In one of the online documents that talks about appcache for HTML5, it indicates that the cached files get updated once an offline user reconnects. I checked the original HTML5 appcache definition by W3, and I am not able to find anything that supports this statement.
Does anyone know if this is to be true?
Thanks in advance
MDN says the following, although if you scroll up on that page it says it's being deprecated.
If an application cache exists, the browser loads the document and its associated resources directly from the cache, without accessing the network. This speeds up the document load time.
The browser then checks to see if the cache manifest has been updated on the server.
If the cache manifest has been updated, the browser downloads a new version of the manifest and the resources listed in the manifest. This is done in the background and does not affect performance significantly.
And logic tells me that it would also depend on the app you're using, server you're trying to connect to and any special settings it might have, how long your browser keeps it's history, what it keeps, and if you saved the page to view offline - whether or not you have all the code/images saved in the right location(s).
Example:
Imagine you saved a page to view offline, and that page has a JS event handler that ran a while loop that did an ajax request every n seconds to do something, like make a number on a page change as long as you were online... As long as the loop is running, you suddenly connect to the internet, and it makes the request to the proper url with the right arguments, then it should go through, even though the url in your browser might say something like file:///C:/Users/you/Desktop/....
I've done this before, even though my url was like the one above. One time I was using braintree's drop-in javascript to a website, and using it's api on my backend. Trying to load the page when offline = Nothing. Online = Updated the spot on the page just fine when I had the required arguments, and it was pointing to the right url. If I got offline again, I could refresh the page, see the same images loaded in the <div>, but I couldn't send any data with it.
I'm making a game that changes some of it's object depending on what music is playing. After each song has ended I want my audio context to load in a new source and analyze that. However whenever I tried to do that I've gotten the error that an audio object or buffer can't be called twice.
After some researching I learned that ctx.createMediaElementSource(MyHTML5AudioEl) lets you create a sourceNode that takes the source from a HTML5 object. With this I was able to loop through different song.
However for my game I need to play/analyze a 30 seconds "remote url" that comes out of the Spotify API. I might be wrong but ctx.createMediaElementSource(MyHTML5AudioEl)does not allow you to analyze a source that is on a remote site.
Also the game needs to work on Mobile Chrome, which createMediaElementSource(MyHTML5AudioEl) does not seem to work on.
I might be on the completely wrong path here but my main question is:
How can I switch remote songs urls in web audio api. With it being compatible with mobile chrome.
Thanks!
First, as you found out, you can't set the buffer again for an AudioBufferSource. The solution is to create a new one. AudioBufferSources are intended to be light-weight objects that you can easily create and use.
Second, in Chrome 42 and newer, createMediaElementSource requires appropriate CORS access so you have to make sure the remote url sends the appropriate headers and you set the crossOrigin attribute appropriately.
Finally, Mobile Chrome currently does not pass the data from an audio element through createMediaElementSource.
I have crawled the web quite a lot these days, but couldn't get any accurate information on how crossdomain.xml files behave in case of 302 redirects; especially with the sandboxes having changed significantly over the last versions!
I am relatively new to flash... so any advice is more than appreciated!
I have been working on a project lately that uses audio streams with some sort of CDN distribution! what happens is that a common url is triggered, and then the user is dynamically redirected to the next best server available. In my case, i have no access at the server side of things (at least not anytime soon). And the only path providing an appropriate crossdomain.xml is the one performing the redirect. All the other dynamic paths provide exclusively content!
http://resource.domain.com (valid crossdomain.xml)
302 => http://dyn1.domain.com/...
302 => http://dyn2.domain.com/...
302 => http://dyn3.domain.com/...
I noticed that flash doesn't care much if i try to load the audio stream with something like...
var req :URLRequest = new URLRequest("http://resource.domain.com");
var sound :Sound = new Sound(req); // ie. effectively playing http://dyn3.domain.com
sound.play();
It gets both redirecting, and streaming done well! and doesn't bother for any crossdomain file and starts playing!
Although when i try something different, like setting up some custom headers to the request and loading the file with URLStream instead, everything gets messy! Well, the redirect gets done, as expected but all of a sudden i need another crossdomain file in the redirected location!
Is there any explanation to whats happening and eventually ways to resolve this?!
