怎么用javascript进行拖拽
本文译自：http://www.webreference.com/programming/javascript/mk/column2/index.html
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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．
获取鼠标移动信息
第一我们需要获取鼠标的坐标．我们加一个用户函数到document.onmousemove就可以了:
document.onmousemove = mouseMove;
function mouseMove(ev){
ev = ev || window.event;
var mousePos = mouseCoords(ev);
}
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
};
}
实现上面的独立脚本，选取存下来，并把<>的全角换成半角，就可以看到效果！
＜script＞
function mouseMove(ev){
ev = ev || window.event;
var mousePos = mouseCoords(ev);
document.getElementById('xxx').value = mousePos.x;
document.getElementById('yyy').value = mousePos.y;
}
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
};
}
document.onmousemove = mouseMove;
＜／script＞
＜input id=xxx type=text＞
＜br＞
＜input id=yyy type=text＞
你首先要声明一个evnet对象．不论何时你移动鼠标／点击／按键等等，会对应一个event的事件．在Internet
Explorer里event是全局变量，会被存储在window.event里．
在firefox中，或者其他浏览器，event事件会被相应的自定义函数获取．当我们将mouseMove函数赋值于document.onmousemove，mouseMove会获取鼠标移动事件．
(ev = ev || window.event) 这样让ev在所有浏览器下获取了event事件，在Firefox下"||window.event"将不起作用，因为ev已经有了赋值．在MSIE下ev是空的，所以ev将设置为window.event.
因为我们在这篇文章中需要多次获取鼠标坐标，所以我们设计了mouseCoords这个函数，它只包含了一个参数，就是the event.
我们需要运行在MSIE与Firefox为首的其他浏览器下．Firefox以event.pageX和event.pageY来代表鼠标相应于文 档左上角的位置．如果你有一个500*500的窗口，而且你的鼠标在正中间，那么paegX和pageY将是250，当你将页面往下滚动500px，那么 pageY将是750.此时pageX不变，还是250.
MSIE和这个相反，MSIE将event.clientX与event.clientY来代表鼠标与ie窗口的位置，并不是文档．当我们有一个 500*500的窗口，鼠标在正中间，那么clientX与clientY也是250，如果你垂直滚动窗口到任何位置，clientY仍然是250，因为 相对ie窗口并没有变化．想得到正确的结果，我们必须加入scrollLeft与scrollTop这两个相对于文档鼠标位置的属性．最后，由于MSIE 并没有0,0的文档起始位置，因为通常会设置2px的边框在周围，边框的宽度包含在document.body.clientLeft与 clientTop这两个属性中，我们再加入这些到鼠标的位置中．
很幸运，这样mouseCoords函数就完成了，我们不再为坐标的事操心了．
捕捉鼠标点击
下次我们将知道鼠标何时点击与何时放开．如果我们跳过这一步，我们在做拖拽时将永远不知道鼠标移动上面时的动作，这将是恼人的与违反直觉的．
这里有两个函数帮助我们:onmousedown与onmouseup.我们预先设置函数来接收document.onmousemove，这样看 起来很象我们会获取document.onmousedown与document.onmouseup．但是当我们获取 document.onmousedown时，我们同时获取了任何对象的点击属性如:text,images,tables等等.我们只想获取那些需要拖 拽的属性，所以我们设置函数来获取我们需要移动的对象．
实现上面的独立脚本，选取存下来，并把<>的全角换成半角，就可以看到效果！
＜script＞
function mouseDown(ev){
ev = ev || window.event;
var target = ev.target || ev.srcElement;
if(target.onmousedown || target.getAttribute('DragObj')){
return false;
}
}
function makeClickable(item){
if(!item) return;
item.onmousedown = function(ev){
document.getElementById('ClickImage').value = this.name;
}
}
document.onmousedown = mouseDown;
window.onload = function(){
makeClickable(document.getElementById('ClickImage1'));
makeClickable(document.getElementById('ClickImage2'));
makeClickable(document.getElementById('ClickImage3'));
makeClickable(document.getElementById('ClickImage4'));
}＜/script＞
＜FIELDSET id=Demo3＞
＜h3＞
Demo - Click any image
＜/h3＞
＜IMG id=ClickImage1
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_spade.gif"
name=Spade＞＜IMG id=ClickImage2
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_heart.gif"
name=Heart＞＜IMG id=ClickImage3
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_diamond.gif"
name=Diamond＞＜IMG id=ClickImage4
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_club.gif"
name=Club＞
＜BR＞You clicked on: ＜INPUT id=ClickImage type="text"＞ ＜/FIELDSET＞
