利用dom-drag实现flash滚动条功能

// //滚动条的可以移动距离,初始位置,x,y是滑块相对父级元素的，即relative
var hDistant='';
var x='';
var y='';
//两个组件
var slider = '';
var content ='';
//内容的top
var contentTop='';
//缓东效果的计数器
var add=0;

function setSlider(){
slider = id("slider");
content = id("scrollContent");
contentTop=content.offsetTop;
x=slider.offsetLeft;
y=slider.offsetTop;
hDistant=slider.parentNode.offsetHeight-slider.offsetHeight;
//x,y是相对父级元素的，即relative
Drag.init(slider,null,x,x,y,y+hDistant,false,false,null,null);
setInterval("onScroll()",30);
}
function id(elem){
return document.getElementById(elem);
}
//文字滚动
function onScroll(){ var addY=(content.offsetHeight-id("mask").offsetHeight)*(slider.offsetTop-y)/hDistant; var currentY=contentTop-addY; add+=parseInt((currentY-content.offsetTop)*0.1); content.style.top=add+"px"; }window.onload =setSlider;
// ]]>
在上一篇《一个拖拽的效果类和dom-drag.js浅析》中，我大概介绍了dom-drag的拖拽功能，这次我们用dom-drag来实现flash上比较常用的滚动条效果。效果如下：

代码

<script language="javascript">

//hDistant,滚动条的可以移动距离,初始位置,x,y是滑块相对父级元素的，即relative
var hDistant='';
var x='';
var y='';
//两个组件
var slider  = '';
var content  ='';
//内容的top
var contentTop='';
//缓东效果的计数器
var add=0;

function setSlider(){
slider  = id("slider");
content  = id("scrollContent");
contentTop=content.offsetTop;
x=slider.offsetLeft;
y=slider.offsetTop;
hDistant=slider.parentNode.offsetHeight-slider.offsetHeight;
//x,y是相对父级元素的，即relative
Drag.init(slider,null,x,x,y,y+hDistant,false,false,null,null);
setInterval("onScroll()",30);
}
function id(elem){
return document.getElementById(elem);
}
//文字滚动
function onScroll(){
var addY=(content.offsetHeight-id("mask").offsetHeight)*(slider.offsetTop-y)/hDistant;
//currentY是最终的文本框最终的Y坐标位置
var currentY=contentTop-addY;
//content.offsetTop每次都会相应减少，
add+=parseInt((currentY-content.offsetTop)*0.1);
content.style.top=add+"px";
}
window.onload =setSlider;
</script>

其中稍为复杂的是缓动的部分：

function onScroll(){
var addY=(content.offsetHeight-id("mask").offsetHeight)*(slider.offsetTop-y)/hDistant;
var currentY=contentTop-addY;
add+=parseInt((currentY-content.offsetTop)*0.1);
content.style.top=add+"px";
}

addY是求出滑块移动的距离对应滚动区域移动的距离，currentY则是最终要移动的y坐标，利用add实现缓动。目前测试可以兼容主流的浏览器。

附件：dom-drag和addEvent类

《利用dom-drag实现flash滚动条功能》

BY 橡树小屋 FROM http://www.cnblogs.com/babyzone2004/

本文地址：/article/5805668.html

// /**************************************************
* dom-drag.js
* 09.25.2001
* www.youngpup.net
**************************************************
* 10.28.2001 - fixed minor bug where events
* sometimes fired off the handle, not the root.
**************************************************/

var Drag = {

obj : null,

init : function(o, oRoot, minX, maxX, minY, maxY, bSwapHorzRef, bSwapVertRef, fXMapper, fYMapper)
{
o.onmousedown = Drag.start;

o.hmode = bSwapHorzRef ? false : true ;
o.vmode = bSwapVertRef ? false : true ;

o.root = oRoot && oRoot != null ? oRoot : o ;

if (o.hmode && isNaN(parseInt(o.root.style.left ))) o.root.style.left = "0px";
if (o.vmode && isNaN(parseInt(o.root.style.top ))) o.root.style.top = "0px";
if (!o.hmode && isNaN(parseInt(o.root.style.right ))) o.root.style.right = "0px";
if (!o.vmode && isNaN(parseInt(o.root.style.bottom))) o.root.style.bottom = "0px";

o.minX = typeof minX != 'undefined' ? minX : null;
o.minY = typeof minY != 'undefined' ? minY : null;
o.maxX = typeof maxX != 'undefined' ? maxX : null;
o.maxY = typeof maxY != 'undefined' ? maxY : null;

o.xMapper = fXMapper ? fXMapper : null;
o.yMapper = fYMapper ? fYMapper : null;

o.root.onDragStart = new Function();
o.root.onDragEnd = new Function();
o.root.onDrag = new Function();
},

