Purchasing a domain and not using it would probably not be trademark infringement. Once you start using the domain, then you could be infringing, but there are so many details to consider that you can't answer that in the abstract.
Where did you read that "Android lovers" would not be trademark infringement? In many situations, that would be trademark infringement. Here are the Android TM guidelines.
Google says you can't create an Android Media Player. Goole appears to allow sites like androidcentral.com and androidcommunity.com to operate, but I bet other companies (e.g., Apple) would take legal action against you in similar situations. You don't see many domains with iphone in the name for example.