How to debug Android source code in Eclipse?

Today, I wanted to know what's going on inside Android because it was keep throwing an exception . So i wanted to check how to debug an Android application right from Eclipse IDE. When I googled I found this link,

http://android.opensourceror.org/2010/01/18/android-source/

but it says how to debug a single version of android eg. Cupcake. Now problem is how to debug multiple versions of Android ?

it's easy.

all you have to do is open the .project in notepad
\workspace\.metadata\.plugins\org.eclipse.jdt.core\.org.eclipse.jdt.core.external.folders

and another element to the section.

         .link0
         2
         C:/Aruna/Android/android-sdk_r08-windows/android-sdk-windows/Cupcake
  
     
         .link1
         2
         C:/Aruna/Android/android-sdk_r08-windows/android-sdk-windows/Donut