ScreenImpl constructor Null safety

1. farmershands
2. screen_impl
3. ScreenImpl
4. ScreenImpl constructor

ScreenImpl class

1. Constructors
2. ScreenImpl
3. Properties
4. hashCode
5. runtimeType
6. title
7. Methods
8. noSuchMethod
9. toString
10. Operators
11. operator ==
12. Constants
13. routeName