Android Near Field Communication

譯自 https://developer.android.google.cn/guide/topics/connectivity/nfc/index.html

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-powered device, or between two Android-powered devices.

近場通訊（NFC）是一系列的短距離無線通信技術。通常需要4cm或更短的距離來發起連接。NFC允許你在NFC標簽和Android設備之間，或兩臺Android設備之間分享小載荷的數據。

Tags can range in complexity. Simple tags offer just read and write semantics, sometimes with one-time-programmable areas to make the card read-only. More complex tags offer math operations, and have cryptographic hardware to authenticate access to a sector. The most sophisticated tags contain operating environments, allowing complex interactions with code executing on the tag. The data stored in the tag can also be written in a variety of formats, but many of the Android framework APIs are based around a NFC Forum standard called NDEF (NFC Data Exchange Format).

標簽的范圍可以很復雜。簡單的標簽只是提供了讀寫簡單語意，有些時候，在一次性編程領域會制作一些只讀的卡片。負責的標簽提供了數學運算，并且有加密固件對訪問的區域進行認證。最復雜的標簽包括操作環境，允許在該標簽上執行復雜的交互代碼。數據可以用各種各樣的格式存儲到標簽上，但是大多數Android框架應用程序接口都基于一個標準的NFC Forum，稱為NDEF（NFC Data Exchange Format）。

Android-powered devices with NFC simultaneously support three main modes of operation:

Reader/writer mode, allowing the NFC device to read and/or write passive NFC tags and stickers.

P2P mode, allowing the NFC device to exchange data with other NFC peers; this operation mode is used by Android Beam.

Card emulation mode, allowing the NFC device itself to act as an NFC card. The emulated NFC card can then be accessed by an external NFC reader, such as an NFC point-of-sale terminal.

帶NFC的Android設備同時支持了以下三種操作：

1. 讀寫模式，允許NFC設備被動地讀或者寫NFC標簽和貼紙。

2. P2P模式，允許NFC設備和其它對等的NFC設備交換數據；該操作模式由Android Beam使用。

3. 模擬卡片模式，允許NFC設備自己作為一張NFC卡片。它模擬的NFC卡片接觸到外部的NFC讀卡器，就像一個NFC銷售點終端機。

NFC Basics

（譯：NFC基礎技術）

This document describes how Android handles discovered NFC tags and how it notifies applications of data that is relevant to the application. It also goes over how to work with the NDEF data in your applications and gives an overview of the framework APIs that support the basic NFC feature set of Android.

該文檔描述了Android如何操作已經發現的NFC標簽和它如何通知相關的應用程序。它也會讓你再溫習一遍在你應用內的NDEF數據是如何工作的，并且給出了Android支持的一系列NFC特性的應用程序框架的概要。

Advanced NFC

（譯：高級的NFC）

This document goes over the APIs that enable use of the various tag technologies that Android supports. When you are not working with NDEF data, or when you are working with NDEF data that Android cannot fully understand, you have to manually read or write to the tag in raw bytes using your own protocol stack. In these cases, Android provides support to detect certain tag technologies and to open communication with the tag using your own protocol stack.

該文檔超過了提供的應用程序接口，允許使用更豐富的Android支持的標簽技術。當你不使用NDEF數據，或者當你使用的NDEF數據Android不能夠頑強理解時，你就必須使用基于你自己的協議棧的原始的字節數組手動地讀寫該標簽。在這種情況下，Android提供檢測已經確定的標簽的支持，和使用你自己的協議棧進行通信。

Host-based Card Emulation

（譯：基于主機的卡片模擬器）

This document describes how Android devices can perform as NFC cards without using a secure element, allowing any Android application to emulate a card and talk directly to the NFC reader.

該文檔描述了如何Android設備在不使用安全元件的情況下怎樣才能表現的和NFC卡一樣，允許任何Android應用模擬一個卡片直接與NFC讀卡器通信。

Android

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