In android R.java is used to resources defined in XML files. It also contains access to resources such as drawables, layout, string, arrays, and basically anything you can declare in resources.
The first step create a simple Android Application using Eclipse IDE. Follow of the some steps.
The Activity class froms the basis for all your user interface (UI) screens. You learn to create Activities and gain an understanding of their lifecycles and how they affect the application lifetime and priority.
Finally , you are introduced to some of the Activitiy subclass that simplify resource management for some common UI patterns, such as map and list based Activities.