Aandroid NDK开发之串口控制

     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