Single page webapp screen transitions with maintaining the scroll position
Question
I'm build a single page web application for mobile phones. The application should implement transitions between "screens" (like any other mobile app eg 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:
- position
topof DIV2 to the currentscrollTopof the window - animate DIV1's and DIV2's
leftproperty so that DIV2 fills the screen - move DIV2's
topto0once the animation has finished so that the user can't scroll back further than the top of this screen - Move the window's scrollTop to 0
- Hide DIV1 (in case it's longer than DIV2)
Transitioning 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.
5 answers
solution1
2 2014-08-20 01:08:11
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
Hope it helps you somehow!!
solution2
1 ACCPTED 2014-08-21 19:30:32
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:
- save the current scroll vertical position
- change the div's to
position: fixed - change the div's
scrollTopto0 - scrollPosition - start horizontal transition
after the transition:
- change the window's scroll position with
scrollTo() - revert
position: fixedon 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:
- if the timings are identical just use the event on one div (used in the example)
- use the event an all div's but just do changes respective to the event's div
- animate a container with all the div's inside. so you will just need one event.
- if you can not use the
transitionEndevent userequestAnimationFrame()and animate manually via js
i 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.
solution3
0 2014-08-16 22:06:36
Using window.scrollTo(0,1); you can make the navigation bar disappear. It's a hack, but it works.
solution4
0 2014-08-19 20:00:40
Why not:
<body>
<div id=header>Header</div>
<div id=content>Scrollable Content</div>
<div id=footer>Footer</div>
</body>
Then the CSS:
#header,#footer,#content{
left:0%;
right:0%;
}
#header,#footer{
position:fixed;
}
#header{
top:0%;
height:30px;
}
#footer{
bottom:0%;
height:30px;
}
#content{
position:absolute;
top:30px;
height:1000px; /*Whatever you need it to be*/
}
The touch screen responds to the <body> tag, not the <div> , so setting position:fixed on #header and #footer allow them to maintain position relative to the window, regardless of scroll position, and then when the user scrolls the content, they scroll the <body>
EDIT: I have implemented this as an example:
Visit on your mobile device.
solution5
0 2014-08-21 19:54:27
I think I figured it out, it's tricky.
In short: in the question I describe my current solution that flickers in iOS. At point 3 you need to add position: fixed to DIV2. That way it's gonna "stick" and you avoid the flickering at point 4. Then you need to delay point 4 a couple of milliseconds ( setTimeout , 500ms worked for me but probably could be smaller) and set position: absolute again to DIV2 right after window.scrollTo . I'm not sure that's the reason you need the delay, but without it the screen still flickers.
If there's interest I can post a PoC later.
As a side note, I found it pretty disappointing that most if the people who answered did not read the question entirely or just completely ignored some criteria (framework-independence, keeping original scroll behavior). Most of them suggested solutions that I already specifically linked in the question as not acceptable. Some of them even reclaim when get downvoted.
EDIT: dreamlab answered just a couple of minutes before I posted my solution. Both solutions use position: fixed . His solution is more detailed too. He deserves the bounty.
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