How to use the new affix plugin in twitter's bootstrap 2.1.0?

The bootstrap documentation on that topic is a little confusing to me. I want to achieve similar behaviour like in the docs with the affix navbar: The navbar is below a paragraph / page heading, and upon scrolling down it should first scroll along until reaching the top of the page, and then stick there fixed for further scrolldowns.

As jsFiddle does not work with the navbar concept, I've set up a separate page for usage as a minimal example: http://i08fs1.ira.uka.de/~s_drr/navbar.html

I use this as my navbar:

<div class="navbar affix-top" data-spy="affix" data-offset-top="50">
    <div class="navbar-inner">
        <div class="container">
            <div class="span12">
                <a class="brand" href="#">My Brand</a> 
                This is my navbar.
             </div>
        </div> <!-- container -->
    </div> <!-- navbar-inner -->
</div> <!-- navbar -->

I thinkg i would want data-offset-top to be of value 0 (since the bar should "stick" to the very top" but with 50 there is at least some effect watchable.

If also put the javascript code in place:

     <script>
        $(document).ready (function (){
            $(".navbar").affix ();
        });
     </script>

Any help appreciated.

Answers


I was having a similar problem, and I believe I found an improved solution.

Don't bother specifying data-offset-top in your HTML. Instead, specify it when you call .affix():

$('#nav').affix({
    offset: { top: $('#nav').offset().top }
});​

The advantage here is that you can change the layout of your site without needing to update the data-offset-top attribute. Since this uses the actual computed position of the element, it also prevents inconsistencies with browsers that render the element at a slightly different position.


You will still need to clamp the element to the top with CSS. Furthermore, I had to set width: 100% on the nav element since .nav elements with position: fixed misbehave for some reason:

#nav.affix {
    position: fixed;
    top: 0px;
    width: 100%;
}

One last thing: When an affixed element becomes fixed, its element no longer takes up space on the page, resulting in the elements below it to "jump". To prevent this ugliness, I wrap the navbar in a div whose height I set to be equal to the navbar at runtime:

<div id="nav-wrapper">
    <div id="nav" class="navbar">
        <!-- ... -->
    </div>
</div>

.

$('#nav-wrapper').height($("#nav").height());

Here's the obligatory jsFiddle to see it in action.


Just implemented this for the first time, and here's what I've found.

The data-offset-top value is the amount of pixels that you must scroll in order for the affixing effect to take place. In your case, once 50px is scrolled, the class on your item is changed from .affix-top to .affix. You'd probably want to set data-offset-top to about 130px in your use case.

Once this class change occurs, you must position your element in css by styling the positioning for class .affix. Bootstrap 2.1 already defines .affix as position: fixed; so all you need to do is add your own position values.

Example:

.affix {
    position: fixed; 
    top: 20px; 
    left: 0px;
}

To fix this very issue I have modified the affix plugin to emit a jQuery event when an object is affixed or unaffixed.

Here is the pull request: https://github.com/twitter/bootstrap/pull/4712

And the code: https://github.com/corbinu/bootstrap/blob/master/js/bootstrap-affix.js

And then do this to attach the navbar:

<script type="text/javascript">
$(function(){
    $('#navbar').on('affixed', function () {
        $('#navbar').addClass('navbar-fixed-top')
    });

    $('#navbar').on('unaffixed', function () {
        $('#navbar').removeClass('navbar-fixed-top')
    });
});
</script>

You need to remove .affix() from your script.

Bootstrap gives the option of accomplishing things either via data-attributes or straight JavaScript most of the time.


I've got this from the twitterbootstrap's source code and it's working pretty well:

HTML:

<div class="row">
    <div class="span3 bs-docs-sidebar">
        <ul id="navbar" class="nav nav-list bs-docs-sidenav">
            ...
        </ul>
    </div>
</div>

CSS:

.bs-docs-sidenav {
    max-height: 340px;
    overflow-y: scroll;
}

.affix {
    position: fixed;
    top: 50px;
    width: 240px;
}

JS:

$(document).ready(function(){
    var $window = $(window);
    setTimeout(function () {
        $('.bs-docs-sidenav').affix({
            offset: {
                top: function (){
                    return $window.width() <= 980 ? 290 : 210
                }
            }
        })
    }, 100);
});

You just need to remove the script. Here is my example:

<!DOCTYPE html>
<html>

<head>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.8.0.min.js"></script>
<script type="text/javascript" src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.1.0/js/bootstrap.min.js"></script>

  <style>
  #content {
    width: 800px;
    height: 2000px;
    background: #f5f5f5;
    margin: 0 auto;
  }
  .menu {
    background: #ccc;
    width: 200px;
    height: 400px;
    float: left;
  }
  .affix {
    position: fixed;
    top: 20px;
    left: auto;
    right: auto;
  }
  </style>

</head>
<body>
    <div id="content">
        <div style="height: 200px"></div>

        <div class="affix-top" data-spy="affix" data-offset-top="180">
            <div class="menu">AFFIX BAR</div>
        </div>
    </div>
</body>
</html>

Thanks to namuol and Dave Kiss for the solution. In my case I had a tiny problem with navbar height and width when I used afflix and collapse plugins together. The problem with width can be easily solved inheriting it from parent element (container in my case). Also I could manage to make it collapsing smoothly with a bit of javascript (coffeescript actually). The trick is to set wrapper height to auto before collapse toggle occurs and fix it back after.

Markup (haml):

#wrapper
  #navbar.navbar
    .navbar-inner
      %a.btn.btn-navbar.btn-collapse
        %span.icon-bar
        %span.icon-bar
        %span.icon-bar

      #menu.nav-collapse
        -# Menu goes here

CSS:

#wrapper {
  width: inherit;
}

#navbar {
  &.affix {
    top: 0;
    width: inherit;
  }
}

Coffeescript:

class Navigation
  @initialize: ->
    @navbar = $('#navbar')
    @menu = $('#menu')
    @wrapper = $('#wrapper')

    @navbar.affix({offset: @navbar.position()})
    @adjustWrapperHeight(@navbar.height())

    @navbar.find('a.btn-collapse').on 'click', () => @collapse()

    @menu.on 'shown', () => @adjustWrapperHeight(@navbar.height())
    @menu.on 'hidden', () => @adjustWrapperHeight(@navbar.height())

  @collapse: ->
    @adjustWrapperHeight("auto")
    @menu.collapse('toggle')

  @adjustWrapperHeight: (height) ->
    @wrapper.css("height", height)

$ ->
  Navigation.initialize()

My solution for attach the navbar :

function affixnolag(){

    $navbar = $('#navbar');
    if($navbar.length < 1)
        return false;

    h_obj = $navbar.height();

    $navbar
        .on('affixed', function(){      
            $navbar.after('<div id="nvfix_tmp" style="height:'+h_obj+'px">');
        })
        .on('unaffixed', function(){
            if($('#nvfix_tmp').length > 0)
                $('#nvfix_tmp').remove();
        });
 }

Similar to the accepted answer, you can also do something like the following to do everything in one go:

$('#nav').affix({
  offset: { top: $('#nav').offset().top }
}).wrap(function() {
  return $('<div></div>', {
    height: $(this).outerHeight()
  });
});​

This not only invokes the affix plugin, but will also wrap the affixed element in a div which will maintian the original height of the navbar.


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