Javascript实现苹果悬浮虚拟按钮

var new_element_N=document.createElement("style");   new_element_N.innerHTML = '#drager {' +    '   position: fixed;' +    '   width: 35px;' +    '   height: 35px;' +    '   background-color: rgba(0, 0, 0, 0.2);' +    '   z-index: 10000;' +    '   cursor: pointer;' +    '   top: 0px;' +    '   left: 0px;' +    '   border-radius: 30%;' +    '   padding: 6px;' +    ' }' +    ' ' +    ' #drager>div {' +    '   border-radius: 50%;' +    '   width: 100%;' +    '   height: 100%;' +    '   background-color: rgba(0, 0, 0, 0.3);' +    '   transition: all 0.2s;' +    '  -webkit-transition: all 0.2s;' +    '  -moz-transition: all 0.2s;' +    '  -o-transition: all 0.2s;' +    ' }' +    ' #drager:hover>div{' +    '   background-color: rgba(0, 0, 0, 0.6);' +    ' } ';  document.body.appendChild(new_element_N);  new_element_N=document.createElement('div');   new_element_N.setAttribute("id","drager");  new_element_N.style.top="100px";  new_element_N.style.left="100px";  new_element_N.innerHTML = ' <div></div>' ;  document.body.appendChild(new_element_N);  //   //     var posX;    var posY;       var screenWidth =document.documentElement.clientWidth;    var screenHeight = document.documentElement.clientHeight;      var fdiv = document.getElementById("drager");     fdiv.onmousedown=function(e)    {       screenWidth =document.documentElement.clientWidth;      screenHeight = document.documentElement.clientHeight;        if(!e){ e = window.event; } //IE      posX = e.clientX - parseInt(fdiv.style.left);      posY = e.clientY - parseInt(fdiv.style.top);      document.onmousemove = mousemove;          }    document.onmouseup = function()//释放时自动贴到最近位置    {      document.onmousemove = null;      if((parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight)/2)<=(screenHeight/2)){//在上半部分        if((parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)<=(screenWidth/2)){//在左半部分          if((parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight)/2)<=(parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)){//靠近上方            fdiv.style.top="0px";          }else{//靠近左边            fdiv.style.left="0px";          }        }else{//在右半部分          if((parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight)/2)<=(screenWidth-(parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)) ){//靠近上方            fdiv.style.top="0px";          }else{//靠近右边            fdiv.style.left=(screenWidth-parseInt(fdiv.clientWidth))+"px";          }         }      }else{ //下半部分         if((parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)<=(screenWidth/2)){//在左半部分          if( (screenHeight-(parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight)/2))<=(parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)){//靠近下方            fdiv.style.top=(screenHeight-parseInt(fdiv.clientHeight))+"px";          }else{//靠近左边            fdiv.style.left="0px";          }        }else{//在右半部分          if( (screenHeight-(parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight)/2))<=(screenWidth-(parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth)/2)) ){//靠近上方            fdiv.style.top=(screenHeight-parseInt(fdiv.clientHeight))+"px";          }else{//靠近右边            fdiv.style.left=(screenWidth-parseInt(fdiv.clientWidth))+"px";          }         }      }     }    function mousemove(ev)    {      if(ev==null){ ev = window.event;}//IE      if((ev.clientY - posY)<=0){//超过顶部         fdiv.style.top="0px";      }else if((ev.clientY - posY) >(screenHeight-parseInt(fdiv.clientHeight))){//超过底部        fdiv.style.top=(screenHeight-parseInt(fdiv.clientHeight))+"px";      }else{        fdiv.style.top = (ev.clientY - posY) + "px";      }              if((ev.clientX- posX)<=0){//超过左边         fdiv.style.left="0px";      }else if((ev.clientX - posX) >(screenWidth-parseInt(fdiv.clientWidth))){//超过右边        fdiv.style.left=(screenWidth-parseInt(fdiv.clientWidth))+"px";      }else{        fdiv.style.left = (ev.clientX - posX) + "px";      }      // console.log( posX +" "+ fdiv.style.left);           }    window.onload = window.onresize = function() { //窗口大小改变事件      screenWidth =document.documentElement.clientWidth;      screenHeight = document.documentElement.clientHeight;        if( (parseInt(fdiv.style.top)+parseInt(fdiv.clientHeight))>screenHeight){//窗口改变适应超出的部分         fdiv.style.top=(screenHeight-parseInt(fdiv.clientHeight))+"px";      }        if( (parseInt(fdiv.style.left)+parseInt(fdiv.clientWidth))>screenWidth){//窗口改变适应超出的部分         fdiv.style.left=(screenWidth-parseInt(fdiv.clientWidth))+"px";      }        document.onmouseup.apply()    };    fdiv.addEventListener('touchstart', fdiv.onmousedown, false);      fdiv.addEventListener('touchmove', function(event) {            // 如果这个元素的位置内只有一个手指的话            if (event.targetTouches.length == 1) {          　　　　 event.preventDefault();// 阻止浏览器默认事件，重要               var touch = event.targetTouches[0];               if((touch.pageY)<=0){//超过顶部                fdiv.style.top="0px";              }else if(touch.pageY>(screenHeight-parseInt(fdiv.clientHeight))){//超过底部                fdiv.style.top=(screenHeight-parseInt(fdiv.clientHeight))+"px";              }else{                fdiv.style.top = (touch.pageY-parseInt(fdiv.clientHeight)/2) + "px";              }                             if(touch.pageX<=0){//超过左边                fdiv.style.left="0px";              }else if( touch.pageX >(screenWidth-parseInt(fdiv.clientWidth))){//超过右边                fdiv.style.left=(screenWidth-parseInt(fdiv.clientWidth))+"px";              }else{                fdiv.style.left = (touch.pageX-parseInt(fdiv.clientWidth)/2) + "px";              }            }          }, false);     fdiv.addEventListener('touchend', document.onmouseup , false);           fdiv.ondblclick=function(){//双击事件可能在手机端浏览器会与网页缩放事件冲突      alert("发挥你们的想象力吧");    }

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