Detailed explanation of the mobile finger zoom in and out plug-in code-JS Tutorial-php.cn

Detailed explanation of the mobile finger zoom in and out plug-in code

Y2J

Release： 2017-05-23 11:44:04

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This article mainly introduces the mobile finger zoom-in and zoom-out plug-in and js source code, which has certain reference value. Interested friends can refer to it

The examples in this article are for everyone The specific code for zooming in and out on the mobile terminal is shared for your reference. The specific content is as follows

<!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">
 <meta name="apple-mobile-web-app-capable" content="yes">
 <meta name="apple-mobile-web-app-status-bar-style" content="black">
 <title>缩放</title>
 <style>
  #box{width:100px;
   height:100px;
  background: red;}
  html,body{width:100%;height:100%; overflow:hidden;}
 </style>
 <script>

   document.addEventListener(&#39;DOMContentLoaded&#39;,function() {
    var c=1;//先定义一个初始值
    var oBox=document.getElementById(&#39;box&#39;);
    document.addEventListener(&#39;touchstart&#39;,function (ev) {//手指点下
     var oldC=c;//把初始值放到oldC里面
     function getC(ev) {
      var x1=ev.targetTouches[0].pageX;
      var y1=ev.targetTouches[0].pageY;//两根手指缩放肯定需要两根手指，【0】第一根手指的Xy的坐标

      var x2=ev.targetTouches[1].pageX;//第二根手指的坐标
      var y2=ev.targetTouches[1].pageY;

      var a=x1-x2;//第一根手指的pageX-第二根手指的pageX，这样正好是一个之间三角形 得到两个直角边；
      var b=y1-y2;//同上
      return Math.sqrt(a*a+b*b)//已知两个直角边开平方得出 斜角边
     }
     if(ev.targetTouches.length==2){//判断是否是两根手指 是的话 把两根手指点上去的时候的 斜脚边的初始值 放到 downC里面
      var downC=getC(ev);
     }
     document.addEventListener(&#39;touchmove&#39;,function (ev) { //手指移动的时候
      if(ev.targetTouches.length==2){//判断移动的时候是否是两根手指
       c=getC(ev)/downC+oldC;//这个时候的getC(ev)是move时候的，用移动后的斜脚边的值除没移动的值加上他的初始值，
       oBox.style.webkitTransform=&#39;scale(&#39;+c+&#39;)&#39;;//通过scale----2D缩放转换
      }

     },false)



    },false)
   },false)

 </script>

</head>
<body>
 <p id="box"></p>
</body>

</html>

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