先上解决方案：
给<transition-group>设置高度即可。
原bug：
官网示例，没错，官网自己的示例都有这个bug。防止修复看不到效果了，把代码还是贴在下面。
bug本b
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>vue.draggable两列或多列之间相互拖动例子</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=no, minimal-ui">
<script src="http://www.itxst.com/package/vue/vue.min.js"></script>
<script src="http://www.itxst.com/package/sortable/Sortable.min.js"></script>
<script src="http://www.itxst.com/package/vuedraggable/vuedraggable.umd.min.js"></script>
<style>
/*定义要拖拽元素的样式*/
.ghostClass {
background-color: blue !important;
}
.chosenClass {
background-color: red !important;
opacity: 1 !important;
}
.dragClass {
background-color: blueviolet !important;
opacity: 1 !important;
box-shadow: none !important;
outline: none !important;
background-image: none !important;
}
.itxst {
margin: 10px;
}
.title {
padding: 6px 12px;
}
.col {
width: 40%;
flex: 1;
padding: 10px;
border: solid 1px #eee;
border-radius: 5px;
float: left;
}
.col + .col {
margin-left: 10px;
}
.item {
padding: 6px 12px;
margin: 0px 10px 0px 10px;
border: solid 1px #eee;
background-color: #f1f1f1;
}
.item:hover {
background-color: #fdfdfd;
cursor: move;
}
.item + .item {
border-top: none;
margin-top: 6px;
}
</style>
</head>
<body style="padding:10px;">
<div id="app">
<!--使用draggable组件-->
<div class="itxst">
<div class="col">
<div class="title">国内网站</div>
<draggable v-model="arr1" group="site" animation="300" dragClass="dragClass" ghostClass="ghostClass" chosenClass="chosenClass" @start="onStart" @end="onEnd">
<transition-group>
<div class="item" v-for="item in arr1" :key="item.id">{{item.name}}</div>
</transition-group>
</draggable>
</div>
<div class="col">
<div class="title">你可以把左边的元素拖到右边</div>
<draggable v-model="arr2" group="site" animation="100" dragClass="dragClass" ghostClass="ghostClass" chosenClass="chosenClass" @start="onStart" @end="onEnd">
<transition-group>
<div class="item" v-for="item in arr2" :key="item.id">{{item.name}}</div>
</transition-group>
</draggable>
</div>
</div>
</div>
<script>
// debugger;
Vue.component('vuedraggable', window.vuedraggable.name)
var app = new Vue({
el: '#app',
components: {
vuedraggable,
},
data() {
return {
drag: false,
arr1: [
{ id: 1, name: 'www.itxst.com' },
{ id: 2, name: 'www.jd.com' },
{ id: 3, name: 'www.baidu.com' },
{ id: 4, name: 'www.taobao.com' }
],
arr2: [
{ id: 1, name: 'www.google.com' },
{ id: 2, name: 'www.msn.com' },
{ id: 3, name: 'www.ebay.com' },
{ id: 4, name: 'www.yahoo.com' }
]
};
},
methods: {
onStart() {
this.drag = true;
},
onEnd() {
this.drag = false;
},
}
});
</script>
</body>
</html>
