Understand the platform basics

Android Platform

Android is a mobile operating system designed primarily for touchscreen devices.

Android boots to the Lock screen, which controls access to the Home screens and thereby access to the device.

Home screen is a place for app shortcuts, folders, and widgets, and a device can have several home screens. Each home screen has a Status bar at the top for notifications and statuses, a Favorites tray at the bottom for app shortcuts and folders, and a Navigation bar after the favorites tray for devices that do not have hardware keys – Back, Home, and Recents. Swiping a home screen panel left or right switches the home screen. The home screen is accessed through the Home button on the navigation bar or the Home key on the device.

All Apps screen lists the entire set of apps and widgets installed on the device, and is accessed through the All Apps button in the favorites tray of the home screen.

Recents Screen lists recently used apps to efficiently switch between multiple ongoing tasks, and is accessed through the Recents button on the navigation bar or the Recents key on the device.

An app typically has an Action bar for controlling important actions in the current view and switching between views, a Navigation drawer for listing the navigation options, and a Content area for displaying the content of the app. Additional action bars are in the form of the Top bar for tabs and spinners, and the Bottom bar for additional actions and action overflow.

The previous screen is accessed through the Back button on the navigation bar or the Back key on the device. The back key is also used to dismiss floating windows, contextual action bars, highlights from selected items, and hiding the onscreen keyboard.