websocket

import 'package:flutter/material.dart';
import 'package:web_socket_channel/io.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  TextEditingController _controller=TextEditingController();
  IOWebSocketChannel channel;
  String _text='...';
  @override
  void initState() {
    // TODO: implement initState
    channel=IOWebSocketChannel.connect('ws://echo.websocket.org');
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('websocket demo'),),
      body: Padding(
        padding:EdgeInsets.all(18),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Form(
              child: TextField(
                controller: _controller,
                decoration: InputDecoration(
                  labelText: 'please input your mind',
                ),
              ),
            ),
            StreamBuilder(
              stream: channel.stream,
              builder:(context,snapshot){
                if (snapshot.hasError) {
                  _text = "网络不通...";
                } else if (snapshot.hasData) {
                  _text = "echo: "+snapshot.data;
                }
                return Padding(
                  padding: const EdgeInsets.symmetric(vertical: 24.0),
                  child: Text(_text),);
              },
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
          child: Icon(Icons.send),
          onPressed: upload,
          ),
    );
  }
  void upload(){
    if(_controller.text.isNotEmpty){
      channel.sink.add(_controller.text);
    }
  }
  @override
  void dispose() {
    // TODO: implement dispose
    channel.sink.close();
    super.dispose();
  }
}