python - 키즈가 라즈베리 파이 3에서 실행되는 창을 표시하지 않음

라즈베리 파이에서 Kivy 애플리케이션을 실행하려고합니다.
유스 케이스는 RFID 제어 커피 머신의 인터페이스를 표시하는 것입니다.
Kivy로 전환하기 전에 TKinter로 테스트 한 이후 스캔 부분이 작동하고 인터페이스가 모두 제대로 작동합니다.

내 코드는 다음과 같습니다 :

import RPi.GPIO as GPIO     #Access to the Raspberry Pi GPIO Pins
import serial               #PySerial for the serial connection to the RFID reader
import time                 #Required for sleep function
import datetime             #Required for timestamp
import MySQLdb as SQL       #Connection to MySQL Database
import threading            #Threading for RFID detection
from subprocess import call #Um die Datei in einem neuen Thread aufzurufen
import kivy                #GUI
kivy.require('1.10.0')
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder

#GPIO Setup
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)
GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.output(18, GPIO.HIGH)
#MySQL DB Connection
db = SQL.connect("localhost", "root", "raspberry", "Coffee")
curs = db.cursor()
#Select NTUser by the read ID from the MySQL Database
def getID(readID):
    try:
        curs.execute("SELECT NTUSER FROM usrlist WHERE id=%s", readID)
        usr = curs.fetchone()
        return usr[0]
    except:
        print("User not registered")

def put_into_db():
    #Input data into the Database
    print('done')

def espresso():
    print('Espresso')
def coffee():
    print('Coffee')

def scanner_thread():
    call(["python", "/RFID_Coffeemachine/RFID_Scanner.py", "&"])
#Thread for RFID reading
thread = threading.Thread(target=scanner_thread)
thread.start()
class Coffee(Screen):
    def __init__ (self,**kwargs):
    #GUI
        layout_coffee = BoxLayout(orientation="vertical")
        header_coffee = BoxLayout(orientation="horizontal")
        body_coffee = BoxLayout(orientation="horizontal")
        footer_coffee = BoxLayout(orientation="horizontal")

        self.greeting = Label(
            text='Welcome to the config screen',
            size_hint=(.5, .25))                        #Greeting Label
        def get_login(self):                                  #Function to update the greeting label -> Later integration with the user DB
            login_file = open('/home/pi/login.txt', "r")
            current_login = login_file.readline()
            login_file.close()
            if current_login == ' ':
                self.greeting.text='Please Scan RFID Token'
            else:
                self.greeting.text = current_login
        body_coffee.add_widget(self.greeting)                   #Adding the Label to the Layout
        Clock.schedule_interval(get_login, 1)              #Updating the greeting text every second
        layout_coffee.add_widget(header_coffee)
        layout_coffee.add_widget(body_coffee)
        layout_coffee.add_widget(footer_coffee)
class Config(Screen):
    def __init__ (self,**kwargs):
    #GUI
        layout_config = BoxLayout(orientation="vertical")
        header_config = BoxLayout(orientation="horizontal")
        body_config = BoxLayout(orientation="horizontal")
        footer_config = BoxLayout(orientation="horizontal")
        greeting = Label(
            text='Welcome to the config screen',
            size_hint=(.5, .25))                           #Greeting Label
        body_config.add_widget(greeting)                   #Adding the Label to the Layout
        layout_config.add_widget(header_config)
        layout_config.add_widget(body_config)
        layout_config.add_widget(footer_config)
class GUIApp(App):
    def build(self):
        screens = ScreenManager()
        coffee = Coffee(name="coffee")
        config = Config(name="config")
        screens.add_widget(coffee)
        screens.add_widget(config)
        return screens  

if __name__ == "__main__":
    GUIApp().run()
#thread.stop()
#db.close()
#ser.close()

내가 imports 를했다고 확신한다  그리고 "__main__"  비슷한 문제가있는 게시물의 문제였습니다. 또한 데모 응용 프로그램이 제대로 실행되므로 Kivy 설치가 Pi에서 제대로 작동했는지 확신합니다.