width property Null safety

1. jrpn
2. view.main_screen
3. ScreenPositioner
4. width property

ScreenPositioner class

1. Constructors
2. ScreenPositioner
3. Properties
4. hashCode
5. height
6. runtimeType
7. width
8. Methods
9. box
10. noSuchMethod
11. toString
12. Operators
13. operator ==