How can I scroll to a page element in jQuery Mobile? - javascript

I have a long jQuery mobile page and would like to scroll to an element halfway down this page after the page loads.
So far I've tried a few things, the most successful being:
jQuery(document).bind("mobileinit", function() {
var target;
// if there's an element with id 'current_user'
if ($("#current_user").length > 0) {
// find this element's offset position
target = $("#current_user").get(0).offsetTop;
// scroll the page to that position
return $.mobile.silentScroll(target);
}
});
This works but then the page position is reset when the DOM is fully loaded. Can anyone suggest a better approach?
Thanks

A bit late, but I think I have a reliable solution with no need for setTimeout(). After a quick look into the code, it seems that JQM 1.2.0 issues a silentScroll(0) on window.load for chromeless viewport on iOS. See jquery.mobile-1.2.0.js, line 9145:
// window load event
// hide iOS browser chrome on load
$window.load( $.mobile.silentScroll );
What happens is that this conflicts with applicative calls to silentScroll(). Called too early, the framework scrolls back to top. Called too late, the UI flashes.
The solution is to bind a one-shot handler to the 'silentscroll' event that calls window.scrollTo() directly (silentScroll() is little more than an asynchronous window.scrollTo() anyway). That way, we capture the first JQM-issued silentScroll(0) and scroll to our position immediately.
For example, here is the code I use for deep linking to named elements (be sure to disable ajax load on inbound links with data-ajax="false"). Known anchor names are #unread and #p<ID>. The header is fixed and uses the #header ID.
$(document).bind('pageshow',function(e) {
var $anchor;
console.log("location.hash="+location.hash);
if (location.hash == "#unread" || location.hash.substr(0,2) == "#p") {
// Use anchor name as ID for the element to scroll to.
$anchor = $(location.hash);
}
if ($anchor) {
// Get y pos of anchor element.
var pos = $anchor.offset().top;
// Our header is fixed so offset pos by height.
pos -= $('#header').outerHeight();
// Don't use silentScroll() as it interferes with the automatic
// silentScroll(0) call done by JQM on page load. Instead, register
// a one-shot 'silentscroll' handler that performs a plain
// window.scrollTo() afterward.
$(document).bind('silentscroll',function(e,data) {
$(this).unbind(e);
window.scrollTo(0, pos);
});
}
});
No more UI flashes, and it seems to work reliably.

The event you're looking for is "pageshow".

I was digging a lot this issue, also at jQuery mobile official forum.
Currently it seems that there is no solution (at least for me).
I tried different events (mobileinit, pageshow) and different functions (silentscroll, scrolltop) as suggested above, but, as a result, I always have page scrolled until all images and html is finished loading, when page is scrolled to top again!
Partial and not really efficient solution is using a timer as suggested in comment to sgliser's answer; unfortunately with a timeout is difficult to know when page will be fully loaded and if scroll happened before that, it will scroll back to top at the end of load, while if it happens too long after page has fully loaded, the user is already scrolling page manually, and further automated scroll will create confusion.
Additionally, would be useful to have silentscroll or other function to address a specific id or class and not plain pixels, because with different browsers, resolutions and devices it may give different and not correct positioning of the scroll.
Hope someone will find a smarter and more efficient solution than this.

Related

Generic code to fade in divs with particular class, remove function after first run

I'm trying to create a generic function that can be placed just once in my site and work across multiple pages, nice and lightweight.
I want to be able to make certain divs on the site fade-in when you reach 10px above them on the scroll.
I want to do this by simply adding the following attributes to my divs:
.fade-in-block
#specific-block-name
The idea is that I could go through the site, add this class and an ID, and the animation would work.
I almost have it working except for one thing, the scroll listening constantly continues to console.log after the function has been called. I don't like this as it feels like it's going to be constantly trying to apply the animation, which won't really be seen from the front-end but I feel the constant maths behind the scenes could slow stuff down.
Here is my jQuery:
$('body .fade-in-block').each(function(){
var block = '#'+$(this).attr('id');
console.log('Block class is = '+block);
var offset = $(block).offset().top;
var $w = $(window).scroll(function () {
if ($w.scrollTop() > offset - 10) {
console.log('reached block turn-on point for '+block);
$(block).removeAttr('id'); // remove the ID from the element so the script doesn't continue to find the element
// fade and rise animation here
}
});
});
And here is a JSFiddle. It works just fine, but once you hit the block you'll see it logs constantly every pixel scrolled.
I tried to remedy this by removing the selecting id from the element once the event has occurred, but it continues to run.
Scroll and resize events both have this problem and the solution is said to be debouncing. However, I've never actually gotten debouncing to work properly. Instead I typically create a sort of switch that is turned off once the scroll condition has activated. In your case, since you have multiple elements, you would need to assign a switch to each element.
$(window).on('scroll', function(){
$('.fade-in-block').each(function(){
var appear = $(this).attr('data-appeared');
if(!appear){
$(this).attr('data-appeared', true);
//do something to $(this)
}
})
})
Here I'm adding a data attribute after it has appeared and checking for it again once it has.

