Expansion File implementation

Hello,

I'm a newbie in the world of the Developement, and It's been two weeks since I'm trying to implement expansion file to my Android application. The application only need to recover some images and I'm a bit stuck when I try to perform that in local. I can access to the path of my .zip using this kind of code :

String path = Environment.getExternalStorageDirectory() + "/expansionfile.zip"

But I can't unzip or access to my data without unzipping the file. Also, I can no longer use the images as drawables in my code, like (R.Drawable.x), and it is pretty troublesome because before exporting my images, I used them like this to display them in an ImageView:

public static int[] images = {R.drawable.1, R.drawable.2 };

And if I put something else as a int, it doesn't work. Is there some sample projects about Expansion Files or something else on which I could rely ? (I've tried to read the Android Developer's guide, but it confuses me much more).

Thanks !