javascript - 延迟加载在 Bootstrap 轮播中不起作用

Question

我像这样使用 bootstrap 3 创建轮播:

HTML:

<div id="myCarousel" class="carousel slide">
    <div class="carousel-inner">
        <div class="active item">
            <img src="http://rivathemes.net/html/envor/img/posts/3.jpg" class="img-big">
        </div>
        <div class="item">
            <img data-lazy-load-src="http://rivathemes.net/html/envor/img/posts/4.jpg" class="img-big">
        </div>
    </div>
    <div class="carousel-controls">
<a class="left carousel-control" href="#myCarousel" data-slide="prev"><i class="fa fa-angle-double-left fa-lg"></i></a>

<a class="right carousel-control" href="#myCarousel" data-slide="next"><i class="fa fa-angle-double-right fa-lg"></i></a>

    </div>
</div>

并添加此代码以添加 img 延迟加载。

JS:

$('#myCarousel').on('slid', function () {
    var $nextImage = $('.active.item', this).next('.item').find('img');
    $nextImage.attr('src', $nextImage.data('lazy-load-src'));
});

但是，这对我不起作用!？可以解决这个问题吗？

重要问题:我可以为延迟加载添加图像预加载器吗？!

演示:FIDDLE

Answer 1

answer by dm4web不考虑通过直接单击轮播指示器来跳过幻灯片。此版本使用 Bootstrap 的 event.relatedTarget(要滑入到位的元素，请参阅 the official documentation)正确加载图像，无论您如何滑动到它。尝试运行下面的代码片段并单击指示器以向前切换几张幻灯片。

var cHeight = 0;

$('#carousel-example-generic').on('slide.bs.carousel', function(e) {

  var $nextImage = $(e.relatedTarget).find('img');

  $activeItem = $('.active.item', this);

  // prevents the slide decrease in height
  if (cHeight == 0) {
    cHeight = $(this).height();
    $activeItem.next('.item').height(cHeight);
  }

  // prevents the loaded image if it is already loaded
  var src = $nextImage.data('lazy-load-src');

  if (typeof src !== "undefined" && src != "") {
    $nextImage.attr('src', src)
    $nextImage.data('lazy-load-src', '');
  }
});

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>

<div class="container-fluid">

  <div id="carousel-example-generic" class="carousel slide" data-ride="carousel">
    <!-- Indicators -->
    <ol class="carousel-indicators">
      <li data-target="#carousel-example-generic" data-slide-to="0" class="active"></li>
      <li data-target="#carousel-example-generic" data-slide-to="1"></li>
      <li data-target="#carousel-example-generic" data-slide-to="2"></li>
      <li data-target="#carousel-example-generic" data-slide-to="3"></li>
      <li data-target="#carousel-example-generic" data-slide-to="4"></li>
    </ol>

    <!-- Wrapper for slides -->
    <div class="carousel-inner" role="listbox">
      <div class="item active">
        <img src="http://placehold.it/5000x1000">
      </div>
      <div class="item">
        <img data-lazy-load-src="http://placehold.it/5001x1000">
      </div>
      <div class="item">
        <img data-lazy-load-src="http://placehold.it/5002x1000">
      </div>
      <div class="item">
        <img data-lazy-load-src="http://placehold.it/5003x1000">
      </div>
      <div class="item">
        <img data-lazy-load-src="http://placehold.it/5004x1000">
      </div>
    </div>

    <!-- Controls -->
    <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
      <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
      <span class="sr-only">Previous</span>
    </a>
    <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
      <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
      <span class="sr-only">Next</span>
    </a>
  </div>

</div>