javascript - Bootstrap 4 Carousel 获取图片大小

Question

这是一个非常基本的 Bootstrap 4 轮播，包含 3 张图片。

我实现了 2 个可用事件:slide.bs.carousel 和 slid.bs.carousel。

我能够在 slid 事件监听器中获取图像宽度(当轮播完成其幻灯片转换时)，但是当我尝试时图像宽度始终为 0在 slide 监听器中获取它(我想知道下一张幻灯片的大小)。

这是为什么？

这是一个片段。观看控制台。

jQuery('#carouselDemo').on('slide.bs.carousel', function(e) {

  console.log('SLIDE event');
  console.log('Image width: ' + e.relatedTarget.querySelector('img').clientWidth);
});

jQuery('#carouselDemo').on('slid.bs.carousel', function(e) {

  console.log('SLID event');
  console.log('Image width: ' + e.relatedTarget.querySelector('img').clientWidth);
});

.carousel {
  background-color: grey;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>

<div id="carouselDemo" class="carousel slide" data-ride="carousel">
  <div class="carousel-inner">
    <div class="carousel-item active">
      <img src="https://via.placeholder.com/700x400">
    </div>
    <div class="carousel-item">
      <img src="https://via.placeholder.com/800x400">
    </div>
    <div class="carousel-item">
      <img src="https://via.placeholder.com/900x400">
    </div>
  </div>
  <a class="carousel-control-prev" href="#carouselDemo" role="button" data-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="carousel-control-next" href="#carouselDemo" role="button" data-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>

https://jsfiddle.net/upsidown/ruo0gt19/

---

编辑

我没有提到我需要下一张幻灯片图像客户端宽度，即。显示宽度而不是原始图像宽度。下面是一个较大图像的示例，使用@gaetanoM 提供的答案强制为 100% 最大宽度。

注意:我不能简单地使用主体或容器元素的宽度，因为在我的用例中，轮播图像以全屏显示，最大高度为 100%，因此宽度可以变化并小于容器宽度。

jQuery('#carouselDemo').on('slide.bs.carousel', function(e) {

    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    console.log('slide: Current element Width is: ' + fromelement[0].width);
    console.log('slide: Next element Width is: ' + toelement[0].width);

});

jQuery('#carouselDemo').on('slid.bs.carousel', function(e) {

    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    console.log('slid: Current element Width is: ' + fromelement[0].width);
    console.log('slid: Next element Width is: ' + toelement[0].width);
});

.carousel {
    background-color: grey;
}

.carousel-item > img {
  max-width: 100%;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>


<div id="carouselDemo" class="carousel slide" data-ride="carousel">
    <div class="carousel-inner">
        <div class="carousel-item active">
            <img src="https://via.placeholder.com/700x400">
        </div>
        <div class="carousel-item">
            <img src="https://via.placeholder.com/800x400">
        </div>
        <div class="carousel-item">
            <img src="https://via.placeholder.com/900x400">
        </div>
    </div>
    <a class="carousel-control-prev" href="#carouselDemo" role="button" data-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="sr-only">Previous</span>
    </a>
    <a class="carousel-control-next" href="#carouselDemo" role="button" data-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="sr-only">Next</span>
    </a>
</div>

Answer 1

根据更新后的答案，问题出在滑动时的下一个/上一个元素上(它是隐藏的，因此没有 clientWidth)。

为了克服这个问题，一个解决方案可以是:

• 切换这个隐藏元素的可见性
• 获取客户端宽度
• 立即重新切换可见性以适应一切。

在代码片段中，每张图片都有不同的宽度以证明结果。

jQuery('#carouselDemo').on('slide.bs.carousel', function(e) {
    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    toelement.parent().toggleClass('active');
    console.log('slide: Current element Width is: ' + fromelement[0].width + ' / ' + fromelement[0].clientWidth);
    console.log('slide: Next element Width is: ' + toelement[0].width + ' / ' + toelement[0].clientWidth);
    toelement.parent().toggleClass('active');
});
jQuery('#carouselDemo').on('slid.bs.carousel', function(e) {
    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    fromelement.parent().toggleClass('active');
    console.log('slid: Current element Width is: ' + fromelement[0].width + ' / ' + fromelement[0].clientWidth);
    console.log('slid: Next element Width is: ' + toelement[0].width + ' / ' + toelement[0].clientWidth);
    fromelement.parent().toggleClass('active');
});

.carousel {
    background-color: grey;
}

.carousel-item > img.n1 {
    width: 100%;
    height: 100vh;
}
.carousel-item > img.n2 {
    width: 50%;
    height: 100vh;
}
.carousel-item > img.n3 {
    width: 75%;
    height: 100vh;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.js"></script>


<div id="carouselDemo" class="carousel slide" data-ride="carousel">
    <div class="carousel-inner">
        <div class="carousel-item active">
            <img class="n1" src="https://via.placeholder.com/700x400">
        </div>
        <div class="carousel-item">
            <img class="n2"  src="https://via.placeholder.com/800x400">
        </div>
        <div class="carousel-item">
            <img class="n3"  src="https://via.placeholder.com/900x400">
        </div>
    </div>
    <a class="carousel-control-prev" href="#carouselDemo" role="button" data-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="sr-only">Previous</span>
    </a>
    <a class="carousel-control-next" href="#carouselDemo" role="button" data-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="sr-only">Next</span>
    </a>
</div>

看完How to get image size (height & width) using JavaScript?我建议使用普通的 HTML img width或 naturalWidth .

jQuery('#carouselDemo').on('slide.bs.carousel', function(e) {

    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    console.log('slide: Current element Width is: ' + fromelement[0].width);
    console.log('slide: Next element Width is: ' + toelement[0].width);

});

jQuery('#carouselDemo').on('slid.bs.carousel', function(e) {

    var fromelement = jQuery('#carouselDemo .carousel-inner img').eq(e.from);
    var toelement = jQuery('#carouselDemo .carousel-inner img').eq(e.to);

    console.log('slid: Current element Width is: ' + fromelement[0].width);
    console.log('slid: Next element Width is: ' + toelement[0].width);
});

.carousel {
    background-color: grey;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>


<div id="carouselDemo" class="carousel slide" data-ride="carousel">
    <div class="carousel-inner">
        <div class="carousel-item active">
            <img src="https://via.placeholder.com/700x400">
        </div>
        <div class="carousel-item">
            <img src="https://via.placeholder.com/800x400">
        </div>
        <div class="carousel-item">
            <img src="https://via.placeholder.com/900x400">
        </div>
    </div>
    <a class="carousel-control-prev" href="#carouselDemo" role="button" data-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="sr-only">Previous</span>
    </a>
    <a class="carousel-control-next" href="#carouselDemo" role="button" data-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="sr-only">Next</span>
    </a>
</div>