When I downloaded the Eclipse Indigo, I got surprised by checking that the intellisense(auto complete) & content assist are not working in my android project which was working fine in Eclipse Galileo version. After searching the forums over the internet, I found out solution to fix this issue.
This screen shot shows the actual problem.
The solution I tried first and worked straight away is
Check Java proposals options from Content Assist
Go to Eclipse Window -> Preferences -> Java -> Editor -> Content Assist -> Advanced -> Check Java Proposals as shown below.
You may also check other options like java type proposal if required, enabling the Java proposal option done the job for me.
There is one another solution I found over the forums try this if above setting does not work for you.
Create new work space
Create new work space and import your existing project in to that work space.