[javascript] Fixed positioning in Mobile Safari

Is it possible to position an element fixed relative to the viewport in Mobile Safari? As many have noted, position: fixed doesn't work, but Gmail just came out with a solution that almost is what I want – see the floating menu bar on the message view.

Getting real-time scroll events in JavaScript would also be a reasonable solution.

You could try using touch-scroll, a jQuery plugin that mimics scrolling with fixed elements on mobile Safari: https://github.com/neave/touch-scroll

View an example with your iOS device at http://neave.github.com/touch-scroll/

Or an alternative is iScroll: http://cubiq.org/iscroll

Our web app requires a fixed header. We are fortunate in that we only have to support the latest browsers, but Safari's behavior in this area caused us a real problem.

The best fix, as others have pointed out, is to write our own scrolling code. However, we can't justify that effort to fix a problem that occurs only on iOS. It makes more sense to hope that Apple may fix this problem, especially since, as QuirksMode suggests, Apple now stands alone in their interpretation of "position:fixed".

http://www.quirksmode.org/blog/archives/2013/12/position_fixed_1.html

What worked for us is to toggle between "position:fixed" and "position:absolute" depending on whether the user has zoomed. This replaces our "floating" header with predictable behavior, which is important for usability. When zoomed, the behavior is not what we want, but the user can easily work around this by reversing the zoom.

// On iOS, "position: fixed;" is not supported when zoomed, so toggle "position: absolute;".
header = document.createElement( "HEADER" );
document.body.appendChild( header );
if( navigator.userAgent.match( /iPad/i ) || navigator.userAgent.match( /iPhone/i )) {
    addEventListener( document.body, function( event ) {
        var zoomLevel = (( Math.abs( window.orientation ) === 90 ) ? screen.height : screen.width ) / window.innerWidth;
        header.style.position = ( zoomLevel > 1 ) ? "absolute" : "fixed";
    });
}

This is how i did it. I have a nav block that is below the header once you scroll the page down it 'sticks' to the top of the window. If you scroll back to top, nav goes back in it's place I use position:fixed in CSS for non mobile platforms and iOS5. Other Mobile versions do have that 'lag' until screen stops scrolling before it's set.

// css
#sticky.stick {
    width:100%;
    height:50px;
    position: fixed;
    top: 0;
    z-index: 1;
}

// jquery 
//sticky nav
    function sticky_relocate() {
      var window_top = $(window).scrollTop();
      var div_top = $('#sticky-anchor').offset().top;

      if (window_top > div_top)
        $('#sticky').addClass('stick');
      else
        $('#sticky').removeClass('stick');
     }

$(window).scroll(function(event){

    // sticky nav css NON mobile way
       sticky_relocate();

       var st = $(this).scrollTop();

    // sticky nav iPhone android mobile way iOS<5

       if (navigator.userAgent.match(/OS 5(_\d)+ like Mac OS X/i)) {
            //do nothing uses sticky_relocate() css
       } else if ( navigator.userAgent.match(/(iPod|iPhone|iPad)/i) || navigator.userAgent.match(/Android/i) || navigator.userAgent.match(/webOS/i) ) {

            var window_top = $(window).scrollTop();
            var div_top = $('#sticky-anchor').offset().top;

            if (window_top > div_top) {
                $('#sticky').css({'top' : st  , 'position' : 'absolute' });
            } else {
                $('#sticky').css({'top' : 'auto' });
            }
        };

it worked for me:

function changeFooterPosition() {   
  $('.footer-menu').css('top', window.innerHeight + window.scrollY - 44 + "px");
}

$(document).bind('scroll', function() {
  changeFooterPosition();
});

(44 is the height of my bar)

Although the bar only moves at the end of the scroll...

<meta name="viewport" content="width=320, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no"/> 

Also making sure height=device-height is not present in this meta tag helps prevent additional footer padding that normally would not exist on the page. The menubar height adds to the viewport height causing a fixed background to become scrollable.

This fixed position div can be achieved in just 2 lines of code which moves the div on scroll to the bottom of the page.

window.onscroll = function() {
  document.getElementById('fixedDiv').style.top =
     (window.pageYOffset + window.innerHeight - 25) + 'px';
};

Here you can see what (mobile) browsers support css position fixed + there version.

http://caniuse.com/css-fixed

This may interest you. It's Apple Dev support page.
http://developer.apple.com/library/ios/#technotes/tn2010/tn2262/

Read the point "4. Modify code that relies on CSS fixed positioning" and you will find out that there is very good reason why Apple made the conscious decision to handle fixed position as static.

See Google's solution to this problem. You basically have to scroll content yourself using JavaScript. Sencha Touch also provides a library for getting this behavior in a very performant manor.

I think gmail just tracks the scroll position on a timer and repositions a div accordingly.

The best solution I've seen is at doctyper.

A simpler jQuery solution that moves an element onscroll: link