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用javascript实现拖动的代码

更新时间:2007-04-26 08:03 作者:冷雨夜点击:
  本文译自:http://www.webreference.com/programming/javascript/mk/column2/index.html所有版权归原文所有

  Javascript的特点是dom的处理与网页效果,大多数情况我们只用到了这个语言的最简单的功能,比如制作图片轮播/网页的tab等等,这篇文章将向你展示如何在自己的网页上制作拖拽.

  有很多理由让你的网站加入拖拽功能,最简单的一个是数据重组.例如:你有一个序列的内容让用户排序,用户需要给每个条目进行输入或者用select选择,替代前面这个方法的就是拖拽.或许你的网站也需要一个用户可以拖动的导航窗口!那么这些效果都是很简单:因为你可以很容易的实现!

  网页上实现拖拽其实也不是很复杂.第一你需要知道鼠标坐标,第二你需要知道用户鼠标点击一个网页元素并实现拖拽,最后我们要实现移动这个元素.

 [html]<STYLE>LI {
    MARGIN-BOTTOM: 10px
}
OL {
    MARGIN-TOP: 5px
}
.DragContainer {
    BORDER-RIGHT: #669999 2px solid; PADDING-RIGHT: 5px; BORDER-TOP: #669999 2px solid; PADDING-LEFT: 5px; FLOAT: left; PADDING-BOTTOM: 0px; MARGIN: 3px; BORDER-LEFT: #669999 2px solid; WIDTH: 100px; PADDING-TOP: 5px; BORDER-BOTTOM: #669999 2px solid
}
.OverDragContainer {
    BORDER-RIGHT: #669999 2px solid; PADDING-RIGHT: 5px; BORDER-TOP: #669999 2px solid; PADDING-LEFT: 5px; FLOAT: left; PADDING-BOTTOM: 0px; MARGIN: 3px; BORDER-LEFT: #669999 2px solid; WIDTH: 100px; PADDING-TOP: 5px; BORDER-BOTTOM: #669999 2px solid
}
.OverDragContainer {
    BACKGROUND-COLOR: #eee
}
.DragBox {
    BORDER-RIGHT: #000 1px solid; PADDING-RIGHT: 2px; BORDER-TOP: #000 1px solid; PADDING-LEFT: 2px; FONT-SIZE: 10px; MARGIN-BOTTOM: 5px; PADDING-BOTTOM: 2px; BORDER-LEFT: #000 1px solid; WIDTH: 94px; CURSOR: pointer; PADDING-TOP: 2px; BORDER-BOTTOM: #000 1px solid; FONT-FAMILY: verdana, tahoma, arial; BACKGROUND-COLOR: #eee
}
.OverDragBox {
    BORDER-RIGHT: #000 1px solid; PADDING-RIGHT: 2px; BORDER-TOP: #000 1px solid; PADDING-LEFT: 2px; FONT-SIZE: 10px; MARGIN-BOTTOM: 5px; PADDING-BOTTOM: 2px; BORDER-LEFT: #000 1px solid; WIDTH: 94px; CURSOR: pointer; PADDING-TOP: 2px; BORDER-BOTTOM: #000 1px solid; FONT-FAMILY: verdana, tahoma, arial; BACKGROUND-COLOR: #eee
}
.DragDragBox {
    BORDER-RIGHT: #000 1px solid; PADDING-RIGHT: 2px; BORDER-TOP: #000 1px solid; PADDING-LEFT: 2px; FONT-SIZE: 10px; MARGIN-BOTTOM: 5px; PADDING-BOTTOM: 2px; BORDER-LEFT: #000 1px solid; WIDTH: 94px; CURSOR: pointer; PADDING-TOP: 2px; BORDER-BOTTOM: #000 1px solid; FONT-FAMILY: verdana, tahoma, arial; BACKGROUND-COLOR: #eee
}
.miniDragBox {
    BORDER-RIGHT: #000 1px solid; PADDING-RIGHT: 2px; BORDER-TOP: #000 1px solid; PADDING-LEFT: 2px; FONT-SIZE: 10px; MARGIN-BOTTOM: 5px; PADDING-BOTTOM: 2px; BORDER-LEFT: #000 1px solid; WIDTH: 94px; CURSOR: pointer; PADDING-TOP: 2px; BORDER-BOTTOM: #000 1px solid; FONT-FAMILY: verdana, tahoma, arial; BACKGROUND-COLOR: #eee
}
.OverDragBox {
    BACKGROUND-COLOR: #ffff99
}
.DragDragBox {
    BACKGROUND-COLOR: #ffff99
}
.DragDragBox {
    FILTER: alpha(opacity=50); BACKGROUND-COLOR: #ff99cc
}
LEGEND {
    FONT-WEIGHT: bold; FONT-SIZE: 12px; COLOR: #666699; FONT-FAMILY: verdana, tahoma, arial
}
FIELDSET {
    PADDING-RIGHT: 3px; PADDING-LEFT: 3px; PADDING-BOTTOM: 3px; PADDING-TOP: 3px
}
.History {
    FONT-SIZE: 10px; OVERFLOW: auto; WIDTH: 100%; FONT-FAMILY: verdana, tahoma, arial; HEIGHT: 82px
}
#DragContainer8 {
    BORDER-RIGHT: #669999 1px solid; PADDING-RIGHT: 0px; BORDER-TOP: #669999 1px solid; PADDING-LEFT: 5px; PADDING-BOTTOM: 0px; BORDER-LEFT: #669999 1px solid; WIDTH: 110px; PADDING-TOP: 5px; BORDER-BOTTOM: #669999 1px solid; HEIGHT: 110px
}
.miniDragBox {
    FLOAT: left; MARGIN: 0px 5px 5px 0px; WIDTH: 20px; HEIGHT: 20px
}
pre{border:1 solid #CCC;background-color:#F8F8F0;padding:10px;}
</STYLE>


