The Android SDK archive now only
contains the tools. It no longer comes
populated with a specific Android
platform or Google add-on. Instead you
use the SDK Manager to install or
update SDK components such as
platforms, tools, add-ons, and
documentation.
This thread is a little old, and I am brand new to this, but I think I found the preferred solution.
First, I assume that you are using Eclipse and the Android ADT plugin.
In Eclipse, choose Window/Android SDK Manager. In the display, expand the entry for the MOST RECENT PLATFORM, even if that is not the platform that your are developing for. As of Jan 2012, it is "Android 4.0.3 (API 15)". When expanded, the first entry is "Documentation for Android SDK" Click the checkbox next to it, and then click the "Install" button.
When done, you should have a new directory in your "android-sdks" called "doc". Look for "offline.html" in there. Since this is packaged with the most recent version, it will document the most recent platform, but it should also show the APIs for previous versions.
select "docs/reference/" in archive extracted directory
press validate... to validate this javadoc.
In your IntelliJ IDEA
at file -> Project Structure
Select SDKs from left panel -> select your sdk from middle panel -> in right panel go to Documentation Paths tab so click plus icon and select docs/reference/ in archive extracted directory.