StreamBuilder Example

stream_builder_example.dart

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final StreamController<String> _events = StreamController<String>();

  void _showError(String message) {
    _events.add(message);
  }

  @override
  Widget build(BuildContext context) {
    print('build...');
    return Scaffold(
      appBar: AppBar(
        title: const Text('StreamBuilder'),
      ),
      body: Center(
        child: StreamBuilder<String>(
          stream: _events.stream,
          initialData: 'No Errors',
          builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
            return ErrorView(snapshot.data);
          },
        ),
      ),
      floatingActionButton: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          FloatingActionButton(
            onPressed: () => _showError('Printing Error!'),
            child: Icon(Icons.print),
          ),
          FloatingActionButton(
            onPressed: () => _showError('Translation Error!'),
            child: Icon(Icons.translate),
          ),
        ],
      ),
    );
  }
}

class ErrorView extends StatelessWidget {
  const ErrorView(this.message);

  final String message;

  @override
  Widget build(BuildContext context) {
    return Text(
      message,
      style: TextStyle(color: Colors.red),
    );
  }
}