StreamBuilder Example

streambuilder.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Stream<int> generateNumbers = (() async* {
    await Future<void>.delayed(const Duration(seconds: 2));

    for (int i = 1; i <= 500; i++) {
      await Future<void>.delayed(const Duration(seconds: 5));
      yield i;
    }
  })();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("title"),
      ),
      body: Center(
        child: StreamBuilder<int>(
          stream: generateNumbers,
          initialData: 0,
          builder: (
            BuildContext context,
            AsyncSnapshot<int> snapshot,
          ) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const CircularProgressIndicator(),
                  Visibility(
                    visible: snapshot.hasData,
                    child: Text(
                      snapshot.data.toString(),
                      style: const TextStyle(color: Colors.black, fontSize: 24),
                    ),
                  ),
                ],
              );
            } else if (snapshot.connectionState == ConnectionState.active ||
                snapshot.connectionState == ConnectionState.done) {
              if (snapshot.hasError) {
                return const Text('Error');
              } else if (snapshot.hasData) {
                return Text(snapshot.data.toString(),
                    style: const TextStyle(color: Colors.teal, fontSize: 36));
              } else {
                return const Text('Empty data');
              }
            } else {
              return Text('State: ${snapshot.connectionState}');
            }
          },
        ),
      ),
    );
  }
}