If you have the “Documentation for Android” package and the javadoc info still isn’t showing up, make sure the Android library settings point to the right folder:
Project -> Settings -> Java Build Path, Libraries tab
Android X.X -> Android.jar -> Javadoc Location:
Should be something like “sdk_root/docs/reference/”.
And to view the docs for a class in editor for example:
you should choose show attached java doc in web browser from to popup that appear when hover the cursor on some declaration.