//计算滚动条的高度
scrollbarHeight: function(elem, height) {
var value = elem.scrollHeight;
return (height / value) * height
}
scrollbarHeight()方法通过简单的数学计算返回滚动条元素应该显示的高度。
复制代码 代码如下:
initEvent: function() {
var that = this,
_default,
elem,
top,
min,
max,
prev,
parent,
sbody,
unit;
//滚动条滚动
squid.on(document, 'mousemove', function(event) {
elem = that.scrolling.elem
if(elem !== null) {
squid.addClass(elem, 'scrolling')
top = event.clientY - that.scrolling.diffy
parent = that.ie6 ? elem.parentNode.parentNode : elem.parentNode
min = that.limits[elem].min
max = that.limits[elem].max
prev = parent.previousSibling
sbody = prev.tagName.toLowerCase() === 'div' ? prev : prev.previousSibling
_default = parseInt(sbody['data-height'] || sbody.getAttribute('data-height'), 10)
unit = (sbody.scrollHeight - _default) / max
squid.addClass(sbody.parentNode, 'unselectable')
if(top < min) {
top = min
}else if(top > max) {
top = max
}
elem.style.top = top + 'px'
that.doScroll(sbody, top * unit)
}
})
//滚动结束
squid.on(document, 'mouseup', function(event) {
elem = that.scrolling.elem
if(elem) {
prev = that.ie6 ? elem.parentNode.parentNode.previousSibling : elem.parentNode.previousSibling
sbody = prev.tagName.toLowerCase() === 'div' ? prev : prev.previousSibling
squid.removeClass(sbody.parentNode, 'unselectable')
}
that.scrolling.elem = null
that.scrolling.diffy = 0
})
}
initEvent()方法实现了为document元素添加mousemove和mouseup事件，mousemove实现了在拖动滚动条元素滚动时查看的内容跟随变化。代码首先判断当前是否有拖动滚动条查看内容的操作，如果有就计算滚动条被拖动到的位置，然后计算查看内容应该到的地方。代码里对ie6的判断，是因为引入的PIE.htc文件破坏了原有的结构（为了实现跨浏览器下显示效果的一致，付出太大了！！！）。mouseup事件处理程序实现了清除上次操作的滚动条元素。
复制代码 代码如下:
//添加滚动条事件
regEvent: function(elem) {
var that = this,
sbody = elem.firstChild,
list = sbody.nextSibling,
//滚动条元素
s = list.firstChild,
//滚动条滚动最小值
min = 0,
//滚动条滚动最大值
max = list.offsetHeight - s.offsetHeight,
_default = parseInt(sbody['data-height'] || sbody.getAttribute('data-height'), 10),
unit = (sbody.scrollHeight - _default) / max,
//firefox浏览器
firefox = 'MozBinding' in document.documentElement.style,
//鼠标滚轮事件
mousewheel = firefox ? 'DOMMouseScroll' : 'mousewheel',
//opera浏览器
opera = window.oprea && navigator.userAgent.indexOf('MSIE') === -1,
//is firing mousedown event
firing = false,
//鼠标点击，定时器执行时间
interval,
//滚动条距离容器高度
top,
//滚动条当前top值
cur,
//每次滚动多少像素
speed = 18;
//变量缓存min, max
this.limits[s] = {
min: 0,
max: max
}
//scroll事件 鼠标滑动滚轮移动滚动条
squid.on(elem, mousewheel, function(event) {
var delta;
if(event.wheelDelta) {
delta = opera ? -event.wheelDelta / 120 : event.wheelDelta / 120
}else{
delta = -event.detail / 3
}
cur = parseInt(s.style.top || 0, 10)
//向上滚动
if(delta > 0) {
top = cur - speed
if(top < min) {
top = min
}
}else{//向下滚动
top = cur + speed
if(top > max) {
top = max
}
}
s.style.top = top + 'px'
that.doScroll(sbody, top * unit)
//阻止body元素滚动条滚动
event.preventDefault()
})
//ie6, 7, 8下，如果鼠标连续点击两次且时间间隔太短，则第二次事件不会触发
//拖动滚动条，点击滚动条可到达区域
squid.on(list, 'mousedown', function(event) {
var target = event.target,
y = event.clientY;
target = event.target
if(target.tagName.toLowerCase() === 'shape')
target = s
//鼠标点击元素是滚动条
if(target === s) {
//invoke elem setCapture
s.setCapture && s.setCapture()
that.scrolling.diffy = y - s.offsetTop
//鼠标移动过程中判断是否正在拖动滚动条
that.scrolling.elem = s
}else if(target.className.match('jscroll-list')){
firing = true
interval = setInterval(function() {
if(firing) {
that.mouseHandle(list, y, unit)
}
}, 80)
}
})
//鼠标松开滚动条停止滚动
squid.on(list, 'mouseup', function() {
//invoke elem releaseCapture
s.releaseCapture && s.releaseCapture()
firing = false
clearInterval(interval)
})
//滚动条元素获取焦点，可以触发keyup事件
squid.on(s, 'click', function() {
this.focus()
})
//滚动条获取焦点后，触发键盘上下键，滚动条滚动
squid.on(s, 'keydown', function(event) {
var keyCode = event.keyCode,
state = false;
cur = parseInt(s.style.top || 0, 10)
switch(keyCode) {
case 38:
top = cur - speed
if(top < min) {
top = min
}
state = true
break
case 40:
top = cur + speed
if(top > max) {
top = max
}
state = true
break
default:
break
}
if(state) {
s.style.top = top + 'px'
that.doScroll(sbody, top * unit)
}
event.preventDefault()
})
}
regEvent()方法实现了以下功能，应该是jscroll组件的核心方法了：
1. 鼠标在包含滚动条的元素区域，上下滚动鼠标滚轮，查看的内容跟随滚轮上下翻的功能