keeping my question short, I have created an application with 3 activities, where A - list of categories, B - list of items, C - single item. Data displayed in B and C is pa
A simple and fast way to cache information or to keep track of the application state, is to extend the Application as described in this blog post.
This blog post forgets to add that you have to set your CustomApplication class in the manifest, like:
In my projects I stick to the singleton style via getInstance.
More resources: this answer, Global Variables in Android Apps and this blog post.