I want to decrease the time where a jQuery Mobile site shows a blank page during pageload. Due to AdSense I had to include data-ajax="false", so there are no smooth transitions anymore and worse, the header disapears as something keeps the page from rendering during page load.
The timeline shows a significant delay after load of the html document and after loading all CSS/JS resources:
What could be the cause of this and would it be possible to eliminate this gap?
Related
I'm using Jquery Mobile in my website, and I have a page with popups. I don't directly navigate to this page, but I inject the content with Ajax :
$("#myDiv").html(data).enhanceWithin();
The problem is that occasionally, when the page is loading, the popups content appear for half a second on the screen and then disappear...
Is there a way to avoid that ?
sometimes, It will show, sometimes, not, so, how to ensure the ajax loading indicator show in jquery mobile?
Unless there's a major problem in your app, what you have described is a normal situation.
While page transition can take a lot of time (usual page loading/transition time on desktop browsers is 670 ms), page loading into the DOM takes only few miliseconds (usually 3-5 ms). AJAX loader will show only if page loading (into the DOM) takes more then 10ms. Other page transition actions don't count into AJAX call so animation will not be shown after page has been loaded into the DOM.
Actions during page loading/transition:
Page load and processing: 3ms (AJAX loader will show only during this action, if it takes more then 10ms)
Page enhance: 45ms
Transition: 604ms
To read more about this take a look at my other ARTICLE, or find it HERE, search for the chapter called: Page Change Times
One more thing, unless you are using normal page loading AJAX loader will not be show (if your link has an attribute rel="external" or data-ajax="false").
In order to ensure that ajax navigation is done by default Jquery Mobile will add ajax navigation to pages loaded into the DOM so long as you do NOT add the data-ajax="false" attribute to your links and buttons. Otherwise chances are you may have added a global modification that has disabled ajax navigation on certain pages.
OR you could have rel="external" as an attribute in some of your links and buttons, which disables ajax navigation.
If you could be more specific, ie post a jsfiddle example of your problem, I could give you a better explanation. Also please mention what version of Jquery Mobile you are using.
when you do this:
$.mobile.changePage( "#page-home", { transition: "none"} );
add this:
$.mobile.showPageLoadingMsg();
don't forget to add
$.mobile.hidePageLoadingMsg();
at the end of the pageLoad function
I've happily developed a mobile website using JQuery Mobile, and everything works beautifully except for a noticeable delay hiding the browser address bar on the homepage (around 5 seconds on iOS Safari).
AJAX transitions mean it's always hidden from that point on, but on the opening page the site logo is hidden for up to 5 seconds after the page has loaded, giving it a very unbranded and confusing feel for the user.
Can anyone think of any reasons for the delay / ways to speed it up? There are no large images loading on the page, putting an alert in the window load event fires way before the address bar is hidden and the setTimeout delays on the code firing in the JQuery Mobile code are only of the order of 20 ms.
Thanks in advance, Ted
I use Mobile Boilerplate's MBP.hideUrlBarOnLoad() and am not experiencing a five second delay.
Hide URL Bar
MBP.hideUrlBarOnLoad is used to hide the URL bar at the top of mobile
Safari on your iOS. Mobile space is limited and this helps to leverage
every pixel on the screen to maximize display area.
Sadly I've had to resort to a pretty hacky solution to this.
I've added a dummy 60px high spacer div at the top of the page, which pushes down the title, so it is visible at all times. This is then hidden by Javascript after 5 second setTimeout call, which is roughly equivalent to the delay we get on the url bar being auto-hidden by JQuery mobile.
This is only necessary on the start page, and other ones that we've had to load on rel="external" links, due to us making the error of mixing an ASP.net site that requires postback with JQuery mobile, but that's another story...
I've seen this happen when the content is Safari "Reader" compatible (when you see the "Reader" label next to the url on the url bar). I'm not sure but if this is the case maybe you could try to make your content less Reader compatible.
UIWebView successfully loaded content, but is not displaying it. UIWebView is just white screen. BUT, if you click on this UIWebView it will process your click. For example, if you click at place where the link should be (but in fact the white space), the click processed and next page loaded and displayed OK.
