防止响应列出现双边框

Question

>想象一下，你正在使用Bootstrap 4并打印一些单元格。细胞数量是不可预测的。

.cell {
  border: 1px solid black;
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet">
<div class="row no-gutters">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
</div>

运行代码时，会看到"双"边框。如果我使用第 n 个子选择器，我必须计算每个断点，因为在特定断点上，它每行显示不同的单元格。你如何解决它？

Answer 1

你可以这样处理它： https://www.codeply.com/go/u5dCBDg1he

.row {
    border-style: solid;
    border-color: black;
    border-width: 1px  0   0  1px;
}
.cell {
    border-color: black;    
    border-style: solid;
    border-width: 0  1px 1px  0;
} 

这将为整个row添加上边框和左边框，然后为每个cell添加右边距和下边距。也可以使用边框实用程序类完成此操作。

<div class="row no-gutters border-left border-top">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2 border-bottom border-right">cell</div>
</div>

Answer 2

您可以将 border-right/border-bottom 与元素一起使用，并将 border-top/border-left 与容器一起使用：

.cell {
  border-right: 1px solid black;
  border-bottom: 1px solid black;
}
.row {
  border-top: 1px solid black;
  border-left: 1px solid black;
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet">
<div class="row no-gutters">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
</div>

使用较少的单元格，您可以尝试使用伪元素进行此破解：

.cell {
  border-right: 1px solid black;
  border-bottom: 1px solid black;
  position:relative;
  z-index:1;
}
.row {
  border-left: 1px solid black;
  margin:10px;
  overflow:hidden; /*hide the overflow*/
  padding-top:1px; /*for the top border*/
}
/*top border for all*/
.cell:first-child:before {
  content:"";
  position:absolute;
  bottom:100%;
  left:0;
  height:1px;
  width:100vw;
  background:#000;
}
/*hide the unwated top border in case of few cells*/
.cell:last-child:before {
  content:"";
  position:absolute;
  bottom:100%;
  left:calc(100% + 1px);
  height:1px;
  width:100vw;
  background:#fff;
}
/*avoid issue with stacking context and 
be sure the cells are on the top of the pseudo element*/
.cell:first-child,
.cell:last-child {
  z-index:auto;
}
/*for one cell*/
.cell:first-child:last-child {
  border-top:1px solid;
}
.cell:first-child:last-child:before {
  content:none;
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet">
<div class="row no-gutters">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
</div>
<div class="row no-gutters">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
</div>
<div class="row no-gutters">
  <div class="cell col-6 col-sm-4 col-md-3 col-lg-2">cell</div>
</div>