FontAwesome unicodes似乎不起作用？

Question

我有一个<li>当hovered时应该将数字改为unicode图标,例如播放按钮.

unicodes不断弹出一个看起来像这样的图标: [?]我假设它找不到它们.我在其他部分使用字体图标就好了,有什么想法吗？

    <ul class="popular-songs">
            <li>
<div class="album-cover"><img src="http://newnoisemagazine.com/wp-content/uploads/2014/04/Expire-Pretty-Low-cover.jpg"></div> 
<span class="number">
<span>1</span>
</span> 
<span>+</span>
<span class="title">Pretty Low</span>
<span class="misc"><i class="fa fa-ellipsis-h"></i></span>
<span class="total-plays">163,957</span></li>
        </ul>

CSS:

.popular-songs li .number{
  position: relative;
  content: '1';
  top:0px;
}
.popular-songs li:hover .number span{
  display: none;
}
.popular-songs li:hover .number:after{
  content: "\f04b";
  position:relative;
  top:15px;
}

我试过以我能想到的每一种可能的方式编写unicode.

content: "/XXXX";

content: "\XXXX";

content: "XXXX";

content: "[XXXX]";

它们似乎都不适合我.

Answer 1

将font-family添加到CSS中,例如:

.popular-songs li:hover .number:after{
  font-family: 'FontAwesome';
  content: "\f04b";
  position:relative;
  top:15px;
}

仅供参考,这里是所有图标的FontAwesomes CSS:

.fa {
  display: inline-block;
  font: normal normal normal 14px/1 FontAwesome;
  font-size: inherit;
  text-rendering: auto;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transform: translate(0, 0);
}