详解Bootstrap进度条组件

在网页中，进度条的效果并不少见，如：平分系统、加载状态等，进度条组件使用了css3的transition和animation属性来完成一些特效，这些特效在IE9及IE9以下版本、Firefox的老版本中并不支持，Opera 12 不支持 animation 属性。

进度条和其他独立组件一样，开发者可以根据自己的需要选择对应的版本：

LESS: progress-bars.less

SASS: _progress-bars.scss

基础进度条

实现原理：

需要两个容器，外容器使用类名.progress，子容器使用类名.progress-bar;其中.progress用来设置进度条容器的背景色，容器的高度，间距等；而.progress-bar设置进度方向，进度条的背景色和过度效果；下面是css源码：

.progress {
  height: 20px;
  margin-bottom: 20px;
  overflow: hidden;
  background-color: #f5f5f5;
  border-radius: 4px;
  -webkit-box-shadow: inset 0 1px 2px rgba(0, 0, 0, .1);
          box-shadow: inset 0 1px 2px rgba(0, 0, 0, .1);
}

.progress-bar {
  float: left;
  width: 0;
  height: 100%;
  font-size: 12px;
  line-height: 20px;
  color: #fff;
  text-align: center;
  background-color: #428bca;
  -webkit-box-shadow: inset 0 -1px 0 rgba(0, 0, 0, .15);
          box-shadow: inset 0 -1px 0 rgba(0, 0, 0, .15);
  -webkit-transition: width .6s ease;
          transition: width .6s ease;
}

例子：

<div class="progress">
         <div class="progress-bar" style="width:30%;" role="progressbar" aria-valuenow="30" aria-valuemin="0" aria-valuemax="100">
             <span class="sr-only">30%</span>
         </div>
     </div>

role属性作用：告诉搜索引擎这个div的作用是进度条；

aria-valuenow=”30”属性作用：当前进度条的进度为40%；

aria-valuemin=”0”属性作用：进度条的最小值为0%；

aria-valuemax=”100”属性作用：进度条的最大值为100%；

可以将设置了.sr-only类的<span>标签从进度条组件中移除，而让当前进度显示出来；

<div class="progress">
        <div class="progress-bar" style="width:40%;" role="progressbar" aria-valuenow="40" aria-valuemin="0" aria-valuemax="100" >40%</div>
    </div>

彩色进度条

彩色进度条和警告进度条一样，为了能给用户一个更好的体验，也根据不同的状态配置了不同的进度条颜色，主要包括以下四种：

progress-bar-info:表示信息进度条，蓝色

progress-bar-success:表示成功进度条，绿色

progress-bar-warning:表示警告进度条，黄色

progress-bar-danger:表示错误进度条，红色

css源码：

.progress-bar-success {
  background-color: #5cb85c;
}

.progress-bar-info {
  background-color: #5bc0de;
}

.progress-bar-warning {
  background-color: #f0ad4e;
}

.progress-bar-danger {
  background-color: #d9534f;
}

使用方法：

只需要在基础进度条上增加对应的类名即可

例子：

<h1>彩色进度条</h1>
     <div class="progress">
         <div class="progress-bar progress-bar-success" style="width:25%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">25%</div>
     </div>
     <div class="progress">
         <div class="progress-bar progress-bar-info" style="width:40%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">40%</div>
     </div>
     <div class="progress">
         <div class="progress-bar progress-bar-warning" style="width:80%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">80%</div>
     </div>
     <div class="progress">
         <div class="progress-bar progress-bar-danger" style="width:60%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">60%</div>
      </div>

效果如下：

条纹进度条

条纹进度条采用css3的线性渐变来实现，并未借助任何图片，使用条纹进度条只需在进度条的容器.progress基础上追加类名”progress-striped”,如果要进度条纹像彩色进度一样，具有彩色效果，只需在进度条上增加相应得颜色类名

下面是.progress-striped样式源码：

.progress-striped .progress-bar {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-size: 40px 40px;
}

条纹进度对应的每种状态也有不同的颜色

.progress-striped .progress-bar-success {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
}

.progress-striped .progress-bar-info {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
}

.progress-striped .progress-bar-warning {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
}

.progress-striped .progress-bar-danger {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
}

