如何在Kivy的kv文件中调用Account类的方法？

Got it, let's get your account balance showing up in that Label. Here's what you need to adjust in your code, step by step:

First, Fix the Account Class (Critical!) #

Right now you're initializing balance as a string "1000"—that'll break your setBalance() method later when you try to add numbers to it. Let's switch it to an integer:

class Account():
    def __init__(self, name, balance):
        self.name = name
        # Use integer instead of string for balance to enable math operations
        self.__balance__ = int(balance)
    def getBalance(self):
        return self.__balance__
    def setBalance(self, zmena):
        # Convert input to int too, since user input will be a string
        self.__balance__ += int(zmena)

Make the Account Instance Accessible to KV #

Your current acc is a global variable, which KV can't easily reference. Instead, attach it to your MainApp class so KV can access it via the app keyword:

import kivy
kivy.require("1.10.1")
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.widget import Widget

class Account():
    def __init__(self, name, balance):
        self.name = name
        self.__balance__ = int(balance)
    def getBalance(self):
        return self.__balance__
    def setBalance(self, zmena):
        self.__balance__ += int(zmena)

class myWidget(Widget):
    pass  # Move KV loading to the App class for cleaner structure

class MainApp(App):
    def build(self):
        # Create the Account instance here and attach it to the app
        self.acc = Account("Account1", "1000")
        # Load the KV file in build() instead of the widget class
        Builder.load_file("MP.kv")
        return myWidget()

    def update_balance(self, amount):
        # Helper method to handle button clicks and update the balance
        self.acc.setBalance(amount)

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

Update the KV File to Display the Balance #

Now you can bind the Label's text to app.acc.getBalance(), converting it to a string since Kivy Labels expect text content. We'll also add logic to the Confirm button to update the balance when clicked:

#:kivy 1.10.1
<Button>
    background_color: 0.1, 0.1, 0.9, 0.9
    font_size: 22
<Label>
    background_color: 0.1, 0.1, 0.9, 0.9
    font_size: 22
<myWidget>:
    Label:
        id: lb
        text: "Account"
        pos: root.width /2-self.width/2, root.top/2+200
    Label:
        id: lb1
        text: f"Account name: {app.acc.name}"
        pos: root.width /2-self.width/2, root.top/2+150
    Label:
        id: lb2
        # Call getBalance() and convert to string for display
        text: f"balance: {str(app.acc.getBalance())}"
        pos: root.width /2-self.width/2, root.top/2+100
    Label:
        id: lb3
        text: "Add/sub money"
        pos: root.width /2-self.width/2, root.top/2+50
    TextInput:
        id: tp
        hint_text: "Enter amount (positive to add, negative to subtract)"
        pos: root.width /2-self.width/2, root.top/2-50
        size_hint: .5, .25
        input_filter: "int"  # Restrict input to integers to avoid errors
    Button:
        id: btn1
        text: "Confirm"
        size_hint: .5, .25
        pos: root.width /2-self.width/2, root.top/2-150
        # Trigger the app's update method when clicked
        on_press: app.update_balance(tp.text)

Why This Works: #

• By attaching the acc instance to MainApp, KV can access it using the app keyword (which refers to your running app instance).
• We convert the balance to a string in KV because the Label's text property requires a string value.
• The input_filter: "int" on the TextInput ensures users can only enter valid numbers, preventing errors in the setBalance() method.

内容的提问来源于stack exchange，提问作者Martin Hofman