Something about an Android Application Components

Android Application Components

Application components are the essential building blocks of an Android application. These components are loosely coupled by the application manifest file AndroidManifest.xml that describes each component of the application and how they interact.

There are following four main components that can be used within an Android application:

Components	Description
Activities	They dictate the UI and handle the user interaction to the smartphone screen
Services	They handle background processing associated with an application.
Broadcast Receivers	They handle communication between Android OS and applications.
Content Providers	They handle data and database management issues.

Activities

An activity represents a single screen with a user interface. For example, an email application might have one activity that shows a list of new emails, another activity to compose an email, and another activity for reading emails. If an application has more than one activity, then one of them should be marked as the activity that is presented when the application is launched.

An activity is implemented as a subclass of Activity class as follows:

public class MainActivity extends Activity {

}

Services

A service is a component that runs in the background to perform long-running operations. For example, a service might play music in the background while the user is in a different application, or it might fetch data over the network without blocking user interaction with an activity.

A service is implemented as a subclass of Service class as follows:

public class MyService extends Service {

}

Broadcast Receivers

Broadcast Receivers simply respond to broadcast messages from other applications or from the system. For example, applications can also initiate broadcasts to let other applications know that some data has been downloaded to the device and is available for them to use, so this is broadcast receiver who will intercept this communication and will initiate appropriate action.

A broadcast receiver is implemented as a subclass of BroadcastReceiver class and each message is broadcasted as an Intent object.

public class MyReceiver  extends  BroadcastReceiver {

}

Content Providers

A content provider component supplies data from one application to others on request. Such requests are handled by the methods of the ContentResolver class. The data may be stored in the file system, the database or somewhere else entirely.

A content provider is implemented as a subclass of ContentProvider class and must implement a standard set of APIs that enable other applications to perform transactions.

public class MyContentProvider extends  ContentProvider {

}

Additional Components

Components	Description
Fragments	Represents a behavior or a portion of user interface in an Activity.
Views	UI elements that are drawn onscreen including buttons, lists forms etc.
Layouts	View hierarchies that control screen format and appearance of the views.
Intents	Messages wiring components together.
Resources	External elements, such as strings, constants and drawables pictures.
Manifest	Configuration file for the application.

Features of Android Operating System

Features of Android

Android is a powerful operating system competing with Apple 4GS and supports great features. Few of them are listed below:

Feature	Description
Beautiful UI	Android OS basic screen provides a beautiful and intuitive user interface.
Connectivity	GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, LTE, NFC and WiMAX.
Storage	SQLite, a lightweight relational database, is used for data storage purposes.
Media support	H.263, H.264, MPEG-4 SP, AMR, AMR-WB, AAC, HE-AAC, AAC 5.1, MP3, MIDI, Ogg Vorbis, WAV, JPEG, PNG, GIF, and BMP
Messaging	SMS and MMS
Web browser	Based on the open-source WebKit layout engine, coupled with Chrome's V8 JavaScript engine supporting HTML5 and CSS3.
Multi-touch	Android has native support for multi-touch which was initially made available in handsets such as the HTC Hero.
Multi-tasking	User can jump from one task to another and same time various application can run simultaneously.
Resizable widgets	Widgets are resizable, so users can expand them to show more content or shrink them to save space
Multi-Language	Supports single direction and bi-directional text.
GCM	Google Cloud Messaging (GCM) is a service that lets developers send short message data to their users on Android devices, without needing a proprietary sync solution.
Wi-Fi Direct	A technology that lets apps discover and pair directly, over a high-bandwidth peer-to-peer connection.
Android Beam	A popular NFC-based technology that lets users instantly share, just by touching two NFC-enabled phones together.

