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问题:

I've run into a problem where I add a web app to my iPad home screen (iOS 5.0.1 iPad 2), and when I open it it appears to be caching something behind the scenes, independent of Safari.

I've cleared out everything from Safari that's available in Settings (Clear History and Clear Cookies & Data), and when I navigate to the web app with Safari I see the app in its current state. However if I open the home screen bookmark I get the app in a pre-changed state.

I've seen a lot of information about using a cache.manifest to cache resources for offline use, but I'm not sure if that's relevant to this since I would like the exact opposite: cache nothing.

I've gone to the level of not even testing external resources; if I change some arbitrary test string in the body element of my index.html, the home screen bookmark does not show the updated text.

回答1:

I think I found a workaround:

The new version of the site only appears when the index.html file changes.
(the first file to be loaded)

If you leave the index.html and only change some js in other files then the site doesn't load the new version.

回答2:

Another workaround is to add ?v=1 to your Javascript and CSS links. For example:

<link rel="stylesheet" type="text/css" media="all" href="./css/ipad.css?v=1">    
<script src="./js/ipad.js?v=1"></script>

It seems one doesn't have to update the number when your file has changed, as far as I can tell. Apparently, on an iPad 2 with the latest software update installed, it is enough to just hint at something dynamic.

回答3:

Create a cache.manifest that instructs it never to cache resources referenced by the main html page:

CACHE MANIFEST

# Version 1.0000

NETWORK:
*

Use it in your index.html:

<!DOCTYPE html>
<html manifest="cache.manifest">

Now whenever you change that manifest file -- for example, by increasing the version number in that comment -- the browser will redownload index.html also.

Ensure your page gets reloaded when the cache is updated:

<script>
function updateSite(event) {
    window.location.reload();
}
window.applicationCache.addEventListener('updateready', updateSite, false);
</script>

The Safari Developer Library has good documentation.

回答4:

For our iOS webclip apps we are using the following. So far no cache problems:

1- We have one cache manifest file called 'manifest.appcache.php'

<?php
    header("Cache-Control: max-age=0, no-cache, no-store, must-revalidate");
    header("Pragma: no-cache");
    header("Expires: Thu, 01 Jan 1970 00:00:01 GMT");
    header('Content-type: text/cache-manifest'); 
?>

CACHE MANIFEST

CACHE:
# Don't cache anything
FALLBACK:
# Nothing
NETWORK:
# Request everything from server
*

2 - In the HTML file we have:

<!DOCTYPE html>
<html lang="en" manifest="manifest.appcache.php">
    <head>
...

回答5:

I have an angular app I'm developing and ran into this issue when trying to test it on an iPad. By adding a meaningless query to the end of the url I was able to get a current version of all the assets.

www.somesite.com?meaninglessquery

回答6:

You can force the open web app to reload without using the cache if you have the Safari Web Inspector open and pointing at your open web app. With the Web Inspector active, press SHIFT + COMMAND + R (on a Mac). You may need to refresh one more time to trigger the updated assets.

回答7:

I've had luck with powering off the device. I had changed the app manifest; but presumably, you need a refresh or something to get the browser to look for it. Since I removed the browser chrome, there's no reset button. We tried "closing" the app (haha) and swiping the app away; but I presume iOS tends to keep things running anyway. Shutting down did the trick to get it to refresh.

Maybe there's some gesture for refresh I don't know. Perhaps one should tuck a little "check for updates" refresh button into cached web apps.