[Eclipse]: Autocomplete Feature Shows only "No Default Proposals" on Eclipse

A Japanese version of this document is in TechRacho. I got new MacBookAir (Mid 2011, Lion) and build my development environment from scratch. When I installed Eclipse 3.7.0 + ADT, the code assist feature (autocomplete) does not work. It shows only "No Default Proposals" and no any other nominations available.

I solved this problem. This may not be ADT dependent, it may apply to all other Eclipse-based IDE.