有时候我们上传图片时希望立即显示出来，也有时候希望图片能根据自己的意愿拖动，下面的代码可以实现我们想要的效果。
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>鼠标拖动测试</title>
<script type="text/javascript" language="javascript">
//为Number增加一个属性,判断当前数据类型是否是数字
Number.prototype.NaN0=function(){return isNaN(this)?0:this;}
//全局变量
var iMouseDown=false;
var dragObject=null;
//获得鼠标的偏移量(对象2-对象1)
function getMouseOffset(target,ev)
{
ev=ev||window.event;
var docPos=getPosition(target);
var mousePos=mouseCoords(ev);
return {x:mousePos.x-docPos.x,y:mousePos.y-docPos.y};
}
//获得事件发生的实际位置----------------------对象1
function getPosition(e)
{
var left=0;
var top=0;
//相对位置累加得到实际位置
while(e.offsetParent)
{
left+=e.offsetLeft+(e.currentStyle?(parseInt(e.currentStyle.borderLeftWidth)).NaN0():0);
top+=e.offsetTop+(e.currentStyle?(parseInt(e.currentStyle.borderTopWidth)).NaN0():0);
e=e.offsetParent;
}
left+=e.offsetLeft+(e.currentStyle?(parseInt(e.currentStyle.borderLeftWidth)).NaN0():0);
top+=e.offsetTop+(e.currentStyle?(parseInt(e.currentStyle.borderTopWidth)).NaN0():0);
return {x:left,y:top};
}
//获得发生事件鼠标的位置----------------------对象2
function mouseCoords(ev)
{
if(ev.pageX||ev.pageY)
{
return {x:ev.pageX,y:ev.pageY};
}
return {x:ev.clientX+document.body.scrollLeft-document.body.clientLeft,y:ev.clientY+document.body.scrollTop-document.body.clientTop};
}
//定义可以拖拽的对象
function makeDragable(item)
{
if(!item) return;
//为可拖拽对象定义一个onmousedown事件的方法
ev=window.event;
item.onmousedown=function(ev)
{
dragObject=this;
mouseOffset=getMouseOffset(this,ev);
return false;
}
}
//定义鼠标点下所调用的方法
function mouseDown(ev)
{
ev=ev||window.event;
var target=ev.target||ev.srcElement;
if(target.onmousedown||target.getAttribute('DragObj'))
{
return false;
}
}
//鼠标抬起后释放对象
function mouseUp(ev)
{
dragObject = null;
//onmouseup事件触发时说明鼠标已经松开，所以设置down变量值为false
iMouseDown = false;
}
//鼠标移动
function mouseMove(ev)
{
ev=ev||window.event;
var target = ev.target || ev.srcElement;
var mousePos = mouseCoords(ev);
if(dragObject)
{
if(dragObject.style)
{
//移动对象
dragObject.style.left=mousePos.x - mouseOffset.x;
dragObject.style.top= mousePos.y - mouseOffset.y;
}
}
//lMouseState = iMouseDown;
if(dragObject) return false;
}
document.onmousedown=mouseDown;
document.onmousemove=mouseMove;
document.onmouseup=mouseUp;
function moveImg()
{
var img1=document.getElementById('img1');
makeDragable(img1);
}
</script>
</head>
<body onload="moveImg()">
<form id="form1">
<input type="file" onchange="javascript:document.getElementById('img1').src=this.value"/>
<img src="a.jpg" alt="" id="img1" style="position:absolute;" />
</form>
</body>
</html>
<head runat="server">
<title>鼠标拖动测试</title>
<script type="text/javascript" language="javascript">
//为Number增加一个属性,判断当前数据类型是否是数字
Number.prototype.NaN0=function(){return isNaN(this)?0:this;}
//全局变量
var iMouseDown=false;
var dragObject=null;
//获得鼠标的偏移量(对象2-对象1)
function getMouseOffset(target,ev)
{
ev=ev||window.event;
var docPos=getPosition(target);
var mousePos=mouseCoords(ev);
return {x:mousePos.x-docPos.x,y:mousePos.y-docPos.y};
}
//获得事件发生的实际位置----------------------对象1
function getPosition(e)
{
var left=0;
var top=0;
//相对位置累加得到实际位置
while(e.offsetParent)
{
left+=e.offsetLeft+(e.currentStyle?(parseInt(e.currentStyle.borderLeftWidth)).NaN0():0);
top+=e.offsetTop+(e.currentStyle?(parseInt(e.currentStyle.borderTopWidth)).NaN0():0);
e=e.offsetParent;
}
left+=e.offsetLeft+(e.currentStyle?(parseInt(e.currentStyle.borderLeftWidth)).NaN0():0);
top+=e.offsetTop+(e.currentStyle?(parseInt(e.currentStyle.borderTopWidth)).NaN0():0);
return {x:left,y:top};
}
//获得发生事件鼠标的位置----------------------对象2
function mouseCoords(ev)
{
if(ev.pageX||ev.pageY)
{
return {x:ev.pageX,y:ev.pageY};
}
return {x:ev.clientX+document.body.scrollLeft-document.body.clientLeft,y:ev.clientY+document.body.scrollTop-document.body.clientTop};
}
//定义可以拖拽的对象
function makeDragable(item)
{
if(!item) return;
//为可拖拽对象定义一个onmousedown事件的方法
ev=window.event;
item.onmousedown=function(ev)
{
dragObject=this;
mouseOffset=getMouseOffset(this,ev);
return false;
}
}
//定义鼠标点下所调用的方法
function mouseDown(ev)
{
ev=ev||window.event;
var target=ev.target||ev.srcElement;
if(target.onmousedown||target.getAttribute('DragObj'))
{
return false;
}
}
//鼠标抬起后释放对象
function mouseUp(ev)
{
dragObject = null;
//onmouseup事件触发时说明鼠标已经松开，所以设置down变量值为false
iMouseDown = false;
}
//鼠标移动
function mouseMove(ev)
{
ev=ev||window.event;
var target = ev.target || ev.srcElement;
var mousePos = mouseCoords(ev);
if(dragObject)
{
if(dragObject.style)
{
//移动对象
dragObject.style.left=mousePos.x - mouseOffset.x;
dragObject.style.top= mousePos.y - mouseOffset.y;
}
}
//lMouseState = iMouseDown;
if(dragObject) return false;
}
document.onmousedown=mouseDown;
document.onmousemove=mouseMove;
document.onmouseup=mouseUp;
function moveImg()
{
var img1=document.getElementById('img1');
makeDragable(img1);
}
</script>
</head>
<body onload="moveImg()">
<form id="form1">
<input type="file" onchange="javascript:document.getElementById('img1').src=this.value"/>
<img src="a.jpg" alt="" id="img1" style="position:absolute;" />
</form>
</body>
</html>