Table of Contents
源码文件:
实现功能
ibe
two
three
源码分析:
Home Web Front-end HTML Tutorial bootstrap源码分析之scrollspy(滚动侦听)_html/css_WEB-ITnose

bootstrap源码分析之scrollspy(滚动侦听)_html/css_WEB-ITnose

Jun 24, 2016 am 11:16 AM

源码文件:

Scrollspy.js

实现功能

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

<div id="selector" class="navbar navbar-default">    <ul class="nav navbar-nav">        <li><a href="#one">one</a> </li>        <li><a href="#two">two</a> </li>        <li><a href="#three">three</a> </li>    </ul></div><div data-spy="scroll" data-target="#selector" style="height:100px; overflow:hidden;overflow-y: auto;" >    <h4 id="ibe">ibe</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p>    <h4 id="two">two</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p>    <h4 id="three">three</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p></div>
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源码分析:

1、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
2、如果滚动区域是body,会将滚动区域元素标记为window(构造函数中判断)

this.$scrollElement = $(element).is(document.body) ? $(window) : $(element)
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3、getScrolHeight: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)
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4、refresh:刷新并存储滚动容器内各hashkey的值
4.1、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

if (!$.isWindow(this.$scrollElement[0])) {      offsetMethod = 'position'      offsetBase   = this.$scrollElement.scrollTop() //获取基础高度,如果滚动区域内有不参与滚动计算的内容   }
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4.2、根据导航上的hashkey来遍历获取 滚动区域内的hashkey对应的offset值:

this.$body     .find(this.selector)      .map(function () {        var $el   = $(this)        var href  = $el.data('target') || $el.attr('href')        var $href = /^#./.test(href) && $(href) //获取滚动区域内的hashkey对应的元素        return ($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])      })
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5、process: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
5.1、获取滚动容器已滚动距离:

var scrollTop    = this.$scrollElement.scrollTop() + this.options.offset
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5.2、滚动容器可以滚动的最大高度

//最大可以滚动高度=滚动设置距离(offset)+ 滚动容器内容高度 - 滚动容器设置的高度var maxScroll    = this.options.offset + scrollHeight - this.$scrollElement.height()
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5.3、设置滚动元素逻辑:

for (i = offsets.length; i--;) {//遍历所有的offset     activeTarget != targets[i] //判断当前target是否等于activeTarget        && scrollTop >= offsets[i] //滚动高度>i元素的offset        && (offsets[i + 1] === undefined || scrollTop < offsets[i + 1]) //i + 1元素不存在,或者i+1元素不大于滚动高度        && this.activate(targets[i]) //设置i为当前活动项    }
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6、active:设置指定的导航菜单高亮
7、clear:清除所有高亮菜单

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