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其實滾動監(jiān)聽使用的情況還是很多的,比如導(dǎo)航居于右側(cè),當(dāng)主題內(nèi)容滾動某一塊的時候,右側(cè)導(dǎo)航對應(yīng)的要高亮。
實現(xiàn)功能
1、當(dāng)滾動區(qū)域內(nèi)設(shè)置的hashkey距離頂點到有效位置時,就關(guān)聯(lián)設(shè)置其導(dǎo)航上的指定項
2、導(dǎo)航必須是 .nav > li > a 結(jié)構(gòu),并且a上href或data-target要綁定hashkey
3、菜單上必須有.nav樣式
4、滾動區(qū)域的data-target與導(dǎo)航父級Id(一定是父級)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" > <h5 id="one" >ibe</h5><p>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/></p> <h5 id="two" >two</h5><p>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/></p> <h5 id="three" >three</h5><p>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/>One的具體內(nèi)容<br/></p> </div>
下面來看一下實現(xiàn)的具體代碼,原理:當(dāng)滾動容器內(nèi)的hashkey位置距離容器頂部只有 offset設(shè)置的值,就會設(shè)置導(dǎo)航中對應(yīng)的href高亮。
ScrollSpy構(gòu)造函數(shù)
首先新建一個構(gòu)造函數(shù),如下:
function ScrollSpy(element, options) { this.$body = $(document.body) this.$scrollElement = $(element).is(document.body) ? $(window) : $(element) this.options = $.extend({}, ScrollSpy.DEFAULTS, options) this.selector = (this.options.target || '') + ' .nav li > a' this.offsets = [] this.targets = [] this.activeTarget = null this.scrollHeight = 0 this.$scrollElement.on('scroll.bs.scrollspy', $.proxy(this.process, this)) this.refresh() this.process() }
該構(gòu)造函數(shù)主要干了啥:
1.基本設(shè)置,主要是設(shè)置當(dāng)前滾動元素是設(shè)置的body還是具體的某一塊元素;其次是導(dǎo)航的結(jié)構(gòu)要是.nav li > a的結(jié)構(gòu),也就是你的菜單中也要有.nav這個class。
2.監(jiān)聽元素滾動的時候,執(zhí)行process方法。
3.同時初始化的時候也執(zhí)行了refresh與process方法。
下面講解一下這幾個方法。
getScrolHeight方法
獲取滾動容器的內(nèi)容高度(包含被隱藏部分)
this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight, document.documentElement.scrollHeight)
refresh方法
刷新并存儲滾動容器內(nèi)各hashkey的值
ScrollSpy.prototype.refresh = function () { var that = this var offsetMethod = 'offset' var offsetBase = 0 this.offsets = [] this.targets = [] this.scrollHeight = this.getScrollHeight() if (!$.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]) }) }
它主要實現(xiàn)了什么呢?
1.默認(rèn)用offset來獲取定位值,如果滾動區(qū)域不是window則用position來獲取
if (!$.isWindow(this.$scrollElement[0])) { offsetMethod = 'position' offsetBase = this.$scrollElement.scrollTop() }
2.根據(jù)導(dǎo)航上的hashkey來遍歷獲取 滾動區(qū)域內(nèi)的hashkey對應(yīng)的offset值:
this.$body .find(this.selector) .map(function () { var $el = $(this) var href = $el.data('target') || $el.attr('href') var $href = /^#./.test(href) && $(href) return ($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]) })
process方法
滾動條事件觸發(fā)函數(shù),用于計算當(dāng)前需要高亮那個導(dǎo)航菜單
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]) } }
主要作用:
1.獲取滾動容器已滾動距離:
var scrollTop = this.$scrollElement.scrollTop() + this.options.offset
2.滾動容器可以滾動的最大高度:
var maxScroll = this.options.offset + scrollHeight - this.$scrollElement.height()
3.設(shè)置滾動元素邏輯,給當(dāng)前匹配元素添加高亮:
for (i = offsets.length; i--;) { activeTarget != targets[i] && scrollTop >= offsets[i] && (offsets[i + 1] === undefined || scrollTop < offsets[i + 1]) && this.activate(targets[i]) }
active方法
設(shè)置指定的導(dǎo)航菜單高亮
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
清除所有高亮菜單
ScrollSpy.prototype.clear = function () { $(this.selector) .parentsUntil(this.options.target, '.active') .removeClass('active') }
源碼
+function ($) { 'use strict'; // SCROLLSPY CLASS DEFINITION // ========================== function ScrollSpy(element, options) { this.$body = $(document.body) this.$scrollElement = $(element).is(document.body) ? $(window) : $(element) this.options = $.extend({}, ScrollSpy.DEFAULTS, options) this.selector = (this.options.target || '') + ' .nav li > a' this.offsets = [] this.targets = [] this.activeTarget = null this.scrollHeight = 0 this.$scrollElement.on('scroll.bs.scrollspy', $.proxy(this.process, this)) this.refresh() this.process() } ScrollSpy.VERSION = '3.3.7' ScrollSpy.DEFAULTS = { offset: 10 } ScrollSpy.prototype.getScrollHeight = function () { return this.$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, href]]) || null }) .sort(function (a, 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);
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