React DND - 拖放事件后无法将新项目添加到状态
React DND - Cannot add new item to state after a drag and drop event
在将这段代码应用到我的图片上传器之前,我正在开发一个简单版本的 ReactDND。
每次添加图像时,都会将其添加到状态并传递给 ReactDND,以便它可以拖放(因此用户可以重新排列他们的图像)。
一切都很好,除了一件事。我遇到的问题是在添加多张图片后,一旦我拖放图片(有效),ReactDND 的状态就不再更新,我无法添加新图片。
下面是我的代码(注意我只是使用一个按钮来向状态添加额外的项目):
主要成分:
import React from 'react';
// Drag and drop stuff
import { DragDropContext } from 'react-dnd';
import HTML5Backend from 'react-dnd-html5-backend';
import Container from './Container';
class ImageUploader extends React.Component {
constructor(props) {
super(props);
this.state = {
list: [],
listCount: 1
};
this.onAddItem = this.onAddItem.bind(this);
}
onAddItem(e) {
e.preventDefault();
var listArray = this.state.list;
var buildObject = {
text: 'Jeremy' + this.state.listCount.toString(),
age: '25',
id: this.state.listCount
};
listArray.push(buildObject);
let newListCount = this.state.listCount + 1;
this.setState({
list: listArray,
listCount: newListCount
});
console.log(this.state.list);
}
render() {
return (
<div>
<h1>Add to List</h1>
<button onClick={this.onAddItem}>Add Item</button>
<h1>The List</h1>
<Container id={1} list={this.state.list} />
</div>
)
}
}
export default DragDropContext(HTML5Backend)(ImageUploader);
容器:
import React, { Component } from 'react';
import update from 'react/lib/update';
import Card from './Card';
import { DropTarget } from 'react-dnd';
class Container extends Component {
constructor(props) {
super(props);
this.state = { cards: props.list };
}
pushCard(card) {
this.setState(update(this.state, {
cards: {
$push: [ card ]
}
}));
}
removeCard(index) {
this.setState(update(this.state, {
cards: {
$splice: [
[index, 1]
]
}
}));
}
moveCard(dragIndex, hoverIndex) {
const { cards } = this.state;
const dragCard = cards[dragIndex];
this.setState(update(this.state, {
cards: {
$splice: [
[dragIndex, 1],
[hoverIndex, 0, dragCard]
]
}
}));
}
render() {
const { cards } = this.state;
const { canDrop, isOver, connectDropTarget } = this.props;
const isActive = canDrop && isOver;
const style = {
width: "200px",
height: "404px",
border: '1px dashed gray'
};
const backgroundColor = isActive ? 'lightgreen' : '#FFF';
return connectDropTarget(
<div className="houzes-dropbox">
{cards.map((card, i) => {
return (
<Card
key={card.id}
index={i}
listId={this.props.id}
card={card}
removeCard={this.removeCard.bind(this)}
moveCard={this.moveCard.bind(this)} />
);
})}
</div>
);
}
}
const cardTarget = {
drop(props, monitor, component ) {
const { id } = props;
const sourceObj = monitor.getItem();
if ( id !== sourceObj.listId ) component.pushCard(sourceObj.card);
return {
listId: id
};
}
}
export default DropTarget("CARD", cardTarget, (connect, monitor) => ({
connectDropTarget: connect.dropTarget(),
isOver: monitor.isOver(),
canDrop: monitor.canDrop()
}))(Container);
卡片:
import React, { Component } from 'react';
import { findDOMNode } from 'react-dom';
import { DragSource, DropTarget } from 'react-dnd';
import flow from 'lodash/flow';
const style = {
border: '1px dashed grey',
padding: '0.5rem 1rem',
margin: '.5rem',
backgroundColor: 'white',
cursor: 'move'
};
class Card extends Component {
render() {
const { card, isDragging, connectDragSource, connectDropTarget } = this.props;
const opacity = isDragging ? 0 : 1;
// Background URL
let backgroundUrl = {
backgroundImage: "url(" + "http://localhost:4000/uploads/2017/8/a3ff91dc-2f80-42f7-951a-e9a74bf954d7-1200x800.jpeg" + ")"
};
console.log(card);
