滚动时隐藏引导导航栏答案

【问题标题】：hide bootstrap navbar when scrolling滚动时隐藏引导导航栏
【发布时间】：2017-08-29 09:31:12
【问题描述】：

我试图在向下/向上滚动时隐藏/显示 Bootstrap 导航栏，但它似乎不起作用。我被困住了，我真的很感激这里的一些帮助。谁能告诉我我做错了什么？请记住，我正在学习如何使用 Bootstrap 并且对 jQuery 了解甚少。当我使用浏览器控制台检查代码时，它没有显示任何错误。我也尝试过fadeIn 和fadeOut 以及addClass 和removeClass 函数，但没有成功。

$(document).ready(function() {

  var banner = $("#navscroll");
  $(window).scroll(function() {
    var scroll = $(window).scrollTop();
    if (scroll >= banner.height()) {
      $("#banner").hide();

    } else {
      $("banner").show();
    }
  });

});

console.log();

body {
  background-color: azure;
}

.divi {
  width: 500px;
  height: 500px;
}

#divi1 {
  background-color: red;
}

#divi2 {
  background-color: greenyellow;
}

<!DOCTYPE html>
<html lang="en">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
  <!-- Stylesheet for Mysite -->


  <title>My Site</title>

</head>

<body>

  <!-- Banner -->
  <div id="banner" class="container-fluid">
    <nav id="navscroll" class="navbar navbar-toggleable-sm navbar-light fixed-top">
      <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <a class="navbar-brand" href="#">My Site</a>
      <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
        <div class="navbar-nav">
          <a class="nav-item nav-link active" href="#">Me<span class="sr-only">(current)</span></a>
          <a class="nav-item nav-link" href="#">What I do</a>
          <a class="nav-item nav-link" href="#">Find Me</a>
        </div>
      </div>
    </nav>
  </div>
  <!-- Banner -->

  <!-- Divs -->
  <div class="container-fluid">
    <div id="divi1" class="divi"></div>
    <div id="divi2" class="divi"></div>
  </div>
  <!-- Divs -->



  <!-- jQuery first, then Tether, then Bootstrap JS. -->

  <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
</body>

</html>

【问题讨论】：

您在$("banner").show(); 中忘记了#
这将有助于jsfiddle.net/nwV2r/699
Sanchit Patiyal 对此表示感谢。我正在尝试在我的代码中实现它，但它不起作用..

标签： javascript jquery html css twitter-bootstrap

【解决方案1】：

有两个问题阻止您的代码在向上滚动时显示导航栏：

$("banner").show(); 行 => 在banner 之前缺少“#”。
隐藏元素时，不会保留其高度。因此，在 nvarbar 隐藏后测试它的高度时，会得到意想不到的结果。因此，我建议提前保存高度并与保存的变量进行比较。

固定代码为：

$(document).ready(function() {
  var banner_height = $("#navscroll").height();
  var lastScrollTop = 0;
  $(window).scroll(function() {
    var scroll = $(window).scrollTop();
    var currScrollTop = $(this).scrollTop();
    if (scroll >= banner_height && currScrollTop > lastScrollTop) {
      $("#banner").hide();
    } else {
      $("#banner").show();
    }
    lastScrollTop = currScrollTop;

  });

});

body {
  background-color: azure;
}

.divi {
  width: 500px;
  height: 500px;
}

#divi1 {
  background-color: red;
}

#divi2 {
  background-color: greenyellow;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!DOCTYPE html>
<html lang="en">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
  <!-- Stylesheet for Mysite -->

  <title>My Site</title>

</head>

<body>

  <!-- Banner -->
  <div id="banner" class="container-fluid">
    <nav id="navscroll" class="navbar navbar-toggleable-sm navbar-light fixed-top">
      <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <a class="navbar-brand" href="#">My Site</a>
      <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
        <div class="navbar-nav">
          <a class="nav-item nav-link active" href="#">Me<span class="sr-only">(current)</span></a>
          <a class="nav-item nav-link" href="#">What I do</a>
          <a class="nav-item nav-link" href="#">Find Me</a>
        </div>
      </div>
    </nav>
  </div>
  <!-- Banner -->

