Detect if data is from cache

[tprochazka]

When I repeat GET request before date defined in Expires header, HTTPUrlCoonection witch enabled cache doesn't make request to server, but return data directly from cache, but I don't found way how to detect this situation.

Only way that I found is
System.currentTimeMillis() - Long.parseLong(getResponseHeader("X-Android-Received-Millis")) > 100;
But this depends on local time precision.
Will be much better if in response will be same special header which allow to recognize data from cache.
But it is probably problem of original AOSP implementation :-(

[swankjesse]

Can you use the cache's statistics reporting?

[tprochazka]

I don't think so. Only that I will remember cache hit counter before request and compare it with state after request, if it will be incremented data are from cache, but I don't know if it is thread save, it would require same external synchronization which completely disallow parallel downloading :-(

[orrc]

What's the issue with "local time precision"?

I'm sure Android's clock resolution is very high (i.e. better than 1 millisecond), or if you mean that the user (or network) can change the value of System.currentTimeMillis() at any point, then in any case you should be using Android's SystemClock.uptimeMillis().

[tprochazka]

I mean that user can have turned off automatic time synchronization and can have wrong system time. And my only solution that I found is compare current system time with time-stamp X-Android-Received-Millis. I can't use SystemClock.uptimeMillis() because it is counted from system start and I can't compare it with unix timestamp. Much better would be if cache will add some flag that data are from cache. But it will work only this library, not in original android implementation :-(

[swankjesse]

Craig and I are working hard to keep this version and the android version in sync! But the Android 4.0 code is complete and we can't add any new behavior there.