PhantomJS Get Document Elements Positions

I am using PhantomJS to get positions of certain elements on the page, for instance iframes or objects. Presently I
page.includeJs("http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js", function() {
page.evaluate(function() {
// Select attr etc..
position = $(this).position();
offset = $(this).offset();
});
});
I've tried adding $(window).load() to the formula but it still isn't returning the correct element position a lot of the time. Especially with iFrames and Objects. Perhaps they're positioned after the DOM has loaded? Either way does anyone have any ideas how I can improve or change method to get much more accurate positions?
Kind regards,
Fab
What position is being returned? How is it incorrect?
A few things.
1) When page.evaluate is invoked the page has already loaded. That happens at page.open time. window.onload will never fire inside page.evaluate; it has already fired.
2) I don't know what this is within page.evaluate.
3) Within a PhantomJS context, there's no real reason to use jQuery. You're better off using standard constructs such as document.documentElement.scrollTop.
Try this:
page.evaluate(function() {
console.log(document.documentElement.scrollTop);
console.log(document.getElementById("my-frame").getBoundingClientRect());
});

Infinite Scroll + Swipe.js

Background:
I'm making a portfolio site utilising both Swipe.js and Infinite Ajax Scroll (JQ).
Problem:
When the content from extra pages is loaded into the current page, it is not processed by the already-loaded Swipe.js script. This means that the new content doesn't have it's mark-up changed (needed for the swipe functionality to work).
I think I need to get the Swipe.js script to fire after each page re-load. Would that fix it? Please explain this to me like I'm an 8yr old. JS is not a strong suit...
Demo:
http://hatchcreative.co.nz/tomo
You can see that as the page loads new content, the buttons on either side of the sliders no longer work.
Yes you're right, after the images are loaded you have to create a new Swipe instance on these new elements (as they weren't there at the beginning, when the page was loaded).
Based on the docs of infinite scroll you can use onRenderComplete.
So you had your jQuery.ias constructor like this:
jQuery.ias({
// ... your settings...
onRenderComplete: function(items) {
$(items).each(function(index, element) {
new Swipe(element);
});
}
});
This should work this way somehow, but I am not exactly sure; I haven't worked with these libraries yet.
Edit:
After some more inspection of your code, I saw you had some inline click handler like: onclick='two.prev();return false;'.
You need to remove this and add your onclick handle in the same onRenderComplete function.
onRenderComplete: function(items) {
var swipe;
$(items).each(function(index, element) {
swipe = new Swipe(element);
});
// find tags with the class 'forward' inside the current element and add the handler
$(element).find('.forward').on('click', function() {
swipe.next();
});
// ... also for previous
}
By the way: Usually you should provide a jsFiddle with your important code parts, so it's easier for us to get the problem, and the question is not getting obsolote when the linked page changes.

