Using builder in Kivy - kivy

Question

I want to create a simple app that has GUI with a button that allows me to vibrate an android phone. Im using a .kv file for the layout and the Builder in my .yp file
.py file:
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.gridlayout import GridLayout
from kivy.lang import Builder
from plyer import vibrator
class AndroidApp(GridLayout):
def vibrate(self):
vibrator.vibrate()
kv = Builder.load_file("android_app.kv")
class MainApp(App):
def build(self):
return kv
if __name__ == "__main__":
MainApp().run()
.kv file:
#:import utils kivy.utils
<AndroidApp>:
FloatLayout:
canvas.before:
Color:
rgb: utils.get_color_from_hex("#ffffff")
Rectangle:
size: self.size
pos: self.pos
GridLayout:
rows: 1
cols: 2
Label:
text:"Android Vibrate"
Button:
text:"Android Vibrate"
on_press:
root.vibrate()
When I try to run the app, I get the following error:
enter image description here
This should be straightforward app but somehow I find a way to make it crash. The android_app.py & .kv files are in the same folder. Any ideas why the window wont be created? I aprreciate any help.
Thanks,
Alex

Answer 1

You have to return the main class, not the result from building. Here I'm using Builder.load_string() for convenience, and not importing player, but otherwise the only substantive change is that I changed return kv to return AndroidApp()
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.gridlayout import GridLayout
from kivy.lang import Builder
KV = '''
#:import utils kivy.utils
<AndroidApp>:
FloatLayout:
canvas.before:
Color:
rgb: utils.get_color_from_hex("#ffffff")
Rectangle:
size: self.size
pos: self.pos
GridLayout:
rows: 1
cols: 2
Label:
text:"Android Vibrate"
Button:
text:"Android Vibrate"
on_press:
root.vibrate()
'''
class AndroidApp(GridLayout):
def vibrate(self):
vibrator.vibrate()
Builder.load_string(KV)
class MainApp(App):
def build(self):
return AndroidApp()
if __name__ == "__main__":
MainApp().run()