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.

eclipse content assist not working

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.

Check Java proposal

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.