Kivy报错weakly-referenced object no longer exists，求基于给定代码的解决方案

Hey there, let's break down this frustrating error you're hitting with your Kivy app. Based on the code snippets you shared, here are the most likely causes and actionable fixes to resolve the issue:

1. ObjectProperty Initialization Pitfall #

Your current code initializes ObjectProperty instances directly at the class level:

class GetAccount(FloatLayout):
    keyandnick = ObjectProperty(KeyAndNick())
    account = ObjectProperty(Account())

Kivy's ObjectProperty uses weak references by default. When you instantiate objects like KeyAndNick() directly in the class definition, there's no strong reference holding onto them long-term. The garbage collector (GC) can clean these objects up prematurely, leading to the "weakly-referenced object no longer exists" error when your code tries to access them later.

Fix: #

Move the object initialization into the __init__ method, where the instance (self) will hold a strong reference:

class GetAccount(FloatLayout):
    keyandnick = ObjectProperty(None)
    account = ObjectProperty(None)
    
    def __init__(self, **kwargs):
        super(GetAccount, self).__init__(**kwargs)
        self.keyandnick = KeyAndNick()
        self.account = Account()

This ensures the KeyAndNick and Account instances stay alive as long as the GetAccount instance exists.

2. Rotate Instruction Reference Issues #

In your KV file, the Rotate canvas instruction binds to self.ang (the button's ang property). If the button instance is accidentally dereferenced (e.g., if the GetAccount widget is removed without proper cleanup), the weak reference to the button in the Rotate instruction can become invalid.

Fix: #

Add a strong reference to the refresh button in your GetAccount class to ensure it's not prematurely collected:

1. Update the Python class:

   class GetAccount(FloatLayout):
       refresh_btn = ObjectProperty(None)
       # ... your other properties and methods
   

2. Update the KV file to link the button to this property:

   <GetAccount>:
       refresh_btn: refresh  # Bind the button to the class property
       Button:
           id: refresh
           ang: 0
           background_normal: 'static/refresh.png'
           size_hint: None, None
           size: sp(50), sp(50)
           pos_hint: {'center_y': .96, 'center_x': .8}
           on_press: root.clean()
           canvas.before:
               Rotate:
                   angle: self.ang
                   origin: self.center
   

This gives your GetAccount instance a strong grip on the button, preventing GC from collecting it while the widget is active.

3. clean() Method Side Effects #

The on_press: root.clean() call might be inadvertently releasing objects that are only weakly referenced. For example, if clean() resets self.keyandnick or self.account to None without ensuring there's another strong reference to those instances, the GC will collect them immediately. Any subsequent code trying to access those objects will throw the error.

Check: #

Review your clean() method implementation. If it's clearing these properties, make sure:

• You don't need to access those instances after clean() runs, or
• You have another strong reference (e.g., a class-level variable, or another widget holding the instance) to keep them alive.

Start with the first fix (adjusting ObjectProperty initialization) — this is the most common cause of this error in Kivy. If that doesn't resolve it, move on to checking the button reference and your clean() method.

内容的提问来源于stack exchange，提问作者user378625