onState<TStateType extends TState> method
Registers a handler to be invoked whenever a state of type
TStateType is encountered.
Implementation
@override
void onState<TStateType extends TState>(
StateCallback<TStateType> handler,
) {
_stateCheckers.add((state) => state is TStateType);
_stateRunners.add((state) => handler(state as TStateType));
}