Bootstrap滚动监听组件scrollspy.js使用方法详解
其实滚动监听使用的情况还是很多的，比如导航居于右侧，当主题内容滚动某一块的时候，右侧导航对应的要高亮。
1、当滚动区域内设置的hashkey距离顶点到有效位置时，就关联设置其导航上的指定项
2、导航必须是 .nav > li > a 结构，并且a上href或data-target要绑定hashkey
3、菜单上必须有.nav样式
4、滚动区域的data-target与导航父级Id（一定是父级）要一致。
下面来看一下实现的具体代码，原理：当滚动容器内的hashkey位置距离容器顶部只有 offset设置的值，就会设置导航中对应的href高亮。
ScrollSpy构造函数
首先新建一个构造函数，如下：
a'
this.offsets = []
this.targets = []
this.activeTarget = null
this.scrollHeight = 0
this.$scrollElement.on('scroll.bs.scrollspy',$.proxy(this.process,this))
this.refresh()
this.process()
}
该构造函数主要干了啥：
1.基本设置，主要是设置当前滚动元素是设置的body还是具体的某一块元素；其次是导航的结构要是.nav li > a的结构，也就是你的菜单中也要有.nav这个class。
2.监听元素滚动的时候，执行process方法。
3.同时初始化的时候也执行了refresh与process方法。
下面讲解一下这几个方法。
getScrolHeight方法
获取滚动容器的内容高度（包含被隐藏部分）
this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight,document.documentElement.scrollHeight)
refresh方法
刷新并存储滚动容器内各hashkey的值
<div class="jb51code">
<pre class="brush:js;">
ScrollSpy.prototype.refresh = function () {
var that = this
var offsetMethod = 'offset'
var offsetBase = 0
this.offsets = []
this.targets = []
this.scrollHeight = this.getScrollHeight()
if (!$.isWindow(this.$scrollElement[0])) {
offsetMethod = 'position'
offsetBase = this.$scrollElement.scrollTop()
}
this.$body
.find(this.selector)
.map(function () {
var $el = $(this)
var href = $el.data('target') || $el.attr('href')
var $href = /^#./.test(href) && $(href)
return ($href
&& $href.length
&& $href.is(':visible')
&& [[$href[offsetMethod]().top + offsetBase,href]]) || null
})
.sort(function (a,b) { return a[0] - b[0] })
.each(function () {
that.offsets.push(this[0])
that.targets.push(this[1])
})
}
它主要实现了什么呢？
1.默认用offset来获取定位值，如果滚动区域不是window则用position来获取
rush:js;">
if (!$.isWindow(this.$scrollElement[0])) {
offsetMethod = 'position'
offsetBase = this.$scrollElement.scrollTop()
}
2.根据导航上的hashkey来遍历获取 滚动区域内的hashkey对应的offset值：
rush:js;">
this.$body
.find(this.selector)
.map(function () {
var $el = $(this)
var href = $el.data('target') || $el.attr('href')
var $href = /^#./.test(href) && $(href)
return ($href
&& $href.length
&& $href.is(':visible')
&& [[$href[offsetMethod]().top + offsetBase,b) { return a[0] - b[0] })
.each(function () {
that.offsets.push(this[0])
that.targets.push(this[1])
})
process方法
滚动条事件触发函数，用于计算当前需要高亮那个导航菜单
if (this.scrollHeight != scrollHeight) {
this.refresh()
}
if (scrollTop >= maxScroll) {
return activeTarget != (i = targets[targets.length - 1]) && this.activate(i)
}
if (activeTarget && scrollTop < offsets[0]) {
this.activeTarget = null
return this.clear()
}
for (i = offsets.length; i--;) {
activeTarget != targets[i]
&& scrollTop >= offsets[i]
&& (offsets[i + 1] === undefined || scrollTop < offsets[i + 1])
&& this.activate(targets[i])
}
}
主要作用：
1.获取滚动容器已滚动距离：
rush:js;">
var scrollTop = this.$scrollElement.scrollTop() + this.options.offset
2.滚动容器可以滚动的最大高度:
rush:js;">
var maxScroll = this.options.offset + scrollHeight - this.$scrollElement.height()
3.设置滚动元素逻辑，给当前匹配元素添加高亮：
= offsets[i]
&& (offsets[i + 1] === undefined || scrollTop < offsets[i + 1])
&& this.activate(targets[i])
}
active方法
设置指定的导航菜单高亮
rush:js;">
ScrollSpy.prototype.activate = function (target) {
this.activeTarget = target
this.clear()
var selector = this.selector +
'[data-target="' + target + '"],' +
this.selector + '[href="' + target + '" rel="external nofollow" rel="external nofollow" ]'
var active = $(selector)
.parents('li')
.addClass('active')
if (active.parent('.dropdown-menu').length) {
active = active
