FROM：http://blog.csdn.net/burly/article/details/50512379

公司有个项目要用到串口通信，同事有写好一个DEMO，用的时候发现会有问题，从jni读串口数据时，经常会被截断，修改select延时还是无济于事，于是想到用Java直接去读/写串口文件，经过搜索在iteye上的一篇博客1可以满足需求，但看到下面留言说有问题，自己试了下确实是有问题，经过一些小小的修改验证后没问题，并整理了一个DEMO。

项目主要代码

CPP代码

/* * Copyright 2009 Cedric Priscal * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
#include <stdlib.h>
#include <stdio.h>
#include <jni.h>
#include <assert.h>  #include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include "log.h"
#include "com_skyworth_splicing_SerialPort.h"
#include <android/log.h>
static const char *TAG = "serial_port";
//#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;  }
}  /* * Class:     cedric_serial_SerialPort * Method:    open * Signature: (Ljava/lang/String;)V */
JNIEXPORT jobject JNICALL Java_com_skyworth_splicing_SerialPort_open(JNIEnv *env, jobject thiz, jstring path,jint baudrate) {  int fd;  speed_t speed;  jobject mFileDescriptor;  LOGD("init native Check arguments");  /* Check arguments */  {  speed = getBaudrate(baudrate);  if (speed == -1) {  /* TODO: throw an exception */  LOGE("Invalid baudrate");  return NULL;  }  }  LOGD("init native Opening device!");  /* Opening device */  {  jboolean iscopy;  const char *path_utf = env->GetStringUTFChars(path, &iscopy);  LOGD("Opening serial port %s", path_utf);
//      fd = open(path_utf, O_RDWR | O_DIRECT | O_SYNC);  fd = open(path_utf, O_RDWR | O_NOCTTY | O_NONBLOCK | O_NDELAY);  LOGD("open() fd = %d", fd);  env->ReleaseStringUTFChars(path, path_utf);  if (fd == -1) {  /* Throw an exception */  LOGE("Cannot open port %d",baudrate);  /* TODO: throw an exception */  return NULL;  }  }  LOGD("init native Configure device!");  /* Configure device */  {  struct termios cfg;  if (tcgetattr(fd, &cfg)) {  LOGE("Configure device tcgetattr() failed 1");  close(fd);  return NULL;  }  cfmakeraw(&cfg);  cfsetispeed(&cfg, speed);  cfsetospeed(&cfg, speed);  if (tcsetattr(fd, TCSANOW, &cfg)) {  LOGE("Configure device tcsetattr() failed 2");  close(fd);  /* TODO: throw an exception */  return NULL;  }  }  /* Create a corresponding file descriptor */  {  jclass cFileDescriptor = env->FindClass("java/io/FileDescriptor");  jmethodID iFileDescriptor = env->GetMethodID(cFileDescriptor,"<init>", "()V");  jfieldID descriptorID = env->GetFieldID(cFileDescriptor,"descriptor", "I");  mFileDescriptor = env->NewObject(cFileDescriptor,iFileDescriptor);  env->SetIntField(mFileDescriptor, descriptorID, (jint) fd);  }  return mFileDescriptor;
}  /* * Class:     cedric_serial_SerialPort * Method:    close * Signature: ()V */
JNIEXPORT jint JNICALL Java_com_skyworth_splicing_SerialPort_close(JNIEnv * env, jobject thiz)
{  jclass SerialPortClass = env->GetObjectClass(thiz);  jclass FileDescriptorClass = env->FindClass("java/io/FileDescriptor");  jfieldID mFdID = env->GetFieldID(SerialPortClass, "mFd", "Ljava/io/FileDescriptor;");  jfieldID descriptorID = env->GetFieldID(FileDescriptorClass, "descriptor", "I");  jobject mFd = env->GetObjectField(thiz, mFdID);  jint descriptor = env->GetIntField(mFd, descriptorID);  LOGD("close(fd = %d)", descriptor);  close(descriptor);  return 1;
}  static JNINativeMethod gMethods[] = {  //{ "open", "(Ljava/lang/String;I)Ljava/io/FileDescriptor;",(void*) native_open },  //{ "close", "()I",(void*) native_close },
};  /* * 为某一个类注册本地方法 */
static int registerNativeMethods(JNIEnv* env, const char* className,  JNINativeMethod* gMethods, int numMethods) {  jclass clazz;  clazz = env->FindClass(className);  if (clazz == NULL) {  return JNI_FALSE;  }  if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {  return JNI_FALSE;  }  return JNI_TRUE;
}  /* * 为所有类注册本地方法 */
static int registerNatives(JNIEnv* env) {  const char* kClassName = "com/skyworth/splicing/SerialPort"; //指定要注册的类  return registerNativeMethods(env, kClassName, gMethods,  sizeof(gMethods) / sizeof(gMethods[0]));
}  /* * System.loadLibrary("lib")时调用 * 如果成功返回JNI版本, 失败返回-1 */
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved) {  JNIEnv* env = NULL;  jint result = -1;  /*if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {  return -1;  }  assert(env != NULL);  if (!registerNatives(env)) { //注册  return -1;  }  *///成功  result=JNI_VERSION_1_6;//result = JNI_VERSION_1_4;  return result;
}

