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javascript实现类似google和msn space的拖拽

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=gb2312">

<title>BlackSoul的拖拽Demo</title>

<!--

 ____________________________________

|--------Author By BlackSoul---------|

|------------2006.03.30--------------|

|--------BlackSoulylk@gmail.com------|

|------------QQ:9136194--------------|

|------http://blacksoul.cnblogs.cn---|

======================================

-->

<style type="text/css">

body

{

    margin:0px;

}

 

#aim /*设置目标层样式*/

{

    position:absolute;/*控制层的位置所必须的style*/

    width:200px;

    height:30px;

    border:1px solid #666666;

    background-color:#FFCCCC;

}

 

#sourceLayer, #cloneLayer

{

    position:absolute;/*控制层的位置所必须的style*/

    width:300px;

    height:50px;

    border:1px solid #666666;

    background-color:#CCCCCC;

    cursor:move;

}

 

.docked

{

    display:none;

    filter:alpha(opacity=100);

}

 

.actived

{

    display:block;

    filter:alpha(opacity=70);

}

</style>

</head>

 

<body >

 

<div id="aim">放置范围</div>

<div id="sourceLayer" unselectable="off"><img src="http://www.knowsky.com/http://blacksoul.gamenews.cn/mail.png" alt="拖拽Demo">拖拽Demo源</div>

<div id="cloneLayer" class="docked" unselectable="off"></div>

 

<script type="text/javascript" language="javascript">

<!--

/*

 ====================================

|--------Author By BlackSoul---------|

|------------2006.03.30--------------|

|--------BlackSoulylk@gmail.com------|

|------------QQ:9136194--------------|

|------http://blacksoul.cnblogs.cn---|

 ====================================

*/

//设置层对象

var aim;

var sourceLayer;

var cloneLayer;

 

//定义各个层初始位置

var aimX;

var aimY;

var orgnX;

var orgnY;

 

//拖拽过程中的变量

var draging = false; //是否处于拖拽中

var offsetX = 0;     //X方向左右偏移量

var offsetY = 0;     //Y方向上下偏移量

var back;            //返回动画对象

var thisX ;          //当前clone层的X位置

var thisY ;          //当前clone层的Y位置

var time ;

var stepX ;          //位移速度

var stepY ;          //位移速度

 

//初始化拖拽信息

/*

  initAimX 目标x坐标

  initAimY 目标y坐标

  initOrgnX 拖拽源x坐标

  initOrgnY 拖拽源y坐标

*/

//获得层对象

 

function getLayer(inAim,inSource,inClone)

{

    aim = document.getElementById(inAim);

    sourceLayer = document.getElementById(inSource);

    cloneLayer = document.getElementById(inClone);

}

 

function initDrag(initAimX,initAimY,initOrgnX,initOrgnY)

{

    aimX = initAimX;

    aimY = initAimY;

    orgnX = initOrgnX;

    orgnY = initOrgnY;

    //设置各个开始层的位置

    aim.style.pixelLeft = aimX;

    aim.style.pixelTop = aimY;

    sourceLayer.style.pixelLeft = orgnX;

    sourceLayer.style.pixelTop = orgnY;

    cloneLayer.style.pixelLeft = orgnX;

    cloneLayer.style.pixelTop = orgnY;

}

 

//准备拖拽

function BeforeDrag()

{

    if (event.button != 1)

    {

        return;

    }

    cloneLayer.innerHTML = sourceLayer.innerHTML; //复制拖拽源内容

    offsetX = document.body.scrollLeft + event.clientX - sourceLayer.style.pixelLeft;

    offsetY = document.body.scrollTop + event.clientY - sourceLayer.style.pixelTop;

    cloneLayer.className = "actived";

    draging = true;

}

 

//拖拽中

function OnDrag()

{

    if(!draging)

    {

        return;

    }

    //更新位置

    event.returnValue = false;

    cloneLayer.style.pixelLeft = document.body.scrollLeft + event.clientX - offsetX;

    cloneLayer.style.pixelTop = document.body.scrollTop + event.clientY - offsetY;

}

 

//结束拖拽

function EndDrag()

{

    if (event.button != 1)

    {

        return;

    }

    draging = false;

 

    if (event.clientX >= aim.style.pixelLeft && event.clientX <= (aim.style.pixelLeft + aim.offsetWidth) &&

        event.clientY >= aim.style.pixelTop && event.clientY <= (aim.style.pixelTop + aim.offsetHeight))

    {

        //拖拽层位于目标中,自动定位到目标位置

        sourceLayer.style.pixelLeft = aim.style.pixelLeft;

        sourceLayer.style.pixelTop = aim.style.pixelTop;

         cloneLayer.className = "docked";

         /*

         **  这里完成之后能用xml保存当前位置.

         **  下次用户进入的时候

         **  就初始化源拖拽层为xml当中的数据了    

         */

    }

    else

    {

    //拖拽位于目标层外,将拖拽源位置复原

     thisX = cloneLayer.style.pixelLeft;

     thisY = cloneLayer.style.pixelTop;

     offSetX = Math.abs(thisX - orgnX);

     offSetY = Math.abs(thisY - orgnY);

     time = 500;//设置动画时间

     stepX = Math.floor((offSetX/time)*20);

     stepY = Math.floor((offSetY/time)*20);

     if(stepX == 0)

         stepX = 2;

     if(stepY == 0)

         stepY = 2;

        

    //开始返回动画

     moveStart();

    }   

}

 

 

function moveStart()

