有没有办法动态更改子元素的填充以填充父元素？

Question

我需要子元素在悬停时表现良好，因为（子元素的）红色边框应该与顶部、左侧、底部和右侧的蓝色边框（父元素）在同一行。我可以通过填充来做到这一点吗？有几个结构相同但宽度和高度不同，文本长度不同的框（其中一些是两行或三行）。

如果padding不行，怎么用别的方法达到同样的效果？

代码在这里

* {
  box-sizing: border-box;
}

.out {
  display: -webkit-box;
  display: flex;
  -webkit-box-pack: center;
          justify-content: center;
  width: 200px;
  height: 200px;
  margin: 2rem auto;
  border: 1px solid blue;
}
.out .in {
  font-size: 20px;
  line-height: 1;
  display: inline-block;
  text-align: center;
  border: 1px solid red;
  padding: 20px;
  margin: auto;
  transition: padding .7s;
}
.out:hover .in {
  padding-top: 90px;
  padding-bottom: 90px;
  padding-left: 40px;
  padding-right: 40px;
  background: rgba(0,0,0,.2);
}

<div class="out">
  <p class="in">
    Hello Friend
  </p>
</div>

<div class="out">
  <p class="in">
    Hello Friend
  </p>
</div>

<div class="out">
  <p class="in">
    Hello Friend this is a new text
  </p>
</div>

<div class="out">
  <p class="in">
    Hello
  </p>
</div>

谢谢

Answer 1

如果你可以添加一个额外的包装器，你可以通过嵌套 flexbox 容器和动画来实现 flex-grow

* {
  box-sizing: border-box;
}

.out {
  display: flex;
  flex-direction: column;
  width: 200px;
  height: 200px;
  margin: 2rem auto;
  justify-content: center;
  border: 1px solid blue;
}

.out > div {
  display: flex;
  justify-content: center;
}

.out .in {
  display: flex;
  font-size: 20px;
  justify-content: center;
  align-items: center;
  text-align: center;
  border: 1px solid red;
  padding: 20px;
  margin: 0;
}

.out * {
  flex-grow: 0;
  transition: flex-grow .5s;
}

.out:hover * {
  flex-grow: 1;
}

.out:hover .in {
  background: rgba(0, 0, 0, .2);
}

<div class="out">
  <div>
    <p class="in">
      Hello Friend
    </p>
  </div>
</div>

<div class="out" style="width:auto">
  <div>
    <p class="in">
      Hello Friend
    </p>
  </div>
</div>

<div class="out" style="height:auto;min-height:300px;">
  <div>
    <p class="in">
      Hello Friend this is a new text
    </p>
  </div>
</div>

<div class="out">
  <div>
    <p class="in">
      Hello
    </p>
  </div>
</div>

Answer 2

您可以在父级悬停时添加子级 100% 的高度和宽度。

* {
  box-sizing: border-box;
}

.out {
  display: -webkit-box;
  display: flex;
  -webkit-box-pack: center;
          justify-content: center;
  width: 200px;
  height: 200px;
  margin: 2rem auto;
  border: 1px solid blue;
}
.out .in {
  font-size: 20px;
  line-height: 1;
  display: inline-block;
  text-align: center;
  border: 1px solid red;
  padding: 20px;
  margin: auto;
  transition: padding .7s;
}
.out:hover .in {
  padding-top: 90px;
  padding-bottom: 90px;
  padding-left: 40px;
  padding-right: 40px;
  background: rgba(0,0,0,.2);
  width: 100%;
  height: 100%;
}

<div class="out">
  <p class="in">
    Hello Friend
  </p>
</div>

<div class="out">
  <p class="in">
    Hello Friend
  </p>
</div>

<div class="out">
  <p class="in">
    Hello Friend this is a new text
  </p>
</div>

<div class="out">
  <p class="in">
    Hello
  </p>
</div>

Answer 3

如果您只需要背景动画并且 - 您可以使用类似这样的东西。这里的元素 ::after 与文本分开缩放。

* {
  box-sizing: border-box;
}

.out {
  display: -webkit-box;
  display: inline-flex;
  vertical-align: top;
  -webkit-box-pack: center;
          justify-content: center;
  width: 200px;
  height: 200px;
  margin: 2rem auto;
  border: 1px solid blue;
  overflow: hidden; /* to hide parent exapnded background */
}
.out .in {
  font-size: 20px;
  line-height: 1;
  display: inline-block;
  text-align: center;
  padding: 20px;
  margin: auto;  
  position: relative;
}
.out .in::after {
  content: '';
  background: rgba(0,0,0,.2);
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%; 
  transform: scale(1);
  transition: all .7s;  
}
.out:hover .in::after {
  transform: scale(5);
}

<div class="out">
  <p class="in">
    Hello Friend
  </p>
</div>

<div class="out">
  <p class="in">
    Hello Friend this is a new text
  </p>
</div>

<div class="out">
  <p class="in">
    Hello
  </p>
</div>

有没有办法动态更改子元素的填充以填充父元素？

Is there a way to dynamically change padding of child element to fill parent element?

css

padding

hover