将功能绑定到Kivy按钮

Question

我正在尝试将以下函数绑定到Kivy中的Button 。

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))

但这不起作用。 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()

Answer 1

我不认为任何答案都很清楚。 这两个问题都没有解释为on_press的回调是通过参数（按钮的实例）调用的，所以LoginScreen.auth必须在self之后接受一个参数：

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

问题不在于on_press必须通过Button.bind给出，或者回调必须是一个函数，它可以是一个绑定方法，其他答案引用的文档和评论链接到ButtonbBhavior ，表明OP使用on_press构造函数很好：

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

如果auth如上所述，那会有效。

Answer 2

如果你阅读Button文档 ，关键似乎是使用bind函数：

def callback(instance):
    print('The button <%s> is being pressed' % instance.text)

btn1 = Button(text='Hello world 1')
btn1.bind(on_press=callback)

Answer 3

替换线

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

您的代码并使用此：

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

在auth函数中添加以下行，看看它是否被调用:)

print "auth called"

并且有许多方法可以执行特定任务。以上代码将以最小的努力修复您的代码，但是如果您想以其他方式执行此操作。 只需使用下面的代码。

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")
        self.hello.bind(on_press=self.auth)
        self.add_widget(self.hello)

    def auth(self,instance):
        print "auth called"
        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()

Answer 4

我报告了在主类中动态创建的按钮的示例，然后触发到单个侦听器：

class allMyApp(TabbedPanel):
    def __init__(self, **kwargs):
        super(allMyApp, self).__init__(**kwargs)

        #[...]

        for y in sorted(set(emissionYears)):
            btn = Button(text = y,
                         size_hint_y = None,
                         height = '48dp',
                         on_release = lambda btn: self.ids.choseEmissionDate.select(btn.text))
            btn.bind(on_press = self.sortByYear)
            self.ids.choseEmissionDate.add_widget(btn)

    def sortByYear(self, instance):
        year = instance.text
        print(year)