我想显示从网络套接字获取的数据。当尚不存在时,将调用render函数。我尝试在websocket发送数据但无法正常工作时使用this.state更新它。我正在使用图表显示BarChart,在数据中,我需要WebSocket中的值。
index.js
import _ from 'lodash';
import style from './style.css';
import React, { PureComponent } from 'react';
import ReactDOM from 'react-dom';
import {
BarChart, Bar, Cell, XAxis, YAxis, CartesianGrid, Tooltip, Legend, LabelList, Label
} from 'recharts';
var data;
class Example extends React.Component {
constructor(props) {
super(props);
//setting a default value
this.state = { data: [{time:23.30,value:288.65},{Energy:0,value:0.0}] };
}
//componentDidMount() {
//this.state = { data: data };
//console.log("compMount");
//}
render() {
//verbinde();
var connection = new WebSocket('ws://next-gen-rz.hs-harz.de:8080/fhem_prototyp2/Test');
connection.onopen = function () {
connection.send('day');
console.log("gesendet: day");
};
// Log errors
connection.onerror = function (error) {
console.log('WebSocket Error ' + error);
};
// Log messages from the server
connection.onmessage = function (e) {
console.log('Server: ' + e.data);
this.setState = {data: e.data };
};
return (
<BarChart
width={800}
height={500}
data={this.state.data}
margin={{
top: 5, right: 30, left: 20, bottom: 5,
}}
>
<CartesianGrid strokeDasharray="3 3" />
<XAxis dataKey="time" tick={{ fill: 'white'}}/>
<YAxis tick={{ fill: 'white' }} label={{ value: 'kWh', angle: -90, position: 'insideLeft' }}>
</YAxis>
<Bar name="Wochenverbrauch" dataKey="value" fill="#f59f4a" >
<LabelList dataKey="value" position="top" fill='white'/>
</Bar>
</BarChart>
);
}
}
ReactDOM.render(<Example />, document.getElementById("left"));
答案 0 :(得分:1)
您只能在componentDidMount
方法生命周期中打开一次websocket连接。
要更新状态,您应该调用setState函数
您还需要在componentWillUnmount
方法中关闭websocket连接,以避免内存泄漏
class Example extends React.Component {
constructor(props) {
super(props);
//setting a default value
this.state = { data: [{time:23.30,value:288.65},{Energy:0,value:0.0}] };
}
componentDidMount() {
const that = this;
that.connection = new WebSocket(
'ws://next-gen-rz.hs-harz.de:8080/fhem_prototyp2/Test'
);
that.connection.onopen = function () {
that.connection.send('day');
};
// Log errors
that.connection.onerror = function (error) {
console.log('WebSocket Error ' + error);
};
// Log messages from the server
that.connection.onmessage = function(e) {
console.log('Server: ' + e.data);
that.setState({data: e.data });
};
}
componentWillUnmount() {
this.connection && this.connection.close();
}
render() {
return (
<BarChart
width={800}
height={500}
data={this.state.data}
margin={{top: 5, right: 30, left: 20, bottom: 5}}
>
<CartesianGrid strokeDasharray="3 3" />
<XAxis dataKey="time" tick={{ fill: 'white'}}/>
<YAxis
tick={{ fill: 'white' }}
label={{ value: 'kWh', angle: -90, position: 'insideLeft' }}
/>
<Bar name="Wochenverbrauch" dataKey="value" fill="#f59f4a" >
<LabelList dataKey="value" position="top" fill='white'/>
</Bar>
</BarChart>
);
}
}
答案 1 :(得分:0)
您无法通过更改状态来进行更新,需要调用该函数:
this.setState(newState)
并提供newState对象。参见https://reactjs.org/docs/react-component.html#setstate
此外,您无法在render函数中设置状态,例如,您需要在componentDidMount
中获取数据,然后在此处设置状态。