本文介绍了react 实现拖拽功能的示例代码，分享给大家，具体如下：
实现效果：
因为工作中会用到 jira 所以想实现一下相似的功能，顺便学习一下 h5 的拖拽。不支持拖拽改变顺序，感觉有点麻烦，而且没必要。感觉相关的博文好少的，大部分都是直接上代码，没有解释。
图片默认可以拖动，其他元素的拖动效果同图片。正常的 div 是不能被拖动的，鼠标点击选择后移动没有效果，需要加 draggable="true" 使得元素可以被拖动。
拖拽相关的几个事件，有被拖动元素的事件，也有拖动进入的容器元素的事件。
被拖拽元素的事件：ondragstart，ondragend
放置元素的事件：ondragenter、ondragover、ondragleave、ondrop
顾名思义，不需要解释。
需要注意是 ondragover 的默认事件 reset the current drag operation to "none". 所以想让一个元素可放置，需要重写 ondragover
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element.ondragover = event => {
event.preventdefault();
// ...
}
当一个元素是可放置的，拖拽经过时鼠标会变成加号（cursor: copy;）
有一个对象 datatransfer 可以用来存储拖拽数据。
dragele.ondragstart = e => e.datatransfer.setdata('item', e.target.id);
然后在 ondrop 的时候 可以获取到这个值 （ondragenter、ondragover、ondragleave 获取不到...）
putele.ondrop = function(e) {
let id = e.datatransfer.getdata('item');
// ...
}
<!doctype html>
<html lang="zh">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>document</title>
<style>
.wrapper {display: flex;border: 1px solid orangered;padding: 10px;}
.col {border: 1px solid #808080;height: 500px;width: 200px;margin: 0 10px;padding: 10px;}
.item {border: 1px solid #808080;margin: 5px 0;}
</style>
</head>
<body>
<div class="wrapper">
<div class="col1 col">
<div class="item" id="item1" draggable="true">item1</div>
<div class="item" id="item2" draggable="true">item2</div>
<div class="item" id="item3" draggable="true">item3</div>
</div>
<div class="col2 col"></div>
<div class="col3 col"></div>
<div class="col4 col"></div>
</div>
<script>
let cols = document.getelementsbyclassname('col');
for (let col of cols) {
col.ondragenter = e => {
console.log('放置元素 ondragenter', '<' + e.datatransfer.getdata('item') + '>');
}
col.ondragover = e => {
e.preventdefault();
console.log('放置元素 ondragover', '<' + e.datatransfer.getdata('item') + '>');
}
col.ondragleave = e => {
console.log('放置元素 ondragleave', '<' + e.datatransfer.getdata('item') + '>');
}
col.ondrop = function(e) {
console.log('放置元素 ondrop', '<' + e.datatransfer.getdata('item') + '>');
this.append(document.getelementbyid(e.datatransfer.getdata('item')));
}
}
let items = document.getelementsbyclassname('item');
for (let item of items) {
item.ondragstart = e => {
console.log('拖拽元素 ondragstart');
e.datatransfer.setdata('item', e.target.id);
}
item.ondragend = e => {
console.log('拖拽元素 ondragend');
}
}
</script>
</body>
</html>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
<style>
.item {
border: 1px solid #1da921;
width: 180px;
border-radius: 5px;
box-shadow: 0 0 5px 0 #b3b3b3;
margin: 5px auto;
background: #fff;
}
.item.active {
border-style: dashed;
}
.item-header {
font-size: 12px;
color: #9e9e9e;
padding: 3px 5px;
}
.item-main {
padding: 5px;
font-size: 14px;
color: #424242;
height: 36px;
overflow: hidden;
text-overflow: ellipsis;
display: -webkit-box;
-webkit-box-orient: vertical;
-webkit-line-clamp: 2;
}
.item-header-point {
background: #ccc;
float: right;
padding: 0 4px;
min-width: 10px;
text-align: center;
color: #fff;
border-radius: 50%;
}
.col {
border: 1px solid #d2d2d2;
flex-grow: 1;
width: 180px;
height: 100%;
margin: 0 2px;
background: #eee;
flex-grow: 1;
display: flex;
flex-direction: column;
}
.col-header {
height: 40px;
line-height: 40px;
background: #1da921;
color: #fff;
text-align: center;
}
.col-main {
overflow: auto;
flex-grow: 1;
}
.col-main.active {
background: #00ad23;
opacity: 0.1;
