Sweep transaction issue I have old (pre-random-number-bug) addresses in my android bitcoin wallet app, with 0 balance. After patch I am using a new address (with balance) and still keeping my old address in my wallet. Should I delete my old addresses from my android app?

Let's say some one cracked my old key, and imported it into his wallet. In this case, is it anyway possible for him to do a sweep transaction? I remember, something like this happened with blockchain.info / mywallet app but I am not very sure.

https://en.bitcoin.it/wiki/Sweepprivkey_proposal
You should be fine as long as you avoid sending coins specifically to that address, but I would delete it just to be safe. The app that I use doesn't let me delete addresses directly, so I just re-installed it.