Thanks for your time!
It comes as a site question : i noticed everything to work flawlessly while being in the local-trusted sandbox and errors happening mainly if not exclusively in the remote sandbox. is it possible that the local-trusted sandbox doesn't care about crossdomain policy files at all!?
Summary
Add crossdomain.xml to each CDN host or adopt to limited Sound functionality.
Details
SWF files that are assigned to the local-trusted sandbox can interact with any other SWF files and can load data from anywhere (remote or local).
Sound can load stuff from other domains that don't allow access using cross-domain policy with certain restrictions:
Certain operations dealing with sound are restricted. The data in a
loaded sound cannot be accessed by a file in a different domain unless
you implement a cross-domain policy file. Sound-related APIs that fall
under this restriction are Sound.id3, SoundMixer.computeSpectrum(),
SoundMixer.bufferTime, and the SoundTransform class.
Flash in general has pretty complex cross-domain policies but in your case the bottom line is that you'll need to have proper crossdmain.xml on each host except the one that serves the SWF:
3.1. If your file is served from http://resource.domain.com it's not required to have http://resource.domain.com/crossdomain.xml but it's really good to have one.
3.2. You will need to have proper http://dyn2.domain.com/crossdomain.xml explicitly allowing your SWF to access dyn2.domain.com to be able to use URLLoader and other APIs that provide access to raw loaded data.
3.3. There's a reason for these restrictions - cookies (and other ambient user credentials). If Flash would not require proper cross-domains after a redirect, one could access any domain with user cookies attached by simply loading his own redirector first. This means accessing all user cookie-protected data (e.g. mail.google.com) from any SWF on the internet that's running in your browser.
I have an unattended touch screen kiosk application which needs to be able to automatically reload the browser home page after a network outage has occurred. At the moment the browser will display an "Unable to connect to the internet" error and will wait for a manual reload to be carried out before proceeding. Can this be automated?
I've searched for plugins and have found some plugins which deal with auto-reload but they don't seem to work in this context. I am guessing that the plugin is only active when a page is loaded so in this case with an error condition, perhaps the plugin is not active.
One alternative might be to override the error page which is displayed by Chrome but I don't know if this is possible. I could then instantiate a Javascript timer to try a reload every n seconds for example. Is this possible?
I saw a suggestion to use frames to allow the outer frame (which is never refreshed) to keep trying the loading of an inner frame but I'm not keen to use frames unless there is no alternative. I also saw a suggestion to use AJAX calls to check if the network was working before attempting a page load but this seems overkill if there is a way to correct the error only when it has occurred rather than pre-empt an error for every page load.
Host system is Windows 7 by the way. I'm keen to keep the browser running if possible rather than kill and create a new browser process.
If you don't want to tackle chrome extension development, you could wrap your site in an iframe, and then periodically refresh the iframe from the parent frame. That way you don't need to worry about OS issues.
if the content were loaded from ajax from the start then the it could simply output a custom message on the page as it does a check via AJAX. Probably prevention over remedy is always recommended
Assuming linux, you could create an ifup script to simply relaunch the browser with something like
#!/bin/sh
killall google-chrome
DISPLAY=:0 google-chrome
On debian/ubuntu, edit /etc/network/interfaces to include a post-up line; Google ifupdown for other distros.
On windows, you'd do roughly the same with a PowerShell script.
If you really want the precise behaviour you describe (without restarting the whole browser), I suggest you develop a plugin/extension: http://code.google.com/chrome/extensions/getstarted.html
I know you are using Chrome, but in Firefox this is trivial by overriding the netError.xhtml page to do a setTimeout(location.reload, 10000);.
I'm writing a web app to be used offline on iOS. I've created a manifest, am serving it up as text/cache-manifest, and it usually works fine, when running inside Safari.
If I add it as an app to my home screen, then turn on Airplane mode, it can't open the app at all -- I get an error and it offers to close the app. (I thought this was the entire purpose of an offline app!)
When I load the app a first time when online, I can see in my logs that it's requesting every page listed in the manifest.
If I turn off Airplane mode, and load the app, I can see the first file it's requesting is my main.html file (which is both listed in the manifest, and has the manifest=... attribute). It then requests the manifest, and all my other files, getting 200's for all (and 304's for anything requested a second time during this load).
