key property Null safety

1. flutter_json_widgets
2. widget
3. FloatingActionButton
4. key property

FloatingActionButton class

1. Constructors
2. FloatingActionButton
3. fromJson
4. Properties
5. autofocus
6. backgroundColor
7. child
8. clipBehavior
9. copyWith
10. disabledElevation
11. elevation
12. enableFeedback
13. focusColor
14. focusElevation
15. foregroundColor
16. hashCode
17. highlightElevation
18. hoverColor
19. hoverElevation
20. isExtended
21. key
22. materialTapTargetSize
23. mini
24. mouseCursor
25. onPressed
26. runtimeType
27. shape
28. splashColor
29. tooltip
30. Methods
31. map
32. mapOrNull
33. maybeMap
34. maybeWhen
35. noSuchMethod
36. toJson
37. toString
38. when
39. whenOrNull
40. Operators
41. operator ==