return connectDragSource(connectDropTarget(
<div className={`uploadedImageWrapper col-md-6 col-sm-12`}>
<div className="uploadedImage">
<span style={backgroundUrl} />
{card.text}
{card.age}
</div>
</div>
));
}
}
const cardSource = {
beginDrag(props) {
return {
index: props.index,
listId: props.listId,
card: props.card
};
},
endDrag(props, monitor) {
const item = monitor.getItem();
const dropResult = monitor.getDropResult();
if ( dropResult && dropResult.listId !== item.listId ) {
props.removeCard(item.index);
}
}
};
const cardTarget = {
hover(props, monitor, component) {
const dragIndex = monitor.getItem().index;
const hoverIndex = props.index;
const sourceListId = monitor.getItem().listId;
// Don't replace items with themselves
if (dragIndex === hoverIndex) {
return;
}
// Determine rectangle on screen
const hoverBoundingRect = findDOMNode(component).getBoundingClientRect();
// Get vertical middle
const hoverMiddleY = (hoverBoundingRect.bottom - hoverBoundingRect.top) / 2;
// Determine mouse position
const clientOffset = monitor.getClientOffset();
// Get pixels to the top
const hoverClientY = clientOffset.y - hoverBoundingRect.top;
// Only perform the move when the mouse has crossed half of the items height
// When dragging downwards, only move when the cursor is below 50%
// When dragging upwards, only move when the cursor is above 50%
// Dragging downwards
if (dragIndex < hoverIndex && hoverClientY < hoverMiddleY) {
return;
}
// Dragging upwards
if (dragIndex > hoverIndex && hoverClientY > hoverMiddleY) {
return;
}
// Time to actually perform the action
if ( props.listId === sourceListId ) {
props.moveCard(dragIndex, hoverIndex);
// Note: we're mutating the monitor item here!
// Generally it's better to avoid mutations,
// but it's good here for the sake of performance
// to avoid expensive index searches.
monitor.getItem().index = hoverIndex;
}
}
};
export default flow(
DropTarget("CARD", cardTarget, connect => ({
connectDropTarget: connect.dropTarget()
})),
DragSource("CARD", cardSource, (connect, monitor) => ({
connectDragSource: connect.dragSource(),
isDragging: monitor.isDragging()
}))
)(Card);
所以回顾一下,我可以将项目添加到状态,它们变得可拖放。但是在拖放一个元素之后,我不能再添加项目到状态。
关于解决方案有什么想法吗?我做错了什么?
感谢您浏览本文以及任何答案。干杯。
@Notorious.
我已经在我这边检查了你的代码并解决了问题。
当您拖放一个改变 Container 状态但不改变 ImageUploader 状态的元素时。
所以我做了一个函数来通知Container的状态已经改变。
我还向 Container 插入了 componentWillReceiveProps() 函数,并在该函数中更新了 Container 的状态。
问题终于解决了
这是更改后的代码。
主要成分:
import React from 'react';
// Drag and drop stuff
import {DragDropContext} from 'react-dnd';
import HTML5Backend from 'react-dnd-html5-backend';
import Container from './Container';
class ImageUploader extends React.Component {
constructor(props) {
super(props);
this.state = {
list: [],
listCount: 1
};
this.onAddItem = this
.onAddItem
.bind(this);
this.listChanged = this.listChanged.bind(this);
}
onAddItem(e) {
e.preventDefault();
var listArray = this.state.list;
var buildObject = {
text: 'Jeremy' + this
.state
.listCount
.toString(),
age: '25',
id: this.state.listCount
};
listArray.push(buildObject);
let newListCount = this.state.listCount + 1;
this.setState({list: listArray, listCount: newListCount});
}
listChanged(newList) {
this.setState({
list: newList
})
}
render() {
return (
<div>
<h1>Add to List</h1>
<button onClick={this.onAddItem}>Add Item</button>
<h1>The List</h1>
<Container id={1} list={this.state.list} listChanged={this.listChanged}/>
</div>
)
}
}
export default DragDropContext(HTML5Backend)(ImageUploader);
