jquery简单的拖动效果实现原理及示例

复制代码代码如下:

<!DOCTYPE html> 
<html> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>简单拖曵原理实例</title> 
<style type="text/css"> 
#drag{width:400px;height:300px;background:url(http://upload.yxgz.cn/uploadfile/2009/0513/20090513052611873.jpg);cursor:move;position:absolute;top:100px;left:100px;border:solid 1px #ccc;} 
h2{color:#fff;background: none repeat scroll 0 0 rgba(16, 90, 31, 0.7);color:#FFFFFF;height:40px;line-height:40px;margin:0;} 
</style> 
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js" type="text/javascript"></script> 
<script type="text/javascript"> 
$(function(){ 
/*--------------拖曳效果---------------- 
*原理：标记拖曳状态dragging ,坐标位置iX, iY 
* mousedown:fn(){dragging = true, 记录起始坐标位置，设置鼠标捕获} 
* mouseover:fn(){判断如果dragging = true, 则当前坐标位置 - 记录起始坐标位置，绝对定位的元素获得差值} 
* mouseup:fn(){dragging = false, 释放鼠标捕获，防止冒泡} 
*/ 
var dragging = false; 
var iX, iY; 
$("#drag").mousedown(function(e) { 
dragging = true; 
iX = e.clientX - this.offsetLeft; 
iY = e.clientY - this.offsetTop; 
this.setCapture && this.setCapture(); 
return false; 
}); 
document.onmousemove = function(e) { 
if (dragging) { 
var e = e || window.event; 
var oX = e.clientX - iX; 
var oY = e.clientY - iY; 
$("#drag").css({"left":oX + "px", "top":oY + "px"}); 
return false; 
} 
}; 
$(document).mouseup(function(e) { 
dragging = false; 
$("#drag")[0].releaseCapture(); 
e.cancelBubble = true; 
}) 

}) 

</script> 
</head> 

<body> 
<div id="drag"> 
<h2>来拖动我啊</h2> 
</div> 
</body> 
</html> 