value property
The current value stored in this notifier.
When the value is replaced with something that is not equal to the old value as evaluated by the equality operator ==, this class notifies its listeners.
Implementation
@override
T get value => _value;This setter should only be called in this class or within tests. Changes
to the _MapControllerState should be done via methods in this class.
Implementation
@visibleForTesting
@override
// ignore: library_private_types_in_public_api
set value(_MapControllerState value) => super.value = value;