AttributeError:'NoneType'对象没有属性'current' [英] AttributeError: 'NoneType' object has no attribute 'current'

问题描述

class LoginScreen(Screen):
    def __init__(self,**kwargs):
        super(LoginScreen, self).__init__(**kwargs)
        print self,self.parent.current

class AppScreenManager(ScreenManager):
    pass

#Base Class
class AppBaseClass(App):
    def build(self):
        icon='app_icon'
        return Builder.load_file('appbase.kv')


________________________________________________________________________________________________

AppScreenManager:
    transition: FadeTransition()
    LoginScreen:

错误:AttributeError:'NoneType'对象没有属性'current'.请帮忙.

Error: AttributeError: 'NoneType' object has no attribute 'current'. Please help.

推荐答案

此刻您拨打电话:

print self,self.parent.current

LoginScreen尚未实例化，因此您正在调用和不存在的对象.

the LoginScreen is not instantiated yet, so you are calling for and object that does not exist.

解决方法是将呼叫延迟1帧，这可以使用Clock类完成:

The workaround is to delay the call by 1 frame, that can be done using Clock class:

 Clock.schedule_once(self._myprintfunction, 1/60)

和后者在您的代码中，但在同一类中:

and latter in your code but in the same class:

    def _myprintfunction(self, dt):
        print '-'*25
        print self
        print self.parent
        # print self.parent.curet <- this will throw you an error 
        print '-'*25

希望有帮助.

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