javascript - 使用 Bootstrap 文本轮播淡入和淡出背景

Question

我有三个背景图像，我想以 5 秒的间隔淡入和淡出。我还利用 native 引导轮播组件以 5 秒的间隔将文本滑入和滑出，以与不断变化和淡出的背景图像相匹配。

场景

• 问题 1:第一个背景图像将是页面加载时的默认背景图像。 5 秒后，第二个背景图像消失，同时轮播滑到第二个文本。又过了 5 秒，第三个背景图像淡入，轮播滑到下一个文本。

• 问题 2:bootstrap 轮播组件有一个指示器，单击该指示器后，它会切换并滑动到该轮播部分中的文本。我希望在单击轮播指示器时更改背景图像。也就是说，如果轮播指示器 1 被点击，背景图像应该淡化到第一个背景图像。这应该适用于第二个和第三个轮播指示器及其各自的背景图像。如果当前是事件轮播元素和背景图片，则背景图片不应更改和淡入被点击的图片。

现状

• 我已经能够使用 jquery 和我也在 stackoverflow 中获得的解决方案实现具有淡入淡出效果的背景图像。我还使用带有选项 (data-interval="5000") 的引导轮播组件完成了文本轮播，它将切换时间设置为 5 秒以匹配背景图像淡入和淡出的相同时间间隔，但仍然有明显的小延迟。如何消除明显的延迟？

• 图像有时会在褪色前闪烁。有没有更好更合适的方式来实现淡入淡出的效果，又不让图片闪烁？

• 即使我在单击时运行该功能，单击轮播指示器也不会切换背景图像并将背景图像淡入下一个图像。如何以正确的方式实现它？

这是我尝试过的:

var bgImageArray = ["1_ozdgvm.jpg", "2_vjtjfy.jpg", "3_oxpdx2.jpg"],
  base = "https://res.cloudinary.com/iolamide/image/upload/v1604569872/home_banner_",
  secs = 5;
bgImageArray.forEach(function(img) {
  new Image().src = base + img;
  // caches images, avoiding white flash between background replacements
});

function backgroundSequence() {
  window.clearTimeout();
  var k = 0;
  for (i = 0; i < bgImageArray.length; i++) {
    setTimeout(function() {
      document.getElementById('animated-bg').style.backgroundImage = "url(" + base + bgImageArray[k] + ")";
      // document.getElementById('animated-bg').style.backgroundSize ="cover";
      if ((k + 1) === bgImageArray.length) {
        setTimeout(function() {
          backgroundSequence()
        }, (secs * 1000))
      } else {
        k++;
      }
    }, (secs * 1000) * i)
  }
}

backgroundSequence();


$('.carousel-item').click(function() {
  backgroundSequence();
})

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
}

html {
  box-sizing: border-box;
}

body {
  box-sizing: inherit;
  color: #fff !important;
}

.animated-bg {
  background-image: url("https://res.cloudinary.com/iolamide/image/upload/v1604569872/home_banner_1_ozdgvm.jpg");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  transition: background 1s;
  height: 694px;
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.animated-bg:before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

.container {
  padding: 3rem;
  border-radius: 20px;
  width: 700px;
  background: rgba(0, 0, 0, 0.3);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.text-top p {
  width: 400px;
  margin: 30px auto;
  text-align: center;
}

h1 {
  margin-top: 0;
  text-align: center;
  font-weight: 600;
}

.carousel-item p {
  width: 330px;
  text-align: center;
}

.carousel-indicators {
  bottom: -50px !important;
}

@media only screen and (max-width: 800px) {
  .container {
    padding: 2rem;
    width: 90%;
  }
}

@media only screen and (max-width: 500px) {
  .text-top p {
    width: 80%;
  }
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<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 class="animated-bg" id="animated-bg">
  <div class="container">
    <div class="text-top" id="texttop">
      <h1>Crossfade and Text Carousel</h1>
      <p>Fade background image and swipe text at the same time. Also fade the background image to the one that matches the carousel's text when the carousel's indicator is clicked</p>
    </div>
    <div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel" data-interval="5000">
      <ol class="carousel-indicators">
        <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
        <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
        <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
      </ol>
      <div class="carousel-inner">
        <div class="carousel-item active">
          <p>
            Carousel Text One
          </p>
        </div>
        <div class="carousel-item">
          <p>Carousel Text Two</p>
        </div>
        <div class="carousel-item">
          <p>Carousel Text Three</p>
        </div>
      </div>
    </div>
  </div>
</div>

Answer 1

您不需要自己对图像施以魔法的所有逻辑。您可以使用 carousel api on('slide.bs.carousel') 收听幻灯片变化并相应地切换图像。

const bgImageArray = ["1_ozdgvm.jpg", "2_vjtjfy.jpg", "3_oxpdx2.jpg"],
  base = "https://res.cloudinary.com/iolamide/image/upload/v1604569872/home_banner_";
  
bgImageArray.forEach(function(img) {
  new Image().src = base + img;
  // caches images, avoiding white flash between background replacements
});
  
$('.carousel'). on('slide.bs.carousel', function(e) {
  $('.animated-bg').css({
    backgroundImage: `url(${base}${bgImageArray[e.to]})`
  });
});

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
}

html {
  box-sizing: border-box;
}

body {
  box-sizing: inherit;
  color: #fff !important;
}

.animated-bg {
  background-image: url("https://res.cloudinary.com/iolamide/image/upload/v1604569872/home_banner_1_ozdgvm.jpg");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  transition: background 1s;
  height: 694px;
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.animated-bg:before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

.container {
  padding: 3rem;
  border-radius: 20px;
  width: 700px;
  background: rgba(0, 0, 0, 0.3);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.text-top p {
  width: 400px;
  margin: 30px auto;
  text-align: center;
}

h1 {
  margin-top: 0;
  text-align: center;
  font-weight: 600;
}

.carousel-item p {
  width: 330px;
  text-align: center;
}

.carousel-indicators {
  bottom: -50px !important;
}

@media only screen and (max-width: 800px) {
  .container {
    padding: 2rem;
    width: 90%;
  }
}

@media only screen and (max-width: 500px) {
  .text-top p {
    width: 80%;
  }
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<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 class="animated-bg" id="animated-bg">
  <div class="container">
    <div class="text-top" id="texttop">
      <h1>Crossfade and Text Carousel</h1>
      <p>Fade background image and swipe text at the same time. Also fade the background image to the one that matches the carousel's text when the carousel's indicator is clicked</p>
    </div>
    <div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel" data-interval="5000">
      <ol class="carousel-indicators">
        <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
        <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
        <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
      </ol>
      <div class="carousel-inner">
        <div class="carousel-item active">
          <p>
            Carousel Text One
          </p>
        </div>
        <div class="carousel-item">
          <p>Carousel Text Two</p>
        </div>
        <div class="carousel-item">
          <p>Carousel Text Three</p>
        </div>
      </div>
    </div>
  </div>
</div>

https://jsbin.com/mewiwuv/edit?js,output