Develop Reference

Substituting text inside buttons with widgets

My app (using kivy) needs to substitute text with widgets inside an unspecified number of buttons using iteration. I don't use kv language. Only the last button displays any content.
My app should display an unspecified number of buttons. Simplified example:
import kivy
kivy.require('2.0.0')
from kivy.app import App
from kivy.core.window import Window
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.anchorlayout import AnchorLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.image import Image
class Layout(Widget):
def __init__(self, app):
super().__init__()
self.layout = BoxLayout(orientation='vertical', size=Window.size)
contents = ['text1', 'text2', 'text3']
for text in contents:
button = Button(height=300, size_hint=(1, None))
button.text = text
self.layout.add_widget(button)
self.add_widget(self.layout)
class MyApp(App):
def build(self):
self.form = Layout(self)
return self.form
def on_pause(self):
return True
if __name__ in ('__main__', '__android__'):
MyApp().run()
Only instead of text buttons display images with descriptions. I change the code:
import kivy
kivy.require('2.0.0')
from kivy.app import App
from kivy.core.window import Window
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.anchorlayout import AnchorLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.image import Image
class Layout(Widget):
def __init__(self, app):
super().__init__()
self.layout = BoxLayout(orientation='vertical', size=Window.size)
contents = [('img1', 'text1'), ('img2', 'text2'), ('img3', 'text3')]
for img, text in contents:
button = Button(height=300, size_hint=(1, None))
button_layout = BoxLayout(orientation='vertical', size_hint=(1, 1))
label = Label(text=text)
image = Image(source=f'{img}.jpg', size_hint=(1, 1), allow_stretch=True)
button_layout.add_widget(image)
button_layout.add_widget(label)
button.add_widget(button_layout)
self.layout.add_widget(button)
self.add_widget(self.layout)
class MyApp(App):
def build(self):
self.form = Layout(self)
return self.form
def on_pause(self):
return True
if __name__ in ('__main__', '__android__'):
MyApp().run()
And only the last button displays content.
As far as I can understand, at some point Python automatically gets read of the content of the previous button. How can I prevent it? Also what is the best way to center it?
I'm not a native speaker, so sorry for bad grammar. Thank you in advance.

Screen manager issue in kivy

I am experimenting with Kivy. When I tried using a screen manager, when the application runs, there is a black screen, nothing appears
That is my code. I have no idea what is the problem. It seems that the GridLayout doesn't get displayed on the screen.
import kivy
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.graphics import *
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen, SlideTransition
class load_file_screen(Screen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.my_layout = GridLayout(cols=1)
self.my_layout.cols = 1
self.label = Label(text="Loading files from here")
self.button = Button(text="Click to change")
self.button.bind(on_press=self.changer)
self.my_layout.add_widget(self.label)
self.my_layout.add_widget(self.button)
def changer(self, *args):
self.manager.current = "ViewFile"
class view_file_screen(Screen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.my_layout = GridLayout(cols=1)
self.label = Label(text="View File here")
self.button = Button(text="Click to change")
self.button.bind(on_press=self.changer)
self.my_layout.add_widget(self.label)
self.my_layout.add_widget(self.button)
def changer(self, *args):
self.manager.current = "LoadFile"
class my_app(App):
def build(self):
self.my_screen_manger = ScreenManager(transition=SlideTransition())
self.my_screen_manger.add_widget(load_file_screen(name="LoadFile"))
self.my_screen_manger.add_widget(view_file_screen(name="ViewFile"))
# self.my_screen_manger.current = "LoadFile"
return self.my_screen_manger
application = my_app()
application.run()

In both your view_file_screen and your load_file_screen, you need to add the line:
self.add_widget(self.my_layout)
in the __init__() method.

Kivy Creating screens as variables

I have a question about kivy. Is it possible to create screens as variables? Lets say I want to create a new screen with a button inside the kivy application. Is it possible to do that? If so how could you do it??