{

     back = setInterval("MoveLayer();",15);

}

 

//设置返回的动画效果

function MoveLayer()

{

    //位于目标左上

     if(cloneLayer.style.pixelLeft <= orgnX && cloneLayer.style.pixelTop <= orgnY)

     {

         cloneLayer.style.pixelLeft += stepX;

         cloneLayer.style.pixelTop += stepY;

         //如果位移超过目标则设置速度为pix.并向反方向回移.此处实现了弹簧效果.下同

         if(cloneLayer.style.pixelLeft > orgnX)

         {

              stepX = 1;

         }

         if(cloneLayer.style.pixelTop > orgnY)

         {

              stepY = 1;

         }

         //在X或Y轴上坐标相同则不发生位移

         if(cloneLayer.style.pixelLeft == orgnX)

         {

              stepX = 0;

         }

         if(cloneLayer.style.pixelTop == orgnY)

         {

              stepY = 0;

         }

         if(cloneLayer.style.pixelLeft == orgnX && cloneLayer.style.pixelTop == orgnY)

         {

              EndMove();

         }

     }

    

     //位于目标左下

     else if(cloneLayer.style.pixelLeft <= orgnX && cloneLayer.style.pixelTop >= orgnY)

     {

         cloneLayer.style.pixelLeft += stepX;

         cloneLayer.style.pixelTop -= stepY;

         if(cloneLayer.style.pixelLeft > orgnX)

         {

              stepX = 1;

         }

         if(cloneLayer.style.pixelTop < orgnY)

         {

              stepY = 1;

         }

         if(cloneLayer.style.pixelLeft == orgnX)

         {

              stepX = 0;

         }

         if(cloneLayer.style.pixelTop == orgnY)

         {

              stepY = 0;

         }

         if(cloneLayer.style.pixelLeft == orgnX && cloneLayer.style.pixelTop == orgnY)

         {

              EndMove();

         }

     }

    

     //位于目标右上

     else if(cloneLayer.style.pixelLeft >= orgnX && cloneLayer.style.pixelTop <= orgnY)

     {

         cloneLayer.style.pixelLeft -= stepX;

         cloneLayer.style.pixelTop += stepY;

         if(cloneLayer.style.pixelLeft < orgnX)

         {

              stepX = 1;

         }

         if(cloneLayer.style.pixelTop > orgnY)

         {

              stepY = 1;

         }

         if(cloneLayer.style.pixelLeft == orgnX)

         {

              stepX = 0;

         }

         if(cloneLayer.style.pixelTop == orgnY)

         {

              stepY = 0;

         }

         if(cloneLayer.style.pixelLeft == orgnX && cloneLayer.style.pixelTop == orgnY)

         {

              EndMove();

         }

     }

    

     //位于目标右上

     else if(cloneLayer.style.pixelLeft >= orgnX && cloneLayer.style.pixelTop >= orgnY)

     {

         cloneLayer.style.pixelLeft -= stepX;

         cloneLayer.style.pixelTop -= stepY;

         if(cloneLayer.style.pixelLeft < orgnX)

         {

              stepX = 1;

         }

         if(cloneLayer.style.pixelTop < orgnY)

         {

              stepY = 1;

         }

         if(cloneLayer.style.pixelLeft == orgnX)

         {

              stepX = 0;

         }

         if(cloneLayer.style.pixelTop == orgnY)

         {

              stepY = 0;

         }

         if(cloneLayer.style.pixelLeft == orgnX && cloneLayer.style.pixelTop == orgnY)

         {

              EndMove();

         }

     }

    

     //到达目标

     else

     {

         EndMove();

     }

}

 

//停止返回动画

function EndMove()

{

         sourceLayer.style.pixelLeft = orgnX;

         sourceLayer.style.pixelTop = orgnY;

         cloneLayer.style.pixelLeft = orgnX;

         cloneLayer.style.pixelTop = orgnY;

         cloneLayer.className = "docked";

         clearInterval(back);

}

 

//主拖拽函数

function startDraging(inAim,inSource,inClone,initAimX,initAimY,initOrgnX,initOrgnY)

{

    getLayer(inAim,inSource,inClone)

    initDrag(initAimX,initAimY,initOrgnX,initOrgnY);

    sourceLayer.onmousedown = BeforeDrag;

    document.onmousemove = OnDrag; //这里如果用cloneLayer,在拖拽中会选中cloneLayer里面内容,进而出现一些bug...

    cloneLayer.onmouseup = EndDrag;   

}

 

//调用

startDraging("aim","sourceLayer","cloneLayer",300,200,20,20);

//-->

</script>

</body>

</html>

需要注意的是:
一.html里面对于div的定义需要有三个. 三个层都必须定义style的position为absolute,以便控制位置
    1.目标层(aim),主要作用是定义拖拽生效的位置.
    2.拖拽源(sourceLayer).注意设置属性unselectable = "off"(这里比较奇怪,设置成on范围会在拖拽过程中选中层内容)
    3.用于复制的层(cloneLayer).
二.函数的调用
    startDraging参数解释:
    initAim   目标层名称     initSource  拖拽源名称    initClone 用于复制的层的名称 
    initAimX  目标层x轴坐标  initAimY    目标层y轴坐标 initOrgnX 拖拽源x坐标        initOrgnY 拖拽源Y轴坐标

    仅IE里面测试通过.代码里面添加了注释.能在拖拽源到达目标之后添加写xml的操作.进而记录用户自定义页面排版的数据