<script>

// iMouseDown represents the current mouse button state: up or down
/*
lMouseState represents the previous mouse button state so that we can
check for button clicks and button releases:

if(iMouseDown && !lMouseState) // button just clicked!
if(!iMouseDown && lMouseState) // button just released!
*/
var mouseOffset = null;
var iMouseDown = false;
var lMouseState = false;
var dragObject = null;

// Demo 0 variables
var DragDrops = [];
var curTarget = null;
var lastTarget = null;
var dragHelper = null;
var tempDiv = null;
var rootParent = null;
var rootSibling = null;

Number.prototype.NaN0=function(){return isNaN(this)?0:this;}

function CreateDragContainer(){
    /*
    Create a new "Container Instance" so that items from one "Set" can not
    be dragged into items from another "Set"
    */
    var cDrag = DragDrops.length;
    DragDrops[cDrag] = [];

    /*
    Each item passed to this function should be a "container". Store each
    of these items in our current container
    */
    for(var i=0; i<arguments.length; i++){
        var cObj = arguments[i];
        DragDrops[cDrag].push(cObj);
        cObj.setAttribute('DropObj', cDrag);

        /*
        Every top level item in these containers should be draggable. Do this
        by setting the DragObj attribute on each item and then later checking
        this attribute in the mouseMove function
        */
        for(var j=0; j<cObj.childNodes.length; j++){

            // Firefox puts in lots of #text nodes...skip these
            if(cObj.childNodes[j].nodeName=='#text') continue;

            cObj.childNodes[j].setAttribute('DragObj', cDrag);
        }
    }
}


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
    };
}

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};
}



function getPosition(e){
    var left = 0;
    var top = 0;
    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};

}


function mouseMove(ev){
    ev = ev || window.event;

    /*
    We are setting target to whatever item the mouse is currently on

    Firefox uses event.target here, MSIE uses event.srcElement
    */
    var target = ev.target || ev.srcElement;
    var mousePos = mouseCoords(ev);

    // mouseOut event - fires if the item the mouse is on has changed
    if(lastTarget && (target!==lastTarget)){
        // reset the classname for the target element
        var origClass = lastTarget.getAttribute('origClass');
        if(origClass) lastTarget.className = origClass;
    }

    /*
    dragObj is the grouping our item is in (set from the createDragContainer function).
    if the item is not in a grouping we ignore it since it can't be dragged with this
    script.
    */
    var dragObj = target.getAttribute('DragObj');

     // if the mouse was moved over an element that is draggable
    if(dragObj!=null){

        // mouseOver event - Change the item's class if necessary
        if(target!=lastTarget){
            var oClass = target.getAttribute('overClass');
            if(oClass){
                target.setAttribute('origClass', target.className);
                target.className = oClass;
            }
        }

        // if the user is just starting to drag the element
        if(iMouseDown && !lMouseState){
            // mouseDown target
            curTarget = target;

