python - I turn the application on android and this application crashes. Why?(Kivy) -

did write correctly? after application turned on, android device must vibrate, after application turns on, crashes. why apps on kivy crashed? code:

from plyer import vibrator kivy.app import app kivy.properties import stringproperty kivy.clock import clock, mainthread kivy.uix.floatlayout import floatlayout #the ui layout kivy.uix.label import label #a label show information class ui(floatlayout):     """docstring ui"""     def __init__(self):         super(ui, self).__init__()          self.lblacce = label(text="vibrate: ") #create label @ center         self.add_widget(self.lblacce) #add label @ screen         time = 2         try:             vibrator.vibrate(time=time)             #if want disable it, run: accelerometer.disable()             clock.schedule_interval(self.update, 1.0/24) #24 calls per second         except:             self.lblacce.text = "failed start vibrate" #error class vibrate(app): #our app     def build(self):         ui = ui()# create ui         return ui #show  if __name__ == '__main__':     vibrate().run() #start our app