Android NFC架构分析

Android中对NFC的实现代码分布在如下几个地方：

./frameworks/base/core/java/android/nfc/

./frameworks/base/core/java/android/nfc/tech

./frameworks/base/core/java/com/android/internal/nfc/

./external/libnfc-nxp

./packages/apps/nfc

其中

./external/libnfc-nxp是用C语言编写的函数库，编译生成libnfc和libnfc_ndef两个函数库。libnfc是一个主要的库，实现了NFC Stack的大部分功能，主要供NFC的服务进程调用。

libnfc_ndef是一个很小的函数库，主要是实现NDEF消息的解析，供Framework调用。

./packages/apps/nfc是一个类似于电话本的应用程序，但这个程序在手机开机后自动启动，一直运行，是作为NFC的服务进程存在的。是NFC架构中的核心。

./frameworks/base/core/java/android/nfc/，./frameworks/base/core/java/android/nfc/tech和./frameworks/base/core/java/com/android/internal/nfc/这三个目录

实现了NFC的应用接口，其中./frameworks/base/core/java/com/android/internal/nfc/是一些内部类或结构，不对外开放，仅供./frameworks/base/core/java/android/nfc/和

./frameworks/base/core/java/android/nfc/tech中的类调用。

./frameworks/base/core/java/android/nfc实现了接口包com.android.nfc，./frameworks/base/core/java/android/nfc/tech实现了接口包com.android.nfc.tech.

图示如下:

附录：

NFC Service的说明

NFC: Move NFC service implementation out of system_server.

NFC service is now an application service in packages/apps/Nfc.

NFC service is registered through ServiceManager.addService(), and the proxy object NfcAdapter obtains a handle to it through

ServiceManager.getService().

**Important** Had to add new symbols AID_NFC / NFC_UID / android.uid.nfc and modify service_manager.c, Process.java and PackageManagerService.java

in order to force the com.android.nfc process to take a fixed uid, so that it can use ServiceManager.addService().

Most of the JNI has moved to packages/apps/Nfc/jni. However NdefRecord and NdefMessage require some in-process native code, so

android_com_NdefMessage.cpp and android_com_NdefRecord.cpp stay in frameworks/base/core/jni. They link to a very small library libnfc_ndef.so

that implements NDEF message parsing. This has been added to core.mk so all devices (even without NFC hardware) can work with NDEF data.