The bug is unstable. I got it only with local HTML file (our homepage, it generated locally), web content loads OK. It happens in 20% cases. But in the same time, it is very sticky. Once got white screen, you can reload this page many times and see white screen (but if you click on invisible link, another page displayed successfully). Sometimes it occasionally appears without any reason. Your can "scroll" this blank screen up and down and it occasionally loaded. This local HTML has a lot of stuff, embedded images, javascripts, etc, and it could be javascript problem, but I can't explain how it can be, that content invisible, but still clickable.
It happens in iPod real device and iPhone simulator 4.3, but can't reproduce it on iPad or iPad simulator.
I spent a whole day trying resolve this. Any ideas?
I solved this!
This really weird behaviour of UIWebView was caused by javascript code. The javascript was like (simplified):
<script>
function onLoad() {
location.href='xxx://pageLoaded';
}
</script>
<body onload='onLoad();'>
The idea of this code was to inform app about the fact that page was loaded. In the app I catch request to xxx://pageLoaded and cancel it (in shouldStartLoadWithRequest). Because request cancellation, I didn't expect any problems here. Espesially, I didn't expect that content will become invisible, but still clicable. I added timer (setTimeout) between onload fires and location.href change. It solves the problem.
NOTE: I know about webViewDidFinishLoad event in UIWebView. This is very simplified example just to explain the problem and the solution. Real javascript is more sophisticated and what it is doing can't be reached by simple use webViewDidFinishLoad.
I've observed this on iOS 4.3 to 5.0. When you create a even a simple offline web app, meaning one HTML file + few assets such as CSS and JS (all present in the cache manifest), it works offline (I tested in Airplane Mode) – BUT, when you add such an app to your home screen and open it in fullscreen mode, it first displays initial content, then everything disappears (page becomes white) for half a second or more, then content reappears again.
You can see this by adding Glyphboard, a well-known and useful offline web app, to your iOS home screen and launching it a few times. You should see the white flash effect every time you load it.
This is a big problem because it gives away the non-nativeness of an app and gives the impression that the app is non-optimized for performance and buggy.
I've tried finding reports about this but all I can find is rumors and misconceptions about the iOS 4.3 JavaScript rendering engine fiasco, which doesn't need at all be related to this issue. But in iOS version 3 I distincly remember not ever seeing the white flash.
Clearing the screen and other artifacts while rendering is a common issue of HTML rendering due to the progressive nature of HTML. The concept is that the browser should draw as early and often as possible and render styles/scripts/content as they become available. It's possible the markup has an issue where all rendering is delayed until some content or a script is available. This could happen if:
You have dynamic heights based on image dimensions but you haven't
set the image dimensions in the markup or CSS.
Your layout is based on tables and you aren't using 'table-layout:fixed` in CSS.
Your HTML uses inline scripts with document.write().
You have some kind of onLoad() function that reveals/modifies content.
You link to an external stylesheet.
You're using uncacheable external content or you've disabled caching.
You're using external content that's returning 404 or isn't available offline.
Has your HTML/CSS changed between testing IOS versions?
I've found this to be caused by the use of:
<meta name="viewport" content="width=device-width initial-scale=1.0 maximum-scale=1.0 user-scalable=0">
With a minimal page, I get a white flash between the apple-touch-startup-image and the page contents if I use the viewport meta tag. If I take out the tag, no flash.
It's possible to work around the problem by setting the tag programatically.
I think what happens here is that iOS takes a screenshot from the page when it is added to the main menu. Then this screenshot is displayed during the application loads (WebKit loads). WebKit starts rendering the page and the page itself is constructed in such a way that the page content is not instantly available, leading to a white flash which is a rendered page when page content is not yet there,
You can avoid the problem to a certain level by building your JS/CSS so that it loads the initial HTML view fast and then lazily loads / builds the rest of the resources on the background. Also you can set a custom loading screen instead of the default screenshot iOS uses from the page.
Maybe if you can take yourself a screenshot of your app and then have something like this:
<body style="background: white url('my-initial-loading-screen.png')" />
... and make sure image is available and comes from manifest.
Or even better, have loading screen which does not require any external resources to show (just plain HTML) so you know the browser doesn't need to load anything.