Introduction to Layouts

Android Layout is used to define the user interface which holds the UI controls or widgets that will dsiplay on the screen of an android application or activity. Generally, every application is combination of View and ViewGroup. An android application contains many activities and we can consider each activity is one page of the application. So, each activities contains multiple user interface components and those components are the instances of the View and ViewGroup.
A View usually draws something the user can see and interact with it e.g. Button,TextView etc.. Whereas a ViewGroup is an invisible container that defines the layout structure for View and other ViewGroup objects.It can hold more than one view or viewgroups.

In late 2007, the Open Handset Alliance (OHA) was formed. The OHA was a group of more than 30 hardware, software and telecommunications companies, including Google, Qualcomm, HTC, Intel, Samsung, Motorola, and other well known companies of then time(except NOKIA). The alliance's goal was to contribute to the development of the first open source platform for mobile devices.

Android OS versions

After acquiring the Android Inc., Google makes incremental changes to the OS with each release. This often includes security patches, performance improvements and other features.

• Android 1.0 : Released on September 23, 2008. Included a suite of Google apps, including Gmail, Maps, Calendar and YouTube.
• Android 1.5 (Cupcake) : Released on April 27, 2009. Introduced an onscreen virtual keyboard and the framework for third-party app widgets.
• Android 1.6 (Donut) : Released on September 15, 2009. Introduced the ability for the OS to run on different screen sizes and resolutions; added support for CDMA networks.
• Android 2.0 (Eclair) : Released on October 26, 2009. Added turn-by-turn voice navigation, real-time traffic information, pinch-to-zoom capability.
• Android 2.2 (Froyo) : Released on May 20, 2010. Added dock at the bottom of the home screen and voice actions, which allows users to tap an icon and speak a command. Also introduced support for Flash to the web browser.
• Android 2.3 (Gingerbread) : Released on December 6, 2010. Introduced black and green into the UI
• Android 3.0 to 3.2 (Honeycomb) : Released on February 22, 2011. This release was exclusive to tablets and introduced a blue, space-themed holographic design.
• Android 4.0 (Ice Cream Sandwich) : Released on October 18, 2011. Introduced a unified UI to both tablets and smartphones; emphasized swiping as a navigational method.
• ndroid 4.1 to 4.3 (Jelly Bean) : Released on July 9, 2012, Nov. 13, 2012, and July 24, 2013, respectively. Introduced Google Now, a day planner service. Added interactive notifications and improved voice search system.
• Android 4.4 (KitKat) : Released on October 31, 2013. Introduced lighter colors into the UI, along with a transparent status bar and white icons.
• Android 5.0 (Lollipop) : Released on November 12, 2014. Incorporated a card-based appearance in the design with elements such as notifications and Recent Apps list. Introduced hands-free voice control with the spoken "OK, Google" command.
• Android 6.0 (Marshmallow) : Released on October 5, 2015. This release marked Google's adoption of an annual release schedule. Introduced more granular app permissions and support for USB-C and fingerprint readers.
• Android 7.0 and 7.1 (Nougat) : Released on August 22, 2016 and Oct. 4, 2016, respectively. Introduced a native split-screen mode and the ability to bundle notifications by app.
• Android 8.0 and 8.1 (Oreo) : Released on August 21, 2017 and Dec. 5, 2017, respectively. These versions introduced a native picture-in-picture (PIP) mode and the ability to snooze notifications. Oreo was the first version to incorporate Project Treble, an effort by OEMs to provide more standardized software updates.
• Android 9.0 (Pie) : Released on August 6, 2018. This version replaced Back, Home and Overview buttons for a multifunctional Home button and a smaller Back button. Introduced productivity features, including suggested replies for messages and brightness management capabilities.
• Android 10 (Android Q) : Released on September 3, 2019. Abandoned the Back button in favor of a swipe-based approach to navigation. Introduced a dark theme and Focus Mode, which enables users to limit distractions from certain apps.
• Android 11 Beta : Released on February 19, 2020. This version introduced Android Trash Can And Bubble notification features.