具有垂直对齐内容和动画状态的卡片

Question

在卡片中垂直对齐内容的最佳方法是什么，同时仍然允许它们在悬停时制作动画，以显示不同的屏幕？

例如，如果我有卡片，每张卡片都有一个显示的正面和一个在悬停时淡入的背面：

<div class="items">
  <div class="item">
      <div class="front">
        <i class="material-icons">build</i>
        <span>Item 1</span>
      </div>
      <div class="back">hello there</div>
  </div>
  <div class="item">
      <div class="front">
        <i class="material-icons">build</i>
        <span>Item 1</span>
      </div>
      <div class="back">hello there</div>
  </div>
  <div class="item">
      <div class="front">
        <i class="material-icons">build</i>
        <span>Item 1</span>
      </div>
      <div class="back">hello there</div>
  </div>
</div>

然后使用这个 css：

.item {
    align-items: center;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    justify-content: center;
    height: 200px;
    background-color: tomato;
    margin: 0 auto 1rem auto;
    width: 200px;
    position: relative;
}
.item .material-icons {
    display: block;
}
.back,
.front {
    opacity: 0;
    position: absolute;
    text-align: center;
    width: 100%;
    -webkit-transition: opacity .25s ease-in-out;
    -moz-transition: opacity .25s ease-in-out;
    -ms-transition: opacity .25s ease-in-out;
    -o-transition: opacity .25s ease-in-out;
    transition: opacity .25s ease-in-out;
}
.front {
    opacity: 1;
}
.item:hover .front {
    opacity: 0;
}
.item:hover .back {
    opacity: 1;
}
.material-icons {
    font-size: 5em !important;
}

但是，在使用绝对位置后，我的垂直居中不起作用，我很确定这可能不是最好的方法！

您可以在此处看到半工作版本：http://jsfiddle.net/kmturley/8o29y7pd/26/

谢谢！

Answer 1

您可以使用

transform进行居中。它适用于绝对位置元素。你根本不需要弹性框。

position: absolute;
left: 50%; top: 50%;
transform: translate(-50%, -50%);
text-align: center;

http://jsfiddle.net/1354hzqb/

Answer 2

只需在.back, .front类中添加50%和transform: translate(0, -50%)的top位置即可。

@import url('https://fonts.googleapis.com/css?family=Material+Icons');
.item {
    cursor: pointer;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 200px;
    background-color: tomato;
    margin: 0 auto 1rem auto;
    width: 200px;
    position: relative;
}
.item .material-icons {
  display: block;
}
.back,
.front {
  opacity: 0;
  position: absolute;
  text-align: center;
  width: 100%;
  top: 50%;
  transform: translate(0, -50%);
  -webkit-transition: opacity .25s ease-in-out;
  -moz-transition: opacity .25s ease-in-out;
  -ms-transition: opacity .25s ease-in-out;
  -o-transition: opacity .25s ease-in-out;
  transition: opacity .25s ease-in-out;
}
.front {
  opacity: 1;
}
.item:hover .front {
  opacity: 0;
}
.item:hover .back {
  opacity: 1;
}
.material-icons {
  font-size: 5em !important;
}

<div class="items">
  <div class="item">
    <div class="front">
      <i class="material-icons">build</i>
      <span>Item 1</span>
    </div>
    <div class="back">hello there</div>
  </div>
  <div class="item">
    <div class="front">
      <i class="material-icons">build</i>
      <span>Item 1</span>
    </div>
    <div class="back">hello there</div>
  </div>
  <div class="item">
    <div class="front">
      <i class="material-icons">build</i>
      <span>Item 1</span>
    </div>
    <div class="back">hello there</div>
  </div>
</div>