python - 使用Builder.load_string在Kivy应用上显示变量

如何在Builder.load_string本身上显示dikt ['r_pi']，并在每次单击更新按钮时对其进行更新？

from kivy.core.window import Window
Window.fullscreen = 0
Window.size = (1000, 500)

from kivy.app import App
from kivy.lang import Builder
import json
import requests
from kivy.properties import ObjectProperty


class MyApp(App):

    url = 'https://podluck-b3df6.firebaseio.com/.json'
    auth_key = '2BKTZfCSuILkpIRKzDAIWOMkhaC5jIq069Eg4oLS'

    def get(self):
        request = requests.get(self.url + '?auth=' + self.auth_key)
        dikt = request.json() #yes it IS a dict i checked
        self.btn.text = "The pod is" + str(dikt['r_pi'])
        print(dikt['r_pi'])

    def build(self):
        return KV

KV = Builder.load_string ("""

ScreenManager:
    id: manager
    Screen:
        BoxLayout:
            orientation: 'vertical'
            GridLayout:
                cols:1
                Button:
                    id: btn
            GridLayout:
                cols:1
                Button:
                    text: 'Update'
                    on_release: app.get()

""")

if __name__ == '__main__':
    MyApp().run()

我希望屏幕上显示“未占用”，这是我的Firebase数据库上“ r_pi”键的值，但我得到的却是以下内容：

“ MyApp”对象没有属性“ btn”

最佳答案

id是相对于所属树的，即您必须首先获取ScreenManager，在这种情况下，它是根，因此解决方案是：

def get(self):
    request = requests.get(self.url + '?auth=' + self.auth_key)
    dikt = request.json() #yes it IS a dict i checked
    self.root.ids.btn.text = "The pod is" + str(dikt['r_pi'])