Bootstrap每天必学之滚动监听

1. Scrollspy currently requires the use of a Bootstrap nav component for proper highlighting of active links.

---- 使用滚动监听的话,导航栏必须采用的nav组件才可以:

下面是源代码中的一段,标红的部分可以证明这一点:

使用ScrollSpy的时候,需要采用<ul>标签,并且在<li>下必须有<a>标签。

注:另外我们需要把<ul>标签放到另一个容器内(如div),并给父容器添加一个id属性(这一点在第4节有介绍)

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() }

2. Navbar links must have resolvable id targets. For example, a <a href="#home">home</a> must correspond to something in the DOM like <div></div>.

--- 简单的说,就是<li>下的<a>标签必须有一个href="#id"属性,并且在滚动的内容里面,必须有对应的<a></a>这样的标签;当内容滚动到<a>标签时,对应的<li>的<a href="#id">就会自动被选中。

--其实这一点做过Web开发的朋友都知道,在之前的HTML版本中,锚标记 通常采用<a>这样的方式,但HTML5中的锚标记已经抛弃了name属性,而是采用id属性

ScrollSpy.prototype.activate = function (target) { this.activeTarget = target this.clear() var selector = this.selector + '[data-target="' + target + '"],' + this.selector + '[href="' + target + '"]' 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') }

3. No matter the implementation method, scrollspy requires the use of position: relative; on the element you're spying on. In most cases this is the <body>. When scrollspying on elements other than the <body>, be sure to have a height set and overflow-y: scroll; applied.

--- 如果监听Body的滚动,那么你必须给body添加position:relative样式

--- 如果监听的不是Body,而是其他得元素[貌似这种方式常见],那么你需要添加三个样式:position:relative;height:500px;overflow-y:scroll;

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() }

4. To easily add scrollspy behavior to your topbar navigation, add data-spy="scroll" to the element you want to spy on (most typically this would be the <body>). Then add the data-target attribute with the ID or class of the parent element of any Bootstrap .navcomponent.

--- 你需要给滚动内容的标签添加 data-spy="scroll"属性和data-target属性

data-spy 属性指明了被监听的元素,data-target属性指明滚动时需要控制的nav高亮显示

再看一次下面的初始化源代码,标红的位置,this.options.target的值,就等于滚动内容元素的data-target的值,看到这里,你或许已经想到,在定义.nav组件的时候,我们需要把.nav放在另一个容器内(比如div),且该容器需要有一个id属性(与这里data-target需要设置的值相同)。

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() }

5. After adding position: relative; in your CSS, call the scrollspy via JavaScript:

$('yourTag').scrollspy({ target: 'nav-parent-div-id' })
-- yourTag 就是要承载滚动内容的元素的ID,nav-parent-div-id 就是.nav元素的父元素的id(也就是data-target的值)

乱七八糟写了一堆,下面总结一个简单的几个步骤:

  1. 添加标签<div>

  2. 在标签内添加.nav组件,并给li->a添加href="#tag"属性

  3. 添加<div data-spy="scroll" data-target="#scrollSpyID">;

  4. 添加样式#content{height:500px;overflow-y:scroll;opsition:relative;}

  5. 添加脚本$('#content').scrollspy({target:'scrollSpyID'});

最后来个小栗子:

<style type="text/css"> #body { position: relative; height: 500px; overflow-y: scroll; } </style>

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