Javascript 为什么不是';clickHandler是否处于更新状态?
我正在尝试设置一个背景,该背景随着活动按钮而改变,clickHandler将向我显示按钮的正确id,但随后无法更新状态…我错过了什么Javascript 为什么不是';clickHandler是否处于更新状态?,javascript,reactjs,Javascript,Reactjs,我正在尝试设置一个背景,该背景随着活动按钮而改变,clickHandler将向我显示按钮的正确id,但随后无法更新状态…我错过了什么 import React, { Component } from "react"; import { NavLink } from "react-router-dom"; import river from "../img/river.jpg"; import snow from "../img/snow.jpeg"; import weather from ".
import React, { Component } from "react";
import { NavLink } from "react-router-dom";
import river from "../img/river.jpg";
import snow from "../img/snow.jpeg";
import weather from "../img/weather.jpg";
export default class LowerHeader extends Component {
state = {
imgUrl: river
};
clickHandler = e => {
if (e.target.id === 1) {
this.setState({
imgUrl: weather
});
} else if (e.target.id === 2) {
this.setState({
imgUrl: snow
});
} else if (e.target.id === 3) {
this.setState({
imgUrl: river
});
}
console.dir(e.target);
};
render() {
let styles = {
backgroundImage: `url(${this.state.imgUrl})`,
backgroundSize: "cover",
backgroundPosition: "0% 70%",
overflow: "hidden"
};
return (
<React.Fragment>
<div
className="link-bg-img"
style={styles}
alt="Background related to tab chosen"
/>
<header className="lower-header">
<ul>
<NavLink
to="/maincontent/weather"
id="1"
onClick={this.clickHandler}
>
Local Weather
</NavLink>
<NavLink to="/maincontent/snow" id="2" onClick={this.clickHandler}>
Snow Report
</NavLink>
<NavLink to="/maincontent/river" id="3" onClick={this.clickHandler}>
River Flows
</NavLink>
</ul>
</header>
</React.Fragment>
);
}
}
import React,{Component}来自“React”;
从“react router dom”导入{NavLink};
从“./img/river.jpg”导入河流;
从“./img/snow.jpeg”导入雪;
从“./img/weather.jpg”导入天气;
导出默认类LowerHeader扩展组件{
状态={
伊姆格尔:河流
};
clickHandler=e=>{
如果(e.target.id==1){
这是我的国家({
伊姆格尔:天气
});
}else if(e.target.id==2){
这是我的国家({
伊姆古尔:雪
});
}else if(e.target.id==3){
这是我的国家({
伊姆格尔:河流
});
}
console.dir(e.target);
};
render(){
让样式={
backgroundImage:`url(${this.state.imgUrl})`,
背景尺寸:“封面”,
背景位置:“0%70%”,
溢出:“隐藏”
};
返回(
当地天气
降雪报告
河流流量
);
}
}
我想与页面加载的初始状态保持不变…它工作。然后应该随着每个按钮的点击而改变。谢谢
e.target.id
是一个字符串,您可以将其与带有=
的数字进行比较。它因类型不同而失败
使用类似以下内容:
clickHandler = e => {
const id = parseInt(e.target.id, 10);
if (id === 1) {
...
正如UjinT34所说,将字符串与带有===运算符的数字进行比较 clickhandler的另一个更优雅的解决方案是:
import React, { Component } from "react";
import { NavLink } from "react-router-dom";
import river from "../img/river.jpg";
import snow from "../img/snow.jpeg";
import weather from "../img/weather.jpg";
export default class LowerHeader extends Component {
state = {
imgUrl: river
};
clickHandler = url => {
this.setState({
imgUrl: url
});
};
render() {
let styles = {
backgroundImage: `url(${this.state.imgUrl})`,
backgroundSize: "cover",
backgroundPosition: "0% 70%",
overflow: "hidden"
};
return (
<>
<div
className="link-bg-img"
style={styles}
alt="Background related to tab chosen"
/>
<header className="lower-header">
<ul>
<NavLink to="/maincontent/weather" id="1" onClick={()=>{this.clickHandler(weather)}}>
Local Weather
</NavLink>
<NavLink to="/maincontent/snow" id="2" onClick={()=>{this.clickHandler(snow)}}>
Snow Report
</NavLink>
<NavLink to="/maincontent/river" id="3" onClick={()=>this.clickHandler(river)}>
River Flows
</NavLink>
</ul>
</header>
</>
);
}
}
import React,{Component}来自“React”;
从“react router dom”导入{NavLink};
从“./img/river.jpg”导入河流;
从“./img/snow.jpeg”导入雪;
从“./img/weather.jpg”导入天气;
导出默认类LowerHeader扩展组件{
状态={
伊姆格尔:河流
};
clickHandler=url=>{
这是我的国家({
imgUrl:url
});
};
render(){
让样式={
backgroundImage:`url(${this.state.imgUrl})`,
背景尺寸:“封面”,
背景位置:“0%70%”,
溢出:“隐藏”
};
返回(
{this.clickHandler(天气)}>
当地天气
{this.clickHandler(snow)}>
降雪报告
这个。clickHandler(river)}>
河流流量
);
}
}
这里有一个项目链接:初始加载可能需要几秒钟谢谢!忽略简单的事情…非常感谢