Javascript 反应挂钩:父组件未重新渲染
我正在尝试使用回调从子组件更新父组件的状态。状态和回调传递给文本输入。正在调用回调,父级的状态已更改,但不会重新加载。输入字段的值保持不变。如果使用强制渲染,则每次添加新角色时(根据需要),文本字段都会更新。我不确定是什么原因导致了这种情况,据我所知,提供的setState钩子应该重新加载,除非状态保持不变 编辑:(添加了父组件,而不仅仅是回调) 下面是父组件Javascript 反应挂钩:父组件未重新渲染,javascript,reactjs,Javascript,Reactjs,我正在尝试使用回调从子组件更新父组件的状态。状态和回调传递给文本输入。正在调用回调,父级的状态已更改,但不会重新加载。输入字段的值保持不变。如果使用强制渲染,则每次添加新角色时(根据需要),文本字段都会更新。我不确定是什么原因导致了这种情况,据我所知,提供的setState钩子应该重新加载,除非状态保持不变 编辑:(添加了父组件,而不仅仅是回调) 下面是父组件 import Card from './Card' import Instructions from './instructions'
import Card from './Card'
import Instructions from './instructions'
import Title from './title'
import React, { useRef, useState, useCallback, useEffect } from 'react'
import { DropTarget } from 'react-dnd'
import ItemTypes from './ItemTypes'
import update from 'immutability-helper'
const Container = ({ connectDropTarget }) => {
const ref = useRef(null)
const titleRef = useRef()
const instructionsRef = useRef()
const appRef = useRef()
useEffect(() => {
// add when mounted
document.addEventListener("mousedown", handleClick);
// return function to be called when unmounted
return () => { document.removeEventListener("mousedown", handleClick);};
}, []);
const handleClick = e => {
if (titleRef.current.contains(e.target)) {
setFocus("Title");
return;
} // outside click
else if(instructionsRef.current.contains(e.target)){
setFocus("Instructions");
return;
}
setFocus(null);
};
const [, updateState] = useState();
const forceUpdate = useCallback(() => updateState({}), []);
const [focus,setFocus] = useState(null);
const [title, setTitle] = useState({id: "Title", text: "Default",type: "Title", data:[]});
const [instructions, setInstructions] = useState({id: "Instructions",type:"Instructions", text: "Instructions", data:[]});
const [cards, setCards] = useState([
{
id: 1,
text: 'Write a cool JS library',
},
{
id: 2,
text: 'Make it generic enough',
},
{
id: 3,
text: 'Write README',
},
{
id: 4,
text: 'Create some examples',
},
{
id: 5,
text: 'Spam in Twitter and IRC to promote it',
},
{
id: 6,
text: '???',
},
{
id: 7,
text: 'PROFIT',
},
])
const moveCard = useCallback(
(id, atIndex) => {
const { card, index } = findCard(id)
setCards(
update(cards, {
$splice: [[index, 1], [atIndex, 0, card]],
}),
)
},
[cards],
)
const findCard = useCallback(
id => {
const card = cards.filter(c => `${c.id}` === id)[0]
return {
card,
index: cards.indexOf(card),
}
},
[cards],
)
const updateItem = useCallback(
(id,field,additionalData,value) => {
return;
},
[cards], //WHat does this do?
