如何在折叠时设置 Bootstrap 4 Accordion 标题的样式？

Question

如何设置 Bootstrap 4 手风琴的样式，以便标题在打开和关闭时具有不同的样式？我需要定位哪些类，例如，当手风琴打开时标题颜色为红色，当手风琴未打开时标题颜色为灰色？

这是代码：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

<div id="accordion">
  <div class="card">
    <div class="card-header" id="headingOne">
      <h5 class="mb-0">
        <button class="btn btn-link" data-toggle="collapse" data-target="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
          Collapsible Group Item #1
        </button>
      </h5>
    </div>

    <div id="collapseOne" class="collapse show" aria-labelledby="headingOne" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-header" id="headingTwo">
      <h5 class="mb-0">
        <button class="btn btn-link collapsed" data-toggle="collapse" data-target="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
          Collapsible Group Item #2
        </button>
      </h5>
    </div>
    <div id="collapseTwo" class="collapse" aria-labelledby="headingTwo" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-header" id="headingThree">
      <h5 class="mb-0">
        <button class="btn btn-link collapsed" data-toggle="collapse" data-target="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
          Collapsible Group Item #3
        </button>
      </h5>
    </div>
    <div id="collapseThree" class="collapse" aria-labelledby="headingThree" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
</div>

谢谢你！

Answer 1

最简单的方法是制作card-header控制元素而不是btn。然后使用CSS改变颜色......

.card-header.collapsed {
    background:#ccc;
}
.card-header:not(.collapsed) {
    background:#ee6666;
}

https://www.codeply.com/go/XCb1Q5Vt0T

<div id="accordion">
  <div class="card">
    <div class="card-header" id="headingOne" data-toggle="collapse" data-target="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
      <h5 class="mb-0">
        <button class="btn btn-link">
          Collapsible Group Item #1
        </button>
      </h5>
    </div>

    <div id="collapseOne" class="collapse show" aria-labelledby="headingOne" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-header collapsed" id="headingTwo" data-toggle="collapse" data-target="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
      <h5 class="mb-0 " >
        <button class="btn btn-link">
          Collapsible Group Item #2
        </button>
      </h5>
    </div>
    <div id="collapseTwo" class="collapse" aria-labelledby="headingTwo" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-header collapsed" id="headingThree" data-toggle="collapse" data-target="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
      <h5 class="mb-0">
        <button class="btn btn-link">
          Collapsible Group Item #3
        </button>
      </h5>
    </div>
    <div id="collapseThree" class="collapse" aria-labelledby="headingThree" data-parent="#accordion">
      <div class="card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird
        on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table,
        raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
</div>