start : function(e)
{
var o = Drag.obj = this;
e = Drag.fixE(e);
var y = parseInt(o.vmode ? o.root.style.top : o.root.style.bottom);
var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
o.root.onDragStart(x, y);

o.lastMouseX = e.clientX;
o.lastMouseY = e.clientY;

if (o.hmode) {
if (o.minX != null) o.minMouseX = e.clientX - x + o.minX;
if (o.maxX != null) o.maxMouseX = o.minMouseX + o.maxX - o.minX;
} else {
if (o.minX != null) o.maxMouseX = -o.minX + e.clientX + x;
if (o.maxX != null) o.minMouseX = -o.maxX + e.clientX + x;
}

if (o.vmode) {
if (o.minY != null) o.minMouseY = e.clientY - y + o.minY;
if (o.maxY != null) o.maxMouseY = o.minMouseY + o.maxY - o.minY;
} else {
if (o.minY != null) o.maxMouseY = -o.minY + e.clientY + y;
if (o.maxY != null) o.minMouseY = -o.maxY + e.clientY + y;
}

document.onmousemove = Drag.drag;
document.onmouseup = Drag.end;

return false;
},

drag : function(e)
{
e = Drag.fixE(e);
var o = Drag.obj;

var ey = e.clientY;
var ex = e.clientX;
var y = parseInt(o.vmode ? o.root.style.top : o.root.style.bottom);
var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
var nx, ny;

if (o.minX != null) ex = o.hmode ? Math.max(ex, o.minMouseX) : Math.min(ex, o.maxMouseX);
if (o.maxX != null) ex = o.hmode ? Math.min(ex, o.maxMouseX) : Math.max(ex, o.minMouseX);
if (o.minY != null) ey = o.vmode ? Math.max(ey, o.minMouseY) : Math.min(ey, o.maxMouseY);
if (o.maxY != null) ey = o.vmode ? Math.min(ey, o.maxMouseY) : Math.max(ey, o.minMouseY);

nx = x + ((ex - o.lastMouseX) * (o.hmode ? 1 : -1));
ny = y + ((ey - o.lastMouseY) * (o.vmode ? 1 : -1));

if (o.xMapper) nx = o.xMapper(y)
else if (o.yMapper) ny = o.yMapper(x)

Drag.obj.root.style[o.hmode ? "left" : "right"] = nx + "px";
Drag.obj.root.style[o.vmode ? "top" : "bottom"] = ny + "px";
Drag.obj.lastMouseX = ex;
Drag.obj.lastMouseY = ey;

Drag.obj.root.onDrag(nx, ny);
return false;
},

end : function()
{
document.onmousemove = null;
document.onmouseup = null;
Drag.obj.root.onDragEnd( parseInt(Drag.obj.root.style[Drag.obj.hmode ? "left" : "right"]),
parseInt(Drag.obj.root.style[Drag.obj.vmode ? "top" : "bottom"]));
Drag.obj = null;
},

fixE : function(e)
{
if (typeof e == 'undefined') e = window.event;
if (typeof e.layerX == 'undefined') e.layerX = e.offsetX;
if (typeof e.layerY == 'undefined') e.layerY = e.offsetY;
return e;
}
};

//监听事件
//Dean Edward所写的addevent库
/*
** element: 绑定事件的元素
** type: 事件类型，鼠标事件等
** handler: 处理方法，
*/

function addEvent(element, type, handler) {
// 为每个事件赋予独立的ID
if (!handler.$$guid) handler.$$guid = addEvent.guid++;
// 为元素建立一个类型的散列表
if (!element.events) element.events = {};
// create a hash table of event handlers for each element/event pair
var handlers = element.events[type];
if (!handlers) {
handlers = element.events[type] = {};
// store the existing event handler (if there is one)
if (element["on" + type]) {
handlers[0] = element["on" + type];
}
}
// store the event handler in the hash table
handlers[handler.$$guid] = handler;
// assign a global event handler to do all the work
element["on" + type] = handleEvent;
};
// a counter used to create unique IDs
addEvent.guid = 1;

function removeEvent(element, type, handler) {
// delete the event handler from the hash table
if (element.events && element.events[type]) {
delete element.events[type][handler.$$guid];
}
};

function handleEvent(event) {
var returnValue = true;
// grab the event object (IE uses a global event object)
event = event || fixEvent(window.event);
// get a reference to the hash table of event handlers
var handlers = this.events[event.type];
// execute each event handler
for (var i in handlers) {
this.$$handleEvent = handlers[i];
if (this.$$handleEvent(event) === false) {
returnValue = false;
}
}
return returnValue;
};

function fixEvent(event) {
// add W3C standard event methods
event.preventDefault = fixEvent.preventDefault;
event.stopPropagation = fixEvent.stopPropagation;
return event;
};
fixEvent.preventDefault = function() {
this.returnValue = false;
};
fixEvent.stopPropagation = function() {
this.cancelBubble = true;
};
// ]]>