容器:
import React, { Component } from 'react';
import update from 'react/lib/update';
import Card from './Card';
import { DropTarget } from 'react-dnd';
class Container extends Component {
constructor(props) {
super(props);
this.state = { cards: this.props.list };
}
pushCard(card) {
this.setState(update(this.state, {
cards: {
$push: [ card ]
}
}));
}
removeCard(index) {
this.setState(update(this.state, {
cards: {
$splice: [
[index, 1]
]
}
}));
}
moveCard(dragIndex, hoverIndex) {
const { cards } = this.state;
const dragCard = cards[dragIndex];
this.setState(update(this.state, {
cards: {
$splice: [
[dragIndex, 1],
[hoverIndex, 0, dragCard]
]
}
}));
}
componentWillReceiveProps(nextProps) {
// You don't have to do this check first, but it can help prevent an unneeded render
if (nextProps.list !== this.state.cards) {
this.props.listChanged(this.state.cards);
}
}
render() {
const { cards } = this.state;
const { canDrop, isOver, connectDropTarget } = this.props;
const isActive = canDrop && isOver;
const style = {
width: "200px",
height: "404px",
border: '1px dashed gray'
};
const backgroundColor = isActive ? 'lightgreen' : '#FFF';
return connectDropTarget(
<div className="houzes-dropbox">
{cards.map((card, i) => {
return (
<Card
key={card.id}
index={i}
listId={this.props.id}
card={card}
removeCard={this.removeCard.bind(this)}
moveCard={this.moveCard.bind(this)} />
);
})}
</div>
);
}
}
const cardTarget = {
drop(props, monitor, component ) {
const { id } = props;
const sourceObj = monitor.getItem();
if ( id !== sourceObj.listId ) component.pushCard(sourceObj.card);
return {
listId: id
};
}
}
export default DropTarget("CARD", cardTarget, (connect, monitor) => ({
connectDropTarget: connect.dropTarget(),
isOver: monitor.isOver(),
canDrop: monitor.canDrop()
}))(Container);
如果对您有所帮助,我真的很高兴
感谢阅读我的post。
弗拉基米尔
在将这段代码应用到我的图片上传器之前,我正在开发一个简单版本的 ReactDND。
每次添加图像时,都会将其添加到状态并传递给 ReactDND,以便它可以拖放(因此用户可以重新排列他们的图像)。
一切都很好,除了一件事。我遇到的问题是在添加多张图片后,一旦我拖放图片(有效),ReactDND 的状态就不再更新,我无法添加新图片。
下面是我的代码(注意我只是使用一个按钮来向状态添加额外的项目):
主要成分:
import React from 'react';
// Drag and drop stuff
import { DragDropContext } from 'react-dnd';
import HTML5Backend from 'react-dnd-html5-backend';
import Container from './Container';
class ImageUploader extends React.Component {
constructor(props) {
super(props);
this.state = {
list: [],
listCount: 1
};
this.onAddItem = this.onAddItem.bind(this);
}
onAddItem(e) {
e.preventDefault();
var listArray = this.state.list;
var buildObject = {
text: 'Jeremy' + this.state.listCount.toString(),
age: '25',
id: this.state.listCount
};
listArray.push(buildObject);
let newListCount = this.state.listCount + 1;
this.setState({
list: listArray,
listCount: newListCount
});
console.log(this.state.list);
}
render() {
return (
<div>
<h1>Add to List</h1>
<button onClick={this.onAddItem}>Add Item</button>
<h1>The List</h1>
<Container id={1} list={this.state.list} />
</div>
)
}
}
export default DragDropContext(HTML5Backend)(ImageUploader);
容器:
import React, { Component } from 'react';
import update from 'react/lib/update';
import Card from './Card';
import { DropTarget } from 'react-dnd';
class Container extends Component {
constructor(props) {
super(props);
this.state = { cards: props.list };
}
pushCard(card) {
this.setState(update(this.state, {
cards: {
$push: [ card ]
}
}));
}
removeCard(index) {
this.setState(update(this.state, {
cards: {
$splice: [
[index, 1]
]
}
}));
}
moveCard(dragIndex, hoverIndex) {
