Detailed explanation of examples of movable-view moving pictures and two-finger zoom in WeChat mini program

<view class="section">
 <view class="section__title">movable-view区域小于movable-area</view>
 <movable-area style="height: 200px;width: 200px;background: red;">
 <movable-view style="height: 50px; width: 50px; background: blue;" x="{{x}}" y="{{y}}" direction="all">
 </movable-view>
 </movable-area>
 <view class="btn-area">
 <button size="mini" bindtap="tap">click me to move to (30px, 30px)</button>
 </view>
 <view class="section__title">movable-view区域大于movable-area</view>
 <movable-area style="height: 100px;width: 100px;background: red;" direction="all">
 <movable-view style="height: 200px; width: 200px; background: blue;">
 </movable-view>
 </movable-area>
</view>

 <movable-area style="height: 100px;width: 100px;background: red;" >
  <movable-view style="height: 200px; width: 200px; background: blue;" direction="all">
  </movable-view>
 </movable-area>

 <!-- 要查看的图片列表 -->
   <view class="flex-wrap flex-pic">
     <view class="picList">   
     <image wx:for="{{item.imglist}}" wx:for-item="itemImg" wx:key="*this" id="{{&#39;rfnd_&#39;+index}}" bindload="imageOnload" src="{{ itemImg}}" bindtap="showResizeModal" src="{{itemImg}}"></image>   
    </view>
   </view>

/**
 * 加载图片
 */
 imageOnload:function(e){
 var id = e.currentTarget.id
 this.data.imgIdList[id] = {
  width:e.detail.width,
  height:e.detail.height
 }
 },
 模板页面
<!--components/resizePicModal/resizePicModal.wxml-->
<template name="resizePic">
 <scroll-view class="backdrop"> 
 <view class="close-icon" bindtap="closeResizeModal"> 
  取消预览
 </view>
 <movable-area style="width:100%;height:100%;" >
  <movable-view direction="all" 
  out-of-bounds="true" x="{{img.x}}" y="{{img.y}}" >
  <image mode="widthFix" class="dtl-img" src="{{img.currentSrc}}"></image>
  </movable-view>
 </movable-area> 
 </scroll-view> 
 </template>
 /**
 * 打开弹窗
 */
 showResizeModal: function (e) {
 var src = e.currentTarget.dataset.src;
 var x = 0
 var y =0
 try {
  var width = this.imgIdList[e.currentTarget.id].width; //图片原宽
  var height = this.imgIdList[e.currentTarget.id].height; //图片原高
  
  //小程序默认固定宽320px,获取top和left值,使图片居中显示
  height = height * (320 / width);
  width = 320;
　　　　
  x = (app.windowWidth - width) / 2 
  y = (app.windowHeight - height) / 2

 } catch (e) { }
 var img = {
  x: x,
  y: y,26  currentSrc: src,
 };
 this.setData({ img: img, isCheckDtl: true });
 
 },

.backdrop{
 background: rgba(0, 0, 0, 1);
 width:100%;
 height: 100%;
 position: fixed;
 top:0;
 left:0;
}

<!-- 缩放 -->
<template name="resizePic">
 <scroll-view class="backdrop" catchtouchmove="bindTouchMove" catchtouchend="bindTouchEnd" bindtouchstart="bindTouchStart" > 
 <view class="close-icon" bindtap="closeResizeModal"> 
  取消预览
 </view>
  <image catchtouchmove="bindTouchMove" bindtouchend="bindTouchEnd" bindtouchstart="bindTouchStart" 
  style=" transform: scale({{img.baseScale}}); position:absolute; top:{{img.top}}px; left:{{img.left}}px; "
  mode="widthFix" class="dtl-img" src="{{img.currentSrc}}"></image> 
 </scroll-view> 
 </template>