移动一个元素
我们知道了怎么捕捉鼠标移动与点击．剩下的就是移动元素了．首先，要确定一个明确的页面位置，css样式表要用'absolute'.设置元素绝对 位置意味着我们可以用样式表的.top和.left来定位，可以用相对位置来定位了．我们将鼠标的移动全部相对页面top-left，基于这点，我们可以 进行下一步了．
当我们定义item.style.position='absolute'，所有的操作都是改变left坐标与top坐标，然后它移动了．
document.onmousemove = mouseMove;
document.onmouseup = mouseUp;
var dragObject = null;
var mouseOffset = null;
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;
top += e.offsetTop;
e = e.offsetParent;
}
left += e.offsetLeft;
top += e.offsetTop;
return {x:left, y:top};
}
function mouseMove(ev){
ev = ev || window.event;
var mousePos = mouseCoords(ev);
if(dragObject){
dragObject.style.position = 'absolute';
dragObject.style.top = mousePos.y - mouseOffset.y;
dragObject.style.left = mousePos.x - mouseOffset.x;
return false;
}
}
function mouseUp(){
dragObject = null;
}
function makeDraggable(item){
if(!item) return;
item.onmousedown = function(ev){
dragObject = this;
mouseOffset = getMouseOffset(this, ev);
return false;
}
}
实现上面效果的代码，注意将<>的全角换成半角
＜script＞
var iMouseDown = false;
var dragObject = null;
var curTarget = null;
function makeDraggable(item){
if(!item) return;
item.onmousedown = function(ev){
dragObject = this;
mouseOffset = getMouseOffset(this, ev);
return false;
}
}
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 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 mouseDown(ev){
ev = ev || window.event;
var target = ev.target || ev.srcElement;
if(target.onmousedown || target.getAttribute('DragObj')){
return false;
}
}
function mouseUp(ev){
dragObject = null;
iMouseDown = false;
}
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);
if(dragObject){
dragObject.style.position = 'absolute';
dragObject.style.top = mousePos.y - mouseOffset.y;
dragObject.style.left = mousePos.x - mouseOffset.x;
}
// track the current mouse state so we can compare against it next time
lMouseState = iMouseDown;
// this prevents items on the page from being highlighted while dragging
if(curTarget || dragObject) return false;
}
document.onmousemove = mouseMove;
document.onmousedown = mouseDown;
document.onmouseup = mouseUp;
window.onload = function() {
makeDraggable(document.getElementById('DragImage5'));
makeDraggable(document.getElementById('DragImage6'));
makeDraggable(document.getElementById('DragImage7'));
makeDraggable(document.getElementById('DragImage8'));
}
＜/script＞
＜FIELDSET id=Demo5 style="HEIGHT: 70px"＞＜h3＞Demo - Drag any of the
images＜/h3＞＜IMG id=DragImage5
src="images/drag_drop_spade.gif"＞＜IMG
id=DragImage6
src="images/drag_drop_heart.gif"＞＜IMG
id=DragImage7
src="images/drag_drop_diamond.gif"＞＜IMG
id=DragImage8
src="images/drag_drop_club.gif"＞ ＜/FIELDSET＞
你会注意到这个代码几乎是前面的全集，将前面的合在一起就实现了拖拽效果了．
当我们点击一个item时，我们就获取了很多变量，如鼠标位置，鼠标位置自然就包含了那个item的坐标信息了．如果我们点击了一个20*20px 图像的正中间，那么鼠标的相对坐标为{x:10,y:10}．当我们点击这个图像的左上角那么鼠标的相对坐标为{x:0,y:0}.当我们点击时，我们用 这个方法取得一些鼠标与图片校对的信息．如果我们不能加载页面item，那么信息将是document信息，会忽略了点击的item信息．
mouseOffset函数使用了另一个函数getPosition.getPosition的作用是返回item相对页面左上角的坐标，如果我们 尝试获取item.offsetLeft或者item.style.left，那么我们将取得item相对与父级的位置，不是整个document．所有 的脚本我们都是相对整个document，这样会更好一些．
为了完成getPosition任务，必须循环取得item的父级，我们将加载内容到item的左／上的位置．我们需要管理想要的top与left列表．
