FormState constructor Null safety

1. Flutter
2. widgets
3. FormState
4. FormState constructor

FormState class

1. Constructors
2. FormState
3. Properties
4. context
5. hashCode
6. mounted
7. runtimeType
8. widget
9. Methods
10. activate
11. build
12. deactivate
13. debugFillProperties
14. didChangeDependencies
15. didUpdateWidget
16. dispose
17. initState
18. noSuchMethod
19. reassemble
20. reset
21. save
22. setState
23. toDiagnosticsNode
24. toString
25. toStringShort
26. validate
27. Operators
28. operator ==