Javascript实现元素的拖曳操作

说明:
拖曳流程
鼠标按下->(鼠标移动->元素移动)
鼠标按键弹起->元素停止移动

针对 IE, 主要使用 obj.attachEvent() && obj.detachEvent()
针对 Firefox 主要使用 DOM 2 的 obj.addEventListener() && obj.removeEventListener
Opera 以上两种方法都支持

在本文中, 需要拖曳的元素必须指定style 属性为 position:absolute;
且应指定 left && top 的坐标值, 如:

linenum
    <div style=" border:1px dashed blue; width: 180px; text-align:center; position:absolute; left:100px; top: 150px;" onmousedown="fDragging(this, event, true);">
        element 1<br/>
        dragging compatibility for IE, Opera, Firefox.  
    </div>

函数 fDragging(obj, e, limit) 的各参数解释:
obj: HTML元素对象, 要拖曳的元素
e: 指定为 event 对象, 主要为兼容 Firefox
limit: 布尔值, 指定是否只能在父元素中拖曳, false 可移动至任何位置.

函数 fDragging(obj, e, limit) 应该在 HTML onmousedown 属性 下使用, 如:

linenum
    <div style=" border:1px dashed blue; width: 180px; text-align:center; position:absolute; left:50px; top: 50px;" onmousedown="fDragging(this, event, true);">
        element <br/>
        dragging compatibility for IE, Opera, Firefox.  
    </div>

shawl.qiu
2006-11-10
http://blog.csdn.net/btbtd

函数: fDragging(obj, e, limit) 及使用演示

linenum
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns=" http://www.w3.org/1999/xhtml">
<!-- DW6 -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>shawl.qiu template</title>
<script type="text/javascript">
//<![CDATA[
    function fDragging(obj, e, limit){
        if(!e) e=window.event;
        var x=parseInt(obj.style.left);
        var y=parseInt(obj.style.top);
         
        var x_=e.clientX-x;
        var y_=e.clientY-y;
         
        if(document.addEventListener){
            document.addEventListener('mousemove', inFmove, true);
            document.addEventListener('mouseup', inFup, true);
        } else if(document.attachEvent){
            document.attachEvent('onmousemove', inFmove);
            document.attachEvent('onmouseup', inFup);
        }
         
        inFstop(e);     
        inFabort(e)
         
        function inFmove(e){
            var evt;
            if(!e)e=window.event;
             
            if(limit){
                var op=obj.parentNode;
                var opX=parseInt(op.style.left);
                var opY=parseInt(op.style.top);
                 
                if((e.clientX-x_)<0) return false;
                else if((e.clientX-x_+obj.offsetWidth+opX)>(opX+op.offsetWidth)) return false;
                 
                if(e.clientY-y_<0) return false;
                else if((e.clientY-y_+obj.offsetHeight+opY)>(opY+op.offsetHeight)) return false;
                //status=e.clientY-y_;
            }
             
            obj.style.left=e.clientX-x_+'px';
            obj.style.top=e.clientY-y_+'px';
             
            inFstop(e);
        } // shawl.qiu script
        function inFup(e){
            var evt;
            if(!e)e=window.event;
             
            if(document.removeEventListener){
                document.removeEventListener('mousemove', inFmove, true);
                document.removeEventListener('mouseup', inFup, true);
            } else if(document.detachEvent){
                document.detachEvent('onmousemove', inFmove);
                document.detachEvent('onmouseup', inFup);
            }
             
            inFstop(e);
        } // shawl.qiu script

        function inFstop(e){
            if(e.stopPropagation) return e.stopPropagation();
            else return e.cancelBubble=true;             
        } // shawl.qiu script
        function inFabort(e){
            if(e.preventDefault) return e.preventDefault();
            else return e.returnValue=false;
        } // shawl.qiu script
    }
//]]>
</script>
</head>
<body>
<div  style=" border:1px dashed blue; width: 760px; height:600px;  text-align:center; position:absolute; left:100px; top: 10px;"> this parent

    <div style=" border:1px dashed blue; width: 180px; text-align:center; position:absolute; left:50px; top: 50px;" onmousedown="fDragging(this, event, true);">
        element <br/>
        dragging compatibility for IE, Opera, Firefox.  
    </div>
    <div style=" border:1px dashed blue; width: 180px; text-align:center; position:absolute; left:100px; top: 150px;" onmousedown="fDragging(this, event, true);">
        element 1<br/>
        dragging compatibility for IE, Opera, Firefox.  
    </div>
    <div style=" border:1px dashed blue; width: 180px; text-align:center; position:absolute; left:200px; top: 250px;" onmousedown="fDragging(this, event, false);">
        element 2<br/>
        dragging compatibility for IE, Opera, Firefox. <br/>
        <font color="red">dragging everywhere</font>
    </div>
</div>
</body>
</html>

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