We need to remember some points before code Android Apps. The points are given below. Package - A package is a namespace. A package is essentially the directory (folder) to which source code belongs. Normally, this is a directory structure that uniquely identifies your application; such as com.helloworld.app. Then you can create packages within your application package that separates your code; such as com.helloworld.app.ui or com.helloworld.app.data. It basically lets you have two classes named Employee if they are in different packages. Class - A class is a blueprint for creating objects in class-based object-oriented programming; you should learn the basics of OOP and understand what an object is, what a class is, what is inheritance, polymorphism, encapsulation before learning anything else about Java. The basic structure for one of the Android project- Let's Explore each file AndroidManifest.xml : This is the Android definition file. It contains...