}
.task-wrapper {
display: flex;
height: 400px;
width: 700px;
}
</style>
</head>
<body>
<div id="app"></div>
<script type="text/babel">
const status_todo = 'status_todo';
const status_doing = 'status_doing';
const status_done = 'status_done';
const status_code = {
status_todo: '待处理',
status_doing: '进行中',
status_done: '已完成'
}
let tasks = [{
id: 0,
status: status_todo,
title: '每周七天阅读五次，每次阅读完要做100字的读书笔记',
username: '小夏',
point: 10
}, {
id: 1,
status: status_todo,
title: '每周七天健身4次，每次健身时间需要大于20分钟',
username: '橘子🍊',
point: 5
}, {
id: 2,
status: status_todo,
title: '单词*100',
username: '┑(￣д ￣)┍',
point: 2
}, {
id: 3,
status: status_todo,
title: '单词*150',
username: '┑(￣д ￣)┍',
point: 2
}, {
id: 4,
status: status_todo,
title: '单词*200',
username: '┑(￣д ￣)┍',
point: 2
}, {
id: 5,
status: status_todo,
title: '单词*250',
username: '┑(￣д ￣)┍',
point: 2
}]
class taskitem extends react.component {
handledragstart = (e) => {
this.props.ondragstart(this.props.id);
}
render() {
let { id, title, point, username, active, ondragend } = this.props;
return (
<div
ondragstart={this.handledragstart}
ondragend={ondragend}
id={`item-${id}`}
classname={'item' + (active ? ' active' : '')}
draggable="true"
>
<header classname="item-header">
<span classname="item-header-username">{username}</span>
<span classname="item-header-point">{point}</span>
</header>
<main classname="item-main">{title}</main>
</div>
);
}
}
class taskcol extends react.component {
state = {
in: false
}
handledragenter = (e) => {
e.preventdefault();
if (this.props.candragin) {
this.setstate({
in: true
})
}
}
handledragleave = (e) => {
e.preventdefault();
if (this.props.candragin) {
this.setstate({
in: false
})
}
}
handledrop = (e) => {
e.preventdefault();
this.props.dragto(this.props.status);
this.setstate({
in: false
})
}
render() {
let { status, children } = this.props;
return (
<div
id={`col-${status}`}
classname={'col'}
ondragenter={this.handledragenter}
ondragleave={this.handledragleave}
ondragover={this.handledragenter}
ondrop={this.handledrop}
draggable="true"
>
<header classname="col-header">
{status_code[status]}
</header>
<main classname={'col-main' + (this.state.in ? ' active' : '')}>
{children}
</main>
</div>
);
}
}
class app extends react.component {
state = {
tasks: tasks,
activeid: null
}
/**
* 传入被拖拽任务项的 id
*/
ondragstart = (id) => {
this.setstate({
activeid: id
})
}
dragto = (status) => {
let { tasks, activeid} = this.state;
let task = tasks[activeid];
if (task.status !== status) {
task.status = status;
this.setstate({
tasks: tasks
})
}
this.cancelselect();
}
cancelselect = () => {
this.setstate({
activeid: null
})
}
render() {
let { tasks, activeid } = this.state;
let { ondragstart, ondragend, cancelselect } = this;
return (
<div classname="task-wrapper">
{
object.keys(status_code).map(status =>
<taskcol
status={status}
key={status}
dragto={this.dragto}
candragin={activeid != null && tasks[activeid].status !== status}>
{ tasks.filter(t => t.status === status).map(t =>
<taskitem
key={t.id}
active={t.id === activeid}
id={t.id}
title={t.title}
point={t.point}
username={t.username}
ondragstart={ondragstart}
ondragend={cancelselect}
/>)
}
</taskcol>
)
}
</div>
)
}
}
reactdom.render(
<app />,
document.getelementbyid('app')
);
</script>
</body>
</html>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
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