When I load the page in Chrome, and click around, the logs show the only thing it's trying to reach on the server is "/favicon.ico" (which is a 404, and which I don't think iOS Safari tries to load, anyway). All of the files listed in the manifest are valid and served without error.
The Chrome inspector lists, under "APPLICATION CACHE", all the cached files I've listed which I expect. The entire set of files is about 50 KB, way under any limit on offline resources that I've found.
Is this supposed to work, i.e., am I supposed to be able to create an offline iOS app using only HTML/CSS/JS? And where do I go about figuring out why it's failing to work offline?
(Related but doesn't sound quite the same to me, since it's about Safari and not a standalone app: "Can't get a web app to work offline on iPod")
I confirm that name 'cache.manifest' solved the offline caching problem in IOS 4.3. Other name simply did not work.
I found debugging HTML5 offline apps to be a pain. I found the code from this article helped me figure out what was wrong with my app:
http://jonathanstark.com/blog/2009/09/27/debugging-html-5-offline-application-cache/
Debugging HTML 5 Offline Application Cache
by Jonathan Stark
If you are looking to provide offline access to your web app, the Offline Application Cache available in HTML5 is killer. However, it’s a giant PITA to debug, especially if you’re still trying to get your head around it.
If you are struggling with the cache manifest, add the following JavaScript to your main HTML page and view the output in the console using Firebug in Firefox or Debug > Show Error Console in Safari.
If you have any questions, PLMK in the comments.
HTH,
j
var cacheStatusValues = [];
cacheStatusValues[0] = 'uncached';
cacheStatusValues[1] = 'idle';
cacheStatusValues[2] = 'checking';
cacheStatusValues[3] = 'downloading';
cacheStatusValues[4] = 'updateready';
cacheStatusValues[5] = 'obsolete';
var cache = window.applicationCache;
cache.addEventListener('cached', logEvent, false);
cache.addEventListener('checking', logEvent, false);
cache.addEventListener('downloading', logEvent, false);
cache.addEventListener('error', logEvent, false);
cache.addEventListener('noupdate', logEvent, false);
cache.addEventListener('obsolete', logEvent, false);
cache.addEventListener('progress', logEvent, false);
cache.addEventListener('updateready', logEvent, false);
function logEvent(e) {
var online, status, type, message;
online = (navigator.onLine) ? 'yes' : 'no';
status = cacheStatusValues[cache.status];
type = e.type;
message = 'online: ' + online;
message+= ', event: ' + type;
message+= ', status: ' + status;
if (type == 'error' && navigator.onLine) {
message+= ' (prolly a syntax error in manifest)';
}
console.log(message);
}
window.applicationCache.addEventListener(
'updateready',
function(){
window.applicationCache.swapCache();
console.log('swap cache has been called');
},
false
);
setInterval(function(){cache.update()}, 10000);
Sometimes an application cache group gets into a bad state in MobileSafari — it downloads every item in the cache and then fires a generic cache error event at the end. An application cache group, as per the spec, is based on the absolute URL of the manifest. I've found that when this error occurs, changing the path to the manifest (eg, cache2.manifest, etc) gives you a fresh cache group and circumvents the problem. I can vouch that all of our web apps work offline in full-screen with 4.2 and 4.3.
No offline web app (as of iOS 4.2) can run without an internet connection (which means Airplane mode, too) when using <meta name="apple-mobile-web-app-capable" content="yes" /> in the html head section. I have verified this with every example I've seen and the ones that use Safari to render the site work fine, but when you throw in that meta tag, it won't work. Try your app without it and you'll see what I mean.
I have found that clearing the Safari cache after enabling Airplane mode to be an effective way of testing whether the app is really functioning offline.
I have sometimes been fooled into thinking that the application cache was working when it wasn't.
I had struggled with this iOS 4.3 "no offline cache" problem since I updated my iPad to 4.3.1 from 4.2. I saw in another post in this site that it was working again in 4.3.2. So I updated by iPad again, now to iOS 4.3.3. But still couldn't get the offline caching to work until I renamed my manifest file to "cache.manifest". Then the caching started working again and I could run my HTML5 offline app from the Home Screen. I did not need to put the favicon.ico in to the cache manifest. And I also had full screen going (setting the "apple-mobile-web-app-capable" to "yes").
