While watching some video tutorials about android development, I found that the lecturer can call out the class completion helper dialog during typing class names. However, I only have the function/variable autocompletion feature after typing a . after a class name in my eclipse. Without entering the class name correctly, I can not get any help from eclipse, which is quite strange comparing to what I've seen for others.

Well, it seems that many people encountered the same problem as I did. This is being discussed on various posts. One way to make it work is to check the "Java Proposal" in Eclipse's Preferences > Java > Editor > Content Assist > Advanced'.

But for me, it seems that something's wrong with my workspace configurations too. The answer from hoipolloi in following reference post helped me to fix this issue. Here's his suggestion:
  • Quit Eclipse
  • Go to workspace/.metadata/.plugins/org.eclipse.jdt.core
  • Remove *.index and savedIndexNames.txt
  • Restart Eclipse and search Ctrl+T for the offending type. The indexes will be rebuilt.