css - 如何使用css3获得这个？

Question

我希望在我的 fontAwesome 图标的边框中使用此动画。我尝试了很多但都失败了。

这是动画。

http://postimg.org/image/8k3al48kr/

Answer 1

我认为仅使用一个 HTML 元素是不可能的，但以下内容应该可行:

.square {
    display: block;
    width: 100px;
    height: 100px;
    position: relative;
}
.left, .top, .right, .bottom {
    position: absolute;
    width: 0px;
    height: 0px;
    background-color: black;
    -moz-animation-duration: 1s;
    -moz-animation-fill-mode: forwards;
    -moz-animation-iteration-count: 1;
    -moz-animation-timing-function: ease-in;
    -webkit-animation-duration: 1s;
    -webkit-animation-fill-mode: forwards;
    -webkit-animation-iteration-count: 1;
    -webkit-animation-timing-function: ease-in;
    -o-animation-duration: 1s;
    -o-animation-fill-mode: forwards;
    -o-animation-iteration-count: 1;
    -o-animation-timing-function: ease-in;
    animation-duration: 1s;
    animation-fill-mode: forwards;
    animation-iteration-count: 1;
    animation-timing-function: ease-in;
}
.left, .right {
    -moz-animation-name: drawVertical;
    -webkit-animation-name: drawVertical;
    -o-animation-name: drawVertical;
    animation-name: drawVertical;
    width: 1px;
}
.top, .bottom {
    -moz-animation-name: drawHorizontal;
    -webkit-animation-name: drawHorizontal;
    -o-animation-name: drawHorizontal;
    animation-name: drawHorizontal;
    height: 1px;
}
.left {
    left: 0;
    bottom: 0;
    -webkit-animation-delay: 0s;
    animation-delay: 0s;
    -moz-animation-delay: 0s;
}
.top {
    top: 0;
    left: 0;
    -webkit-animation-delay: 1s;
    animation-delay: 1s;
}
.right {
    right: 0;
    top: 0;
    -webkit-animation-delay: 2s;
    animation-delay: 2s;
}
.bottom {
    bottom: 0;
    right: 0;
    height: 1px;
    -webkit-animation-delay: 3s;
    animation-delay: 3s;
}
@keyframes drawHorizontal {
    from {
        width: 0;
    }
    to {
        width: 100%;
    }
}
@keyframes drawVertical {
    from {
        height: 0;
    }
    to {
        height: 100%;
    }
}

<div class="square">
    <span class="left"></span>
    <span class="top"></span>
    <span class="right"></span>
    <span class="bottom"></span>
</div>