Bootstrap introductory book (5) Navigation bar, paging navigation_javascript skills

Navigation bar

Navigation bar (navbar) and the Bootstrap introductory book - (4) menu, button and navigation introduced in the previous section. Navigation (nav) is only one word different, with an additional word "bar". In fact, they are still obviously different in the Bootstrap framework. There is a background color in the navigation bar (navbar), and the navigation bar can be a pure link (similar to navigation), a form, or a combination of form and navigation. They collapse (and can be opened and closed) on mobile devices and gradually expand horizontally as the viewport width increases.

Basic navigation bar

Actually, the difference in appearance between navigation bar and navigation is not that big, but in actual use, navigation bar is much more complicated than navigation. Let's implement a basic navigation bar.

<div class="navbar navbar-default" role="navigation"><!--role是为了方便屏幕阅读器理解此处内容-->
 <ul class="nav navbar-nav">
 <li class="active"><a href="#">HTML</a></li>
 <li><a href="#">CSS</a></li>
 <li><a href="#">JavaScript</a></li>
 <li><a href="#">PHP</a></li>
 </ul>
</div>

The effect that can be achieved is as follows:

Widescreen:

Narrow screen:

When making a basic navigation bar, pay attention to the following points:

1. First, add the class name .navbar-nav
based on the navigation list (

)

2. Add a container (div) outside the list. If allowed here, it is recommended to use

and use the class names .navbar and .navbar-default


3. The main function of the navbar class is to set effects such as left and right padding and rounded corners. Use .navbar-default to control the color of the navigation bar, such as .navbar-inverse.


With title, secondary menu

In web page production, you can usually see a title in front of the menu (the text size is slightly larger than other text). In fact, the Bootstrap framework has also taken this into consideration for everyone, through .navbar-header And .navbar-brand to achieve, such as:

<div class="navbar-header">
 <a href="##" class="navbar-brand">WEB开发</a>
</div>

Of course it can also be used to make a logo, as described on the Chinese official website, which will not be described in detail here.

Needless to say more about the secondary menu. It has been explained in detail in the previous blog. If you still don’t understand it, you can read my previous blog again. Let’s take a look at the following paragraph. Code and achievable effects: (note that the navbar-inverse navigation bar is used here)

<div class="navbar navbar-inverse" role="navigation">
 <div class="navbar-header">
 <a href="##" class="navbar-brand">WEB开发</a>
 </div>
 <ul class="nav navbar-nav">
 <li class="active"><a href="#">HTML</a></li>
 <li><a href="#">CSS</a></li>
 <li class="dropdown" >
 <a href="#" class="dropdown-toggle" data-toggle="dropdown">JavaScript
 <span class="caret"></span></a>
 <ul class="dropdown-menu">
 <li><a href="#">jQuery</a></li>
 <li><a href="#">Vue</a></li>
 <li><a href="#">NodeJS</a></li>
 </ul>
 </li>
 <li ><a href="#">PHP</a></li>
 </ul>
</div>

The effect is as follows:




With form

We often see search forms in the navigation bar, such as Zhihu, Sina Weibo, etc. Of course, the Bootstrap framework cannot lack such a thing. The method of use is also very simple:

A .navbar-form is provided in the Bootstrap framework. Place a form with the .navbar-form class name in the .navbar container; then add .navbar-left to make the form float left for better alignment.

In Bootstrap, the .navbar-right style is also provided to align elements to the right of the navigation bar.

Copy this code into the code and see the effect:

<form action="##" class="navbar-form navbar-left" rol="search">
 <div class="form-group">
 <input type="text" class="form-control" placeholder="请输入关键词" />
 </div>
 <button type="submit" class="btn btn-default">搜索</button>
</form>

Buttons, text and links

In addition to some of the styles above, the bootstrap framework provides three other styles:

1. The button navbar-btn in the navigation bar makes the buttons not in the

vertically centered in the navigation bar

2. The text navbar-text in the navigation bar generally uses the

element to achieve optimal line spacing

3. Normal links in the navigation bar navbar-link, non-navigation links, add this class to have the correct default color and inverse color settings
However, these three styles are subject to certain restrictions when used in the framework and need to be used in conjunction with navbar-brand and navbar-nav. There is also a certain limit on the quantity. Generally, there will be no problem if you use one or two, but there will be problems if you use more than two.

Fixed navigation bar

Sometimes, we want the navigation bar to be fixed at the top or bottom of the browser. Bootstrap conveniently provides us with two classes to achieve such a style:

.navbar-fixed-top: The navigation bar is fixed at the top of the browser window
.navbar-fixed-bottom: The navigation bar is fixed at the bottom of the browser window

The method of use is very simple. You only need to append the corresponding class name to the outermost container (navbar) of the navigation bar.

