Android Basics

R. Java

 It is an autogenerated file generated by AAPT (Android Asset packaging Tool) that contains resources ID in the form of integer ID for all the resources in res folder.

View

It is the basic building block by which interface is made up of or we can say View is the control by which user interact with the app i.e TextView, Button, Checkbox, EditText etc. View is inherited from android.view.View. 

NOTE- We can also write the view code in JAVA file but for separation purpose we write  it in xml file.