Get value from a function in main.py file and pass it to kivy screen to display as a label
Prabhat K.C.
Okay so I am very new to python and kivy. I was learning to make a simple GUI so I can upgrade it later once I learn more. Everything is good so far except I want to pass
the value of tempData from the function FitToInches to be displayed as a Label in <ResultWindow>. I have tried going back and forth with many techniques and this is the
closest where I got before being stuck. Can anyone help me how to do it without using too many new things other than this, since I couldn't understand some of the answers
I found on the google. For what it's worth, I can print the value of tempData, so basically I have successfully accessed UserSource from <AskUserWindow>. I created a
PassResult Function but I don't know if I even did it right. I'd appreciate any help. Thank you.
convertunit.kv
scrManager:
AskUserWindow:
ResultWindow:
<AskUserWindow>:
name: "askUser"
userSource: userSource
GridLayout:
cols: 2
Label:
text: "Input the number: "
TextInput:
id: userSource
multiline: False
Button:
id: toFootBtn
text: "Convert Inches to Foot"
on_press:
app.root.InchToFeet(userSource)
on_release:
app.root.current = "result"
root.manager.transition.direction = "left"
Button:
id: toInchBtn
text: "Convert Foot to Inches"
on_press:
app.root.FeetToInches(userSource)
on_release:
app.root.current = "result"
root.manager.transition.direction = "left"
<ResultWindow>:
name: "result"
GridLayout:
cols: 1
Label:
text: "Your result is :" + app.resultData2
Button:
text: "Convert More numbers"
on_release:
app.root.current = "askUser"
root.manager.transition.direction = "right"
main.py
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
class AskUserWindow(Screen):
pass
class ResultWindow(Screen):
pass
class scrManager(ScreenManager):
def PassResult(self, stringInput):
MyMainApp.resultData2 = stringInput
def FeetToInches(self, userSource):
feetData = userSource
tempInput = userSource
tempData = str(12 * int(tempInput.text))
self.PassResult(tempData)
def InchToFeet(self, userSource):
inchData = userSource.text
#tempData2 = str(int(inchData) / 12)
kv = Builder.load_file("convertunit.kv")
class MyMainApp(App):
def build(self):
resultData2 = "buildAlter"
return kv
if __name__ == "__main__":
MyMainApp().run()
Elliot Garbus
I tried to make a minimum number of changes. Happy to answer any questions.
The KV code:
ScrManager:
id: sm
AskUserWindow:
name: "askUser" # name goes with instance not definition
ResultWindow:
name: "result"
<AskUserWindow>:
# userSource: userSource
GridLayout:
cols: 2
Label:
text: "Input the number: "
TextInput:
id: userSource
multiline: False
Button:
id: toFootBtn
text: "Convert Inches to Foot"
on_press:
app.root.InchToFeet(userSource)
on_release:
app.root.current = "result"
root.manager.transition.direction = "left"
Button:
id: toInchBtn
text: "Convert Foot to Inches"
on_press:
app.root.FeetToInches(userSource)
on_release:
app.root.current = "result"
root.manager.transition.direction = "left"
<ResultWindow>:
on_enter:
answer.text = 'Your Result: ' + app.result # need an event to reevaluate the string,
GridLayout:
cols: 1
Label:
id:answer
Button:
text: "Convert More numbers"
on_release:
app.root.current = "askUser"
root.manager.transition.direction = "right"
The Python Code:
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty
class AskUserWindow(Screen):
pass
class ResultWindow(Screen):
pass
class ScrManager(ScreenManager):
# def PassResult(self):
# app = App.get_running_app() # get the pointer to app using get_running_app()
# app.resultData2 = stringInput
def FeetToInches(self, usersource):
# feetData = userSource
# tempInput = userSource
# tempData = str(12 * int(tempInput.text))
#self.PassResult(tempData)
app = App.get_running_app()
app.result = str(12 * int(usersource.text))
def InchToFeet(self, user_source):
#inchData = userSource.text
#tempData2 = str(int(inchData) / 12)
app = App.get_running_app()
app.result = f'{int(user_source.text)/12:0.2f}'
kv = Builder.load_file("convertunit.kv")
class
MyMainApp(App):
result = StringProperty("buildAlter") # Create a kivy string property
def build(self):
return kv
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Prabhat K.C.
Elliot Garbus
For #2: Start with: https://kivy.org/doc/stable/guide/packaging-android.html
I have not done any android packaging, but many others have. Follow the directions, if you have problems others will help.
An id is a pointer to a widget. In kv you can use the id to access all of the attributes of a widget. In python the id is stored in a dict called ids.
from kivy.app import App
from kivy.lang import
Builder
kv = """
<CustomButton@Button>:
font_size: sp(50)
BoxLayout:
orientation: 'vertical'
Label:
id: label_1
font_size: sp(50)
text: 'Button Test'
CustomButton:
id: b1 # ids is created from the id in kv
text: 'Print all ids'
on_release:
print(f'The ids: {app.root.ids}') # print all the ids, you can also use ids from python
label_1.text = 'Button 1 Pressed' # using an id to write to an attribute
CustomButton:
id: b2
text: 'Button 2'
on_release: label_1.text = 'Button 2 Pressed' # using the id label_1 to write to the text in the label
CustomButton:
id: b3
text: 'Button 3'
on_release:
label_1.text = 'Button 3 Pressed'
b1.text = 'Text Changed by Button 3'
"""
class BoxesApp(App):
def build(self):
return Builder.load_string(kv)
BoxesApp().run()
From: 'Prabhat K.C.' via Kivy users support
Sent: Sunday, February 16, 2020 3:09 PM
To: Kivy users support
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Prabhat K.C.
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Robert Flatt
2. What is the best way to package pycharm + kivy file as an android app? Since that is where I am trying to head to.
Robert Flatt
2. What is the best way to package pycharm + kivy file as an android app? Since that is where I am trying to head to.
On Sunday, February 16, 2020 at 12:09:20 PM UTC-10, Prabhat K.C. wrote:
Elliot Garbus
That's exactly what I want. Now in my code, if I want to use a same button (I am thinking of a home button) at various screens, where do I put the original custom button@button such that I won't be thrown a KV file only allow one root object. Thank you.
Kivy has a global name space. So you can put you home button in any kivy file – even if you have multiple kivy files and use it anywhere.
You are creating a ‘rule’ when you use the <MyButton@Button>, this is analogous to creating a class in python. This is the not the root widget of the app.
Alternately you can create:
In Kv:
<MyButton> :
And in Python:
Class MyButton(Button):
# if you want to define additional methods in your custom button.
def my_method(self):
# your custom code here….
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