i property Null safety

1. appmayor
2. contactList
3. Contacts
4. i property

Contacts class

1. Constructors
2. Contacts
3. Properties
4. callbackFunction
5. hashCode
6. i
7. key
8. runtimeType
9. Methods
10. createElement
11. createState
12. debugDescribeChildren
13. debugFillProperties
14. noSuchMethod
15. toDiagnosticsNode
16. toString
17. toStringDeep
18. toStringShallow
19. toStringShort
20. Operators
21. operator ==