Kivy：如何在按钮 on_press 时调用某个函数

Question

我正在制作一个生成票据的应用程序。生成票据的脚本已经完成。

当我按下“Generera”按钮（英文是“Generate”，意思是“生成”）时，它应该在终端打印出生成的票据。

一切都运行正常，但当我按下生成按钮时，我遇到了这个错误：

AttributeError: StockholmTicket 实例没有 call 方法

我不知道如何在按下 gen_btn 时调用 StockholmTicket，希望能得到一些帮助。

以下是代码：

from kivy.app import App

from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout

from datetime import datetime, timedelta
import random


class Fejkbiljett(App):

    def build(self):
        gen_btn = Button(text='Generera',
                         size_hint=(.90, .10),
                         pos=(5, 5),
                         font_size=21)

        gen_btn.bind(on_press=StockholmTicket())

        l = BoxLayout()

        l.add_widget(gen_btn)

        return l


class StockholmTicket():

    def getMessage():
        # gNumbers
        gNumbers = random.randint(100, 999)
        gNumbers = str(gNumbers)

        gLetters = 'EAOXE'
        gLetters = gLetters * 2
        gLetters = ''.join(random.sample(gLetters, len(gLetters)))
        gLetters2 = 'EAOXA'
        gLetters2 = gLetters2 * 2
        gLetters2 = ''.join(random.sample(gLetters2, len(gLetters2)))
        gLetters3 = 'EAOXA'
        gLetters3 = gLetters3 * 2
        gLetters3 = ''.join(random.sample(gLetters3, len(gLetters3)))

        sCode = '123456789123456'
        sCode = ''.join(random.sample(sCode, len(sCode)))
        sCode = sCode[:6] + ' ' + sCode[6:]

        iPrice = '20'
        sPriceText = 'Red pris'
        sPricetype = 'R'
        mZones = 'A'
        mTime = datetime.now()
        mTime = mTime + timedelta(hours=1, minutes=15)
        mTime = str(mTime)
        mTime = mTime[11:16]
        mDate = str(datetime.now())
        mDate = mDate[:10]

        print((sPricetype + "-" + mZones + " " + mTime + " "
              + gNumbers + "\n\n"

              + gLetters + "\n"
              + gLetters2 + "\n"
              + gLetters3 + "\n"
              + "EEEEEEEEEE\n\n"

              + "SL biljett giltig till " + mTime + ", " + "\n" + mDate + "\n"
              + sPriceText + " " + iPrice + " kr ink 6% moms\n"

              + sCode + "\n"
              + "m.sl.se"))

    getMessage()

if __name__ == "__main__":
    Fejkbiljett().run()

Answer 1

你只需要输入 gen_btn.on_press = 你的函数

Answer 2

但是这样可以吗？

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout


class Fejkbiljett(App):

    def build(self):
        gen_btn = Button(text='Generera',
                         size_hint=(.90, .10),
                         pos=(5, 5),
                         font_size=21)
        gen_btn.bind(on_press=StockholmTicket.getMessage)
        l = BoxLayout()
        l.add_widget(gen_btn)
        return l


class StockholmTicket(object):

    def getMessage(self):
        print "2. this is called on the method getMessage of StockholmTicket"

if __name__ == "__main__":
    Fejkbiljett().run()

Answer 3

这里的“StockholmTicket()”是一个类，不能直接调用（除非你特别设置，但那是另一个话题）。试试这个代码，它会创建一个实例，用来保存要调用的函数。

    gen_btn.bind(on_press=StockholmTicket().getMessage)

而不是

    gen_btn.bind(on_press=StockholmTicket())

你还需要重新定义“getMessage”函数，因为它现在还不接受参数，但将来需要接受。试试这个：

class StockholmTicket():
    def getMessage(self, * args):

希望这能帮到你？谢谢！

Answer 4

我不太确定为什么（我猜是因为这个类的定义方式），但是当你在一个不属于你绑定的类的方法上调用时，它是无法工作的。你可以在这个类里面创建一个方法，然后在另一个类中调用这个方法。就像这样：

from kivy.app import App

from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout


class Fejkbiljett(App):

    def build(self):
        self.gen_btn = Button(text='Generera',
                         size_hint=(.90, .10),
                         pos=(5, 5),
                         font_size=21)
        self.gen_btn.bind(on_press=self.getMessageFejkbiljett)
        l = BoxLayout()
        l.add_widget(self.gen_btn)
        return l

    def getMessageFejkbiljett(self, *args):
        print "1. this is called on the method getMessageFejkbiljett of Fejkbiljett"
        st = StockholmTicket()
        st.getMessage(self)


class StockholmTicket():

    def getMessage(self, source):
        source.gen_btn.text = "the event was called"
        print "2. this is called on the method getMessage of StockholmTicket"

if __name__ == "__main__":
    Fejkbiljett().run()