下面来看看条纹进度条的运用：

<h1>条纹进度条</h1>
     <div class="progress progress-striped">
         <div class="progress-bar progress-bar-success" style="width:25%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">25%</div>
     </div>
     <div class="progress progress-striped">
         <div class="progress-bar progress-bar-info" style="width:40%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">40%</div>
     </div>
     <div class="progress progress-striped">
         <div class="progress-bar progress-bar-warning" style="width:80%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">80%</div>
     </div>
     <div class="progress progress-striped">
         <div class="progress-bar progress-bar-danger" style="width:60%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">60%</div>
     </div>

动态条纹进度条

在进度条.progress 、.progress-striped两个类的基础上在加入类名.active就能实现动态条纹进度条。

其实现原理主要是通过css3的animation来完成。首先通过@keyframes创建了一个progress-bar-stripes的动画，这个动画主要做了一件事，就是改变背景图像的位置，也就是 background-position的值。因为条纹进度条是通过CSS3的线性渐变来制作的，而linear-gradient实现的正是对应背景中的背景图片

下面是css源码：

@-webkit-keyframes progress-bar-stripes {
  from {
    background-position: 40px 0;
  }
  to {
    background-position: 0 0;
  }
}
@keyframes progress-bar-stripes {
  from {
    background-position: 40px 0;
  }
  to {
    background-position: 0 0;
  }
}

@keyframes仅仅是创建了一个动画效果，如果要让进度条真正的动起来，我们需要通过一定的方式调用@keyframes创建的动画 “progress-bar-stripes”，并且通过一个事件触发动画生效。在Bootstrap框架中，通过给进度条容器“progress”添加一个类名“active”，并让文档加载完成就触“progress-bar-stripes”动画生效

调用动画对应的样式代码如下：

.progress.active .progress-bar {
  -webkit-animation: progress-bar-stripes 2s linear infinite;
  animation: progress-bar-stripes 2s linear infinite;
}

例子：

<h1>动态条纹进度条</h1>
     <div class="progress progress-striped active">
         <div class="progress-bar progress-bar-success" style="width:25%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">25%</div>
     </div>
     <div class="progress progress-striped active">
         <div class="progress-bar progress-bar-info" style="width:40%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">40%</div>
     </div>
     <div class="progress progress-striped active">
         <div class="progress-bar progress-bar-warning" style="width:80%;" role="progressbar" aria-valuenow="25" aria-valuemin="0" aria-valuemax="100">80%</div>
     </div>
     <div class="progress progress-striped active">
         <div class="progress-bar progress-bar-danger" style="width:60%;" role="progressbar" aria-valuenow="40" aria-valuemax="100" aria-valuemin="0">60%</div>
     </div>

效果如下（由于是直接从网页上结果来的图，这里并看不到它的动态效果）：

层叠进度条：

层叠进度可以将不容状态的进度条放在一起，按水平方式排列

例子：

<div class="progress">
    <div class="progress-bar progress-bar-success" style="width:20%"></div>
    <div class="progress-bar progress-bar-info" style="width:10%"></div>
    <div class="progress-bar progress-bar-warning" style="width:30%"></div>
    <div class="progress-bar progress-bar-danger" style="width:15%"></div>
</div>

除了层叠彩色进度条之外，还可以层叠条纹进度条，或者说条纹进度条和彩色进度条混合层叠，仅需要在“progress”容器中添加对应的进度条，同样要注意，层叠的进度条之和不能大于100%。

下面来看一个例子：

<div class="progress">
    <div class="progress-bar progress-bar-success" style="width:20%"></div>
    <div class="progress-bar progress-bar-info" style="width:20%"></div>
    <div class="progress-bar progress-bar-warning" style="width:30%"></div>
    <div class="progress-bar progress-bar-danger" style="width:15%"></div>
</div>
<div class="progress">
    <div class="progress-bar progress-bar-success progress-bar-striped" style="width:20%"></div>
    <div class="progress-bar progress-bar-info progress-bar-striped" style="width:20%"></div>
    <div class="progress-bar progress-bar-striped progress-bar-warning" style="width:30%"></div>
    <div class="progress-bar progress-bar-danger progress-bar-striped" style="width:15%"></div>
</div>
<div class="progress">
    <div class="progress-bar progress-bar-success" style="width:20%"></div>
    <div class="progress-bar progress-bar-info progress-bar-striped" style="width:20%"></div>
    <div class="progress-bar progress-bar-warning" style="width:30%"></div>
    <div class="progress-bar progress-bar-danger progress-bar-striped" style="width:15%"></div>
</div>