将代码重写到Bootstrap 3.3.7

Question

我使用Bootstrap不正确，因此我正在重写我的代码。我可以理解遵循以下结构是很重要的：container > row > col。我使用的是卡片，所以当视口低于768px时，块元素将是卡片。演示可以在这里看到：

在我使用引导之前正确：在重写之前

在我重写到正确的引导之后：在重写到引导之后

在我重写以正确使用Bootstrap之后，块元素在彼此之上飞行。在我看来，是类<div class="index-content">导致了这个问题。如果该类低于row，它就可以工作，但如果我将<div class="index-content">设置在<div class="col-sm-4">内，块就会四处乱飞。

有人知道我该怎么解决这个问题吗？

我在那里工作的原始代码是这样的：

<div class="row">
<div class="index-content">
<div class="container">
<div class="col-sm-4 small-padding right bottom">
<div class="card">
<img src="https://image.ibb.co/iiWA2T/bmw_1.jpg"></img>
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
<div class="col-sm-8 small-padding left">
<div class="card">
<img src="https://image.ibb.co/nJ97Go/bmw.jpg"></img>
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<!-- <p>Brødtekst</p> -->
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
</div>
</div>
</div>

重写到正确的引导后：

<div class="container">
<div class="row">
<div class="col-sm-4 small-padding right bottom">
<div class="index-content">
<div class="card">
<img src="https://image.ibb.co/iiWA2T/bmw_1.jpg"></img>
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
<div class="col-sm-8 small-padding left">
<div class="card">
<img src="https://image.ibb.co/nJ97Go/bmw.jpg"></img>
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<!-- <p>Brødtekst</p> -->
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
</div>
</div>
</div>
<style>
/* Card and Button */
.index-content a:hover {
color: black;
text-decoration: none;
}
.index-content {
/*margin-bottom: 20px;*/
/*padding: 50px 0px;*/
}
.index-content .row {
margin-top: 20px;
}
.index-content a {
color: black;
}
.index-content .card {
background-color: #FFFFFF;
padding: 0;
-webkit-border-radius: 4px;
-moz-border-radius: 4px;
border-radius: 4px;
box-shadow: 0 4px 5px 0 rgba(0, 0, 0, 0.14), 0 1px 10px 0 rgba(0, 0, 0, 0.12), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
}
.index-content .card:hover {
box-shadow: 0 16px 24px 2px rgba(0, 0, 0, 0.14), 0 6px 30px 5px rgba(0, 0, 0, 0.12), 0 8px 10px -5px rgba(0, 0, 0, 0.3);
color: black;
}
.index-content .card img {
width: 100%;
border-top-left-radius: 4px;
border-top-right-radius: 4px;
height: 350px;
}
.index-content .card h4 {
margin: 20px;
}
.index-content .card p {
margin: 20px;
opacity: 0.65;
}
.index-content .blue-button {
width: 100px;
-webkit-transition: background-color 1s, color 1s;
/* For Safari 3.1 to 6.0 */
transition: background-color 1s, color 1s;
min-height: 20px;
background-color: #002E5B;
color: #ffffff;
border-radius: 4px;
text-align: center;
font-weight: lighter;
margin: 0px 20px 15px 20px;
padding: 5px 0px;
display: inline-block;
}
.index-content .blue-button:hover {
background-color: #dadada;
color: #002E5B;
}
@media (max-width: 768px) {
.index-content .col-lg-4 {
margin-top: 20px;
}
}
@media (min-width: 768px) {
.card {
position: relative;
}
.card-content {
position: absolute;
bottom: 0;
width: 100%;
background: rgba(0, 0, 0, 0.5);
}
.card-content h4,
.card-content p {
color: white;
width: 100%;
float: left;
margin: 0 0 5px;
}
.card-content a {
float: right;
}
.index-content .card h4,
.index-content .card p {
padding: 15px 20px;
margin: 0;
}
.index-content .card p {
padding: 0 20px 15px;
margin: 0;
}
}
/* GRID ELEMENTS */
/* Set width between block elements */
.small-padding.top {
padding-top:10px;
}
.small-padding.bottom {
padding-bottom:10px;
} 
.small-padding.left {
padding-left:5px;
}
.small-padding.right {
padding-right:5px;
}
/* Media quries */
@media only screen and (max-width: 768px) {
.small-padding.bottom {
padding-bottom:10px;
} 
}
@media only screen and (max-width: 768px) {
.row [class*="col-"] {
padding-left: 5px;
padding-right: 5px;
}
}
</style>

Answer 1

<div class="row">
<div class="col-sm-4">
<div class="index-content">
<div class="card">
<img src="https://image.ibb.co/iiWA2T/bmw_1.jpg">
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
</div>
<div class="col-sm-8">
<div class="card">
<img src="https://image.ibb.co/nJ97Go/bmw.jpg" style="width: 100%;">
<div class="card-content">
<h4>BMW NEW MODELS</h4>
<!-- <p>Brødtekst</p> -->
<a href="#" class="blue-button">Read More</a>
</div>
</div>
</div>
</div>