            // Record the mouse x and y offset for the element
            rootParent = curTarget.parentNode;
            rootSibling = curTarget.nextSibling;

            mouseOffset = getMouseOffset(target, ev);

            // We remove anything that is in our dragHelper DIV so we can put a new item in it.
            for(var i=0; i<dragHelper.childNodes.length; i++) dragHelper.removeChild(dragHelper.childNodes[i]);

            // Make a copy of the current item and put it in our drag helper.
            dragHelper.appendChild(curTarget.cloneNode(true));
            dragHelper.style.display = 'block';

            // set the class on our helper DIV if necessary
            var dragClass = curTarget.getAttribute('dragClass');
            if(dragClass){
                dragHelper.firstChild.className = dragClass;
            }

            // disable dragging from our helper DIV (it's already being dragged)
            dragHelper.firstChild.removeAttribute('DragObj');

            /*
            Record the current position of all drag/drop targets related
            to the element. We do this here so that we do not have to do
            it on the general mouse move event which fires when the mouse
            moves even 1 pixel. If we don't do this here the script
            would run much slower.
            */
            var dragConts = DragDrops[dragObj];

            /*
            first record the width/height of our drag item. Then hide it since
            it is going to (potentially) be moved out of its parent.
            */
            curTarget.setAttribute('startWidth', parseInt(curTarget.offsetWidth));
            curTarget.setAttribute('startHeight', parseInt(curTarget.offsetHeight));
            curTarget.style.display = 'none';

            // loop through each possible drop container
            for(var i=0; i<dragConts.length; i++){
                with(dragConts[i]){
                    var pos = getPosition(dragConts[i]);

                    /*
                    save the width, height and position of each container.

                    Even though we are saving the width and height of each
                    container back to the container this is much faster because
                    we are saving the number and do not have to run through
                    any calculations again. Also, offsetHeight and offsetWidth
                    are both fairly slow. You would never normally notice any
                    performance hit from these two functions but our code is
                    going to be running hundreds of times each second so every
                    little bit helps!

                    Note that the biggest performance gain here, by far, comes
                    from not having to run through the getPosition function
                    hundreds of times.
                    */
                    setAttribute('startWidth', parseInt(offsetWidth));
                    setAttribute('startHeight', parseInt(offsetHeight));
                    setAttribute('startLeft', pos.x);
                    setAttribute('startTop', pos.y);
                }

                // loop through each child element of each container
                for(var j=0; j<dragConts[i].childNodes.length; j++){
                    with(dragConts[i].childNodes[j]){
                        if((nodeName=='#text') || (dragConts[i].childNodes[j]==curTarget)) continue;

                        var pos = getPosition(dragConts[i].childNodes[j]);

                        // save the width, height and position of each element
                        setAttribute('startWidth', parseInt(offsetWidth));
                        setAttribute('startHeight', parseInt(offsetHeight));
                        setAttribute('startLeft', pos.x);
                        setAttribute('startTop', pos.y);
                    }
                }
            }
        }
    }

    // If we get in here we are dragging something
    if(curTarget){
        // move our helper div to wherever the mouse is (adjusted by mouseOffset)
        dragHelper.style.top = mousePos.y - mouseOffset.y;
        dragHelper.style.left = mousePos.x - mouseOffset.x;

        var dragConts = DragDrops[curTarget.getAttribute('DragObj')];
        var activeCont = null;

        var xPos = mousePos.x - mouseOffset.x + (parseInt(curTarget.getAttribute('startWidth')) /2);
        var yPos = mousePos.y - mouseOffset.y + (parseInt(curTarget.getAttribute('startHeight'))/2);

        // check each drop container to see if our target object is "inside" the container
        for(var i=0; i<dragConts.length; i++){
            with(dragConts[i]){
                if(((getAttribute('startLeft')) < xPos) &&
                    ((getAttribute('startTop')) < yPos) &&
                    ((getAttribute('startLeft') + getAttribute('startWidth')) > xPos) &&
                    ((getAttribute('startTop') + getAttribute('startHeight')) > yPos)){

                        /*
                        our target is inside of our container so save the container into
                        the activeCont variable and then exit the loop since we no longer
                        need to check the rest of the containers
                        */
                        activeCont = dragConts[i];

                        // exit the for loop
                        break;
                }
            }
        }

        // Our target object is in one of our containers. Check to see where our div belongs
        if(activeCont){
            // beforeNode will hold the first node AFTER where our div belongs
            var beforeNode = null;