Reload the page just once if a div is above certain position

I want to reload the page only once if a given div is positioned higher than position:absolute; top:15%.
I think this could be done with jQuery's .css method, something like:
if ('#mydive').css('top') > '15%' {
//reload the page
}
Could someone suggest a simple solution, preferably jQuery or pure JavaScript?
If what you meant is the top of the document, you can probably try:
var percent = .15; // 15%
if ($('#yourdiv').offset().top > ($(document).height() * percent)) {
window.location.reload();
}
// if by pixels
var pixels = 10; // 10px
if ($('#yourdiv').offset().top > pixels) {
window.location.reload();
}
You can check the current position of a div using the Computed Style
If you are have a like an animation or a drag and drop, you can use the onmousemove event to track the position of the div. but be careful the mousemove will be trigger for every pixel it moves and it my use lots of process time, so be wise on how you use it :)
Well, it is rather hard to say how you should determine the position of the div since you presented no code, but basically you should write a function that fetches the window height and the offset of the div relative to the top of the window to determine whether it is higher than 15%. You then need to call this function every time using the window.onscroll event listener. When the function returns true, trigger trigger window.location.reload(true) to reload the page. I imagine this could be done fairly easily in jQuery as well.
the above answers point you in the right way, but in order to "reload the page only once", you need an extra ingredient. you need a way to store a flag that points out whether the page has already been reloaded or not.
Say you follow tradyblix's code.
You should check for that flag before reloading your page :
if (hasReloaded() && $('#yourdiv').offset().top > ($(document).height() * percent)) {
reload();
}
where hasReloaded is a function that determins if the page has been reloaded, and it can be either a function that sends an ajax request to a server, that checks a cookie or even the localStorage object:
function hasReloaded(){
return !!localStorage['reloaded'];
}
In order to set that flag, your reload function needs to access the localStorage (or cookie or ajax server response) :
function reload(){
localStorage['reloaded'] = true;
window.location.reload();
}
This is just a sketch of how you should write this functionality.

Prevent/stop auto anchor link from occurring

I need to prevent the automatic scroll-to behavior in the browser when using link.html#idX and <div id="idX"/>.
The problem I am trying to solve is where I'm trying to do a custom scroll-to functionality on page load by detecting the anchor in the url, but so far have not been able to prevent the automatic scrolling functionality (specifically in Firefox).
Any ideas? I have tried preventDefault() on the $(window).load() handler, which did not seem to work.
Let me reiterate this is for links that are not clicked within the page that scrolls; it is for links that scroll on page load. Think of clicking on a link from another website with an #anchor in the link. What prevents that autoscroll to the id?
Everyone understand I'm not looking for a workaround; I need to know if (and how) it's possible to prevent autoscrolling to #anchors on page load.
NOTE
This isn't really an answer to the question, just a simple race-condition-style kluge.
Use jQuery's scrollTo plugin to scroll back to the top of the page, then reanimate the scroll using something custom. If the browser/computer is quick enough, there's no "flash" on the page.
I feel dirty just suggesting this...
$(document).ready(function(){
// fix the url#id scrollto "effect" (that can't be
// aborted apparently in FF), by scrolling back
// to the top of the page.
$.scrollTo('body',0);
otherAnimateStuffHappensNow();
});
Credit goes to wombleton for pointing it out. Thanks!
This seems the only option I can see with ids:
$(document).ready(function() {
$.scrollTo('0px');
});
It doesn't automatically scroll to classes.
So if you identify your divs with unique classes you will lose a bit of speed with looking up elements but gain the behaviour you're after.
(Thanks, by the way, for pointing out the scroll-to-id feature! Never knew it existed.)
EDIT:
I know this is an old thread but i found something without the need to scroll. Run this first before any other scripts. It puts an anchor before the first element on the page that prevents the scroll because it is on top of the page.
function getAnchor(sUrl)
{
if( typeof sUrl == 'string' )
{
var i = sUrl.indexOf( '#' );
if( i >= 0 )
{ return sUrl.substr( i+1 ).replace(/ /g, ''); }
}
return '';
};
var s = getAnchor(window.location.href);
if( s.length > 0 )
{ $('<a name="'+s+'"/>').insertBefore($('body').first()); }
Cheers!
Erwin Haantjes
Scroll first to top (fast, no effects pls), and then call your scroll function. (I know its not so pretty)
or just use a prefix
This worked well for me:
1- put this on your css file
a[name] { position: absolute; top: 0px }
2- put this on your document.ready bind right before you start animating (if you're animating at all)
$("a[name]").css("position","relative");
Might need tweaking depending on your stylesheet/code but you get the idea.
Credit to: http://cssbeauty.com/skillshare/discussion/1882/disable-anchor-jump/

Categories

Resources