位置粘性与 z-index 结合

Question

在下面的HTML 和CSS 中，我创建了一个标题和一个图像动画，您也可以在JSfiddle here 中找到它们：

body {
  margin: 0;
}


/* 01.00 HEADER: Items in header */

.header_01 {
  width: 80%;
  height: 10vh;
  
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  z-index:99;
  
  
  text-align: center;
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: orange;    
}

.header_02 {
  width: 80%;
  height: 10vh;
  
  margin: 10vh auto 0;
  position: sticky;
  z-index:99;
  
  top:0;
  display: flex;
  justify-content: space-between;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.image {
  width: 30%;
  height: 100%;
  display: flex;
  justify-content: center;
  text-align: center;
  align-items: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: green;
}

.navigation {
  width: 70%;
  height: 100%;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: aqua;
}


/* 02.00 NAVIGATION */

.navigation>ul {
  height: 100%;
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: blue;
}

.navigation>ul>li {
  width: 100%;
  display: flex;
  justify-content: center;
  text-align: center;
  align-items: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
}



/* 03.00 CONTENT */

.image_animation {
 width: 80%;
 margin-left: 10%;
 margin-top: 15%;
 float: left;
 display: flex;
 justify-content: space-between;

 background-color: green;
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
}
 
.image_list {
 width: 100%;
 position: relative;
	
 background-color: red;
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
}
	
.image_list img {
 width: 100%;
 height: 100%;
}
 
.image1 {
 height: 100%;
 width: 100%;
 float: left;
 position: absolute;
}
 
.image2 {
 height: 100%;
 width: 100%;
 float: left;
 animation-delay: 2s;
}
 
.image_list div {
 animation-name: animation_home_images;
 animation-duration:4s;
 animation-iteration-count:infinite;
 animation-fill-mode: forwards;
 opacity:0;
 }

@keyframes animation_home_images {
  50.0% {
    opacity: 1
  }
  0%, 100%{
    opacity: 0
  }
}

<div class="header_01">
This is our webpage.
</div>


<div class="header_02">	

      <div class="image">
      Image
      </div>
  
      <nav class="navigation"> 
      
        <ul>
        
          <li class="button_01"> 1.0 Main Menu </li>
          <li class="button_01"> 2.0 Main Menu </li>
          <li class="button_01"> 3.0 Main Menu </li>
          
        </ul>
        
      </nav>
      
</div>	


<div class="image_animation">
    
  <div class="image_list">
    <div class="image1"><img src="http://placehold.it/101x101"></div>
		<div class="image2"><img src="http://placehold.it/201x201"></div>
	</div>
        
</div>

如您所见，我有一个header，由两部分组成。一旦用户向下滚动页面，第一个.header_01 应该消失，而第二个.header_02 应该保持固定。我最初通过问题here 的答案实现了这一点。

到目前为止，这一切都很好。

---

现在我在标题下方添加了一个 .image-animation 和一个 postion: absolute; 属性，这是使动画工作所必需的。因此，我还在CSS 中添加了z-index，如答案here 中所述，以便在用户向下滚动页面后获得标题下方的动画。

但是，不知何故，我无法使 z-index 与 position: sticky; 属性结合使用，因为当我向下滚动时，两个标题都消失了。

你知道我需要在我的代码中改变什么，所以一旦用户向下滚动：

a) 第一个 .header_01 消失，
b) 第二个.header_02 保持不变，
c) .image-animation 在标题后面。

Answer 1

只需删除使主体仅具有顶部标题的高度的浮动（不需要），因此粘性将无法按预期工作：

body {
  margin: 0;
}


/* 01.00 HEADER: Items in header */

.header_01 {
  width: 80%;
  height: 10vh;
  
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  z-index:99;
  
  
  text-align: center;
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: orange;    
}

.header_02 {
  width: 80%;
  height: 10vh;
  
  margin: 10vh auto 0;
  position: sticky;
  z-index:99;
  
  top:0;
  display: flex;
  justify-content: space-between;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.image {
  width: 30%;
  height: 100%;
  display: flex;
  justify-content: center;
  text-align: center;
  align-items: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: green;
}

.navigation {
  width: 70%;
  height: 100%;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: aqua;
}


/* 02.00 NAVIGATION */

.navigation>ul {
  height: 100%;
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: blue;
}

.navigation>ul>li {
  width: 100%;
  display: flex;
  justify-content: center;
  text-align: center;
  align-items: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
}



/* 03.00 CONTENT */

.image_animation {
 width: 80%;
 margin-left: 10%;
 margin-top: 15%;
 display: flex;
 justify-content: space-between;

 background-color: green;
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
}
 
.image_list {
 width: 100%;
 position: relative;
 overflow:hidden;
	
 background-color: red;
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
}
	
.image_list img {
 width: 100%;
 height: 100%;
}
 
.image1 {
 height: 100%;
 width: 100%;
 position: absolute;
}
 
.image2 {
 height: 100%;
 width: 100%;
 display:block;
 animation-delay: 2s;
}
 
.image_list div {
 animation-name: animation_home_images;
 animation-duration:4s;
 animation-iteration-count:infinite;
 animation-fill-mode: forwards;
 opacity:0;
 }

@keyframes animation_home_images {
  50.0% {
    opacity: 1
  }
  0%, 100%{
    opacity: 0
  }
}

<div class="header_01">
This is our webpage.
</div>


<div class="header_02">	

      <div class="image">
      Image
      </div>
  
      <nav class="navigation"> 
      
        <ul>
        
          <li class="button_01"> 1.0 Main Menu </li>
          <li class="button_01"> 2.0 Main Menu </li>
          <li class="button_01"> 3.0 Main Menu </li>
          
        </ul>
        
      </nav>
      
</div>	


<div class="image_animation">
    
  <div class="image_list">
    <div class="image1"><img src="http://placehold.it/101x101"></div>
		<div class="image2"><img src="http://placehold.it/201x201"></div>
	</div>
        
</div>