Android Operating System Architecture

Android Operating System Architecture

Android Operating System Versions & Its API Levels

Versions Detail

Version name	Key user features added	Key developer features added	Release date	Android market share	API Level
Android 4.4.4	KitKat	Fix Heartbleed / OpenSSL vulnerability		2014 Jun 23	13.6 % (4.4 - 4.4.4)	19
Android 4.4.3	KitKat	Bug fixes Enable Sprint Spark band 26 and band 41		2014 Apr 14	13.6 % (4.4 - 4.4.4)	19
Android 4.4.2	KitKat	Bug fixes Security enhancements		2013 Dec 9	13.6 % (4.4 - 4.4.4)	19
Android 4.4.1	KitKat	Bug fixes Enhance the camera on the Nexus 5		2013 Dec 5	13.6 % (4.4 - 4.4.4)	19
Android 4.4	KitKat	Screen recording New Translucent system UI Enhanced notification access System-wide settings for closed captioning Performance improvements	Public API for SMS management. Improved memory usage Security enhancements (SELinux enforcing mode, new cryptographic algorithms, VPN per user...) NFC Host Card Emulation (for wireless payment, loyalty programs...) Printing Framework Storage Access Framework Hardware Sensor Batching Full-screen immersive mode GLES2.0 SurfaceFlinger Chromium WebView Audio tunneling to DSP Audio monitoring Wi-Fi certified Miracast New Bluetooth profile IR Blasters API Wi-Fi Tunneled Direct Link Setup (TDLS) support Tools for analyzing memory use (procstats, on-device memory status and profiling)	2013 Oct 31	13.6 % (4.4 - 4.4.4)	19
Android 4.3	Jelly Bean	Dial pad auto-complete Photo Sphere enhancements Camera app UI updated 4K resolution support Ability to create restricted profiles for tablets Hebrew and Arabic right-to-left (RTL) support Bluetooth Low Energy (BLE) support Bluetooth Audio/Video Remote Control Profile (AVRCP) 1.3 support Security and performance enhancements	OpenGL for Embedded Systems 3.0 graphics support Logging and analyzing enhancements Wi-Fi scanning API Improved DRM (digital rights management) API VP8 encoding	2013 Jul 24	10.3 % (4.3)	18
Android 4.2.2	Jelly Bean	Allow toggling Wi-Fi and Bluetooth state in Quick Settings using long-press Shows the percentage and estimated time remaining in the active download notifications Wireless charging and low battery sounds changed Gallery app updated for faster loading with new image transition Performance enhancements and bug fixes (Bluetooth A2DP audio streaming fix...)	Secure USB debugging (allow debugging to authenticated computers only)	2013 Feb 11	19.1 % (4.2 - 4.2.2)	17
Android 4.2.1	Jelly Bean	Fix missing december bug in the People app Add support for Bluetooth gamepads and joysticks HID devices		2012 Nov 27	19.1 % (4.2 - 4.2.2)	17
Android 4.2	Jelly Bean	Lockscreen widgets 360 degree images with Photo Sphere Gesture Typing, for faster typing Wireless display with Miracast Daydream to display information when idle or docked Multi-user for tablets	vsync timing Triple buffering reduced touch latency CPU input boost Native RTL support - mirrors the display from manifest prop External display support - Display Manager Nested fragments Renderscript Compute - run tasks on the GPU (supported devices) Renderscript ScriptGroups, built-in intrinsics like blur, FilterScript is a subset of Renderscript made for high performance image processing	2012 Nov 13	19.1 % (4.2 - 4.2.2)	17
Android 4.1.2	Jelly Bean	Enable Home screen rotation Fix bugs and enhance performances		2012 Oct 9	29 % (4.1 - 4.1.2)	16
Android 4.1.1	Jelly Bean	Fix a bug on screen orientation		2012 Jul 23	29 % (4.1 - 4.1.2)	16
Android 4.1	Jelly Bean	Google Now ( http://youtu.be/pPqliPzHYyc ) Voice Search Speed enhancements Camera app improvements Accessibility: gesture mode, enable braille external keyboards...	app stack navigation to define a parent activity in manifest for deep navigation MediaActionSound class to make sounds like when a camera takes a photo NFC supports large payloads over bluetooth WIFI/WIFI-Direct service discovery Large, detailed, multi-action notifications Input manager allows you to query input devices	2012 Jul 9	29 % (4.1 - 4.1.2)	16
Android 4.0.4	Ice Cream Sandwich	stability improvements better camera performance smoother screen rotation		2012 Mar 28	12.3 % (4.0.3 - 4.0.4)	15
Android 4.0.3	Ice Cream Sandwich	Social stream API in Contacts provider to show updates associated to your contacts Video stabilization and QVGA video resolution API access Accessibility API refinements for screen readers Calendar provider updates		2011 Dec 16	12.3 % (4.0.3 - 4.0.4)	15
Android 4.0.2	Ice Cream Sandwich	Minor fixes		2011 Nov 28	0 %	14
