Bloc (State Management) Check Connectivity Example Using Bloc

 abstract class InternetEvent {}

class InternetLostEvent extends InternetEvent {}

class InternetGainedEvent extends InternetEvent {}

abstract class InternetState {}

class InternetInitialState extends InternetState {}

class InternetLostState extends InternetState {}

class InternetGainedState extends InternetState {}
import "dart:async";
import "package:connectivity/connectivity.dart";
import "package:firebase/Stateless_Component_UI/Bloc/internet_bloc/internet_event.dart";
import "package:firebase/Stateless_Component_UI/Bloc/internet_bloc/internet_state.dart";
import "package:flutter_bloc/flutter_bloc.dart";
/// Difference between Cubit and Bloc is that Cubit is based on Function and
/// Bloc is based on Event
/// In short, Cubit is Function based and Bloc is Event based
class InternetBloc extends Bloc<InternetEvent, InternetState>
{
  final Connectivity _connectivity = Connectivity();
  StreamSubscription? connectivitySubscription;

  InternetBloc() : super(InternetInitialState()) {

    on<InternetLostEvent>((event, emit) {
      return emit(InternetLostState());
    },);

    on<InternetGainedEvent>((event, emit) {
      return emit(InternetGainedState());
    },);

     connectivitySubscription = _connectivity.onConnectivityChanged.listen((result) {
      if(result == ConnectivityResult.mobile || result == ConnectivityResult.wifi)
        {
          add(InternetGainedEvent());
        }
      else
        {
          add(InternetLostEvent());
        }
    });
  }

  @override
  Future<void> close()
  {
    connectivitySubscription?.cancel();
    return super.close();
  }
}

import "package:firebase/Stateless_Component_UI/Bloc/internet_bloc/internet_bloc.dart";
import "package:firebase/Stateless_Component_UI/Bloc/internet_bloc/internet_state.dart";
import "package:flutter/material.dart";
import "package:flutter_bloc/flutter_bloc.dart";

void main()
{
  runApp(const MyApp());
}
class MyApp extends StatelessWidget
{
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (context) {
        return InternetBloc();
      },
      child: MaterialApp(
        title: "Bloc Check Connectivity",
        debugShowCheckedModeBanner: false,
        theme: ThemeData(
          primarySwatch: Colors.grey,
        ),
        home: const HomeScreen2(),
      ),
    );
  }
}
class HomeScreen2 extends StatelessWidget
{
  const HomeScreen2({super.key});
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Check Connectivity"),
        centerTitle: true,
        backgroundColor: Colors.grey,
      ),
      body: Center(
        /// BlocConsumer is the combination of background Listener and UI builder
        /// BlocBuilder is provide only UI builder
        /// BlocListener is provide only Listener in background
        /// as shown below
        child: BlocConsumer<InternetBloc, InternetState>(
          listener: (context, state) {
            if(state is InternetGainedState)
              {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(
                    content: Text("Internet Connected!"),
                    backgroundColor: Colors.green,
                  ),
                );
              }
            else if(state is InternetLostState)
              {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(
                    content: Text("Internet not Connected!"),
                    backgroundColor: Colors.red,
                  ),
                );
              }
          },
          builder: (context, state) {
            if(state is InternetGainedState)
            {
              return const Text("Connected!");
            }
            else if(state is InternetLostState)
            {
              return const Text("Not Connected!");
            }
            else
            {
              return const Text("Loading...");
            }
          },
        ),
      ),
    );
  }
}