python - 使用 Builder.load_string 在 Kivy 应用程序上显示变量

Question

如何在 Builder.load_string 本身上显示 dikt['r_pi']，并在每次点击更新按钮时更新它？

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()

我希望屏幕显示“未占用”，这是我的 firebase 数据库上“r_pi”键的值，但我得到的是以下内容:

“MyApp”对象没有属性“btn”

Answer 1

id是相对于所属树的，也就是说，你必须先获取ScreenManager，在这种情况下它是根，所以解决方案是:

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'])