[英]React.js not re-rendering app on state update
我正在研究基于React.js的大纲器(类似于工作流)。 我陷入了困境。 当我在任何一项上按Enter键时,我想在其下方插入另一项。
因此,我已经使用setState函数将一个项目插入到当前项目的正下方,如下面的代码片段所示:
this.setState({
items: this.state.items.splice(this.state.items.map((item) => item._id).indexOf(itemID) + 1, 0, {_id: (new Date().getTime()), content: 'Some Note'})
})
但是,该应用程序重新呈现为空白,没有出现任何错误。
到目前为止,我的完整资料来源:
import './App.css';
import React, { Component } from 'react';
import ContentEditable from 'react-contenteditable';
const items = [
{
_id: 0,
content: 'Item 1 something',
note: 'Some note for item 1'
},
{
_id: 5,
content: 'Item 1.1 something',
note: 'Some note for item 1.1'
},
{
_id: 1,
content: 'Item 2 something',
note: 'Some note for item 2',
subItems: [
{
_id: 2,
content: 'Sub Item 1 something',
subItems: [{
_id: 3,
content: 'Sub Sub Item 4'
}]
}
]
}
];
class App extends Component {
render() {
return (
<div className="App">
<Page items={items} />
</div>
);
}
}
class Page extends Component {
constructor(props) {
super(props);
this.state = {
items: this.props.items
};
this.insertItem = this.insertItem.bind(this);
}
render() {
return (
<div className="page">
{
this.state.items.map(item =>
<Item _id={item._id} content={item.content} note={item.note} subItems={item.subItems} insertItem={this.insertItem} />
)
}
</div>
);
}
insertItem(itemID) {
console.log(this.state.items);
this.setState({
items: this.state.items.splice(this.state.items.map((item) => item._id).indexOf(itemID) + 1, 0, {_id: (new Date().getTime()), content: 'Some Note'})
})
console.log(this.state.items);
}
}
class Item extends Component {
constructor(props) {
super(props);
this.state = {
content: this.props.content,
note: this.props.note
};
this.saveItem = this.saveItem.bind(this);
this.handleKeyPress = this.handleKeyPress.bind(this);
}
render() {
return (
<div key={this.props._id} className="item">
<ContentEditable html={this.state.content} disabled={false} onChange={this.saveItem} onKeyPress={(event) => this.handleKeyPress(this.props._id, event)} />
<div className="note">{this.state.note}</div>
{
this.props.subItems &&
this.props.subItems.map(item =>
<Item _id={item._id} content={item.content} note={item.note} subItems={item.subItems} insertItem={this.insertItem} />
)
}
</div>
);
}
saveItem(event) {
this.setState({
content: event.target.value
});
}
handleKeyPress(itemID, event) {
if (event.key === 'Enter') {
event.preventDefault();
console.log(itemID);
console.log(event.key);
this.props.insertItem(itemID);
}
}
}
export default App;
github仓库: https : //github.com/Hirvesh/mneme
任何人都可以帮助我了解为什么更新项目后无法再次渲染吗?
编辑:
我已经更新了代码以添加键,如下所示,尽管状态正在更新,但仍呈现为空白:
import './App.css';
import React, { Component } from 'react';
import ContentEditable from 'react-contenteditable';
const items = [
{
_id: 0,
content: 'Item 1 something',
note: 'Some note for item 1'
},
{
_id: 5,
content: 'Item 1.1 something',
note: 'Some note for item 1.1'
},
{
_id: 1,
content: 'Item 2 something',
note: 'Some note for item 2',
subItems: [
{
_id: 2,
content: 'Sub Item 1 something',
subItems: [{
_id: 3,
content: 'Sub Sub Item 4'
}]
}
]
}
];
class App extends Component {
render() {
return (
<div className="App">
<Page items={items} />
</div>
);
}
}
class Page extends Component {
constructor(props) {
super(props);
this.state = {
items: this.props.items
};
this.insertItem = this.insertItem.bind(this);
}
render() {
return (
<div className="page">
{
this.state.items.map(item =>
<Item _id={item._id} key={item._id} content={item.content} note={item.note} subItems={item.subItems} insertItem={this.insertItem} />
)
}
</div>
);
}
insertItem(itemID) {
console.log(this.state.items);
this.setState({
items: this.state.items.splice(this.state.items.map((item) => item._id).indexOf(itemID) + 1, 0, {_id: (new Date().getTime()), content: 'Some Note'})
})
console.log(this.state.items);
}
}
class Item extends Component {
constructor(props) {
super(props);
this.state = {
content: this.props.content,
note: this.props.note
};
this.saveItem = this.saveItem.bind(this);
this.handleKeyPress = this.handleKeyPress.bind(this);
}
render() {
return (
<div className="item">
<ContentEditable html={this.state.content} disabled={false} onChange={this.saveItem} onKeyPress={(event) => this.handleKeyPress(this.props._id, event)} />
<div className="note">{this.state.note}</div>
{
this.props.subItems &&
this.props.subItems.map(item =>
<Item _id={item._id} key={item._id} content={item.content} note={item.note} subItems={item.subItems} insertItem={this.insertItem} />
)
}
</div>
);
}
saveItem(event) {
this.setState({
content: event.target.value
});
}
handleKeyPress(itemID, event) {
if (event.key === 'Enter') {
event.preventDefault();
console.log(itemID);
console.log(event.key);
this.props.insertItem(itemID);
}
}
}
export default App;
编辑2:
根据以下建议,添加了key = {i._id}仍然无法正常工作,如果有人想看一下,将最新代码推送到github。
this.state.items.map((item, i) =>
<Item _id={item._id} key={i._id} content={item.content} note={item.note} subItems={item.subItems} insertItem={this.insertItem} />
)
您错过了在Item上放置密钥的原因,因为该React无法识别您的状态是否改变。
<div className="page">
{
this.state.items.map((item, i) =>
<Item _id={item._id}
key={i} // <---- HERE!!
content={item.content}
note={item.note}
subItems={item.subItems}
insertItem={this.insertItem} />
)}
</div>
您的代码存在多个问题:
this.insertItem
传递给SubItems(不存在) this.state.items.splice
,更改this.state.items
,但返回[]
。 因此,您的新州为[]
尝试这个:
this.state.items.splice(/* your splice argument here */)
this.setState({ items: this.state.items }, () => {
// this.setState is async! so this is the proper way to check it.
console.log(this.state.items);
});
要完成您真正想要的,这还远远不够。但是至少,在您修复它之后,您可以看到一些结果。
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