            // loop through each child node (skipping text nodes).
            for(var i=activeCont.childNodes.length-1; i>=0; i--){
                with(activeCont.childNodes[i]){
                    if(nodeName=='#text') continue;

                    // if the current item is "After" the item being dragged
                    if(
                        curTarget != activeCont.childNodes[i] &&
                        ((getAttribute('startLeft') + getAttribute('startWidth')) > xPos) &&
                        ((getAttribute('startTop') + getAttribute('startHeight')) > yPos)){
                            beforeNode = activeCont.childNodes[i];
                    }
                }
            }

            // the item being dragged belongs before another item
            if(beforeNode){
                if(beforeNode!=curTarget.nextSibling){
                    activeCont.insertBefore(curTarget, beforeNode);
                }

            // the item being dragged belongs at the end of the current container
            } else {
                if((curTarget.nextSibling) || (curTarget.parentNode!=activeCont)){
                    activeCont.appendChild(curTarget);
                }
            }

            // make our drag item visible
            if(curTarget.style.display!=''){
                curTarget.style.display = '';
            }
        } else {

            // our drag item is not in a container, so hide it.
            if(curTarget.style.display!='none'){
                curTarget.style.display = 'none';
            }
        }
    }

    // track the current mouse state so we can compare against it next time
    lMouseState = iMouseDown;

    // mouseMove target
    lastTarget = target;

    // track the current mouse state so we can compare against it next time
    lMouseState = iMouseDown;

    // this helps prevent items on the page from being highlighted while dragging
    return false;
}

function mouseUp(ev){
    if(curTarget){
        // hide our helper object - it is no longer needed
        dragHelper.style.display = 'none';

        // if the drag item is invisible put it back where it was before moving it
        if(curTarget.style.display == 'none'){
            if(rootSibling){
                rootParent.insertBefore(curTarget, rootSibling);
            } else {
                rootParent.appendChild(curTarget);
            }
        }

        // make sure the drag item is visible
        curTarget.style.display = '';
    }
    curTarget = null;
    iMouseDown = false;
}

function mouseDown(){
    iMouseDown = true;
    if(lastTarget){
        return false;
    }
}

document.onmousemove = mouseMove;
document.onmousedown = mouseDown;
document.onmouseup = mouseUp;

window.onload = function(){
    // Create our helper object that will show the item while dragging
    dragHelper = document.createElement('DIV');
    dragHelper.style.cssText = 'position:absolute;display:none;';
        
    CreateDragContainer(
        document.getElementById('DragContainer1'),
        document.getElementById('DragContainer2'),
        document.getElementById('DragContainer3')
    );

    document.body.appendChild(dragHelper);
}

</script>

<!--the mouse over and dragging class are defined on each item-->

<div class="DragContainer" id="DragContainer1">
    <div class="DragBox" id="Item1" overClass="OverDragBox" dragClass="DragDragBox">Item #1</div>
    <div class="DragBox" id="Item2" overClass="OverDragBox" dragClass="DragDragBox">Item #2</div>
    <div class="DragBox" id="Item3" overClass="OverDragBox" dragClass="DragDragBox">Item #3</div>
    <div class="DragBox" id="Item4" overClass="OverDragBox" dragClass="DragDragBox">Item #4</div>
</div>
<div class="DragContainer" id="DragContainer2">
    <div class="DragBox" id="Item5" overClass="OverDragBox" dragClass="DragDragBox">Item #5</div>
    <div class="DragBox" id="Item6" overClass="OverDragBox" dragClass="DragDragBox">Item #6</div>
    <div class="DragBox" id="Item7" overClass="OverDragBox" dragClass="DragDragBox">Item #7</div>
    <div class="DragBox" id="Item8" overClass="OverDragBox" dragClass="DragDragBox">Item #8</div>
</div>
<div class="DragContainer" id="DragContainer3">
    <div class="DragBox" id="Item9" overClass="OverDragBox" dragClass="DragDragBox">Item #9</div>
    <div class="DragBox" id="Item10" overClass="OverDragBox" dragClass="DragDragBox">Item #10</div>
    <div class="DragBox" id="Item11" overClass="OverDragBox" dragClass="DragDragBox">Item #11</div>
    <div class="DragBox" id="Item12" overClass="OverDragBox" dragClass="DragDragBox">Item #12</div>[/html]
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