我把它修改成JNI通用的那种模式，把文件名和函数名改成对应JAVA文件的包名和类名，这个一定要一致，不然无法调用成功，并增加.H文件见DEMO源码的jni目录。CPP的编译直接在源码服务器编译的，没有在WINDOWS NDK下编译，有源码就没去折腾了。

JAVA代码

JAVA相关基本没改，去掉一些业务相关的代码：

SerialPort.java

package com.skyworth.splicing;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;
/*** 串口操作* * @author guoxiao* */
public class SerialPort {private static final String TAG = "SerialPort";/** Do not remove or rename the field mFd: it is used by native method close();*/private FileDescriptor mFd;private FileInputStream mFileInputStream;private FileOutputStream mFileOutputStream;public SerialPort(File device, int baudrate) throws SecurityException, IOException {mFd = open(device.getAbsolutePath(), baudrate);if (mFd == null) {throw new IOException();}mFileInputStream = new FileInputStream(mFd);mFileOutputStream = new FileOutputStream(mFd);}public InputStream getInputStream() {return mFileInputStream;}public OutputStream getOutputStream() {return mFileOutputStream;}private native FileDescriptor open(String path, int baudrate);public native int close();static {System.loadLibrary("serial_port");}
}

SerialPortUtil.java

package com.skyworth.splicing;import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;/*** 串口操作* * @author guoxiao* */
public class SerialPortUtil {private String TAG = SerialPortUtil.class.getSimpleName();private SerialPort mSerialPort;private OutputStream mOutputStream;private InputStream mInputStream;private ReadThread mReadThread;private String path = "/dev/ttyS3";private int baudrate = 115200;private static SerialPortUtil portUtil;private OnDataReceiveListener onDataReceiveListener = null;private boolean isStop = false;public interface OnDataReceiveListener {public void onDataReceive(byte[] buffer, int size);}public void setOnDataReceiveListener(OnDataReceiveListener dataReceiveListener) {onDataReceiveListener = dataReceiveListener;}public static SerialPortUtil getInstance() {if (null == portUtil) {portUtil = new SerialPortUtil();portUtil.onCreate();}return portUtil;}/*** 初始化串口通信*/private void onCreate() {try {mSerialPort = new SerialPort(new File(path), baudrate);mOutputStream = mSerialPort.getOutputStream();mInputStream = mSerialPort.getInputStream();mReadThread = new ReadThread();isStop = false;mReadThread.start();} catch (Exception e) {e.printStackTrace();}}/*** 发送指令到串口* * @param cmd* @return*/public boolean sendCmds(String cmd) {boolean result = true;byte[] mBuffer = cmd.getBytes();try {if (mOutputStream != null) {mOutputStream.write(mBuffer);} else {result = false;}} catch (IOException e) {e.printStackTrace();result = false;}return result;}public boolean sendBuffer(byte[] mBuffer) {boolean result = true;String tail = "";byte[] tailBuffer = tail.getBytes();byte[] mBufferTemp = new byte[mBuffer.length+tailBuffer.length];System.arraycopy(mBuffer, 0, mBufferTemp, 0, mBuffer.length);System.arraycopy(tailBuffer, 0, mBufferTemp, mBuffer.length, tailBuffer.length);try {if (mOutputStream != null) {mOutputStream.write(mBufferTemp);} else {result = false;}} catch (IOException e) {e.printStackTrace();result = false;}return result;}private class ReadThread extends Thread {@Overridepublic void run() {super.run();while (!isStop && !isInterrupted()) {int size;try {if (mInputStream == null)return;byte[] buffer = new byte[512];size = mInputStream.read(buffer);if (size > 0) {
//                          String str = new String(buffer, 0, size);
//                          Logger.d("length is:"+size+",data is:"+new String(buffer, 0, size));if (null != onDataReceiveListener) {onDataReceiveListener.onDataReceive(buffer, size);}}Thread.sleep(10);} catch (Exception e) {e.printStackTrace();return;}}}}/*** 关闭串口*/public void closeSerialPort() {isStop = true;if (mReadThread != null) {mReadThread.interrupt();}if (mSerialPort != null) {mSerialPort.close();}}}

串口工具类的调用：

package com.example.serialutil;import com.skyworth.splicing.SerialPortUtil;
import com.skyworth.splicing.SerialPortUtil.OnDataReceiveListener;import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
/** @author guoxiao* */
public class SerialActivity extends Activity {SerialPortUtil mSerialPortUtil;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_hello_world);//单模式mSerialPortUtil = SerialPortUtil.getInstance();mSerialPortUtil.setOnDataReceiveListener(new OnDataReceiveListener() {@Overridepublic void onDataReceive(byte[] buffer, int size) {// TODO Auto-generated method stubLog.d("[gx]", " DataReceive:" + new String(buffer,0,size));}});}public void onWrite(View view){mSerialPortUtil.sendCmds("<open,1,0,3,0,0,0,0,0,0,1910,1070>");}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.hello_world, menu);return true;}}

总结：

CPP的文件名和函数名一定要和JAVA的包名和类名对应
串口读操作时使用了一个线程
写串口时最终是byte类型，注意符号位的问题

DEMO下载地址：http://download.csdn.net/detail/burly/9402739

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项目主要代码

CPP代码

JAVA代码

总结：

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