Debugging a native library on Android

Question

I want to debug and put breakpoints in my C ++ library. Now my workspace is as follows:

/-Main App
/-Library1 (just Android library)
/-NativeLibrary

MainApp has included both libraries, Library1 and NativeLibrary, and I want to be able to put breakpoints in my NativeLibrary. I have read this post: https://stackoverflow.com/a/3129605/2327 , but when I try to select my MainApp as a project, I cannot do this.

So how can I debug my own library?