or never changed.
I'm trying to learn Kivy using their examples, however I'm having an issue. I'm using their button doc example:
from kivy.uix.button import Button
def callback(instance):
print('The button <%s> is being pressed' % instance.text)
btn1 = Button(text='Hello world 1')
btn1.bind(on_press=callback)
btn2 = Button(text='Hello world 2')
btn2.bind(on_press=callback)
However, the program runs and immediately closes. I assumed maybe its tkinter, where the program runs on a constant loop and you need to add something at the end so it doesn't close, but I couldn't find anything on their docs about that.
To reiterate, I don't get any errors, the file just runs, I get a very brief pop up, and then it ends. I don't get an interface.
Firstly, kivy need to loop for control all own functions. So we need a App class and have to return our layouts directly or layouts under Screen Manager. In Kivy-Button documentation, Kivy shows you only related part. So there is a no any App class or loop for control.So program runs and closes immediately because app class doesn't loop window.
If you're beginner and trying to learn kivy from documentation, you need to figure how Kivy actually works and how documentation explain things. I'm sharing this code below for you, you need to understand add-remove widgets ,set layouts,... in kivy from documentations or search for full-code examples not part.
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
class TestLayout(BoxLayout):
def __init__(self, **kwargs):
super(TestLayout, self).__init__(**kwargs)
self.orientation = 'vertical'
but1 = Button(text='Button1')
self.add_widget(but1)
but2 = Button(text='Button2')
self.add_widget(but2)
class MyApp(App):
def build(self):
return TestLayout()
if __name__ == '__main__':
MyApp().run()
When you understand how it works, you should start to use Screen Manager for easily create pages, send-get values (and many things) for your applications.I hope these helps you at the beginning. Good luck.
I'm new to Python and Kivy, and I'm trying to create multipage display of letters of the braille alphabet, with the corresponding braille's letter picture present in every page. I really want to learn more about creating Kivy desktop apps. I really hope you can help me. What I'm trying to do is have a page look like this:
I know how images and buttons are placed and customized in terms of size and position in the KV file. However what I need to learn is how add_widget() and clear_widget() will factor in this. I have read the Kivy docs but they barely explain how I could achieve what I need. What I thought of doing is using the from kivy.uix.screenmanager import ScreenManager, Screen feature, and then just create 26 screens and route them via on_click in the kv file. But that's tedious and too manual. Here's my code so far:
class LetterAScreen(Screen):
pass
class LetterBScreen(Screen):
pass
class LetterCScreen(Screen):
pass
class LetterDScreen(Screen):
pass
class LetterEScreen(Screen):
pass
class LetterFScreen(Screen):
pass
class LetterGScreen(Screen):
pass
#.... so and so until Letter Z
sm = ScreenManager(transition=SwapTransition())
#LearnScreen - Alphabet
sm.add_widget(LetterAScreen(name='lettera'))
sm.add_widget(LetterBScreen(name='letterb'))
sm.add_widget(LetterCScreen(name='letterc'))
sm.add_widget(LetterDScreen(name='letterd'))
sm.add_widget(LetterEScreen(name='lettere'))
sm.add_widget(LetterFScreen(name='letterf'))
sm.add_widget(LetterGScreen(name='letterg'))
sm.add_widget(LetterHScreen(name='letterh'))
sm.add_widget(LetterIScreen(name='letteri'))
sm.add_widget(LetterJScreen(name='letterj'))
sm.add_widget(LetterKScreen(name='letterk'))
sm.add_widget(LetterLScreen(name='letterl'))
sm.add_widget(LetterMScreen(name='letterm'))
sm.add_widget(LetterNScreen(name='lettern'))
sm.add_widget(LetterOScreen(name='lettero'))
sm.add_widget(LetterPScreen(name='letterp'))
sm.add_widget(LetterQScreen(name='letterq'))
sm.add_widget(LetterRScreen(name='letterr'))
sm.add_widget(LetterSScreen(name='letters'))
sm.add_widget(LetterTScreen(name='lettert'))
sm.add_widget(LetterUScreen(name='letteru'))
sm.add_widget(LetterVScreen(name='letterv'))
sm.add_widget(LetterWScreen(name='letterw'))
sm.add_widget(LetterXScreen(name='letterx'))
sm.add_widget(LetterYScreen(name='lettery'))
sm.add_widget(LetterZScreen(name='letterz'))
I haven't gotten around the kv file because i'm clueless how this will pan out. What I need to do is create widgets or a function that will swap out the images of the current letter and display those of the next or previous ones when the next/button is clicked, without having to switch screens every single time. I'm really unfamiliar with how functions work in Kivy and Python. I hope you could help me. Thank you.