<nav class="navbar navbar-default navbar-static-top">
 ...
</nav>

这个固定的导航条会 遮住页面上的其它内容 ，除非你给

元素底部设置了 padding 。提示：导航条的 默认高度 是 50px。如： body { padding-bottom: 70px; } ，当然你也可以使用你自己的值。

响应式导航条

在上面的例子中，导航条就仅仅能大屏幕下有一个不错的效果，在屏幕变小的情况下，还 直接把所有的导航项直接展现出来就不适合了 。为了有一个更好的显示效果，响应式的导航条设计也就随之而来。我们先来看看效果，再一步一步分析它！

 

窄屏时，点击右边的按钮图标可展开，效果与上面的展开效果除了 active 状态不再溢出容器外，其他基本相同。实现代码如下：

<div class="navbar navbar-default" role="navigation">
 <div class="navbar-header">
 <!-- .navbar-toggle样式用于toggle收缩的内容，即nav-collapse collapse样式所在元素 -->
 <button class="navbar-toggle" type="button" data-toggle="collapse" data-target=".navbar-responsive-collapse">
 <span class="sr-only">Toggle Navigation</span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>
 </button>
 <!-- 确保无论是宽屏还是窄屏，navbar-brand都显示 -->
 <a href="#" class="navbar-brand">WEB开发</a>
 </div>
 <!-- 屏幕宽度小于768px时，div.navbar-responsive-collapse容器里的内容都会隐藏，显示icon-bar图标，当点击icon-bar图标时，再展开。屏幕大于768px时，默认显示。 -->
 <div class="collapse navbar-collapse navbar-responsive-collapse">
 <ul class="nav navbar-nav">
 <li class="active"><a href="#">HTML</a></li>
 <li><a href="#">CSS</a></li>
 <li><a href="#">JavaScript</a></li>
 <li><a href="#">PHP</a></li>
 </ul>
 </div>
</div>

分析：

和普通导航条一样，最外层使用

容器包裹，主要是 .navbar 和 .navbar-default 类。

保证在窄屏时 需要折叠的内容必须 包裹在带一个div内，并且为这个div加入 .collapse 、 .navbar-collapse 两个类名。最后为这个div 添加一个class类名或者id名 。

保证在窄屏时要显示的图标样式（固定写法）：

<button class="navbar-toggle" type="button" data-toggle="collapse">
 <span class="sr-only">Toggle Navigation</span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>
 <span class="icon-bar"></span>
</button>

并为button添加 data-target=”.类名/#id名” ，究竞是类名还是id名呢？由 需要折叠的div 来决定。（这里很关键，你可以把上面的代码在这里进行修改，会发现无法展开）

分页导航

分页导航几乎在所有的网站都可以看到，好的分页导航可以给用户带来更好额用户体验，还可以方便爬虫在网页中进行搜索。

带页码的分页导航

带页码的分页导航，应该是最常见的一种分页导航，特别是在列表页内容很多的时候，会给用户提供带页码的分页导航方式，在Bootstrap中使用的是 ul>li>a 这样的结构，在ul标签上加入 pagination 类：

<ul class="pagination ">
 <li><a href="#">&laquo;第一页</a></li>
 <li><a href="#">6</a></li>
 <li class="active"><a href="#">7</a></li>
 <li><a href="#">8</a></li>
 <li><a href="#">9</a></li>
 <li><a href="#">10</a></li>
 <li class="disabled"><a href="#">最后一页&raquo;</a></li>
</ul>

实现效果如下：

 

可以看到同样会有 hover 、 active 、 disabled 等等状态，当然它也可以调整大小：在外层容器中的 .pagination 类后，添加 .pagination-lg 让分页导航变大； .pagination-sm 让分页导航变小：

翻页分页导航

其实这种方式，就是看不到具体的页码，只会提供一个 上一页 和 下一页 的按钮。

使用方式很简单，也就是在ul标签上添加 pager 类：

<ul class="pager">
 <li><a href="#">&laquo;上一页</a></li>
 <li><a href="#">下一页&raquo;</a></li>
</ul>

它默认是居中显示的，如果我们需要一个居左一个居右显示的话，添加两个样式： previous 让“上一步”按钮居左； next 让“下一步”按钮居右。（同样可以使用 disabled 表示禁用状态）

<ul class="pager">
 <li class="previous disabled"><a href="#">&laquo;上一页</a></li>
 <li class="next"><a href="#">下一页&raquo;</a></li>
</ul>

其他

标签

在一些Web页面中常常会添加一个标签用来告诉用户一些额外的信息，比如说在导航上添加了一个新导航项，可能就会加一个“new”标签，来告诉用户。这是新添加的导航项。

在Bootstrap专门将这样的效果提取成为了单独的标签组件。可以使用 这样的行内标签添加 .label 类来控制大小，再使用情景类来控制高亮显示的颜色如： label-default 、 label-danger 等等（在原来笔记中说到过这样的情景类，只不过这里需要加上不同的前缀）

 

徽章（角标）

其实和上面的标签效果很大一部分是类似的，一般用作信息提示，例如剩余多少未读信息等等，也就是我们常常能在右上角看到的未读信息提示。在Bootstrap中，把这种效果称作为徽章效果，使用 badge 类来实现。

给链接、导航等元素嵌套 元素，可以很醒目的展示新的或未读的信息条目。

<a href="#">Inbox <span class="badge">42</span></a>
<button class="btn btn-primary" type="button">
 Messages <span class="badge">4</span>
</button>

 

通过查看源码，我们可以发现Bootstrap同样使用 :empty 伪元素，来设置当没有内容的时候隐藏：

.badge:empty {
 display: none;
}

需要注意的是IE8 不支持 :empty 选择符，所以不会默认隐藏；

Bootstrap 中的徽章会适配导航元素的激活状态。

<ul class="nav nav-pills" role="tablist">
 <li role="presentation" class="active"><a href="#">Home <span class="badge">42</span></a></li>
 <li role="presentation"><a href="#">Profile</a></li>
 <li role="presentation"><a href="#">Messages <span class="badge">3</span></a></li>
</ul>

 

关于Bootstrap入门书籍之（五）导航条、分页导航就给大家介绍到这里，希望对大家有所帮助！