  <!-- Divs -->
  <div class="container-fluid">
    <div id="divi1" class="divi"></div>
    <div id="divi2" class="divi"></div>
  </div>
  <!-- Divs -->

  <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
</body>

</html>

【讨论】：

非常感谢。它就像一个魅力！我不知道为什么我以前看不到这个。
很高兴我能帮上忙 :)
对不起@Tomer，还有一件事。无论我的滚动位置如何，当我向上滚动时，我的导航栏都不会显示。它仅显示我是否位于页面顶部。我怎样才能解决这个问题？谢谢
@AtlantisNaranja，我在 sn-p 中编辑了 javascript 代码，以便在向上滚动时始终显示导航栏，无论滚动位置如何。我所做的更改：添加了另一个变量来记住最后的滚动位置以确定滚动方向。完成后，我将其添加到条件中，以确保我们每次都执行相关操作。如果它满足您的要求，请为答案投票:)
再次感谢！这正是我的目标！ :)

【解决方案2】：

尝试在滚动功能之外定义横幅高度，但你忘了#，你的脚本看起来像这样

$(document).ready(function(){

                var banner = $("#navscroll");
                var bannerHeight = banner.height();
                $(window).scroll(function(){
                    var scroll = $(window).scrollTop();
                    if (scroll >= bannerHeight){
                        $("#banner").hide();
                    } else {
                        $("#banner").show();
                    }
                });

        });

【讨论】：

【解决方案3】：

我已经为您修复了代码并添加了一些 cmets，尝试打开控制台并滚动查看发生了什么。

基本上，您将滚动高度与隐藏时从 40 变为 -16 的横幅高度进行比较，因此您必须先保存它。

        $(document).ready(function(){
            var banner = $("#navscroll");
             var bannerStartHeight = $("#navscroll").height();
            $(window).scroll(function(){
                var scroll = $(window).scrollTop();
                console.log("SCROLL: "+scroll)
                console.log("BANNER HEIGHT:"+banner.height())
                console.log("BANNER START HEIGHT: "+bannerStartHeight)
                if (scroll >= bannerStartHeight){
                    $("#banner").hide();
                } else {
                    $("#banner").show(); //here u forgot a #
                }
            });
    });

希望对你有帮助

【讨论】：

【解决方案4】：

Banner height 应该在scroll 函数之外计算。

$(document).ready(function() {

  var banner = $("#navscroll");
  var bannerHgt = banner.height();
  $(window).scroll(function() {
    var scroll = $(window).scrollTop();
    if (scroll >= bannerHgt) {
      $("#banner").hide();
    } else {
      $("#banner").show();
    }
  });

});

console.log();

 body{
    
            background-color: azure;
        }

        .divi{

            width: 500px;
            height: 500px;
        }

        #divi1{

            background-color: red;
        }

        #divi2{

            background-color: greenyellow;
        }

<!DOCTYPE html>
<html lang="en">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
    <script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
    <!-- Stylesheet for Mysite -->  
      
      
    <title>My Site</title> 
         
  </head>
            
  <body>
      
    <!-- Banner --> 
    <div id="banner" class="container-fluid">
        <nav id="navscroll" class="navbar navbar-toggleable-sm navbar-light fixed-top">
          <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
          <a class="navbar-brand" href="#">My Site</a>
          <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
            <div class="navbar-nav">
              <a class="nav-item nav-link active" href="#">Me<span class="sr-only">(current)</span></a>
              <a class="nav-item nav-link" href="#">What I do</a>
              <a class="nav-item nav-link" href="#">Find Me</a>
            </div>
          </div>
        </nav>  
    </div> 
    <!-- Banner -->
    
    <!-- Divs -->
    <div class="container-fluid">
        <div id="divi1" class="divi"></div>  
        <div id="divi2" class="divi"></div>  
    </div>  
    <!-- Divs -->  
      
 

    <!-- jQuery first, then Tether, then Bootstrap JS. -->
    
    <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
  </body>
</html>

【讨论】：