html - 我的 css3 in position 标签有问题

Question

我的下拉导航栏有问题，当我在 css 中定义位置时，下拉导航栏位于图像后面。我希望你理解我的问题。请帮助我，也很抱歉英语不好。

.img-slider-ul {
  list-style: none;
  margin: 0;
  padding: 0;
  height:350px;
  overflow:hidden;
  position:relative;
}
.img-slider-li {
  position:absolute;
}
.img-slider{
  border: 1px solid #000;
  border-radius: 3px;
  box-shadow: 0 0 5px 0 hsla(0,0%,30%, .3);
  height:350px;
}
.img-slider-li:nth-child(4) {
  animation: xfade 16s 0s infinite;
}
.img-slider-li:nth-child(3) {
  animation: xfade 16s 4s infinite;
}
.img-slider-li:nth-child(2) {
  animation: xfade 16s 8s infinite;
}
.img-slider-li:nth-child(1) {
  animation: xfade 16s 12s infinite;
}
@keyframes xfade{
  17% {
    opacity:1;
  }
  25% {
    opacity:0;
  }
  92% {
    opacity:0;
  }
}

<ul class="img-slider-ul">
  <li class="img-slider-li"><img class="img-slider" title="" alt="css3" src="https://image.ibb.co/dnt83v/img01.png" /></li>
  <li class="img-slider-li"><img class="img-slider" title="" alt="css3" src="https://image.ibb.co/iJuFiv/img02.png" /></li>
  <li class="img-slider-li"><img class="img-slider" title="" alt="css3" src="https://image.ibb.co/nf8VGF/img03.png" /></li>
  <li class="img-slider-li"><img class="img-slider" title="" alt="css3" src="https://preview.ibb.co/hJZ4bF/img04.png" /></li>
</ul>

Answer 1

与 slider 部分相比，添加“下拉菜单”Z-index 应该较高

 .img-slider-ul {
      list-style: none;
       margin: 0;
       padding: 0;
       height:350px;
       overflow:hidden;
       position:relative;
       z-index:99;
  }

为下拉菜单类添加z-index:999;