var startPoint
Page({
 data: {
 //按钮位置参数
 buttonTop: 0,
 buttonLeft: 0,
 windowHeight: '',
 windowWidth: '',
 //角标显示数字
 corner_data:0,
 },
 onLoad:function(){
 //定义角标数字
 this.setData({
  corner_data:3
 })
 // 获取购物车控件适配参数
 var that =this;
 wx.getSystemInfo({
  success: function (res) {
  console.log(res);
  // 屏幕宽度、高度
  console.log('height=' + res.windowHeight);
  console.log('width=' + res.windowWidth);
  // 高度,宽度 单位为px
  that.setData({
   windowHeight: res.windowHeight,
   windowWidth: res.windowWidth,
   buttonTop:res.windowHeight*0.70,//这里定义按钮的初始位置
   buttonLeft:res.windowWidth*0.70,//这里定义按钮的初始位置
  })
  }
 })
 },
 //可拖动悬浮按钮点击事件
 btn_Suspension_click:function(){
 //这里是点击购物车之后将要执行的操作
 wx.showToast({
  title: '点击成功',
  icon:'success',
  duration:1000
 })
 },
 //以下是按钮拖动事件
 buttonStart: function (e) {
 startPoint = e.touches[0]//获取拖动开始点
 },
 buttonMove: function (e) {
 var endPoint = e.touches[e.touches.length - 1]//获取拖动结束点
 //计算在X轴上拖动的距离和在Y轴上拖动的距离
 var translateX = endPoint.clientX - startPoint.clientX
 var translateY = endPoint.clientY - startPoint.clientY
 startPoint = endPoint//重置开始位置
 var buttonTop = this.data.buttonTop + translateY
 var buttonLeft = this.data.buttonLeft + translateX
 //判断是移动否超出屏幕
 if (buttonLeft+50 >= this.data.windowWidth){
  buttonLeft = this.data.windowWidth-50;
 }
 if (buttonLeft<=0){
  buttonLeft=0;
 }
 if (buttonTop<=0){
  buttonTop=0
 }
 if (buttonTop + 50 >= this.data.windowHeight){
  buttonTop = this.data.windowHeight-50;
 }
 this.setData({
  buttonTop: buttonTop,
  buttonLeft: buttonLeft
 })
 },
 buttonEnd: function (e) {
 }
})

<!--可拖动按钮控件表-->
<!--buttonStart和buttonEnd一定不能用catch事件，否则按钮点击事件会失效-->
<view class="btn_Suspension" bindtap="btn_Suspension_click" catchtouchmove="buttonMove" bindtouchstart="buttonStart" bindtouchend="buttonEnd" style="top:{{buttonTop}}px;left:{{buttonLeft}}px;">
 <image class="Suspension_logo" src="/UploadFiles/2021-04-02/Suspension.png">

wxss：


Page{
 background: #f5f5f5;
}
/**可拖动悬浮按钮样式表**/
.btn_Suspension{
 position: fixed;
 height: 100rpx;
 width: 100rpx;
 background-color: rgba(255, 255, 255, 0.755);
 border-radius: 100%;
 display: flex;
 align-items: center;
 justify-content: center;
 z-index: 99999;
 box-shadow: 1px 0px 1px 1px #ede7e7;
}
.Suspension_logo{
 position:absolute;
 height:50%;
 width:50%;
 left:23%;
 top:27%
}
.cornorMark{
 position:absolute;
 background: rgb(242, 109, 38);
 border:1px solid rgb(242, 109, 38);
 border-radius: 100px;
 width:30rpx;
 height:30rpx;
 top:-17rpx;
 right:3rpx;
 color:#fff;
 font-size: 12px;
 text-align: center;
}
.cornorMark text{
 position:absolute;
 width:100%;
 left:0%;
 text-align: center;
 top:-1px;
}


图标素材下载地址：

Iconfont阿里巴巴矢量图标库：https://www.iconfont.cn/