You just have to create a Screen object that you want to create and add it to the ScreenManager:
screen = Your_Screen(name="some_name")
your_screen_manager.add_widget(screen)
Example:
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.button import Button
class TestScreen(Screen):
def __init__(self, **kwargs):
Screen.__init__(self, **kwargs)
layout = BoxLayout(orientation="vertical")
self.add_widget(layout)
layout.add_widget(Label(text=self.name))
button = Button(text="{}: Add Screen".format(self.name))
layout.add_widget(button)
button.bind(on_press=self.add_screen)
def add_screen(self, *args):
n = len(self.manager.screen_names)
screen = TestScreen(name="screen {}".format(n))
self.manager.add_widget(screen)
self.manager.current = screen.name
# Create the screen manager
sm = ScreenManager()
sm.add_widget(TestScreen(name='screen 0'))
class TestApp(App):
def build(self):
return sm
if __name__ == '__main__':
TestApp().run()

Kivy: chow to obtain coordinates of FloatLayout center

I want to draw circle in center of FloatLayout. With my knowledges I obtained only default values for this. Why circle in showed code isn't red? Can You explain me process for obtaining necessary coordinates, please?
import kivy
from kivy.config import Config
kivy.config.Config.set('graphics','resizable', False)
from kivy.app import App
from kivy.graphics import Color, Ellipse
from kivy.uix.widget import Widget
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.button import Button
class Scene(FloatLayout):
def __init__(self, **kwargs):
super(Scene, self).__init__(**kwargs)
def draw_circle(self):
with self.canvas:
Color=(1,0,0)
circ = Ellipse(pos = (self.center_x, self.center_y), size=(20,20))
def on_touch_down(self, touch):
pass
class Game(BoxLayout):
def __init__ (self,**kwargs):
super(Game, self).__init__(**kwargs)
self.orientation = 'vertical'
but1 = Button(text = 'button 1')
self.add_widget(but1)
self.scene = Scene()
self.add_widget(self.scene)
class TestApp(App):
def build(self):
game = Game()
game.scene.draw_circle()
return game
if __name__ == '__main__':
TestApp().run()

You should define the size of your float layout when you create it.
self.scene = Scene(size=(300, 300))
Then your circle should be at the center of the FloatLayout dimensions.
I also think FloatLayout is better used with size_hint and pos_hint instead of fixed coordinates.

You can call draw_circle with Clock to make sure the layout is completely initiated first.
Then make sure to create your color like this Color(1, 0, 0). Not Color = ()
from kivy.config import Config
Config.set('graphics','resizable', False)
from kivy.app import App
from kivy.graphics import Color, Ellipse
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.clock import Clock
class Scene(FloatLayout):
def draw_circle(self, dt):
with self.canvas:
Color(1,0,0)
circ = Ellipse(pos = (self.center_x, self.center_y), size=(20,20))
class Game(BoxLayout):
def __init__ (self,**kwargs):
super(Game, self).__init__(**kwargs)
self.orientation = 'vertical'
but1 = Button(text = 'button 1')
self.add_widget(but1)
self.scene = Scene()
self.add_widget(self.scene)
class TestApp(App):
def build(self):
game = Game()
Clock.schedule_once(game.scene.draw_circle) # call draw_circle on next frame
return game
if __name__ == '__main__':
TestApp().run()

How to display slider value as it changes in python kivy

how do i change the text of a label to the value of the slider immediately.
this is my current code
import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.uix.slider import Slider
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label``
class app(App):
def build(self):
layout = BoxLayout(orientation='vertical')
slide = Slider(min=-100, max=100,value=0)
label = Label(text=str(slide.value))
layout.add_widget(slide)
layout.add_widget(label)
return layout
app().run()
i want the answer in python

You need to create a Kivy Property and bind the slider value to an on_ event where you can then update the label's text. Here's one way to do that:
from kivy.app import App
from kivy.uix.slider import Slider
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.properties import NumericProperty
import kivy
kivy.require('1.10.0')
class Container(BoxLayout):
slider_val = NumericProperty(0)
def __init__(self, *args, **kwargs):
super(Container, self).__init__(*args, **kwargs)
self.orientation = 'vertical'
slide = Slider(min=-100, max=100, value=0)
slide.fbind('value', self.on_slider_val)
self.label = Label(text=str(self.slider_val))
self.add_widget(slide)
self.add_widget(self.label)
def on_slider_val(self, instance, val):
self.label.text = str(val)
class app(App):
def build(self):
return Container()
app().run()