Develop Reference

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, ScreenManager: how to access a variable defined in another screen?

I am writing an app with two screens using ScreenManager. In one screen I have a text input, and a button that reads such text input. If a certain condition from the input is satisfied, the second screen is activated. From this screen, I want to be able to grab the content of the text input from the first screen.
I have made multiple attempts and looked at many similar questions (this one for example), but none of them really seemed to work.
Below is a minimal non-working version of my code:
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.textinput import TextInput
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import ScreenManager, Screen
class RootWindow(Screen):
def __init__(self, **kwargs):
super(RootWindow, self).__init__(**kwargs)
box = BoxLayout()
self.add_widget(box)
self.searchInput = TextInput(multiline=False)
box.add_widget(self.searchInput)
self.searchButton = Button(text="Search")
self.searchButton.bind(on_press=self.searchRecipe)
box.add_widget(self.searchButton)
def searchRecipe(self, instance):
src = self.searchInput.text
if not src == "Go":
pass
else:
WMan.current = 'result'
class ResultWindow(Screen):
def __init__(self, **kwargs):
super(ResultWindow, self).__init__(**kwargs)
titleBox = BoxLayout()
self.add_widget(titleBox)
print(src)
WMan = ScreenManager()
WMan.add_widget(RootWindow(name='root'))
WMan.add_widget(ResultWindow(name='result'))
class RecipApp(App):
def build(self):
return WMan
if __name__ == "__main__":
RecipApp().run()

If you save a reference to titlebox like this:
class ResultWindow(Screen):
def __init__(self, **kwargs):
super(ResultWindow, self).__init__(**kwargs)
self.titleBox = BoxLayout()
self.add_widget(self.titleBox)
Then you can access the titlebox via the WMan, like this:
def searchRecipe(self, instance):
src = self.searchInput.text
if not src == "Go":
pass
else:
WMan.current = 'result'
WMan.current_screen.titlebox.add_widget(Label(text=src))

How can I prevent widgets from overlapping?

How to resolve widget overlapping in kivy framework, I am adding widgets in for cycle so I have more than one widget but all of them comes to be in one place, how can I prevent this?
My python code:
from kivy.app import App
from kivymd.app import MDApp
from kivy.uix.label import Label
from kivy.clock import Clock
from kivy.graphics import Color
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.gridlayout import GridLayout
from kivymd.uix.card import MDCard
from kivy.properties import StringProperty
from kivy.lang import Builder
import requests, time, collections
class request_sender():
return 'DATA'
class CustomLabel(Label):
pass
class CustomBox(BoxLayout):
pass
class AuctionCard(Widget):
auc_timer = ''
auc_img = ''
auc_name = ''
def __init__(self, **kwargs):
super(AuctionCard, self).__init__(**kwargs)
with self.canvas.before: Color(1, 0, .4, mode='rgb')
Clock.schedule_once(self.load_info)
def load_info(self, dt):
print(self.auc_name)
self.size_hint = None, None
box = BoxLayout(orientation='vertical', size = (800, 600))
box.size_hint_x = 50;
box.height = 100
AuctionName = CustomLabel(text=self.auc_name, pos_hint={'top': 300.9})
AuctionImage = CustomLabel(text=self.auc_img)
AuctionTimer = CustomLabel(text=self.auc_name)
box.add_widget(AuctionName)
box.add_widget(AuctionTimer)
box.add_widget(AuctionImage)
self.add_widget(box)
class MyWidget(Widget):
prop = StringProperty('')
array_of_labels = []
prop1 = StringProperty('Second card')
n = 0
all_cards = collections.defaultdict()
def __init__(self, **kwargs):
super(MyWidget, self).__init__(**kwargs)
self.screen_load()
def timer_le(self, dt):
returned_data = request_sender().sender_update('ajax.php')
for key in self.all_cards:
for data in returned_data:
if data['pid'] == key:
self.all_cards[key][0].text = str(data['remaining_time'])
def screen_load(self):
returned_data = request_sender().sender_update('ajax.php')
box = GridLayout(cols=2)
self.size_hint = None, None
for data in returned_data:
AucCard = AuctionCard()
AucCard.auc_name = str(data['auc_name'])+'\n\n'
AucCard.auc_timer = str(data['remaining_time'])+'\n\n'
AucCard.auc_img = str(data['auc_img'])+'\n\n'
box.add_widget(AucCard)
print('Widget added')
self.add_widget(box)
#self.all_cards[str(data['pid'])] = [AucCard]
#Clock.schedule_interval(self.timer_le, 1/30)
class TestApp(App):
def build(self):
box = GridLayout(cols=2)
return MyWidget()
TestApp().run()
My kv code:
<CustomLabel>:
size_hint_y: None
text_size: self.width, None
height: self.texture_size[1]
Result:
Kind of result that I want to create:

