What is Android App?
The Android operating system is the world's leading smartphone operating system. It has a global market share of 87.5% as of the third quarter of 2016.
As a UX designer, you will typically come across two operating systems: Android and iOS. Android is Google’s open-source mobile operating system. An operating system is system software that supports a product’s key functions. (just like the brain of your smartphone). Android is Google’s mobile operating system and a competitor to iOS (the OS for Apple Devices).
The UI or user interface for Android apps is designed as a hierarchy of layouts and widgets. Layouts are ViewGroup objects and containers that control how their child's views are positioned on the screen. All UI elements in an Android app are created using View and ViewGroup objects. A view is an object that draws something on the screen that the user can interact with it. A ViewGroup is an object that holds other View (and ViewGroup) objects to define the layout of the interface.
A mobile user interface (mobile UI) is the graphical and mostly touch-sensitive display on a mobile device, such as a smartphone or tablet. Widgets are visual objects and UI components such as buttons and text boxes.