)
const updateTitle = text => {
console.log("Updating title")
let tempTitle = title;
tempTitle['text'] = text;
//console.log(text);
//console.log(title);
//console.log(tempTitle);
setTitle(tempTitle);
//console.log(title);
//console.log("done");
forceUpdate(null);
}
connectDropTarget(ref)
return (
<div ref={appRef}>
<div ref={titleRef} >
<Title item={title} focus={focus} updateFunction={updateTitle}/>
</div>
<div ref={instructionsRef} >
<Instructions item={instructions} focus={focus}/>
</div>
<div className="Card-list" ref={ref}>
{cards.map(card => (
<Card
key={card.id}
id={`${card.id}`}
text={card.text}
moveCard={moveCard}
findCard={findCard}
item={card}
focus={focus}
/>
))}
</div>
</div>
)
}
export default DropTarget(ItemTypes.CARD, {}, connect => ({
connectDropTarget: connect.dropTarget(),
}))(Container)
从“./Card”导入卡
从“./指令”导入指令
从“./Title”导入标题
从“React”导入React,{useRef,useState,useCallback,useffect}
从'react dnd'导入{DropTarget}
从“./ItemTypes”导入项目类型
从“不变性助手”导入更新
常量容器=({connectDropTarget})=>{
const ref=useRef(空)
const titleRef=useRef()
const instructionsRef=useRef()
常量appRef=useRef()
useffect(()=>{
//安装时添加
文件。添加的列表(“鼠标向下”,handleClick);
//卸载时要调用的返回函数
return()=>{document.removeEventListener(“mousedown”,handleClick);};
}, []);
常量handleClick=e=>{
if(标题引用当前包含(如目标)){
setFocus(“标题”);
返回;
}//外部单击
else if(指令参考当前包含(如目标)){
setFocus(“说明”);
返回;
}
设置焦点(空);
};
const[,updateState]=useState();
constforceupdate=useCallback(()=>updateState({}),[]);
const[focus,setFocus]=useState(null);
const[title,setTitle]=useState({id:“title”,text:“Default”,type:“title”,data:[]);
const[instructions,setInstructions]=useState({id:“指令”,类型:“指令”,文本:“指令”,数据:[]});
const[cards,setCards]=使用状态([
{
id:1,
文本:“编写一个很酷的JS库”,
},
{
id:2,
文本:“让它足够通用”,
},
{
id:3,
文本:“编写自述文件”,
},
{
id:4,
文本:“创建一些示例”,
},
{
id:5,
文字:“推特和IRC中的垃圾邮件,以促进它”,
},
{
id:6,
正文:“???”,
},
{
id:7,
正文:"利润",,
},
])
const moveCard=useCallback(
(id,atIndex)=>{
const{card,index}=findCard(id)
赛卡(
更新(卡片、{
$splice:[[index,1],[atIndex,0,card]],
}),
)
},
[卡片],
)
const findCard=useCallback(
id=>{
const card=cards.filter(c=>`${c.id}`==id)[0]
返回{
卡片
索引:卡片。索引(卡片),
}
},
[卡片],
)
const updateItem=useCallback(
(id、字段、附加数据、值)=>{
返回;
},
[卡片],//这是做什么的?
)
const updateTitle=text=>{
console.log(“更新标题”)
让诱惑=标题;
TENTITLE['text']=文本;
//console.log(文本);
//控制台日志(标题);
//console.log(testitle);
setTitle(TENTITLE);
//控制台日志(标题);
//控制台日志(“完成”);
强制更新(空);
}
connectDropTarget(参考)
返回(
{cards.map(card=>(
))}
)
}
导出默认DropTarget(ItemTypes.CARD,{},connect=>({
connectDropTarget:connect.dropTarget(),
}))(集装箱)
调用此函数的组件的代码为:
import React from 'react'
function Title(props) {
if(props.focus === "Title")
return(
<input
id="Title"
class="Title"
type="text"
value={props.item['text']}
onChange = { e => props.updateFunction(e.target.value)}
/>
);
else
return (
<h1> {props.item['text']} </h1>
);
}
export default Title
从“React”导入React
功能名称(道具){
如果(道具焦点==“标题”)
返回(
props.updateFunction(e.target.value)}
/>
);
其他的
返回(
{props.item['text']}
);
}
导出默认标题
问题就在这里
const updateTitle = text => {
let tempTitle = title; // These two variables are the same object
tempTitle['text'] = text;
setTitle(tempTitle); // problem is here
}
React使用object.is()方法比较前后两个值
您应该使“title”和“entitle”成为不同的对象,如下所示
const updateTitle = text => {
let tempTitle = {...title}; // tempTitle is a new object
tempTitle['text'] = text;
setTitle(tempTitle);
}
这是一个可变对象的演示
var a={name:1}
var b=a;
b、 name=2
var result=Object.is(a,b)
console.log(结果)
//正确
问题就在这里
const updateTitle = text => {
let tempTitle = title; // These two variables are the same object
tempTitle['text'] = text;
setTitle(tempTitle); // problem is here
}
React使用object.is()方法比较前后两个值
您应该使“title”和“entitle”成为不同的对象,如下所示
const updateTitle = text => {
let tempTitle = {...title}; // tempTitle is a new object
tempTitle['text'] = text;
setTitle(tempTitle);
}
这是一个可变对象的演示
var a={name:1}
var b=a;
b、 name=2
var result=Object.is(a,b)
console.log(结果)
//正确
您能显示两个组件的完整代码吗