在 carousel 中更改幻灯片的问题，仅用 js 和 css 编写

Question

抱歉可能重复，但我没有找到解决问题的方法。关于我的问题。我正在尝试仅使用 js 和 css 创建幻灯片轮播。我需要的是当我们按下“前进”或“后退”按钮时交替播放幻灯片（例如，上一张幻灯片向左移动，而当按下“前进”按钮时新幻灯片同时从右侧出现）。

代码在这里：

var slideIndex = 0;
var prev_slideIndex = slideIndex;

function myanimate() {
  str = 'slideIndex=' + slideIndex + ' prev_slideIndex=' + prev_slideIndex;

  var slides = document.getElementsByClassName("child");
  for (var i = 0; i < slides.length; i++) slides[i].style.display = "none";

  if (prev_slideIndex < slideIndex) {
    if (slideIndex > 3) slideIndex = 0;
    slides[prev_slideIndex].style.left = '-100%';
    slides[prev_slideIndex].style.marginleft = '0%';
    slides[slideIndex].style.left = '0%';
    slides[slideIndex].style.marginleft = '0%';
    slides[prev_slideIndex].style.animation = slides[slideIndex].style.animation = 'caroussel 1.5s';
  } else {
    if (slideIndex < 0) slideIndex = 3;
    slides[prev_slideIndex].style.left = '100%';
    slides[prev_slideIndex].style.marginleft = '0%';
    slides[slideIndex].style.left = '0%';
    slides[slideIndex].style.marginleft = '0%';
    slides[prev_slideIndex].style.animation = slides[slideIndex].style.animation = 'caroussel_back 1.5s';
  }

  slides[prev_slideIndex].style.display = 'block';
  slides[slideIndex].style.display = 'block';
  prev_slideIndex = slideIndex;

  str += ' final prev_slideIndex=' + prev_slideIndex;
  document.getElementById("text").innerHTML = str;
}

.parent {
  background-color: red;
  display: block;
  position: relative;
  width: 600px;
  height: 100px;
  padding-top: 10px;
  padding-bottom: 10px;
  overflow: hidden;
}

.child {
  background-color: green;
  display: block;
  position: absolute;
  width: 100%;
  height: 100px;
  color: #FFFFFF;
  font-size: 24px;
  text-align: center;
}

@keyframes caroussel {
  from {
    margin-left: 100%
  }
  to {
    margin-left: 0%
  }
}

@keyframes caroussel_back {
  0% {
    margin-left: -100%
  }
  100% {
    margin-left: 0%
  }
}

<input type="submit" value='forward' title="sdg" onclick="slideIndex++;myanimate();">
<input type="submit" value='backward' title="sdg" onclick="slideIndex--;myanimate();">
<br>
<div class="parent">
  <div class="child" style="background-color:yellow;left:0%;">
    Caption1<br>Caption1 Caption1 Caption1 Caption Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="left:100%;">
    Caption2<br>Caption2 Caption2 Caption2 Caption2 Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="background-color:magenta;left:100%;">
    Caption3<br>Caption3 Caption3 Caption3 Caption3 Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="background-color:cyan;left:100%;">
    Caption4<br>Caption4 Caption4 Caption4 Caption4 Caption Caption Caption Caption Caption
  </div>
</div>
<br>
<span id="text"></span>

如果我们交替按下“前进”和“后退”按钮（我们可以观察到两张幻灯片），它可以正常工作，但是如果我们多次按下这些按钮中的一个（前一张幻灯片消失），它就无法正常工作。

有谁知道为什么它不能正常工作，或者有任何改进代码的想法？

提前致谢。

我在 Firefox 74.0（32 位）中进行了测试。 css 中的 'transform: translateX(...)' 给了我相同的行为。

Answer 1

带有 prev_slideIndex 的幻灯片在轮播的上一次迭代中已经获得与 animation 相同的值。因此，您需要使用 reflow 强制此幻灯片再次播放相同的动画：

slides[prev_slideIndex].offsetHeight; /* trigger reflow */

var slideIndex = 0;
var prev_slideIndex = slideIndex;

function myanimate() {
  str = 'slideIndex=' + slideIndex + ' prev_slideIndex=' + prev_slideIndex;

  var slides = document.getElementsByClassName("child");
  for (var i = 0; i < slides.length; i++) slides[i].style.display = "none";

  if (prev_slideIndex < slideIndex) {
    if (slideIndex > 3) slideIndex = 0;
    slides[prev_slideIndex].style.left = '-100%';
    slides[prev_slideIndex].style.marginleft = '0%';
    slides[slideIndex].style.left = '0%';
    slides[slideIndex].style.marginleft = '0%';
    slides[prev_slideIndex].offsetHeight; /* trigger reflow */
    slides[prev_slideIndex].style.animation = slides[slideIndex].style.animation = 'caroussel 1.5s';
  } else {
    if (slideIndex < 0) slideIndex = 3;
    slides[prev_slideIndex].style.left = '100%';
    slides[prev_slideIndex].style.marginleft = '0%';
    slides[slideIndex].style.left = '0%';
    slides[slideIndex].style.marginleft = '0%';
    slides[prev_slideIndex].offsetHeight; /* trigger reflow */
    slides[prev_slideIndex].style.animation = slides[slideIndex].style.animation = 'caroussel_back 1.5s';
  }

  slides[prev_slideIndex].style.display = 'block';
  slides[slideIndex].style.display = 'block';
  prev_slideIndex = slideIndex;

  str += ' final prev_slideIndex=' + prev_slideIndex;
  document.getElementById("text").innerHTML = str;
}

.parent {
  background-color: red;
  display: block;
  position: relative;
  width: 600px;
  height: 100px;
  padding-top: 10px;
  padding-bottom: 10px;
  overflow: hidden;
}

.child {
  background-color: green;
  display: block;
  position: absolute;
  width: 100%;
  height: 100px;
  color: #FFFFFF;
  font-size: 24px;
  text-align: center;
}

@keyframes caroussel {
  from {
    margin-left: 100%
  }
  to {
    margin-left: 0%
  }
}

@keyframes caroussel_back {
  0% {
    margin-left: -100%
  }
  100% {
    margin-left: 0%
  }
}

<input type="submit" value='forward' title="sdg" onclick="slideIndex++;myanimate();">
<input type="submit" value='backward' title="sdg" onclick="slideIndex--;myanimate();">
<br>
<div class="parent">
  <div class="child" style="background-color:yellow;left:0%;">
    Caption1<br>Caption1 Caption1 Caption1 Caption Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="left:100%;">
    Caption2<br>Caption2 Caption2 Caption2 Caption2 Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="background-color:magenta;left:100%;">
    Caption3<br>Caption3 Caption3 Caption3 Caption3 Caption Caption Caption Caption Caption
  </div>
  <div class="child" style="background-color:cyan;left:100%;">
    Caption4<br>Caption4 Caption4 Caption4 Caption4 Caption Caption Caption Caption Caption
  </div>
</div>
<br>
<span id="text"></span>

在 carousel 中更改幻灯片的问题，仅用 js 和 css 编写

Problem with changing slides in carousel, written only in js and css

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