flutter streambuilder

import 'dart:async';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('StreamBuilder Example')),
        body: CounterStream(),
      ),
    );
  }
}

class CounterStream extends StatefulWidget {
  @override
  _CounterStreamState createState() => _CounterStreamState();
}

class _CounterStreamState extends State<CounterStream> {
  final StreamController<int> _controller = StreamController<int>();
  int _counter = 0;

  @override
  void initState() {
    super.initState();
    _startTimer();
  }

  @override
  void dispose() {
    _controller.close();
    super.dispose();
  }

  void _startTimer() {
    Timer.periodic(Duration(seconds: 1), (Timer timer) {
      setState(() {
        _counter++;
      });
      _controller.add(_counter);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: StreamBuilder<int>(
        stream: _controller.stream,
        initialData: _counter,
        builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
          if (snapshot.hasData) {
            return Text('Counter: ${snapshot.data}');
          } else if (snapshot.hasError) {
            return Text('Error: ${snapshot.error}');
          }
          return CircularProgressIndicator();
        },
      ),
    );
  }
}