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I'm build a single page web application for mobile phones. The application should implement transitions between "screens" (like any other mobile app e.g. Facebook, Twitter) and these transitions should be animated (slide left-right). Each screen has to preserve its scroll position between transitions.
One obvious solution that comes in mind is this:
Viewport
+----------+
|+--------+| +--------+ +--------+ +--------+
|| DIV1 || | DIV2 | | DIV3 | | DIV4 |
|| || | | | | | |
|| || | | | | | |
|| || | | | | | |
|| || | | | | | |
|+--------+| +--------+ +--------+ +--------+
+----------+
The different screens are put into containers (DIV1, DIV2, ...) which are styled to fit the screen (position: absolute; width: 100%; height: 100%; top: 0) and have overflow-x: scroll. The containers are positioned next to each other and the transition is as easy as animating their left property.
Easy so far.
The problem is the following: in this implementation the address bar doesn't disappear in the mobile browser when the user scrolls down.
I'm talking about this feature:
It's because mobile browsers do this only if the user scrolls the body - not a container in the body. There are several suggestions for solution but they don't work in all targeted platforms (Android Chrome and native browser, iPhone Safari) and are quite hacky. I'd like to preserve the original behavior of the browser as it is.
For that reason - apparently - need to leave the scrolling on the body. This means that containers have to be "full-length" (and not overflow-scroll), still positioned next to each other. This is where transitions become difficult if you think about it.
My current solution has the following steps when transitioning from DIV1 to DIV2:
top of DIV2 to the current scrollTop of the windowleft property so that DIV2 fills the screentop to 0 once the animation has finished so that the user can't scroll back further than the top of this screenTransitioning back to DIV1 is similar, in reverse. This actually works quite nice (although it's insanely complex and uses transition event listeners) but unfortunately there's a really ugly flickering effect between step 3 and 4 under iOS Safari because it renders the page right after step 3 without waiting for step 4.
I am looking for a framework-independent (vanilla JS) solution.
979
your approach was quite right. you probably get the flickering due to the scroll change position. the trick is to change the div's to position: fixed when scrolling and, than change them back afterwards.
the steps are:
position: fixed
scrollTop to 0 - scrollPosition
after the transition:
scrollTo()
position: fixed on the div's so the natural browser behavior works.here is a plain vanilla javascript example (also as fiddle):
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title></title>
<style type="text/css">
body {
margin: 0;
padding: 0;
}
.container {
position: absolute;
overflow: hidden;
width: 320px;
height: 5000px;
}
.screen {
position: absolute;
width: 320px;
height: 5000px;
transition: left 0.5s;
}
#screen1 {
background: linear-gradient(red, yellow);
}
#screen2 {
left: 320px;
background: linear-gradient(green, blue);
}
#button {
position: fixed;
left: 20px;
top: 20px;
width: 100px;
height: 50px;
background-color: white;
color: black;
}
</style>
</head>
<body>
<div class="container">
<div id="screen1" class="screen"></div>
<div id="screen2" class="screen"></div>
</div>
<div id="button">transition</div>
<script type="text/javascript">
var screenActive = 1;
var screen1 = document.getElementById('screen1');
var screen2 = document.getElementById('screen2');
var screen1ScrollTop = 0;
var screen2ScrollTop = 0;
function onClick()
{
console.log('getting the event');
if ( screenActive === 1 ) {
// will show screen 2
screen1ScrollTop = document.body.scrollTop;
screen1.style.position = 'fixed';
screen2.style.position = 'fixed';
screen1.style.top = (0 - screen1ScrollTop) + 'px';
screen2.style.top = (0 - screen2ScrollTop) + 'px';
screenActive = 2;
screen1.style.left = '-320px';
screen2.style.left = '0px';
}
else {
// will show screen 1
screen2ScrollTop = document.body.scrollTop;
screen1.style.position = 'fixed';
screen2.style.position = 'fixed';
screen1.style.top = (0 - screen1ScrollTop) + 'px';
screen2.style.top = (0 - screen2ScrollTop) + 'px';
screenActive = 1;
screen1.style.left = '0px';
screen2.style.left = '320px';
}
}
function onTransitionEnd(event)
{
if ( screenActive === 1 ) {
window.scrollTo(0, screen1ScrollTop);
}
else {
window.scrollTo(0, screen2ScrollTop);
}
screen1.style.position = 'absolute';
screen1.style.top = '0px';
screen2.style.position = 'absolute';
screen2.style.top = '0px';
}
screen1.addEventListener('webkitTransitionEnd', onTransitionEnd);
document.getElementById('button').addEventListener('click', onClick);
</script>
</body>
</html>
in this example i used the transitionEnd event. have in mind that if you have this event on both animating div's the event will fire twice. solutions to this are:
transitionEnd event use requestAnimationFrame() and animate manually via jsi also use a fixed height container for the transitions in this example. if you have div's with different height's you will have to change the containers height after the transition. ideally before reverting from position: fixed.
have in mind that changing a div to position: fixed will show it even if it is in a container with overflow: hidden. in the case of a mobile webapp this will not be an issue because the div's are outside of the screen. on a pc you might have to put another div over the other to hide the one transitioning in.
116
You can do something like this if you jquery is loaded
$(document).ready(function() {
if (navigator.userAgent.match(/Android/i)) {
window.scrollTo(0,0); // reset in case prev not scrolled
var nPageH = $(document).height();
var nViewH = window.outerHeight;
if (nViewH > nPageH) {
nViewH -= 250;
$('BODY').css('height',nViewH + 'px');
}
window.scrollTo(0,1);
}
});
For Iphone you have to do something like mentioned in below link
http://matt.might.net/articles/how-to-native-iphone-ipad-apps-in-javascript/
and for safari
https://developer.apple.com/library/safari/documentation/AppleApplications/Reference/SafariHTMLRef/Articles/MetaTags.html
Hope it helps you somehow!!
39
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