const { cards } = this.state;
const dragCard = cards[dragIndex];
this.setState(update(this.state, {
cards: {
$splice: [
[dragIndex, 1],
[hoverIndex, 0, dragCard]
]
}
}));
}
render() {
const { cards } = this.state;
const { canDrop, isOver, connectDropTarget } = this.props;
const isActive = canDrop && isOver;
const style = {
width: "200px",
height: "404px",
border: '1px dashed gray'
};
const backgroundColor = isActive ? 'lightgreen' : '#FFF';
return connectDropTarget(
<div className="houzes-dropbox">
{cards.map((card, i) => {
return (
<Card
key={card.id}
index={i}
listId={this.props.id}
card={card}
removeCard={this.removeCard.bind(this)}
moveCard={this.moveCard.bind(this)} />
);
})}
</div>
);
}
}
const cardTarget = {
drop(props, monitor, component ) {
const { id } = props;
const sourceObj = monitor.getItem();
if ( id !== sourceObj.listId ) component.pushCard(sourceObj.card);
return {
listId: id
};
}
}
export default DropTarget("CARD", cardTarget, (connect, monitor) => ({
connectDropTarget: connect.dropTarget(),
isOver: monitor.isOver(),
canDrop: monitor.canDrop()
}))(Container);
卡片:
import React, { Component } from 'react';
import { findDOMNode } from 'react-dom';
import { DragSource, DropTarget } from 'react-dnd';
import flow from 'lodash/flow';
const style = {
border: '1px dashed grey',
padding: '0.5rem 1rem',
margin: '.5rem',
backgroundColor: 'white',
cursor: 'move'
};
class Card extends Component {
render() {
const { card, isDragging, connectDragSource, connectDropTarget } = this.props;
const opacity = isDragging ? 0 : 1;
// Background URL
let backgroundUrl = {
backgroundImage: "url(" + "http://localhost:4000/uploads/2017/8/a3ff91dc-2f80-42f7-951a-e9a74bf954d7-1200x800.jpeg" + ")"
};
console.log(card);
return connectDragSource(connectDropTarget(
<div className={`uploadedImageWrapper col-md-6 col-sm-12`}>
<div className="uploadedImage">
<span style={backgroundUrl} />
{card.text}
{card.age}
</div>
</div>
));
}
}
const cardSource = {
beginDrag(props) {
return {
index: props.index,
listId: props.listId,
card: props.card
};
},
endDrag(props, monitor) {
const item = monitor.getItem();
const dropResult = monitor.getDropResult();
if ( dropResult && dropResult.listId !== item.listId ) {
props.removeCard(item.index);
}
}
};
const cardTarget = {
hover(props, monitor, component) {
const dragIndex = monitor.getItem().index;
const hoverIndex = props.index;
const sourceListId = monitor.getItem().listId;
// Don't replace items with themselves
if (dragIndex === hoverIndex) {
return;
}
// Determine rectangle on screen
const hoverBoundingRect = findDOMNode(component).getBoundingClientRect();
// Get vertical middle
const hoverMiddleY = (hoverBoundingRect.bottom - hoverBoundingRect.top) / 2;
// Determine mouse position
const clientOffset = monitor.getClientOffset();
// Get pixels to the top
const hoverClientY = clientOffset.y - hoverBoundingRect.top;
// Only perform the move when the mouse has crossed half of the items height
// When dragging downwards, only move when the cursor is below 50%
// When dragging upwards, only move when the cursor is above 50%
// Dragging downwards
if (dragIndex < hoverIndex && hoverClientY < hoverMiddleY) {
return;
}
// Dragging upwards
if (dragIndex > hoverIndex && hoverClientY > hoverMiddleY) {
return;
}
// Time to actually perform the action
if ( props.listId === sourceListId ) {
props.moveCard(dragIndex, hoverIndex);
// Note: we're mutating the monitor item here!
