当我尝试使用python中的kivy库从一个类调用一个类中定义的“屏幕切换”函数时,我遇到了一个AttributionError。= "left"
AttributeError: 'NoneType' object has no attribute 'transition' 在上面的代码中,我在ScreenA类中定义了屏幕切换函数但奇怪的是,错误消息似乎表明screenA<
\lang\parser.py", line 70, in _ensure_app AttributeError:'NoneType' object has no attribute 'bind'
During handling of the above exception, another exceptionAttributeError: 'NoneType'