A GlobalKey was used multiple times inside one widget's child list.

The offending GlobalKey was: [GlobalObjectKey _MaterialAppState#a4dea]
The parent of the widgets with that key was: ScrollConfiguration
behavior: _MaterialScrollBehavior
The first child to get instantiated with that key became: WidgetsApp-[GlobalObjectKey _MaterialAppState#a4dea]
dirty
state: _WidgetsAppState#2e51e(lifecycle state: created)
The second child that was to be instantiated with that key was: ScrollConfiguration
behavior: _MaterialScrollBehavior
A GlobalKey can only be specified on one widget at a time in the widget tree.
The relevant error-causing widget was:
MaterialApp file:///Users/alfredo/Documents/SPP_Flutter/Flutter_FAR_copies/flutter_localization_tutorial/lib/main.dart:11:12
When the exception was thrown, this was the stack:
#0 Element._retakeInactiveElement. (package:flutter/src/widgets/framework.dart:3134:11)
#1 Element._retakeInactiveElement (package:flutter/src/widgets/framework.dart:3148:8)
#2 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3176:32)
#3 Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
...

Thanks.