.closest('li.dropdown')
.addClass('active')
}
active.trigger('activate.bs.scrollspy')
}
clear方法
清除所有高亮菜单
rush:js;">
ScrollSpy.prototype.clear = function () {
$(this.selector)
.parentsUntil(this.options.target,'.active')
.removeClass('active')
}
源码
// SCROLLSPY CLASS DEFINITION
// ==========================
function ScrollSpy(element,this))
this.refresh()
this.process()
}
ScrollSpy.VERSION = '3.3.7'
ScrollSpy.DEFAULTS = {
offset: 10
}
ScrollSpy.prototype.getScrollHeight = function () {
return this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight,document.documentElement.scrollHeight)
}
ScrollSpy.prototype.refresh = function () {
var that = this
var offsetMethod = 'offset'
var offsetBase = 0
this.offsets = []
this.targets = []
this.scrollHeight = this.getScrollHeight()
if (!$.isWindow(this.$scrollElement[0])) {
offsetMethod = 'position'
offsetBase = this.$scrollElement.scrollTop()
}
this.$body
.find(this.selector)
.map(function () {
var $el = $(this)
var href = $el.data('target') || $el.attr('href')
var $href = /^#./.test(href) && $(href)
return ($href
&& $href.length
&& $href.is(':visible')
&& [[$href[offsetMethod]().top + offsetBase,b) { return a[0] - b[0] })
.each(function () {
that.offsets.push(this[0])
that.targets.push(this[1])
})
}
ScrollSpy.prototype.process = function () {
var scrollTop = this.$scrollElement.scrollTop() + this.options.offset
var scrollHeight = this.getScrollHeight()
var maxScroll = this.options.offset + scrollHeight - this.$scrollElement.height()
var offsets = this.offsets
var targets = this.targets
var activeTarget = this.activeTarget
var i
if (this.scrollHeight != scrollHeight) {
this.refresh()
}
if (scrollTop >= maxScroll) {
return activeTarget != (i = targets[targets.length - 1]) && this.activate(i)
}
if (activeTarget && scrollTop < offsets[0]) {
this.activeTarget = null
return this.clear()
}
for (i = offsets.length; i--;) {
activeTarget != targets[i]
&& scrollTop >= offsets[i]
&& (offsets[i + 1] === undefined || scrollTop < offsets[i + 1])
&& this.activate(targets[i])
}
}
ScrollSpy.prototype.activate = function (target) {
this.activeTarget = target
this.clear()
var selector = this.selector +
'[data-target="' + target + '"],' +
this.selector + '[href="' + target + '" rel="external nofollow" rel="external nofollow" ]'
var active = $(selector)
.parents('li')
.addClass('active')
if (active.parent('.dropdown-menu').length) {
active = active
.closest('li.dropdown')
.addClass('active')
}
active.trigger('activate.bs.scrollspy')
}
ScrollSpy.prototype.clear = function () {
$(this.selector)
.parentsUntil(this.options.target,'.active')
.removeClass('active')
}
// SCROLLSPY PLUGIN DEFinitioN
// ===========================
function Plugin(option) {
return this.each(function () {
var $this = $(this)
var data = $this.data('bs.scrollspy')
var options = typeof option == 'object' && option
if (!data) $this.data('bs.scrollspy',(data = new ScrollSpy(this,options)))
if (typeof option == 'string') data[option]()
})
}
var old = $.fn.scrollspy
$.fn.scrollspy = Plugin
$.fn.scrollspy.Constructor = ScrollSpy
// SCROLLSPY NO CONFLICT
// =====================
$.fn.scrollspy.noConflict = function () {
$.fn.scrollspy = old
return this
}
// SCROLLSPY DATA-API
// ==================
$(window).on('load.bs.scrollspy.data-api',function () {
$('[data-spy="scroll"]').each(function () {
var $spy = $(this)
Plugin.call($spy,$spy.data())
})
})
}(jQuery);
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程之家。