// Generally it's better to avoid mutations,
// but it's good here for the sake of performance
// to avoid expensive index searches.
monitor.getItem().index = hoverIndex;
}
}
};
export default flow(
DropTarget("CARD", cardTarget, connect => ({
connectDropTarget: connect.dropTarget()
})),
DragSource("CARD", cardSource, (connect, monitor) => ({
connectDragSource: connect.dragSource(),
isDragging: monitor.isDragging()
}))
)(Card);
所以回顾一下,我可以将项目添加到状态,它们变得可拖放。但是在拖放一个元素之后,我不能再添加项目到状态。
关于解决方案有什么想法吗?我做错了什么?
感谢您浏览本文以及任何答案。干杯。
@Notorious.
我已经在我这边检查了你的代码并解决了问题。 当您拖放一个改变 Container 状态但不改变 ImageUploader 状态的元素时。
所以我做了一个函数来通知Container的状态已经改变。 我还向 Container 插入了 componentWillReceiveProps() 函数,并在该函数中更新了 Container 的状态。
问题终于解决了
这是更改后的代码。
主要成分:
import React from 'react';
// Drag and drop stuff
import {DragDropContext} from 'react-dnd';
import HTML5Backend from 'react-dnd-html5-backend';
import Container from './Container';
class ImageUploader extends React.Component {
constructor(props) {
super(props);
this.state = {
list: [],
listCount: 1
};
this.onAddItem = this
.onAddItem
.bind(this);
this.listChanged = this.listChanged.bind(this);
}
onAddItem(e) {
e.preventDefault();
var listArray = this.state.list;
var buildObject = {
text: 'Jeremy' + this
.state
.listCount
.toString(),
age: '25',
id: this.state.listCount
};
listArray.push(buildObject);
let newListCount = this.state.listCount + 1;
this.setState({list: listArray, listCount: newListCount});
}
listChanged(newList) {
this.setState({
list: newList
})
}
render() {
return (
<div>
<h1>Add to List</h1>
<button onClick={this.onAddItem}>Add Item</button>
<h1>The List</h1>
<Container id={1} list={this.state.list} listChanged={this.listChanged}/>
</div>
)
}
}
export default DragDropContext(HTML5Backend)(ImageUploader);
容器:
import React, { Component } from 'react';
import update from 'react/lib/update';
import Card from './Card';
import { DropTarget } from 'react-dnd';
class Container extends Component {
constructor(props) {
super(props);
this.state = { cards: this.props.list };
}
pushCard(card) {
this.setState(update(this.state, {
cards: {
$push: [ card ]
}
}));
}
removeCard(index) {
this.setState(update(this.state, {
cards: {
$splice: [
[index, 1]
]
}
}));
}
moveCard(dragIndex, hoverIndex) {
const { cards } = this.state;
const dragCard = cards[dragIndex];
this.setState(update(this.state, {
cards: {
$splice: [
[dragIndex, 1],
[hoverIndex, 0, dragCard]
]
}
}));
}
componentWillReceiveProps(nextProps) {
// You don't have to do this check first, but it can help prevent an unneeded render
if (nextProps.list !== this.state.cards) {
this.props.listChanged(this.state.cards);
}
}
render() {
const { cards } = this.state;
const { canDrop, isOver, connectDropTarget } = this.props;
const isActive = canDrop && isOver;
const style = {
width: "200px",
height: "404px",
border: '1px dashed gray'
};
const backgroundColor = isActive ? 'lightgreen' : '#FFF';
return connectDropTarget(
<div className="houzes-dropbox">
{cards.map((card, i) => {
return (
<Card
key={card.id}
index={i}
listId={this.props.id}
card={card}
removeCard={this.removeCard.bind(this)}
moveCard={this.moveCard.bind(this)} />
);
})}
</div>
);
}
}
const cardTarget = {
drop(props, monitor, component ) {
const { id } = props;
const sourceObj = monitor.getItem();
if ( id !== sourceObj.listId ) component.pushCard(sourceObj.card);
return {
listId: id
};
}
}
export default DropTarget("CARD", cardTarget, (connect, monitor) => ({
connectDropTarget: connect.dropTarget(),
isOver: monitor.isOver(),
canDrop: monitor.canDrop()
}))(Container);
如果对您有所帮助,我真的很高兴
感谢阅读我的post。
弗拉基米尔