自从定义了mousemove这个函数，mouseMove就会一直运行．第一我们确定item的style.position为 absolute，第二我们移动item到前面定义好的位置．当mouse点击被释放，dragObject被设置为null，mouseMove将不在 做任何事．
Dropping an Item
前面的例子目的很简单，就是拖拽item到我们希望到的地方．我们经常还有其他目的如删除item，比如我们可以将item拖到垃圾桶里，或者其他页面定义的位置．
很不幸，我们有一个很大的难题，当我们拖拽，item会在鼠标之下，比如mouseove,mousedown,mouseup或者其他mouse action．如果我们拖拽一个item到垃圾桶上，鼠标信息还在item上，不在垃圾桶上．
怎么解决这个问题呢？有几个方法可以来解决．第一，这是以前比较推荐的，我们在移动鼠标时item会跟随鼠标，并占用了 mouseover/mousemove等鼠标事件，我们不这样做，只是让item跟随着鼠标，并不占用mouseover等鼠标事件，这样会解决问题， 但是这样并不好看，我们还是希望item能直接跟在mouse下．
另一个选择是不做item的拖拽．你可以改变鼠标指针来显示需要拖拽的item，然后放在鼠标释放的位置．这个解决方案，也是因为美学原因不予接受．
最后的解决方案是，我们并不去除拖拽效果．这种方法比前两种繁杂许多，我们需要定义我们需要释放目标的列表，当鼠标释放时，手工去检查释放的位置是否是在目标列表位置上，如果在，说明是释放在目标位置上了．
/*
All code from the previous example is needed with the exception
of the mouseUp function which is replaced below
*/
var dropTargets = [];
function addDropTarget(dropTarget){
dropTargets.push(dropTarget);
}
function mouseUp(ev){
ev = ev || window.event;
var mousePos = mouseCoords(ev);
for(var i=0; i<dropTargets.length; i++){
var curTarget = dropTargets[i];
var targPos = getPosition(curTarget);
var targWidth = parseInt(curTarget.offsetWidth);
var targHeight = parseInt(curTarget.offsetHeight);
if(
(mousePos.x > targPos.x) &&
(mousePos.x < (targPos.x + targWidth)) &&
(mousePos.y > targPos.y) &&
(mousePos.y < (targPos.y + targHeight))){
// dragObject was dropped onto curTarget!
}
}
dragObject = null;
}
实现上面效果的代码，注意将<>的全角换成半角
＜script＞
var iMouseDown = false;
var dragObject = null;
Number.prototype.NaN0=function(){return isNaN(this)?0:this;}
// Demo 0 variables
var DragDrops = [];
var curTarget = null;
var lastTarget = null;
function makeDraggable(item){
if(!item) return;
item.onmousedown = function(ev){
dragObject = this;
mouseOffset = getMouseOffset(this, ev);
return false;
}
}
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 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 mouseDown(ev){
ev = ev || window.event;
var target = ev.target || ev.srcElement;
if(target.onmousedown || target.getAttribute('DragObj')){
return false;
}
}
function mouseUp(ev){
//dragObject = null;
if(dragObject){
ev = ev || window.event;
var mousePos = mouseCoords(ev);
var dT = dragObject.getAttribute('droptarget');
if(dT){
var targObj = document.getElementById(dT);
var objPos = getPosition(targObj);
if((mousePos.x ＞ objPos.x) && (mousePos.y ＞ objPos.y)
&& (mousePos.x＜(objPos.x+parseInt(targObj.offsetWidth)))
&& (mousePos.y＜(objPos.y+parseInt(targObj.offsetHeight)))){
var nSrc = targObj.getAttribute('newSrc');
if(nSrc){
dragObject.src = nSrc;
setTimeout(function(){
if(!dragObject || !dragObject.parentNode) return;
dragObject.parentNode.removeChild(dragObject);
dragObject = null;
}, parseInt(targObj.getAttribute('timeout')));
} else {
dragObject.parentNode.removeChild(dragObject);
}
}
}
}
dragObject = null;
iMouseDown = false;
}
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);
if(dragObject){
dragObject.style.position = 'absolute';
dragObject.style.top = mousePos.y - mouseOffset.y;
dragObject.style.left = mousePos.x - mouseOffset.x;
}
// track the current mouse state so we can compare against it next time
lMouseState = iMouseDown;
// this prevents items on the page from being highlighted while dragging
if(curTarget || dragObject) return false;