Actually I found easy way to solve this issue. The problem was in parent class of my AuctionCard and MyWidget classes, I set parent class to Widget but for the AuctionCard it should be BoxLayout and for MyWidget GridLayout. So from there I managed to set cols = 2 and size to window.size. From here it works exactly how it should work.
from kivy.lang import Builder
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.label import Label
from kivy.clock import Clock
from kivy.uix.gridlayout import GridLayout
class AuctionCard(BoxLayout):
auc_timer = ''
auc_img = ''
auc_name = ''
def __init__(self, **kwargs):
super(AuctionCard, self).__init__(**kwargs)
Clock.schedule_once(self.load_info)
def load_info(self, dt):
self.orientation = 'vertical'
AuctionName = Label(text=self.auc_name)
AuctionImage = Label(text=self.auc_img)
AuctionTimer = Label(text=self.auc_timer)
self.add_widget(AuctionName)
self.add_widget(AuctionTimer)
self.add_widget(AuctionImage)
class MyWidget(GridLayout):
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.cols = 2
self.size = (Window.size[0], self.size[1])
self.load_app()
print('MyWidget size: '+str(self.size))
def load_app(self):
self.size_hint = None, None
returned_data = [{'auc_name':'name 1', 'remaining_time':'100', 'auc_img':'https://img.src'},
{'auc_name':'name 2', 'remaining_time':'200', 'auc_img':'https://img.src'},
{'auc_name':'name 3', 'remaining_time':'300', 'auc_img':'https://img.src'}]
for data in returned_data:
AucCard = AuctionCard()
AucCard.auc_name = str(data['auc_name'])+'\n\n'
AucCard.auc_timer = str(data['remaining_time'])+'\n\n'
AucCard.auc_img = str(data['auc_img'])+'\n\n'
self.add_widget(AucCard)
print('Widget added')
class MyTestApp(App):
def __init__(self, **kwargs):
self.title = "My Material Application"
super().__init__(**kwargs)
def build(self):
return MyWidget()
if __name__ == "__main__":
MyTestApp().run()
Result:
Result

Bind function to Kivy button

I'm trying to bind the following function to a Button in Kivy.
def auth(self):
print(self.username)
if self.username == "Hendricko":
print("self.username == Hendricko")
popup = Popup(title="success",
content=Label(text="Howdy !"),
size=(100, 100),
size_hint=(0.3, 0.3),
auto_dismiss=False)
popup.open()
I've tried
class Foo():
def initUI(self):
self.add_widget(Button(text="Auth User and Password", on_press=self.auth))
but this doesn't work. What am I doing wrong?
here is my whole code
from kivy.uix.popup import Popup
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.stacklayout import StackLayout
class LoginScreen(GridLayout):
def __init__(self, **kwargs):
super(LoginScreen, self).__init__(**kwargs)
self.cols = 2
self.row = 2
self.add_widget(Label(text='User Name'))
self.username = TextInput(multiline=False)
self.add_widget(self.username)
self.add_widget(Label(text='password'))
self.password = TextInput(password=True, multiline=False)
self.add_widget(self.password)
self.hello = Button(text="hello", on_press=self.auth)
self.add_widget(self.hello)
def auth(self):
if self.username == "Hendricko":
popup = Popup(title="success",
content=Label(text="Howdy !"),
size=(100, 100),
size_hint=(0.3, 0.3),
auto_dismiss=False)
popup.open()
class MyApp(App):
def build(self):
return LoginScreen()
if __name__ == '__main__':
MyApp().run()

