Material You NavBar solution with bloc

navigation_bloc.dart

import 'package:bloc/bloc.dart';
import 'package:equatable/equatable.dart';
import 'package:meta/meta.dart';

part 'navigation_event.dart';
part 'navigation_state.dart';

class NavigationBloc extends Bloc<NavigationEvent, NavigationState> {
  NavigationBloc() : super(const NavMealSteate(1)) {
    on<NavHomeEvent>(_onHome);
    on<NavMealEvent>(_onMeal);
    on<NavWorkoutEvent>(_onWorkout);
  }

  void _onHome(NavHomeEvent event, Emitter<NavigationState> emit) {
    emit(NavHomeState(event.index));
  }

  void _onMeal(NavMealEvent event, Emitter<NavigationState> emit) {
    emit(NavMealSteate(event.index));
  }

  void _onWorkout(NavWorkoutEvent event, Emitter<NavigationState> emit) {
    emit(NavWorkoutState(event.index));
  }
}

navigation_event.dart

part of 'navigation_bloc.dart';

@immutable
abstract class NavigationEvent extends Equatable {
  const NavigationEvent();

  @override
  List<Object> get props => [];
}

class NavHomeEvent extends NavigationEvent {
  const NavHomeEvent({required this.index});
  final int index;
}

class NavMealEvent extends NavigationEvent {
  const NavMealEvent({required this.index});
  final int index;
}

class NavWorkoutEvent extends NavigationEvent {
  const NavWorkoutEvent({required this.index});
  final int index;
}

navigation_state.dart

part of 'navigation_bloc.dart';

@immutable
abstract class NavigationState extends Equatable {
  const NavigationState(this.index);
  final int index;

  @override
  List<Object> get props => [index];
}

class NavigationInitial extends NavigationState {
  const NavigationInitial(int index) : super(index);
}

class NavHomeState extends NavigationState {
  const NavHomeState(int index) : super(index);
}

class NavMealSteate extends NavigationState {
  const NavMealSteate(int index) : super(index);
}

class NavWorkoutState extends NavigationState {
  const NavWorkoutState(int index) : super(index);
}

root_page.dart

class RootPage extends StatelessWidget {
  const RootPage({Key? key}) : super(key: key);
  @override
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (_) => NavigationBloc(),
      child: const RootView(),
    );
  }
}

class RootView extends StatelessWidget {
  const RootView({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: BlocBuilder<NavigationBloc, NavigationState>(
        buildWhen: (prev, state) => prev.runtimeType != state.runtimeType,
        builder: (context, state) {
          if (state is NavHomeState) { return const HomePage(); }
          if (state is NavMealSteate) { return const MealPage(); }
          if (state is NavWorkoutState) { return const WorkoutPage(); }
          return Container();
        },
      ),
      bottomNavigationBar: BlocBuilder<NavigationBloc, NavigationState>(
        builder: (_, state) {
          //Material You NavigationBar Widget
          return NavigationBar(
            height: 65,
            selectedIndex: state.index,
            labelBehavior: NavigationDestinationLabelBehavior.alwaysShow,
            animationDuration: const Duration(seconds: 1),
            onDestinationSelected: (index) {
              switch (index) {
                case 0: context.read<NavigationBloc>().add(NavHomeEvent(index: index));
                break;
                case 1: context.read<NavigationBloc>().add(NavMealEvent(index: index));
                break;
                case 2: context.read<NavigationBloc>().add(NavWorkoutEvent(index: index));
                break;
              }
            },
            destinations: const [
              NavigationDestination(
                icon: Icon(Icons.home),
                label: 'Home',
                selectedIcon: Icon(Icons.home_outlined),
              ),
              NavigationDestination(
                icon: Icon(Icons.restaurant),
                label: 'Meal',
                selectedIcon: Icon(Icons.restaurant_outlined),
              ),
              NavigationDestination(
                icon: Icon(Icons.fitness_center),
                label: 'Workout',
                selectedIcon: Icon(Icons.fitness_center_outlined),
              ),
            ],
          );
        },
      ),
    );
  }
}