最近一个项目是android的系统,由于是工业产品,所以要用到串口,想着怎么去控制串口,有好些办法,最简单有效而且规范的办法就是google提供的NDK啦，其实还是蛮复杂的，因为android系统是个很花的系统，涉及到的知识面太广了。把代码贴在这，以后就不会忘了，嘎嘎.

下面是NDK部分所有的代码，需要注意的地方在最后面再讲:

/*

*Copyright 2100 Smallfish

*

*

*

*

*I love you.

*/

#include

#include

#include

#include

#include

#include

#include

#include

/*Android log

*/

#include

static const char *TAG="serialport for NFC Demo";

#define LOGI(fmt, args...) __android_log_print(ANDROID_LOG_INFO,TAG, fmt, ##args)

#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG,TAG, fmt, ##args)

#define LOGE(fmt, args...) __android_log_print(ANDROID_LOG_ERROR,TAG, fmt, ##args)

static speed_t getBaudrate(jint baudrate)

{

switch(baudrate) {

case 0: return B0;

case 50: return B50;

case 75: return B75;

case 110: return B110;

case 134: return B134;

case 150: return B150;

case 200: return B200;

case 300: return B300;

case 600: return B600;

case 1200: return B1200;

case 1800: return B1800;

case 2400: return B2400;

case 4800: return B4800;

case 9600: return B9600;

case 19200: return B19200;

case 38400: return B38400;

case 57600: return B57600;

case 115200: return B115200;

case 230400: return B230400;

case 460800: return B460800;

case 500000: return B500000;

case 576000: return B576000;

case 921600: return B921600;

case 1000000: return B1000000;

case 1152000: return B1152000;

case 1500000: return B1500000;

case 2000000: return B2000000;

case 2500000: return B2500000;

case 3000000: return B3000000;

case 3500000: return B3500000;

case 4000000: return B4000000;

default: return -1;

}//end of switch

}//end of getBaudrate

/*

*Class:  SerialPort

*Method:  open

*Signature:  (Ljava/lang/String;)V

*/

JNIEXPORT jobject JNICALL Java_android_serialport_SerialPort_open

(JNIEnv *env,jobject thiz,jstring path,jint baudrate)

{

int fd;

jobject mFileDescriptor;

speed_t speed;

/*Check baudrate */

{

speed = getBaudrate(baudrate);

if(-1 == speed)

{

LOGE("Invalid baudrate passed");

return NULL;

}

}//end of check baudrate

/* Open device */

{

jboolean iscopy;

const char *path_utf = (*env)->GetStringUTFChars(env,path,&iscopy);

LOGD("Opening serial port is:%s",path_utf);

fd = open(path_utf,O_RDWR);

LOGD("opend device fd:%d",fd);

(*env)->ReleaseStringUTFChars(env,path,path_utf);

if(-1 == fd)

{

LOGD("Open serial port Failed...");

return NULL;

}

}//end of Open Device

/* Configure device*/

{

struct termios s_cfg;

if(tcgetattr(fd,&s_cfg))

{

LOGE("Get default config failed...");

return NULL;

}

cfmakeraw(&s_cfg);

cfsetispeed(&s_cfg,speed);

cfsetospeed(&s_cfg,speed);

if(tcsetattr(fd,TCSANOW,&s_cfg))

{

close(fd);

LOGE("Configure serial port failed");

return NULL;

}

}//end of Configure device

/* Create a corresponding file descriptor via opend serial port*/

{

jclass cFileDescriptor = (*env)->FindClass(env,"java/io/FileDescriptor");

jmethodID iFileDescriptor = (*env)->GetMethodID(env,cFileDescriptor,"","()V");

jfieldID  descriptorID = (*env)->GetFieldID(env,cFileDescriptor,"descriptor","I");

mFileDescriptor = (*env)->NewObject(env,cFileDescriptor,iFileDescriptor);

(*env)->SetIntField(env,mFileDescriptor,descriptorID,(jint)fd);

}

return mFileDescriptor;

}//end of open

/*

* Class: serial__SerialPort

* Method: close

* Signature: ()V

*/

JNIEXPORT void JNICALL Java_android_serialport_SerialPort_close

(JNIEnv *env,jobject thiz)

{

jclass SerialPortClass = (*env)->GetObjectClass(env,thiz);

jclass FileDescriptorClass = (*env)->FindClass(env,"java/io/FileDescriptor");

jfieldID mFdID = (*env)->GetFieldID(env,SerialPortClass,"mFd","java/io/FileDescriptor");

jfieldID descriptorID = (*env)->GetFieldID(env,FileDescriptorClass,"descriptor","I");

jobject mFd = (*env)->GetObjectField(env,thiz,mFdID);

jint descriptor = (*env)->GetIntField(env,mFd,descriptorID);

LOGD("Close device fd:%d",descriptor);

close(descriptor);

}

需要注意的是函数名称：Java_android_serialport_SerialPort_close

分解如下：Java_这个是不变的，照写就是了，android_serialport这个是包名，这里是什么，在上层里也必须是什么，SerialPort_close这个前面部分是类名，而后面的当然就是函数名称了。

好吧：就这样,以后补上.mk文件.

下面是整个java串口类的代码,就不多说了:

package android.serialport;

import java.io.File;

import java.io.FileDescriptor;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import android.util.Log;

public class SerialPort

{

private FileDescriptor mFd;

private FileInputStream mFileInputStream;

private FileOutputStream mFileOutputStream;

//这是构造函数了,是做什么的我也不知道啊

public SerialPort(File device,int baudrate) throws SecurityException,IOException

{

//open device

mFd = open(device.getAbsolutePath(),baudrate);

if(mFd == null)

{

Log.e(TAG, "native open return NULL");

throw new IOException();

}

//建立输入输出流,就可以使用这2个流来发送和接收数据了

mFileInputStream = new FileInputStream(mFd);

mFileOutputStream = new FileOutputStream(mFd);

}//end of SerialPort

//获取输入流

public InputStream GetInputStream()

{

return mFileInputStream;

}

//获取输出流

public OutputStream GetOutputStream()

{

return mFileOutputStream;

}

//加载库和声明函数的

private native static FileDescriptor open(String path,int baudrates);

private native void close();

static {

System.loadLibrary("serialport");

}

}//end of calss