onTap property Null safety

1. flutter_json_widgets
2. preferred_size_widget
3. TabBar
4. onTap property

TabBar class

1. Constructors
2. TabBar
3. fromJson
4. Properties
5. automaticIndicatorColorAdjustment
6. copyWith
7. dividerColor
8. dragStartBehavior
9. enableFeedback
10. hashCode
11. indicator
12. indicatorColor
13. indicatorPadding
14. indicatorSize
15. indicatorWeight
16. isScrollable
17. key
18. labelColor
19. labelPadding
20. labelStyle
21. mouseCursor
22. onTap
23. overlayColor
24. padding
25. physics
26. runtimeType
27. splashBorderRadius
28. tabs
29. unselectedLabelColor
30. unselectedLabelStyle
31. Methods
32. map
33. mapOrNull
34. maybeMap
35. maybeWhen
36. noSuchMethod
37. toJson
38. toString
39. when
40. whenOrNull
41. Operators
42. operator ==