Crash when using ScreenManager
This theme is not compatible with ScreenManager because in this case the app
becomes unreachable and the Widgets can't access this vital variable.
Well, the value of app is None and thus hasn't got any attributes.
BuilderException: Parser: File "<inline>", line 45:
...
43: font_name: 'Roboto'
44: #foreground_color: root.theme_cls.text_color
>> 45: foreground_color: app.theme_cls.text_color
46: font_size: sp(16)
47: bold: False
...
AttributeError: 'NoneType' object has no attribute 'bind'
File "/home/blumenmensch/kivyinstall/lib/python2.7/site-packages/kivy/lang/builder.py", line 249, in create_handler
return eval(value, idmap), bound_list
File "<string>", line 45, in <module>
File "/home/blumenmensch/kivyinstall/lib/python2.7/site-packages/kivy/lang/parser.py", line 75, in __getattribute__
object.__getattribute__(self, '_ensure_app')()
File "/home/blumenmensch/kivyinstall/lib/python2.7/site-packages/kivy/lang/parser.py", line 70, in _ensure_app
app.bind(on_stop=lambda instance:
File "/home/blumenmensch/kivyinstall/lib/python2.7/site-packages/kivy/lang/builder.py", line 615, in _apply_rule
rctx['ids'])
File "/home/blumenmensch/kivyinstall/lib/python2.7/site-packages/kivy/lang/builder.py", line 254, in create_handler
cause=tb)