Android 4.0	Ice Cream Sandwich	New lock screen actions Improved text input and spell-checking Control over network data Email app supports EAS v14 WI-FI direct BlueTooth Health Device Profile	Low-level streaming multimedia (Khronos OpenMAX AL Grid Layout Spell checking service Address Space Layout Randomization VPN client API Remote Device camera enable/disable ZSL exposure, continuous focus, and image zoom Flags to help control system ui elements like system bar from apps		0 %	14
Android 4.0.1	Ice Cream Sandwich	Facial recognition (Face Unlock) UI use Hardware acceleration Better voice recognition (dictating/Voice typing) Web browser, allows up to 16 tabs Updated launcher (customizable) Android Beam app to exchange data through NFC		2011 Oct 19	0 %	14
Android 3.2.6	Honeycomb	Minor fixes		2012 Feb 15	0 %	13
Android 3.2.4	Honeycomb	Added "Pay as you go" for tablets		2011 Dec 15	0 %	13
Android 3.2.2	Honeycomb	Minor fixes		2011 Sep 30	0 %	13
Android 3.2.1	Honeycomb	Android Market updates including easier automatic updates Google Books updates Wi-Fi improvements Chinese handwriting prediction improved		2011 Sep 20	0 %	13
Android 3.2	Honeycomb	Optimizations for a wider range of tablets Compatibility display mode (zoom for fixed-sized apps) Media sync from SD card	Extended API for managing screens support New resource qualifiers for screens support New manifest attributes for screen-size compatibility Screen compatibility mode which allows for phone apps to appear as if they were still on a phone	2011 Jul 15	0 %	13
Android 3.1	Honeycomb	UI improvements Open Accessory API USB host API Mice, joysticks, gamepads... support Resizable Home screen widgets MTP notifications RTP API for audio		2011 May 10	0 %	12
Android 3.0	Honeycomb	Multi core support Better tablet support Updated 3D UI customizable homescreens recent applications viewing redone keyboard layout Media/Picture transport protocol Google Talk video chat Google eBooks "Private browsing" System-wide Clipboard HTTP Live streaming	contextual action bar Fragments first introduced(support library now supports it as well) Hardware-accelerated 2D graphics Renderscript 3D graphics engine Pluggable DRM framework device administration High performance Animation Framework RTP streaming API Forced rendering of layers High performance WIFI lock Vew network traffic stats ADTS AAC and FLAC audio LRU cache	2011 Feb 22	0 %	11
Android 2.3.4	Gingerbread	Voice or video chat using Google Talk	Open Accessory API	2011 May 10	14.9 % (2.3.3 - 2.3.7)	10
Android 2.3.7	Gingerbread	Google Wallet support for the Nexus S 4G			14.9 % (2.3.3 - 2.3.7)	10
Android 2.3.6	Gingerbread	Voice search issue fixed			14.9 % (2.3.3 - 2.3.7)	10
Android 2.3.5	Gingerbread	Improved network performance for the Nexus S 4G Fixed Bluetooth issues on the Samsung Galaxy S Gmail app. improvements		2011 Jul 25	14.9 % (2.3.3 - 2.3.7)	10
Android 2.3.3	Gingerbread		NFC API improvements (peer to peer communication...) added unsecure bluetooth sockets	2011 Feb 9	14.9 % (2.3.3 - 2.3.7)	10
Android 2.3	Gingerbread	Updated UI Improved keyboard ease of use Improved copy/paste Improved power management Social networking features Near Field Communication support Native VoIP/SIP support Video call support	performance - concurrent garbage collection, faster event distribution, updated video drivers NDK - Native Asset Manager, Native Activities + event handling, khronos api audio effects api VP8, WebM, AAC, AMR wideband Multiple camera sensor support strictmode debugging media framework replaces OpenCore	2010 Dec 6	0 % (2.3 - 2.3.2)	9
Android 2.2	Froyo	Speed improvements JIT implementation USB Tethering Applications installation to the expandable memory Upload file support in the browser Animated GIFs		2010 May 20	0.8 % (2.2)	8
Android 2.1	Eclair	Updated UI		2010 Jan 12	0 %	7
Android 2.0.1	Eclair			2009 Dec 3	0 %	6
Android 2.0	Eclair	HTML Digital zoom Microsoft Exchange support Bluetooth 2.1 Live Wallpapers Updated UI		2009 Oct 26	0 %	5
Android 1.6	Donut	Gesture framework Turn-by-turn navigation		2009 Sep 15	0 %	4
Android 1.5	Cupcake	Bluetooth A2DP, AVRCP support Soft-keyboard with text-prediction Record/watch videos		2009 Apr 30	0 %	3
Android 1.1	Banana bread	"Show" & "Hide" numeric keyboard, in caller application Ability to save MMS attachments		2009 Feb 9	0 %	2
Android 1.0	Apple pie	Download and updates via Android Market Web Browser Camera support Gmail, Contacts and Google Agenda synchronization Google Maps YouTube application		2008 Sep 23	0 %	1
Android 0.9				2008 Aug 18	0 %

