position: fixed doesn't work on iPad and iPhon

问题:

I have been struggling with fixed positioning in iPad for a while. I know iScroll and it does not always seem to work (even in their demo). I also know that Sencha has a fix for that, but I couldn\'t Ctrl + F the source code for that fix.

I am hoping that someone may have the solution. The problem is that fixed positioned elements do not get updated when the user pans down/up on an iOS powered mobile Safari.

回答1:

A lot of mobile browsers deliberately do not support position:fixed; on the grounds that fixed elements could get in the way on a small screen.

The Quirksmode.org site has a very good blog post that explains the problem: http://www.quirksmode.org/blog/archives/2010/12/the_fifth_posit.html

Also see this page for a compatibility chart showing which mobile browsers support position:fixed;: http://www.quirksmode.org/m/css.html

(but note that the mobile browser world is moving very quickly, so tables like this may not stay up-to-date for long!)

Update: iOS 5 and Android 4 are both reported to have position:fixed support now.

I tested iOS 5 myself in an Apple store today and can confirm that it does work with position fixed. There are issues with zooming in and panning around a fixed element though.

I found this compatibility table far more up to date and useful than the quirksmode one: http://caniuse.com/#search=fixed

It has up to date info on Android, Opera (mini and mobile) & iOS.

回答2:

Fixed positioning doesn\'t work on iOS like it does on computers.

Imagine you have a sheet of paper (the webpage) under a magnifying glass(the viewport), if you move the magnifying glass and your eye, you see a different part of the page. This is how iOS works.

Now there is a sheet of clear plastic with a word on it, this sheet of plastic stays stationary no matter what (the position:fixed elements). So when you move the magnifying glass the fixed element appears to move.

Alternatively, instead of moving the magnifying glass, you move the paper (the webpage), keeping the sheet of plastic and magnifying glass still. In this case the word on the sheet of plastic will appear to stay fixed, and the rest of the content will appear to move (because it actually is) This is a traditional desktop browser.

So in iOS the viewport moves, in a traditional browser the webpage moves. In both cases the fixed elements stay still in reality; although on iOS the fixed elements appear to move.

---

The way to get around this, is to follow the last few paragraphs in this article

(basically disable scrolling altogether, have the content in a separate scrollable div (see the blue box at the top of the linked article), and the fixed element positioned absolutely)

---

\"position:fixed\" now works as you\'d expect in iOS5.

回答3:

position: fixed does work on android/iphone for vertical scrolling. But you need to make sure your meta tags are fully set. e.g

<meta name=\"viewport\" content=\"width=device-width, height=device-height, initial-scale=1.0, user-scalable=0, minimum-scale=1.0, maximum-scale=1.0\">

Also if you\'re planning on having the same page work on android pre 4.0, you need to set the top position also, or a small margin will be added for some reason.

回答4:

now apple support that

overflow:hidden;
-webkit-overflow-scrolling:touch;

回答5:

Fixed Footer (here with jQuery):

if (navigator.platform == \'iPad\' || navigator.platform == \'iPhone\' || navigator.platform == \'iPod\' || navigator.platform == \'Linux armv6l\') 
{
    window.ontouchstart = function () 
    {
        $(\"#fixedDiv\").css(\"display\", \"none\");
    }

    window.onscroll = function() 
    { 
        var iPadPosition = window.innerHeight + window.pageYOffset-45; // 45 is the height of the Footer
         $(\"#fixedDiv\").css(\"position\", \"absolute\");
         $(\"#fixedDiv\").css(\"top\", iPadPosition);
         $(\"#fixedDiv\").css(\"display\", \"block\");
    }
}

// in the CSS file should stand:
#fixedDiv {position: fixed; bottom: 0; height: 45px;  whatever else}

Hope it helps.

回答6:

I had this problem on Safari (iOS 10.3.3) - the browser was not redrawing until the touchend event fired. Fixed elements did not appear or were cut off.

The trick for me was adding transform: translate3d(0,0,0); to my fixed position element.

.fixed-position-on-mobile {
  position: fixed;
  transform: translate3d(0,0,0);
}

EDIT - I now know why the transform fixes the issue: hardware-acceleration. Adding the 3D transformation triggers the GPU acceleration making for a smooth transition. For more on hardware-acceleration checkout this article: http://blog.teamtreehouse.com/increase-your-sites-performance-with-hardware-accelerated-css.

回答7:

Avoid on the same box using transform:--- and position:fixed. Element will stay in position:static if there is any transform.

回答8:

I ended up using the new jQuery Mobile v1.1: http://jquerymobile.com/blog/2012/04/13/announcing-jquery-mobile-1-1-0/

We now have a solid re-write that provides true fixed toolbars on the a lot of popular platforms and safely falls back to static toolbar positioning in other browsers.

The coolest part about this approach is that, unlike JS-based solutions that impose the unnatural scrolling physics across all platforms, our scrolling feels 100% native because it is. This means that scrolling feels right everywhere and works with touch, mousewheel and keyboard user input. As a bonus, our CSS-based solution is super lightweight and doesn’t impact compatibility or accessibility.

回答9:

using jquery i am able to come up with this. it doesnt scroll smooth, but it does the trick. you can scroll down, and the fixed div pops up on top.

