麻烦将Div划分为Div

Question

我已尝试过我在此处看到的解决方案：更改z-index，absolute定位等。当我尝试使用绝对位置时，它会缩小{{1}到600px。关于我做错了什么想法？

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navbar

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body, html {
  height: 100%;
}

.jumbotron {
  height: 100vh;
  padding: 0;
  margin: 0;
  background-image: url('https://www.w3schools.com/css/trolltunga.jpg');
  background-size: cover;
  z-index: 0;
}

.topnav {
  background-color: #3b4e6b;
  overflow: hidden;
  z-index: 1;
}

.topnav a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  text-decoration: none;
  font-size: 20px;
  padding: 20px 25px;
 }

.topnav .icon {
   /* Hide icon to expand menu */
  display: none;
}

/* When screen is less than 600px wide, hide all links except the first one, and display the icon to expand the menu */
@media screen and (max-width: 600px) {
   .topnav a:not(:first-child) {display: none;}
   .topnav a.icon {
   float: right;
   display: block;
   }
}

/* When screen is less than 600px wide, display all links vertically when icon is clicked */
@media screen and (max-width: 600px) {
  .topnav.responsive {position: relative;}
  .topnav.responsive a.icon {
   position: absolute;
   right: 0;
   top: 0;
 }
 .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
  }
}

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Answer 1

task仅在分配了z-index属性时才有效，

所以在position使用z-index: -1和position:relative（使用.jumbotron）

top: negative value at your choice

body,
html {
  height: 100%;
}

.jumbotron {
  height: 100vh;
  padding: 0;
  margin: 0;
  background-image: url('//lorempixel.com/600/600');
  background-size: cover;
  z-index: -1;
  position: relative;
  top: -64px /* value of topnav height */
}

.topnav {
  background-color: rgba(0, 0, 0, 0.5);  /* changed for demo purposes*/
  overflow: hidden
}

.topnav a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  text-decoration: none;
  font-size: 20px;
  padding: 20px 25px;
}

.topnav .icon {
  /* Hide icon to expand menu */
  display: none;
}