}
function addDropTarget(item, target){
item.setAttribute('droptarget', target);
}
document.onmousemove = mouseMove;
document.onmousedown = mouseDown;
document.onmouseup = mouseUp;
window.onload = function (){
makeDraggable(document.getElementById('DragImage9'));
makeDraggable(document.getElementById('DragImage10'));
makeDraggable(document.getElementById('DragImage11'));
makeDraggable(document.getElementById('DragImage12'));
addDropTarget(document.getElementById('DragImage9'), 'TrashImage1');
addDropTarget(document.getElementById('DragImage10'), 'TrashImage1');
addDropTarget(document.getElementById('DragImage11'), 'TrashImage1');
addDropTarget(document.getElementById('DragImage12'), 'TrashImage1');
}
＜/script＞
＜FIELDSET id=Demo6 style="HEIGHT: 70px"＞＜h3＞Demo - Drag any image onto the
trashcan＜/h3＞＜IMG id=TrashImage1
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_trash.gif"
timeout="600" newSrc="images/transparent.gif"＞
＜IMG
id=DragImage9
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_spade.gif"＞
＜IMG
id=DragImage10
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_heart.gif"＞
＜IMG
id=DragImage11
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_diamond.gif"＞
＜IMG
id=DragImage12
src="http://www.webreference.com/programming/javascript/mk/column2/Dragging and Dropping in JavaScript_files/drag_drop_club.gif"＞
＜/FIELDSET＞
鼠标释放时会去取是否有drop属性，如果存在，同时鼠标指针还在drop的范围内，执行drop操作．我们检查鼠标指针位置是否在目标范围是用 (mousePos.x>targetPos.x)，而且还要符合条件(mousePos.x<(targPos.x + targWidth))．如果所有的条件符合，说明指针确实在范围内，可以执行drop指令了．
Pulling It All Together
最后我们拥有了所有的drag/drop的脚本片断！下一个事情是我们将创建一个DOM处理．如果你不是很熟悉，请先阅读我的JavaScript Primer on DOM Manipulation.
下面的代码将创建container(容器),而且使任何一个需要drag/drop的item变成一个容器的item.代码在这个文章第二个demo的后面，它可以用户记录一个list(列表)，定为一个导航窗口在左边或者右边，或者更多的函数你可以想到的．
下一步我们将通过"假代码"让reader看到真代码，下面为推荐:
- 当document第一次载入时，创建dragHelper DIV.dragHelper将给移动的item加阴影．真实的item没有被dragged，只是用了insertBefor和appendChild来移动了，我们隐藏了dragHelper
- 有了mouseDown与mouseUp函数．所有的操作会对应到当到iMouseDown的状态中，只有当mouse左键为按下时iMouseDown才为真，否则为假．
- 我 们创建了全局变量DragDrops与全局函数CreateDragContainer.DragDrops包含了一系列相对彼此的容器．任何参数 (containers)将通过CreatedcragContainer进行重组与序列化，这样可以自由的移动． CreateDragContainer函数也将item进行绑定与设置属性．
- 现在我们的代码知道每个item的加入，当我们移动处mouseMove，mouseMove函数首先会设置变量target，鼠标移动在上面的item，如果这个item在容器中(checked
with getAttribute):
- 运行一小段代码来改变目标的样式．创造rollover效果
- 检查鼠标是否没有放开，如果没有
- 设置curTarget代表当前item
- 记录item的当前位置，如果需要的话，我们可以将它返回
- 克隆当前的item到dragHelper中，我们可以移动带阴影效果的item.
- item拷贝到dragHelper后，原有的item还在鼠标指针下，我们必须删除掉dragObj，这样脚本起作用，dragObj被包含在一个容器中．
- 抓取容器中所有的item当前坐标，高度/宽度，这样只需要记录一次，当item被drag时，每随mouse移动，每移钟就会记录成千上万次．
- 如果没有，不需要做任何事，因为这不是一个需要移动的item
- 检查curTarget，它应该包含一个被移动的item,如果存在，进行下面操作
- 开始移动带有阴影的item，这个item就是前文所创建的
- 检查每个当前容器中的container，是否鼠标已经移动到这些范围内了
- 我们检查看一下正在拖动的item是属于哪个container
- 放置item在一个container的某一个item之前，或者整个container之后
- 确认item是可见的
- 如果鼠标不在container中，确认item是不可见了．
- 剩下的事就是捕捉mouseUp的事件了
实现一个拖动的全代码，注意将＜＞换成半角
＜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＞
＜/div＞
你现在拥有了拖拽的所有东西．
下面的三个demo是记录事件历史．当你的鼠标在item上移动，将记录所生的事件，如果你不明白可以尝试一下鼠标的划过或者拖动，看有什么发生．
关于译者
雪山老人，lamp程序员，web开发者，你可以访问sohotx.com来了解他！
关于作者
Mark Kahn是一个web开发者与DBA.你可以访问他的主页 http://www.jslibrary.org联系他！