Near Field Communication

Near Field Communication (NFC) is a set of short-range wireless technologies, typically requiring a distance of 4cm or less to initiate a connection. NFC allows you to share small payloads of data between an NFC tag and an Android device, or between two Android devices.

Each tag has it s own characteristics, some tags provide information which is read-only like the tags on information billboard or on a price tag. Some other had the ability to do some math and had the environment to do some simple programming like on a discount tag.

The data that stored in a tag can be written on a variety of formats, but many of the Android framework APIs are based around a NFC Forum standard called NDEF (NFC Data Exchange Format)

There are two major uses cases when working with NDEF data and Android:

• Reading NDEF data from an NFC tag
• Beaming NDEF messages from one device to another with Android Beam

Reading NDEF data from an NFC tag is handled with the tag dispatch system, which analyzes discovered NFC tags, appropriately categorizes the data, and starts an application that is interested in the categorized data. An application that wants to handle the scanned NFC tag can declare an intense filter and request to handle the data.
The Android Beam feature allows a device to push an NDEF message onto another device by physically tapping the devices together. This interaction provides an easier way to send data than other wireless technologies like Bluetooth, because with NFC, no manual device discovery or pairing is required. The connection is automatically started when two devices come into range. Android Beam is available through a set of NFC APIs, so any application can transmit information between devices. For example, the Contacts, Browser, and YouTube applications use Android Beam to share contacts, web pages, and videos with other devices.