onLongPressUp property Null safety

1. flutter_json_widgets
2. widget
3. GestureDetector
4. onLongPressUp property

GestureDetector class

1. Constructors
2. GestureDetector
3. fromJson
4. Properties
5. behavior
6. child
7. copyWith
8. dragStartBehavior
9. excludeFromSemantics
10. hashCode
11. key
12. onDoubleTap
13. onDoubleTapCancel
14. onHorizontalDragCancel
15. onLongPress
16. onLongPressCancel
17. onLongPressUp
18. onPanCancel
19. onSecondaryLongPress
20. onSecondaryLongPressCancel
21. onSecondaryLongPressUp
22. onSecondaryTap
23. onSecondaryTapCancel
24. onTap
25. onTapCancel
26. onTertiaryLongPress
27. onTertiaryLongPressCancel
28. onTertiaryLongPressUp
29. onTertiaryTapCancel
30. onVerticalDragCancel
31. runtimeType
32. supportedDevices
33. Methods
34. map
35. mapOrNull
36. maybeMap
37. maybeWhen
38. noSuchMethod
39. toJson
40. toString
41. when
42. whenOrNull
43. Operators
44. operator ==