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滚动时隐藏Bootstrap导航栏

javascriptjqueryhtmlcsstwitter-bootstrap
3
我正在尝试在向下/向上滚动时隐藏/显示Bootstrap导航栏，但似乎无效。我卡住了，真的很需要帮助。有人能告诉我我做错了什么吗？请记住，我正在学习如何使用Bootstrap，对jQuery知之甚少。 当我用浏览器控制台检查代码时，没有显示任何错误。 我还尝试了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>

你在 $("banner").show(); 中忘记了 #。 - Mosh Feu
这将有所帮助 http://jsfiddle.net/nwV2r/699/ - Sanchit Patiyal
Sanchit Patiyal感谢您的帮助。我正在尝试在我的代码中实现它，但它并不起作用。 - AtlantisNaranja
4个回答
3

您的代码出现了两个问题，导致滚动回顶部时无法显示导航栏：

  1. 代码中的 $("banner").show(); 行缺少 "#" 符号。
  2. 隐藏元素时未保留其高度。因此，在隐藏导航栏后进行高度测试会得到意外的结果。建议预先保存高度并将其与保存的变量进行比较。

修正后的代码如下：

$(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>

非常感谢。它像魔法一样运行！我不知道为什么以前看不到这个。 - AtlantisNaranja
很高兴我能够帮到你 :) - Tomer Shay
抱歉@Tomer，还有一件事。当我向上滚动页面时，无论我的滚动位置在哪里，我的导航栏都不会显示。它只会在我在页面顶部时显示。我该如何解决这个问题？谢谢 - AtlantisNaranja
@AtlantisNaranja，我编辑了代码片段中的JavaScript代码，使其在向上滚动时始终显示导航栏，而不管滚动位置如何。我所做的更改是：添加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，以确保我们每次执行相关操作。如果满足您的要求，请为答案投票 :) - Tomer Shay
非常感谢！这正是我所追求的！ :) - AtlantisNaranja
0

Banner height 应该在 scroll 函数之外进行计算。

$(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>

0
尝试在滚动函数之外定义横幅高度，同时您忘记了 #，您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();
                    }
                });

        });
0

我已经为你修复了代码并添加了一些注释， 尝试打开控制台并滚动查看正在发生的情况。

基本上，您正在将滚动高度与横幅高度进行比较，而横幅高度在隐藏时从40更改为-16，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 #
                }
            });
    });

希望能有所帮助
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