THE CSS

<style type=\"text/css\">
    .btn_cardDetailsPg {height:5px !important;margin-top:-20px;}
    html, body {overflow-x:hidden;overflow-y:auto;}
    #lockDiv {
  background-color: #fff;
  color: #000;
  float:left;
  -moz-box-shadow: 0px 4px 2px 2px #ccc;-webkit-box-shadow: 0px 4px 2px 2px #ccc;box-shadow:0px 4px 2px 2px #ccc;
  }
#lockDiv.stick {
  position: fixed;
  top: 0;
  z-index: 10000;
  margin-left:0px;
  }
</style>

THE HTML

<div id=\"lockSticky\"></div>
<div id=\"lockDiv\">fooo</div>

THE jQUERY

<script type=\"text/javascript\">
    function sticky_relocate() {
        var window_top = $(window).scrollTop();
        var div_top = $(\'#lockSticky\').offset().top;
        if (window_top > div_top)
            $(\'#lockDiv\').addClass(\'stick\')
        else
            $(\'#lockDiv\').removeClass(\'stick\');
    }
    $(function() {
        $(window).scroll(sticky_relocate);
        sticky_relocate();
    });
</script>

Finally we want to determine if the ipod touch in landscape or portrait mode to display accordingly

<script type=\"text/javascript\">
    if (navigator.userAgent.match(/like Mac OS X/i)) {
        window.onscroll = function() {

        if (window.innerWidth > window.innerHeight) {
            //alert(\"landscape [ ]\");
            document.getElementById(\'lockDiv\').style.top =
            (window.pageYOffset + window.innerHeight - 268) + \'px\';
        }

        if (window.innerHeight > window.innerWidth) {
            //alert(\"portrait ||\");
            document.getElementById(\'lockDiv\').style.top =
            (window.pageYOffset + window.innerHeight - 418) + \'px\';
        }
        };
    }
</script>

回答10:

Even though the CSS attribute {position:fixed;} seems (mostly) working on newer iOS devices, it is possible to have the device quirk and fallback to {position:relative;} on occasion and without cause or reason. Usually clearing the cache will help, until something happens and the quirk happens again.

Specifically, from Apple itself Preparing Your Web Content for iPad:

Safari on iPad and Safari on iPhone do not have resizable windows. In Safari on iPhone and iPad, the window size is set to the size of the screen (minus Safari user interface controls), and cannot be changed by the user. To move around a webpage, the user changes the zoom level and position of the viewport as they double tap or pinch to zoom in or out, or by touching and dragging to pan the page. As a user changes the zoom level and position of the viewport they are doing so within a viewable content area of fixed size (that is, the window). This means that webpage elements that have their position \"fixed\" to the viewport can end up outside the viewable content area, offscreen.

What is ironic, Android devices do not seem to have this issue. Also it is entirely possible to use {position:absolute;} when in reference to the body tag and not have any issues.

I found the root cause of this quirk; that it is the scroll event not playing nice when used in conjunction with the HTML or BODY tag. Sometimes it does not like to fire the event, or you will have to wait until the scroll swing event is finished to receive the event. Specifically, the viewport is re-drawn at the end of this event and fixed elements can be re-positioned somewhere else in the viewport.

So this is what I do: (avoid using the viewport, and stick with the DOM!)

<html>
  <style>
    .fixed{
      position:fixed;
      /*you can set your other static attributes here too*/
      /*like height and width, margin, etc.*/
      }
    .scrollableDiv{
      position:relative;
      overflow-y:scroll;
      /*all children will scroll within this like the body normally would.*/
      } 
    .viewportSizedBody{
      position:relative;
      overflow:hidden;
      /*this will prevent the body page itself from scrolling.*/
      } 
  </style>
  <body class=\"viewportSizedBody\">
    <div id=\"myFixedContainer\" class=\"fixed\">
       This part is fixed.
    </div>
    <div id=\"myScrollableBody\" class=\"scrollableDiv\">
       This part is scrollable.
    </div>
  </body>
  <script type=\"text/javascript\" src=\"{your path to jquery}/jquery-1.7.2.min.js\"></script>
  <script>
    var theViewportHeight=$(window).height();
    $(\'.viewportSizedBody\').css(\'height\',theViewportHeight);
    $(\'#myScrollableBody\').css(\'height\',theViewportHeight);
  </script>
</html>

In essence this will cause the BODY to be the size of the viewport and non-scrollable. The scrollable DIV nested inside will scroll as the BODY normally would (minus the swing effect, so the scrolling does stop on touchend.) The fixed DIV stays fixed without interference.

As a side note, a high z-index value on the fixed DIV is important to keep the scrollable DIV appear to be behind it. I normally add in window resize and scroll events also for cross-browser and alternate screen resolution compatibility.

If all else fails, the above code will also work with both the fixed and scrollable DIVs set to {position:absolute;}.

回答11:

In my case, scrolling showed the position: fixed element that didn\'t originally show when added to the DOM. So I just manually triggered the scroll event which in turn triggered a redraw and voila.

window.scrollTo(window.scrollX, window.scrollY);

回答12:

here is my solution to this...

CSS

#bgimg_top {
    background: url(images/bg.jpg) no-repeat 50% 0%; 
    position: fixed; 
    top:0; 
    left: 0; 
    right:0 ; 
    bottom:0;
}

HTML

<body>
<div id=\"bgimg_top\"></div>
....
</body>

Explanation is that position fixed for the div will keep the div on the background at all time, then we stretch the div to go on all corners of the browser (provided the body margin = 0) using the (left,right,top,bottom) simultaneously.

Please make sure you do not use the width and height as this will override the top,left,right,bottom options.