imgCom.js
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import React, { Component } from 'react';
import "./imgCom.css"
export default class imgCom extends Component {
constructor() {
super();
this.state = {
imgUrl: "",
httpImg:"",
base64Url:""
}
}
static getDerivedStateFromProps(props,state){
let {httpImg,imgUrl} = props;
if(httpImg&&httpImg!==state.httpImg){
return {
httpImg,
imgUrl
}
}else if(imgUrl!==state.imgUrl){
return {
imgUrl
}
}
return null
}
shouldComponentUpdate(nextProps){
if(this.props.imgUrl !== nextProps.imgUrl){
this.count=0;
this.getImage(nextProps.imgUrl)
return true
}else{
if(this.count===0){
this.count ++;
return true
}else{
return false
}
}
}
componentDidMount(){
this.count = 0
if(this.state.httpImg){
this.getImage(this.props.imgUrl)
}
}
getImage(imgUrl) {
let {httpImg} = this.state
var xhr = new XMLHttpRequest();
xhr.open('POST', httpImg);
xhr.setRequestHeader('Content-Type', 'application/json');
var data = {
reqInfo: {
imgPath: imgUrl
},
request: "getImgDataByPath"
}
xhr.send(JSON.stringify(data));
xhr.onreadystatechange = () =>{
if (xhr.readyState === 4) {
if (xhr.status === 200 || xhr.status === 304) {
var result = JSON.parse(xhr.responseText)
if(result.status === 0){
this.setImgUrl("data:image/png;base64,"+result.resInfo.imgData)
}else{
this.setImgUrl(require("./asstes/err.png"))
}
}
}
}
}
setImgUrl(url){
this.setState({
base64Url:url
})
}
render() {
let {base64Url} = this.state
return <img className="imageObject" src={base64Url} alt="" ></img>
}
}