I don't think any of the answers are very clear. Neither explains that problem is that the callback given to on_press gets called with a parameter, the instance of button, so LoginScreen.auth must accept a parameter after the self:
def auth(self, button):
print('button pressed:', instance)
The problem is not that on_press must be given via Button.bind or that the callback must be a function, it can be a bound method, and the docs cited by other answer and by comments link to ButtonbBhavior which indicates that OP use of on_press in constructor was fine:
self.hello = Button(text="hello", on_press=self.auth)
would have worked if auth had been as described above.

If you read the Button documentation, the key seems to be to use the bind function:
def callback(instance):
print('The button <%s> is being pressed' % instance.text)
btn1 = Button(text='Hello world 1')
btn1.bind(on_press=callback)

Replace line
self.hello = Button(text="hello", on_press=lambda a:self.auth())
of your code and use this :
self.hello = Button(text="hello", on_press=lambda a:self.auth())
Also add below line in auth function to see if its called :)
print "auth called"
and There are many ways to perform a particular task .Above code will be to fix your code in minimum effort , However If you would like to do it in another way . Just use code below .
from kivy.uix.popup import Popup
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.stacklayout import StackLayout
class LoginScreen(GridLayout):
def __init__(self, **kwargs):
super(LoginScreen, self).__init__(**kwargs)
self.cols = 2
self.row = 2
self.add_widget(Label(text='User Name'))
self.username = TextInput(multiline=False)
self.add_widget(self.username)
self.add_widget(Label(text='password'))
self.password = TextInput(password=True, multiline=False)
self.add_widget(self.password)
self.hello = Button(text="hello")
self.hello.bind(on_press=self.auth)
self.add_widget(self.hello)
def auth(self,instance):
print "auth called"
if self.username == "Hendricko":
popup = Popup(title="success",
content=Label(text="Howdy !"),
size=(100, 100),
size_hint=(0.3, 0.3),
auto_dismiss=False)
popup.open()
class MyApp(App):
def build(self):
return LoginScreen()
if __name__ == '__main__':
MyApp().run()

I report an example of buttons created dynamically within the main class, and then triggered into a single listener:
class allMyApp(TabbedPanel):
def __init__(self, **kwargs):
super(allMyApp, self).__init__(**kwargs)
#[...]
for y in sorted(set(emissionYears)):
btn = Button(text = y,
size_hint_y = None,
height = '48dp',
on_release = lambda btn: self.ids.choseEmissionDate.select(btn.text))
btn.bind(on_press = self.sortByYear)
self.ids.choseEmissionDate.add_widget(btn)
def sortByYear(self, instance):
year = instance.text
print(year)

widget won't display until screen size changed

I want to make a game and I have chosen Kivy for my GUI, as I have written my backend in Python. I am currently using runTouchApp(appwindow) to run the application, where appwindow is a FloatLayout() object. The way I update my screen is that I run appwindow.clear_widgets() and then appwindow.add_widget(new_screen) where new_screen is the layout object which contains all other widgets.
It worked fine till now, but for some reason I can't understand the widget I add gets loaded properly (according to the cmd running in the background) but won't display till I change the screen size.
Here is a sample code:
import kivy
kivy.require('1.1.1')
from kivy.base import runTouchApp
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.image import Image
appwindow = FloatLayout()
class MenuScreen():
def build(self):
bg = Image(source = 'Images/bg/bg.jpg',allow_stretch= True,keep_ratio= False)
box = BoxLayout(orientation = 'vertical')
menu_items = []
for i in range (0,4):
button = Button(text = 'Menu item no:'+str(i))
button.bind(state = checkMenuPress)
menu_items.append(button)
for button in menu_items:
box.add_widget(button)
floater = FloatLayout(size = bg.size)
floater.add_widget(bg)
floater.add_widget(box)
floater.size_hint = 1,1
return floater
class SecondScreen():
def build(self):
bg = Image(source = 'Images/bg/bg.jpg',allow_stretch= True,keep_ratio= False)
box = BoxLayout(orientation = 'vertical')
box.add_widget(bg)
return box
def checkMenuPress(button,*args):
if button.state == 'normal':
sc = SecondScreen().build()
appwindow.clear_widgets()
appwindow.add_widget(sc)
if __name__ == '__main__':
menuscreen = MenuScreen().build()
appwindow.add_widget(menuscreen)
runTouchApp(appwindow)

