不透明度的 CSS 过渡不起作用答案

【问题标题】：CSS transition for opacity does not work不透明度的 CSS 过渡不起作用
【发布时间】：2016-12-08 20:13:49
【问题描述】：

我的问题已经在标题中说明了。我认为我做的一切都是正确的。但是，没有出现过渡效果。请注意，实际上出现了悬停效果，并且出现了 h5 标签内的文字，但没有过渡效果。这让我发疯，任何建议将不胜感激。

a.jobBoxLink {
  color: #B2B2B2;
  -moz-box-shadow: 3px 0 0px 0 #F2F2F2;
  -webkit-box-shadow: 3px 0 0px 0 #F2F2F2;
  box-shadow: 3px 0 0px 0 #F2F2F2;
}
.jobBoxLink:hover {
  text-decoration: none;
  color: black;
  display: block;
  background #B2B2B2;
}
.text-content {
  background: rgba(0, 0, 0, 0.5);
  color: white;
  cursor: pointer;
  height: 200px;
  position: absolute;
  width: 200px;
  margin: 0;
  opacity: 0;
  -webkit-transition: opacity 5000ms;
  -moz-transition: opacity 5000ms;
  -o-transition: opacity 5000ms;
  transition: opacity 5000ms;
}
a.jobBoxLink:hover .text-content {
  opacity: 1;
}
.books {
  -moz-box-shadow: 0 0 8px 3px #F2F2F2;
  -webkit-box-shadow: 0 0 8px 3px #F2F2F2;
  box-shadow: 0 0 8px 3px #F2F2F2;
  border-radius: 5px;
  height: 200px;
  width: 200px;
  margin-bottom: 10px;
  margin-top: 10px;
  padding-left: -100px;
  alignment-adjust: central;
}

<div class="col-sm-4 col-md-2 BoxCol">
  <a href="#" class="jobBoxLink ">

    <div class="books" style="background-image:  url('images/dummy/design.jpg'); background-size: cover; background-repeat: no-repeat; background-position: 50% 50%;">
      <h5 class="text-content">Place Name</h5>
    </div>
    <!-- Job boxes -->
  </a>
  <div class="caption">
    <a href="#" class="icon"> <span class="fa fa-thumbs-up fa-lg"></span> &nbsp;</a>
    <span class="greyCaption"> 22</span> 
    <a href="#" class="icon">   &nbsp;<span class="fa fa-thumbs-down fa-lg"></span> </a> 
  </div>
  <!--like caption -->
</div>

【问题讨论】：

标签： html css hover transition

【解决方案1】：

这是因为您在锚点悬停时应用 css，默认情况下 <a> 是内联元素，如果检查元素，您会看到实际上没有 <a> 的高度和宽度。

在<a> 中使用display:block 将其转换为块元素，css 可以正常工作

a.jobBoxLink {
  color: #B2B2B2;
  display:block;
  -moz-box-shadow: 3px 0 0px 0 #F2F2F2;
  -webkit-box-shadow: 3px 0 0px 0 #F2F2F2;
  box-shadow: 3px 0 0px 0 #F2F2F2;
}
.jobBoxLink:hover {
  text-decoration: none;
  color: black;
  display: block;
  background #B2B2B2;
}
.text-content {
  background: rgba(0, 0, 0, 0.5);
  color: white;
  cursor: pointer;
  height: 200px;
  position: absolute;
  width: 200px;
  margin: 0;
  opacity: 0;
  -webkit-transition: opacity 5000ms;
  -moz-transition: opacity 5000ms;
  -o-transition: opacity 5000ms;
  transition: opacity 5000ms;
}
a.jobBoxLink:hover .text-content {
  opacity: 1;
}
.books {
  -moz-box-shadow: 0 0 8px 3px #F2F2F2;
  -webkit-box-shadow: 0 0 8px 3px #F2F2F2;
  box-shadow: 0 0 8px 3px #F2F2F2;
  border-radius: 5px;
  height: 200px;
  width: 200px;
  margin-bottom: 10px;
  margin-top: 10px;
  padding-left: -100px;
  alignment-adjust: central;
}

<div class="col-sm-4 col-md-2 BoxCol">
  <a href="#" class="jobBoxLink ">

    <div class="books" style="background-image:  url('images/dummy/design.jpg'); background-size: cover; background-repeat: no-repeat; background-position: 50% 50%;">
      <h5 class="text-content">Place Name</h5>
    </div>
    <!-- Job boxes -->
  </a>
  <div class="caption">
    <a href="#" class="icon"> <span class="fa fa-thumbs-up fa-lg"></span> &nbsp;</a>
    <span class="greyCaption"> 22</span> 
    <a href="#" class="icon">   &nbsp;<span class="fa fa-thumbs-down fa-lg"></span> </a> 
  </div>
  <!--like caption -->
</div>

【讨论】：

【解决方案2】：

使用这个

.text-content:hover{opacity : 1;}

而不是这个

 a.jobBoxLink:hover .text-content{ opacity: 1;}

 a.jobBoxLink{
 color: #B2B2B2;
 -moz-box-shadow:    3px 0 0px 0 #F2F2F2;
 -webkit-box-shadow: 3px 0 0px 0 #F2F2F2;
    box-shadow:        3px 0 0px 0 #F2F2F2; 

 }
.jobBoxLink:hover{
text-decoration:none;
color: black;
display:block;
background #B2B2B2; 
  }


  .text-content {
 background: rgba(0,0,0,0.5);
  color: white;
  cursor: pointer;
  height: 200px;
   position: absolute;
   width: 200px;
      display:block;
  margin:0;
  opacity : 0;  
 -webkit-transition: opacity  2s;
-moz-transition: opacity  2s;
-o-transition: opacity  2s;
 transition: opacity  2s;

 } 

 .text-content:hover{
  opacity : 1;
  
  } 


 .books{
 -moz-box-shadow:    0 0 8px 3px #F2F2F2;
 -webkit-box-shadow: 0 0 8px 3px #F2F2F2;
    box-shadow:         0 0 8px 3px #F2F2F2;  
 border-radius: 5px; 
 height: 200px;
 width: 200px; 
 margin-bottom:10px;
 margin-top: 10px;
 padding-left: -100px;
 alignment-adjust: central;
  }

<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
  <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
  <div class="col-sm-4 col-md-2 BoxCol">
<a href="#" class="jobBoxLink ">

<div class="books" style="background-image:  url('images/dummy/design.jpg'); background-size: cover; background-repeat: no-repeat; background-position: 50% 50%;">
        <h5 class="text-content">Place Name</h5>
</div> <!-- Job boxes -->
</a>
<div class="caption">   
<a href="#" class="icon"> <span class="fa fa-thumbs-up fa-lg"></span>  &nbsp;  </a> 
<span class="greyCaption"> 22</span> 
    <a href="#" class="icon">   &nbsp;<span class="fa fa-thumbs-down fa-lg"></span> </a> 
   </div> <!--like caption -->
  </div>
  </body>
  
  </html>

【讨论】：