有事没事搞个图：
demo：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0 maximum-scale=1.0, user-scalable=0">
<title>九宫格</title>
<script src="http://libs.baidu.com/jquery/1.9.1/jquery.min.js"></script>
<style>
html,body{
margin: 0;
padding: 0;
height: 98%;
100%;
padding-top: 2%;
}
#app{
100%;
position: relative;
left: 0;
}
#box{
position: fixed;
bottom: 0;
margin: 0 auto;
100px;
height:100px;
background-color: gray;
}
#box>div{
color: skyblue;
}
</style>
<script type="text/javascript">
window.onload=function(){
var app = new Vue({
el: '#app',
data: {
X:0,
Y:0
},
created(){
},
methods:{
touchmove(event){
this.X = event.targetTouches[0].clientX
this.Y = event.targetTouches[0].clientY
let screenWid = $(window).width()
let screenHei = $(window).height()
let midLeft = event.targetTouches[0].clientX-($('#box').width()/2)
let midRight = $(window).width()-(event.targetTouches[0].clientX+($('#box').width()/2))
let midBottom = $(window).height()-(event.targetTouches[0].clientY+($('#box').width()/2))
let midTop = event.targetTouches[0].clientY-($('#box').height()/2)
if(midLeft<0) midLeft = 0
if(midTop<0) midTop = 0
if(midRight<0) return
if(midBottom<0) return
$('#box').css({left:midLeft,top:midTop})
}
}
})
}
</script>
<!-- 引入vue -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<div id="app">
<div id="box" @touchmove='touchmove'>
<div>鼠标x:{{X}}</div>
<div>鼠标y:{{Y}}</div>
</div>
</div>
</body>
</html>