Android Versions & Its API Levels:-

Android 1.0 (API level 1)[edit]   Android 1.0 (API level 1)

Android 1.1 (API level 2)[edit]   Android 1.1 (API level 2)

Android 1.5 Cupcake (API level 3)[edit]   Android 1.5 Cupcake (API level 3)

Android 1.6 Donut (API level 4)[edit]   Android 1.6 Donut (API level 4)

Android 2.0 Eclair (API level 5)[edit]   Android 2.0 Eclair (API level 5)

Android 2.0.1 Eclair (API level 6)[edit]   Android 2.0.1 Eclair (API level 6)

Android 2.1 Eclair (API level 7)[edit]   Android 2.1 Eclair (API level 7)

Android 2.2–2.2.3 Froyo (API level 8)[edit]   Android 2.2–2.2.3 Froyo (API level 8)

Android 2.3–2.3.2 Gingerbread(API level 9)[edit]   Android 2.3–2.3.2 Gingerbread (API level 9)

Android 2.3.3–2.3.7 Gingerbread (API level 10)[edit]   Android 2.3.3–2.3.7 Gingerbread (API level 10)

Android 3.0 Honeycomb (API level 11)[edit]   Android 3.0 Honeycomb (API level 11)

Android 3.1 Honeycomb (API level 12)[edit]   Android 3.1 Honeycomb (API level 12)

Android 3.2 Honeycomb (API level 13)[edit]   Android 3.2 Honeycomb (API level 13)

Android 4.0–4.0.2 Ice Cream Sandwich (API level 14)[edit]   Android 4.0–4.0.2 Ice Cream Sandwich (API level 14)

Android 4.0.3–4.0.4 Ice Cream Sandwich (API level 15)[edit]   Android 4.0.3–4.0.4 Ice Cream Sandwich (API level 15)

Android 4.1 Jelly Bean(API level 16)[edit]   Android 4.1 Jelly Bean (API level 16)

Android 4.2 Jelly Bean(API level 17)[edit]   Android 4.2 Jelly Bean (API level 17)

Android 4.3 Jelly Bean(API level 18)[edit]   Android 4.3 Jelly Bean (API level 18) ]

Android 4.4 KitKat (API level 19)[edit]   Android 4.4 KitKat (API level 19)