Okay, there are a few things wrong here. To create an app, you should subclass kivy.app.App and have it's build method return the "root" widget. Only this class needs build method: any others are redundant.
Once you have a root widget, it's just a matter of inserting and removing widgets. This is how I would approach it.
import kivy
kivy.require('1.1.1')
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.image import Image
from kivy.app import App
class MenuScreen(App):
floater = None
def build(self):
bg = Image(source='Images/bg/bg.jpg',
allow_stretch= True,
keep_ratio= False)
box = BoxLayout(orientation='vertical')
menu_items = []
for i in range(0, 4):
button = Button(text='Menu item no:'+str(i))
button.bind(state=self.checkMenuPress)
menu_items.append(button)
for button in menu_items:
box.add_widget(button)
self.floater = FloatLayout(size=bg.size)
self.floater.add_widget(bg)
self.floater.add_widget(box)
self.floater.size_hint = 1, 1
return self.floater
def checkMenuPress(self, button,*args):
if button.state == 'normal':
self.floater.clear_widgets()
self.floater.add_widget(SecondScreen())
class SecondScreen(FloatLayout):
def __init__(self, **kwargs):
super(SecondScreen, self).__init__(**kwargs)
self.add_widget(Image(source='Images/bg/bg.jpg',
allow_stretch=True,
keep_ratio=False))
if __name__ == '__main__':
MenuScreen().run()

Okay, so here's a quick rework of the example using Screens. It's difficult without knowing what you are trying to do, so if this does not help, try writing summary of the behavior you are looking for.
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.image import Image
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
class MenuScreen(Screen):
"""
The Screen containing the menu
"""
def __init__(self, sm, **kwargs):
super(MenuScreen, self).__init__(**kwargs)
self.sm = sm # Store a reference to the screen manager
bg = Image(source='Images/bg/bg.jpg',
allow_stretch= True,
keep_ratio= False)
box = BoxLayout(orientation='vertical')
menu_items = []
for i in range(0, 4):
button = Button(text='Menu item no:'+str(i))
button.bind(state=self.check_menu_press)
menu_items.append(button)
for button in menu_items:
box.add_widget(button)
floater = FloatLayout(size=bg.size)
floater.add_widget(bg)
floater.add_widget(box)
floater.size_hint = 1, 1
self.add_widget(floater)
def check_menu_press(self, button, *args):
if button.state == 'normal':
self.sm.current = "second"
class SecondScreen(Screen):
def __init__(self, sm, **kwargs):
super(SecondScreen, self).__init__(**kwargs)
self.add_widget(Image(source='Images/bg/bg.jpg',
allow_stretch=True,
keep_ratio=False))
self.sm = sm # Store a reference to the screen manager
def on_touch_down(self, touch):
self.sm.current = "menu"
class MainApp(App):
def build(self):
sm = ScreenManager()
sm.add_widget(MenuScreen(sm, name="menu"))
sm.add_widget(SecondScreen(sm, name="second"))
return sm
if __name__ == '__main__':
MainApp().run()

looks like i have found a source of the crashing problem. I had used multi-threading for a server client interaction. i had been using two extra threads, one for the server and another for the client. If i try to integrate the client thread with the GUI it raises another problem. even if the socket.recv() is after the ScreenManager.current = "newscreen" line, the app's screen does not change. it freezes in the way i left it. it resumes only after it gets a message from the server.