How to correctly implement the BloC pattern in Flutter?

Question

Dart

Greetings!
Question about the implementation of the Bloc pattern in flutter.
There are several DropDownButton widgets on the screen.
How to correctly implement the Bloc pattern so that when the element in the DropDownButton changes, only this dropdown is redrawn.
Is it necessary to write a separate bloc for each dropdown widget and wrap each dropdown in its own BlocBuilder?
Or is it possible to implement this while creating only one bloc and one BlocBuiler for this screen?

Answer 1

And what do you mean here: so that when the element changes in the DropDownButton, only this dropdown is redrawn.
When an element is selected, the selected value is set