Android的串口通信

最近有两个项目用到了串口通信，就在网上找了些串口通信的资料研究了下。Android的串口通信分为两种方式，一种是开发系统app就可以直接调用  android.hardware.SerialManager， android.hardware.SerialPort这两个类完成串口通信。由于这两个类不对应该层提供，所以下面主要讲讲第二种方式，用jni完成对串口的操作。

1：AS配置ndk开发环境（这个比较简单，不会的可以问问度娘）；

2：编写串口类

import android.util.Log;

import com.tiannuo.usbandserialapi.utils.LOG;

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;

public class SerialPort {

   private static final String TAG = "android_serialport_api";

   /*
    * 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, int flags) throws SecurityException, IOException {

      /* Check access permission */
      if (!device.canRead() || !device.canWrite()) {
         try {
            /* Missing read/write permission, trying to chmod the file */
            Process su;
            su = Runtime.getRuntime().exec("/system/bin/su");
            String cmd = "chmod 666 " + device.getAbsolutePath() + "\n"
                  + "exit\n";
            su.getOutputStream().write(cmd.getBytes());
            if ((su.waitFor() != 0) || !device.canRead()
                  || !device.canWrite()) {
               throw new SecurityException();
            }
         } catch (Exception e) {
            e.printStackTrace();
            throw new SecurityException();
         }
      }

      mFd = open(device.getAbsolutePath(), baudrate, flags);
      if (mFd == null) {
         Log.e(TAG, "native open returns null");
         throw new IOException();
      }
      mFileInputStream = new FileInputStream(mFd);
      mFileOutputStream = new FileOutputStream(mFd);
   }

   // Getters and setters
   public InputStream getInputStream() {
      return mFileInputStream;
   }

   public OutputStream getOutputStream() {
      return mFileOutputStream;
   }

   // JNI
   private native static FileDescriptor open(String path, int baudrate, int flags);
   public native void close();
   static {
      try {
         System.loadLibrary("serial_port");
      }catch (Exception e){
         LOG.e("loadLibrary error");
      }

   }
}

3:make生成头文件；

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class android_serialport_api_SerialPort */

#ifndef _Included_android_serialport_api_SerialPort
#define _Included_android_serialport_api_SerialPort
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     android_serialport_api_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
 */
JNIEXPORT jobject JNICALL Java_android_1serialport_1api_SerialPort_open
  (JNIEnv *, jclass, jstring, jint, jint);

/*
 * Class:     android_serialport_api_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_android_1serialport_1api_SerialPort_close
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

4：根据文件编写C文件

#include <termios.h>