js碰撞检测 JavaScript碰撞检测原理及其实现代码

时间:2021-04-21 SuperluminalSnails 人气:0

1.模拟碰撞

简单模拟碰撞过程,用一个可以拖拽的div2去尝试碰撞一个固定的div1(均用绝对定位)

2.碰撞检测原理

如图所示:
使得div分别有4个距离属性( L(left),T(top),R(right),B(bottom) ).
对于div1来说,画出一个九宫格,div2在除中心以为的8个格子任意移动都不会发送碰撞.

也就是说,只要满足条件:oDiv2.div2R小于oDiv1.div1L|| oDiv2.div2L大于oDiv1.div1R || oDiv2.div2B小于oDiv1.div1T|| oDiv2.div2T大于oDiv1.div1B就不会发送碰撞

3.具体测试代码

<html>
<head>
 <title></title>
 <style type="text/css">
 body{margin: 0;padding: 0;}
 #div2{height: 100px;width: 200px;background-color: orange;position: absolute;left: 0px;top:0px;z-index: 1;}
 #div1{height: 100px;width: 100px;background-color: #a6e22e;position: absolute;left: 600px;top:400px;}
 </style>
 <script type="text/javascript">
 //获取对象样式属性值
 function getObjStyle(obj,attr)
 {
  return getComputedStyle(obj)?getComputedStyle(obj)[attr]:obj.currentStyle[attr];
 }
 </script>
 <script type="text/javascript">
 window.οnlοad=function (){
  var oDiv1=document.getElementById('div1');
  var oDiv2=document.getElementById('div2');



  oDiv2.οnmοusedοwn=function (onEvent,obj){//对div1实现拖拽,并对碰撞进行检测
   obj=this;
   var ev=onEvent||event;
   var distance={};
   distance.disX=ev.clientX-obj.offsetLeft;//到左边框的距离
   distance.disY=ev.clientY-obj.offsetTop;//到上边框的距离

   //获取div1的四个值
   oDiv1.div1L=getObjStyle(oDiv1,'left');
   oDiv1.div1R=parseInt(getObjStyle(oDiv1,'left'))+parseInt(getObjStyle(oDiv1,'width'))+'px';
   oDiv1.div1T=getObjStyle(oDiv1,'top');
   oDiv1.div1B=parseInt(getObjStyle(oDiv1,'top'))+parseInt(getObjStyle(oDiv1,'height'))+'px';




   if(obj.setCapture)
    obj.setCapture();

   document.οnmοusemοve=function (onEvent){
    var ev=onEvent||event;
    obj.style.left=ev.clientX-distance.disX+'px';
    obj.style.top=ev.clientY-distance.disY+'px';

    //获取div2的四个值
    oDiv2.div2L=getObjStyle(oDiv2,'left');
    oDiv2.div2R=parseInt(getObjStyle(oDiv2,'left'))+parseInt(getObjStyle(oDiv2,'width'))+'px';
    oDiv2.div2T=getObjStyle(oDiv2,'top');
    oDiv2.div2B=parseInt(getObjStyle(oDiv2,'top'))+parseInt(getObjStyle(oDiv2,'height'))+'px';

    /*console.log('oDiv2.div2L:'+oDiv2.div2L+' oDiv2.div2R:'+oDiv2.div2R+' oDiv2.div2T:'+oDiv2.div2T+' oDiv2.div2B:'+oDiv2.div2B);*/

    //碰撞检测
    if(oDiv2.div2R<oDiv1.div1L || oDiv2.div2L>oDiv1.div1R || oDiv2.div2B<oDiv1.div1T || oDiv2.div2T>oDiv1.div1B){
     //未发送碰撞
    }else{
     //发生碰撞
     alert('发生碰撞');
    }

   }

   document.οnmοuseup=function (){
    document.οnmοuseup=document.οnmοusemοve=null;
    if(obj.setCapture)
     obj.releaseCapture();
   }
   return false;
  }
 }
 </script>
</head>
<body>
 <div id="div2">div2</div>
 <div id="div1">div1</div>
</body>
</html>

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