Flutter StreamController

readme.md

Flutter StreamController

Created with <3 with dartpad.dev.

main.dart

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

void main() {
  ///
  /// Example 1
  ///
//   final myStream = NumberCreator().stream;
//   final subscription = myStream.listen(
//     (data) => print('s: $data'),
//   );
    
  ///
  /// Example 2
  ///
//   final myStream = NumberCreator()
//     .stream
//     .asBroadcastStream();
  
//   final subscription1 = myStream.listen(
//     (data) => print('s1: $data'),
//   );
  
//   final subscription2 = myStream.listen(
//     (data) => print('s2: $data'),
//   );
    
  ///
  /// Example 3
//   ///
//   final myStream = NumberCreator().stream;
  
  
//   final subscription = myStream.listen(
//     (data) => print('s: $data'),
//     onError: (err) => print('Error!'),
//     cancelOnError: false,
//     onDone: () => print('Done'),
//   );
  
  // Subscription:
  // - subscription.pause();
  // - subscription.resume();
  // - subscription.cancel();
    
  ///
  /// Example 4
  ///
//   final myStream = NumberCreator()
//     .stream
//     .where((i) => i % 2 == 0)
//     .map((i) => '${i + 1}')
//     .listen(print); // Без подписчиков myStream.listen
  
  
  runApp(
    MaterialApp(
      home: MyWidget(),
    ),
  );
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return  Scaffold(
      body: Center(
          ///
          /// Example 1-4
          ///
//         child: Text('Text'),

          ///
          /// Example 5
          ///
//         child: FutureBuilder<String>(
//           future: _fetchNetworkData(),
//           builder: (context, snapshot) {
//             //
//           },
//         ),

        ///
        /// Example 6
        ///
        child: StreamBuilder<String>(
          stream: NumberCreator().stream
            .map((i) => '${i + 1}'),
          builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
            if(snapshot.connectionState == ConnectionState.waiting) {
              return const Text('No data yet.');
            } else if(snapshot.connectionState == ConnectionState.done) {
              return const Text('Done');
            } else if(snapshot.hasError) {
              return const Text('Error!', style: TextStyle(color: Colors.red));
            } else {
              return Text(snapshot.data ?? '');
           }
          },
        ),
      ),
    );
  }
}

class NumberCreator {
  final _controller = StreamController<int>();
  int _count = 0;
  
  NumberCreator() {
    // Увеличиваем счётчик на 1 каждую секунду.
    Timer.periodic(const Duration(seconds: 1), (Timer timer) {
    
    // Выполняем увеличение счётчика на 1 в течение 5 секунд.
//     Timer(const Duration(seconds: 5), () {
        _controller.sink.add(_count);
        _count++;
      
      
        if(_count == 3) {
          _controller.addError(Exception('Ta-da!'));
        }
        if(_count >= 5) {
          timer.cancel();
        }
      },
    );
  }
    
  Stream<int> get stream => _controller.stream;
}