I have several working offline and on/offline web apps.
When I turn off airport mode, I get a request for the manifest and some other files.
I don't get requests for images, JavaScript, CSS or cached AJAX files.
If you see requests for your resources, IOS doesn't have them cached.
Safari in general is more picky with manifests.
I suggest you try Safari on your computer.
I have run into the same problem today on iOS 4.3. I was able to fix the problem by adding a favicon.ico file and also adding it to the manifest.
I've written an offline app that still seems to work in 4.2 and 4.2.1; the post is a little dusty, but the code still runs:
http://kentbrewster.com/backchannel/
Remy Sharp has a newer post with code that also works, here:
http://remysharp.com/2011/01/31/simple-offline-application/
His app:
http://rem.im/boggle/
After days of messing with getting offline web apps to work on an iPhone/iPod Touch using the Webserver's HTTP authentication, I discovered these useful nuggets:
Make sure Safari is at the URL root of the web app when tapping "Add to Home Screen". I used jQuery Mobile and was sometimes adding the link with"/#pageId". Caused trouble.
Run your Ajax calls in serial. This might only be important if your web app is using HTTP authentication, but my app was firing a whole slew of Ajax calls on page load in parallel and it caused the app to hang on the "apple-touch-startup-image".
Ajax calls are "successful" when offline (at least using Prototype.js). Test for an actual piece of data in the Ajax response, not just on the HTTP status. I used this to test for displaying cached (SQL) or live data.
In the manifest use "NETWORK:\n*\n". From what I could muster, this is a catch-all statement for anything not explicit in the "CACHE:" section. Use Chrome to make sure your manifest is correct. Look at Chrome's console for errors.
Not directly related, but tripped me up for a bit, openDatabase.transaction() calls are ASYNCHRONOUS! Meaning, the line of JS code after transaction (execute(), error(), success()) will execute BEFORE the success() function.
Good luck!
I found this solution that seemed to work for me, since I also ran into this problem during my development. This fix has worked fine for me so far and also for other people that I've asked to test it with, and I'm able to get it running offline (in airplane mode) and off the home screen after caching and whatnot. I've written a post about it on my site:
http://www.offlinewebapp.com/solved-apple-mobile-web-app-capable-manifest-error/
Delete your current web app icon on the home screen.
Go to settings and clear your Safari browser cache.
Double tap your home button to open the multitasking bar. Find the Safari one, hold your
finger down on it, and exit it.
Please let me know if this works for you also! Good luck!
I've written an app and it works fine through the mobile browser, but when adding the desktop... Doesnt work. I guess apple have given up on IOS4 and all efforts are now on OS5. Shame :(
I have one potential workaround for this - it seems a bit crazy, but here goes... I work with the cache.manifest and full screen apps a lot (here's a test if you need: http://www.mrspeaker.net/2010/07/12/argy-bargy/ - add to home screen then turn on flight mode and it launches - at least, as of iOS 4.2.1)
One weird thing I found is that sometimes it seems that some kind of "meta" information in files can mess them up from being cached - Have you ever noticed that in bash that if you do a "ls" some files (depending on your colour settings) are highlighted for no apparent reason? Files can have meta data that the operating system (I think) adds automagically - and there are ways to remove it... I can't remember why but here's some more details: Strip metadata from files in Snow Leopard
After tearing my hair out one day - and refusing to give up because I knew it SHOULD have worked... Chrome was saying it loaded all the files, but ended with a generic error. In the end I recreated the project structure with blank files and copy/pasted the contents over. It worked - started caching as it was supposed to!
When I looked at the files I noticed there was some meta info. I tried scrubbing this info and the original project worked again. I'm not sure this was the reason it worked again - perhaps it was just a coincidence.
Because it worked, I didn't think too much about it. The same problem happened again some months later and the copy/paste trick worked again. I was busy, so I didn't investigate further - but vowed I would get to the bottom of it the next time it happened.... but I haven't had to yet.
Phew. Anyway, glad I got to write that down somewhere...
[UPDATE: months and months later - I've not been able to reproduce this, so I don't think it's the metadata]