UI and screen layout design elements of Android

Android Screen UI Components

Up to this point, you have seen that the basic unit of an Android application is an Activity. An Activity displays the user interface of your application, which may contain widgets like buttons, labels, text boxes, etc. Typically, you define your UI using an XML file (for example, the main.xml file located in the res/layout folder), which may look like this:

 version="1.0" encoding="utf-8"?>