将函数绑定到 Kivy 按钮

我正在尝试将以下函数绑定到Button在基维。

def auth(self):
    print(self.username)
    if self.username == "Hendricko":
        print("self.username == Hendricko")
        popup = Popup(title="success",
            content=Label(text="Howdy !"),
            size=(100, 100),
            size_hint=(0.3, 0.3),
            auto_dismiss=False)
        popup.open()

我试过了

class Foo():
   def initUI(self):
    self.add_widget(Button(text="Auth User and Password", on_press=self.auth))

但这行不通。我究竟做错了什么？

这是我的整个代码

from kivy.uix.popup import Popup
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.stacklayout import StackLayout


class LoginScreen(GridLayout):
    def __init__(self, **kwargs):
        super(LoginScreen, self).__init__(**kwargs)
        self.cols = 2
        self.row = 2
        self.add_widget(Label(text='User Name'))
        self.username = TextInput(multiline=False)
        self.add_widget(self.username)
        self.add_widget(Label(text='password'))
        self.password = TextInput(password=True, multiline=False)
        self.add_widget(self.password)
        self.hello = Button(text="hello", on_press=self.auth)
        self.add_widget(self.hello)

    def auth(self):
        if self.username == "Hendricko":
            popup = Popup(title="success",
                content=Label(text="Howdy !"),
                size=(100, 100),
                size_hint=(0.3, 0.3),
                auto_dismiss=False)
            popup.open()


class MyApp(App):
    def build(self):
        return LoginScreen()


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

我认为任何答案都不是很清楚。都没有解释这个问题是回调给on_press使用参数（按钮的实例）进行调用，因此LoginScreen.auth必须在之后接受一个参数self:

def auth(self, button):
    print('button pressed:', instance)

问题是not that on_press必须通过Button.bind或者回调必须是一个函数，它可以是一个绑定方法，并且其他答案和评论引用的文档链接到ButtonbBhavior这表明 OP 使用on_press在构造函数中很好：

self.hello = Button(text="hello", on_press=self.auth)

如果auth已经如上所述。