如何通过web_socket_channel颤抖地聆听PHP MySQL服务器的更改

Question

我正在尝试将数据从API端点获取到我的Flutter应用中。我可以使用http请求来执行此操作，但是只要有更新数据库就可以接收更改。我发现这可以通过web_socket_channel来完成。

到目前为止，我已经尝试过

final WebSocketChannel channel = IOWebSocketChannel.connect("ws://127.0.0.1:3306/codeishweb/getData.php");

// In the StreamBuilder

StreamBuilder(
strema: channel.stream,
builder:(context, snapshot){
return Center(child:Text(snapshot.hasData? snapshot.data: "nothing available"));
}
);

这不起作用，并且我还收到错误消息Unsupported operation: Platform._version。

我如何产生我想要实现的目标。预先感谢。

Answer 1

您需要安装WebSocket服务器。如果您需要确保代码正常运行，请使用doc（http://www.websocket.org/echo.html）

中提供的服务器

连接到websocket.org提供的测试服务器。服务器发回与您发送给它的相同消息。此食谱使用以下步骤：

• 连接到WebSocket服务器
• 听来自服务器的消息
• 将数据发送到服务器
• 关闭WebSocket连接

您可以使用的演示（在flutter cookbook中可用）

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final title = 'WebSocket Demo';
    return MaterialApp(
      title: title,
      home: MyHomePage(
        title: title,
        channel: IOWebSocketChannel.connect('ws://echo.websocket.org'),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;
  final WebSocketChannel channel;

  MyHomePage({Key key, @required this.title, @required this.channel})
      : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController _controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
        padding: const EdgeInsets.all(20.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Form(
              child: TextFormField(
                controller: _controller,
                decoration: InputDecoration(labelText: 'Send a message'),
              ),
            ),
            StreamBuilder(
              stream: widget.channel.stream,
              builder: (context, snapshot) {
                return Padding(
                  padding: const EdgeInsets.symmetric(vertical: 24.0),
                  child: Text(snapshot.hasData ? '${snapshot.data}' : ''),
                );
              },
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _sendMessage,
        tooltip: 'Send message',
        child: Icon(Icons.send),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }

  void _sendMessage() {
    if (_controller.text.isNotEmpty) {
      widget.channel.sink.add(_controller.text);
    }
  }

  @override
  void dispose() {
    widget.channel.sink.close();
    super.dispose();
  }
}

These all details are available here with sample code。