[英]React not re-rendering / adding new element to DOM after setState
[英]React rendering deleted array element after setState()
我有一个问题,在我从组件状态的数组中删除它后,React似乎正在渲染一个已删除的数组元素。 在setState()之后,触发渲染,但会显示已删除的项目,而不是剩余的项目(请参阅下面的GIF视频)。
虽然组件非常简单,我花了几个小时来解决这个问题,但我还是无法解决这个问题。 奇怪的是,newState对象实际上包含有效的新列表,但它没有被渲染。
我真的希望有人可以帮我解决这个问题!
import React from "react";
import Button from "@material-ui/core/Button";
import update from "immutability-helper";
import Grid from "@material-ui/core/Grid";
import TextField from "@material-ui/core/TextField";
import * as R from "ramda";
class SessionNoteGroup extends React.Component {
state = {
id: this.props.id,
notes: this.props.notes
};
render() {
const { classes } = this.props;
const { id, notes } = this.state;
return (
<div>
<Grid container>
<Grid item xs={12}>
<TextField
multiline
fullWidth
id="notes"
name="notes"
label="Notes"
rows="2"
value={notes}
onChange={this.handleValueChange}
/>
</Grid>
</Grid>
<Button variant="outlined" color="primary" onClick={this.handleDelete}>
Delete
</Button>
</div>
);
}
handleValueChange = event => {
const { name, value } = event.target;
const { id, notes } = this.state;
let newState = {
id: id,
notes: value
};
this.setState(newState);
};
handleDelete = () => {
this.props.onDelete(this.state.id);
};
}
class SessionNotes extends React.Component {
state = {
notes: this.props.notes.slice(),
deleted: []
};
next_id = 2;
createNotes = () => {
let notesList = [];
for (let i = 0; i < this.state.notes.length; i++) {
const { id, notes } = this.state.notes[i];
notesList.push(
<SessionNoteGroup
id={id}
notes={notes}
onDelete={this.handleDelete}
index={i + 1}
/>
);
}
console.log(notesList);
return notesList;
};
handleDelete = id => {
const newNotes = R.filter(note => note.id !== id, this.state.notes);
this.setState({ notes: newNotes });
};
handleClickAdd = async () => {
const note = {
id: this.next_id,
notes: ""
};
this.next_id++;
const newState = update(this.state, { notes: { $push: [note] } });
this.setState(newState);
};
render() {
return (
<div>
{this.createNotes()}
<Button
variant="outlined"
color="primary"
onClick={this.handleClickAdd}
>
Add
</Button>
</div>
);
}
}
export default SessionNotes;
一些事情。
如果要根据prev状态设置状态,请使用带有回调的setState
,该回调将prevState作为参数。 那么下一个代码:
handleValueChange = event => {
const { name, value } = event.target;
const { id, notes } = this.state;
let newState = {
id: id,
notes: value
};
this.setState(newState);
};
将是这样的:
handleValueChange = event => {
const { name, value } = event.target;
const { id, notes } = this.state;
this.setState(prevState => ({ id: prevState.id, notes: value}));
};
在以下组件中相同:
handleDelete = id => {
const newNotes = ;
this.setState(prevState => ({ notes: R.filter(note => note.id !== id, prevState.notes) }));
};
依此类推,您可以根据以前的状态值更新状态。
然后,当您在react中创建元素列表时,使用key
属性:
<SessionNoteGroup
key={id}
id={id}
notes={notes}
onDelete={this.handleDelete}
index={i + 1}
/>
反应用于管理项目列表的渲染
尝试将一个键添加到渲染的容器div中
return (
<div key = {this.props.id}>
<Grid container>
<Grid item xs={12}>
<TextField
multiline
fullWidth
id="notes"
name="notes"
label="Notes"
rows="2"
value={notes}
onChange={this.handleValueChange}
/>
</Grid>
</Grid>
<Button variant="outlined" color="primary" onClick={this.handleDelete}>
Delete
</Button>
</div>
);
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