I don't have enough karma to comment on Joe's answer above :(

Since Google's code search is discontinued, here is a direct link to the issue:

http://code.google.com/p/libs-for-android/source/browse/src/com/google/android/filecache/FileResponseCache.java#38

Original post:

Regarding the elegant connection.setUseCaches solution above: sadly, it won't work without some additional effort. You will need to install a ResponseCache using ResponseCache.setDefault. Otherwise, HttpURLConnection will silently ignore the setUseCaches(true) bit.

See the comments at the top of FileResponseCache.java for details:

Google's libs-for-android has a nice libraries for managing image and file cache.

http://code.google.com/p/libs-for-android/