Here is a simple solution to your problem. I'll leave it to you to modify and make it look and work exactly how you want :)
Learning the kv language is INCREDIBLY helpful, easy, and it can be picked up quite quickly.
main.py
from kivy.app import App
class MainApp(App):
alphabet = 'abcdefghijklmnopqrstuvwxyz'
def next_letter(self):
# Get a reference to the widget that shows the letters
# self.root refers to the root widget of the kv file -- in this case,
# the GridLayout
current_letter_widget = self.root.ids['the_letter_label']
# Get the letter currently shown
current_letter = current_letter_widget.text
# Find the next letter in the alphabet
next_letter_index = self.alphabet.find(current_letter) + 1
next_letter = self.alphabet[next_letter_index]
# Set the new letter in the widget that shows the letters
current_letter_widget.text = next_letter
MainApp().run()
main.kv
GridLayout: # This is the `root` widget of the main app class
cols: 1
Label:
text: "g"
id: the_letter_label # Setting an id for a widget lets you refer to it later
Button:
text: "Previous"
Button:
text: "Next"
on_release:
# the keyword `app` references the main app class, so we can call
# the `next_letter` function
app.next_letter()
I'm happy to address specific questions if you have them.
Follow up from Kivy class in .py and .kv interaction , but more complex.
Here is the full code of what I'm writing:
The data/screens/learnkanji_want.kv has how I want the code to be, but I don't fully understand how the class KanjiOriginScreen() plays it's role in screen management.
data/screens/learnkanji.kv works how I want it, but for this to work I have to put keyb_height in class KanjiOriginScreen() (main.py). However I want that code to be in the class LayoutFunction() (learnkanji.py).
Question
How can I put keyb_height in the function LayoutFunction() and access this in the .kv file in <LayoutFunction>?
Could you also explain why KanjiOriginScreen: can be put in learnkanji.kv without < > and the program still recognizes it should use this?
If anything is unclear, please ask :)
Edit
I found out that I didn't import the learnkanji.py in the learnkanji.kv file and that caused that it couldn't find the class 'LayoutFunction'.
#:import learnkanji data.screens.learnkanji
To answer your questions:
The way you are doing it should work. You should be able to access object attributes from kv. If your attribute is going to change, however, and you want the UI to update when it does, you should use Kivy Properties. If it is constant, a normal attribute works fine.
From the Kivy Docs, <Widget>: is a class rule that will be applied to every instance of that class. Widget: will create an actual instance of that class (in this case it is your root widget).
As for ScreenManager and Screens, you can think of them this way. Each Screen is it's own individual UI (it's own root widget). The screen manager is a container that holds your Screen and can swap between different Screens. This lets you create separate UIs that you can toggle between. Each UI is a separate widget tree with a Screen at its root. The docs are actually pretty good at describing ScreenManager.
How can I put keyb_height in the function LayoutFunction() and access this in the .kv file in ?
You can't do this with a function. You need to make LayoutFunction into a class to do this. Like so:
main.py
class LayoutClass(BoxLayout): # I made it a boxlayout, you could make it anything you want
keyb_height = NumericProperty(260) # from kivy.properties import NumericProperty
kv file:
<LayoutClass>: # can only access it this way if it's a class in main.py
something: root.keyb_height
Could you also explain why KanjiOriginScreen: can be put in learnkanji.kv without < > and the program still recognizes it should use this?
It sounds like you're asking how you can achieve this.. but I can't think why?
Unless you want it managed by a ScreenManager perhaps? However, the only way you can have KanjiOriginScreen within the kv file without the <> is if it is inside another root widget. For instance, see Testy and ScreenTwo as they are in the kv file under <Manager> in my answer to your other question(here). They are without <> because they are class instances, WITHIN another class(the Manager class). Only root widgets have the <> around them in the kv file. If none of this makes sense to you, you need to do a tutorial on kivy.
Check out this tutorial I made a while back, it explains a little about root widgets in kv(at around 4.30).
Sorry I was not clear with my question, but with the help on IRC on #Kivy I ended up with the following:
learnkanji.py
class LayoutFunctioning(BoxLayout):
keyb_height = NumericProperty(260)
learnkanji.kv
KanjiOriginScreen:
name: 'LearnKanji'
fullscreen: True
LayoutFunction:
id: lfunc
#...code...
height: lfunc.keyb_height #Instead of root.keyb_height
Now I understand how to use the id, I can use lfunc to call my code in LayoutFunction() :)