 /**
 * 使用方法:
 * 1) WXHTML要缩放的图片 必须 传入 src 以及绑定 bindtap事件,
 * e.g:  
 * <image bindtap="toggleDtl" src="{{item}}" wx:for="{{productCard.arrImg}}" wx:key="*this" src="{{item}}" style="width:100%" mode="widthFix"></image>
 * 2) WXHTML 要引入Modal模板(isCheckDtl无需再定义):
 *  <view wx:if="{{isCheckDtl}}">
 *  <import src="/components/resizePicModal/resizePicModal.wxml"/>
 *  <template is="resizePic" data="{{img}}"></template>
 *  </view>
 * 3) JS页面要引入JS文件,覆盖当前页面的事件:
 * var resizePicModalService = require (&#39;../../components/resizePicModal/resizePicModal.js&#39;)
 * var resizePicModal = {}
 * 4) 在onLoad事件中,实例化ResizePicModal
 *  resizePicModal = new resizePicModalService.ResizePicModal()
 */
var app = getApp()
let modalEvent = {
 distanceList: [0, 0],//存储缩放时,双指距离.只有两个数据.第一项为old distance.最后一项为new distance
 disPoint: { x: 0, y: 0 },//手指touch图片时,在图片上的位置
 imgIdList:{},
 /**
 * 打开弹窗
 */
 showResizeModal: function (e) {
 var src = e.currentTarget.dataset.src;
 var x = 0
 var y =0
 try {
  var width = this.imgIdList[e.currentTarget.id].width; //图片原宽
  var height = this.imgIdList[e.currentTarget.id].height; //图片原高
  //小程序固定宽320px
  height = height * (320 / width);
  width = 320;
  x = (app.windowWidth - width) / 2 //> 0 ? (app.windowWidth - width) / 2 : 0;
  y = (app.windowHeight - height) / 2// > 0 ? (app.windowHeight - height) / 2 : 0;
 } catch (e) { }
 var img = {
  top: y,
  left: x,
  x: x, y: y,
  width: &#39;100%&#39;,
  baseScale: 1,
  currentSrc: src,
 };
 this.setData({ img: img, isCheckDtl: true });
 },
 /**
 * 关闭弹窗
 */
 closeResizeModal:function(){
 this.setData({ isCheckDtl: false })
 },
 /**
 * 加载图片
 */
 imageOnload:function(e){
 var id = e.currentTarget.id
 this.imgIdList[id] = {
  width:e.detail.width,
  height:e.detail.height
 }
 },
 /**
 * bindtouchmove
 */
 bindTouchMove: function (e) {
 if (e.touches.length == 1) {//一指移动当前图片
  this.data.img.left = e.touches[0].clientX - this.disPoint.x
  this.data.img.top = e.touches[0].clientY - this.disPoint.y
  this.setData({ img: this.data.img })
 }
 if (e.touches.length == 2) {//二指缩放
  var xMove = e.touches[1].clientX - e.touches[0].clientX
  var yMove = e.touches[1].clientY - e.touches[0].clientY
  var distance = Math.sqrt(xMove * xMove + yMove * yMove);//开根号
  this.distanceList.shift()
  this.distanceList.push(distance)
  if (this.distanceList[0] == 0) { return }
  var distanceDiff = this.distanceList[1] - this.distanceList[0]//两次touch之间, distance的变化. >0,放大图片.<0 缩小图片
  // 假设缩放scale基数为1: newScale = oldScale + 0.005 * distanceDiff
  var baseScale = this.data.img.baseScale + 0.005 * distanceDiff
  if(baseScale>0){
  this.data.img.baseScale = baseScale
  var imgWidth = baseScale * parseInt(this.data.img.imgWidth) 
  var imgHeight = baseScale * parseInt(this.data.img.imgHeight)
  this.setData({ img: this.data.img })
  }else{
  this.data.img.baseScale = 0
  this.setData({ img: this.data.img })
  }
 }
 },
 /**
 * bindtouchend
 */
 bindTouchEnd: function (e) {
 if (e.touches.length == 2) {//二指缩放
  this.setData({ isCheckDtl: true })
 }
 },
 /**
 * bindtouchstart
 */
 bindTouchStart: function (e) {
 this.distanceList = [0, 0]//回复初始值
 this.disPoint = { x: 0, y: 0 }
 if (e.touches.length == 1) {
  this.disPoint.x = e.touches[0].clientX - this.data.img.left
  this.disPoint.y = e.touches[0].clientY - this.data.img.top
 }
 }
}
function ResizePicModal(){
 let pages = getCurrentPages()
 let curPage = pages[pages.length - 1]
 Object.assign(curPage, modalEvent)//覆盖原生页面事件
 this.page = curPage
 curPage.resizePicModal = this
 return this
}
module.exports = {
 ResizePicModal
}

<view class="flex-wrap flex-pic">
    <view class="picList">   
     <image wx:for="{{item.imglist}}" wx:for-item="itemImg" wx:key="*this" id="{{&#39;rfnd_&#39;+index}}" bindload="imageOnload" src="{{ itemImg}}" bindtap="showResizeModal" src="{{itemImg}}"></image>   
    </view>
 </view>
<!-- 缩放 -->
 <view wx:if="{{isCheckDtl}}">
 <import src="/components/resizePicModal/resizePicModal.wxml"/>
 <template is="resizePic" data="{{img}}"></template>
 </view>

var that
 var resizePicModal = {}
 var app = getApp()
 var resizePicModalService = require('../../components/resizePicModal/resizePicModal.js')
 /**
  * 生命周期函数--监听页面加载
  */
 onLoad: function (options) {
  that = this 8  resizePicModal = new resizePicModalService.ResizePicModal()
 }