In my new app, I want to use a common theme for jelly bean, ics and gingerbread phones. That is, my app should not look different in different platforms.
I have seen some app like 'fancy' which is using jelly bean like theme in gingerbread also.
I'm new to android.
You can apply the Holo theme using the HoloEverywhere library. I use it in all my apps, and it works very well.
You have to add it as a library project to use it. If you use Git, you can add it as a submodule.