Android实现串口通信

本文实例为大家分享了Android实现串口通信的具体代码，供大家参考，具体内容如下生成so文件首先确保已经安装了NDK和CMake然后创建一个SerialPort.java文件主要用来处理so文件注意...

本文实例为大家分享了android实现串口通信的具体代码，供大家参考，具体内容如下

生成so文件

首先确保已经安装了NDK和CMake

然后创建一个SerialPort.Java文件

主要用来处理so文件

注意包名一旦写好不要更改位置，具体代码：

import android.util.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;
/**
* Created by abc on 2021/1/23.
*/

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, int flags) throws SecurityException, IOException {

    if (device == null) {
      System.out.println("device is null");
      return;
    }


    /* 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 777 " + 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 {
    System.loadLibrary("serial_port");
  }


}

然后clean project 再rebuild project 生成class文件，
这时候打开如下图的文件夹看是否生成了classes文件夹，没有生成请重新再试一遍。

当然你也不一定会生成compileDebugJavaWithJavac 只要javac->debug下存在classes就可以

再打开Terminal输入指令
cd app/build/intermediates/javac/debug/classes（具体位置定位到classes）
然后再输入指令
javah -jni 包名.SerialPort
注意 这里javah -jni后面跟的是 SerialPort.java 的全路径，如果javah报不存在之类的，是你的Java环境没有配置好。

这时候打开 debug/classes下面的文件发现多了一个以 .h 结尾文件

编写处理C文件

在main下创建一个jni包 将生成的.h文件复制进去

然后创建SerialPort.c文件

#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 <jni.h>
#include 这里是生成.h文件全称(com_***_***_serialport_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:   android_serialport_SerialPort
* Method:  open
* Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
*/
//这里同样是生成.h文件全称
JNIEXPORT jobject JNICALL Java_com_***_***_serialport_SerialPort_open
    (JNIEnv *env, jclass thiz, jstring path, jint baudrate, jint flags)
{
  int fd;
  speed_t speed;
  jobject mFileDescriptor;

  /* Check arguments */
  {
    speed = getBaudrate(baudrate);
    if (speed == -1) {
      /* TODO: throw an exception */
      LOGE("Invalid baudrate");
      return NULL;
    }
  }

  /* Opening device */
  {
    jboolean iscopy;
    const char *path_utf = (*env)->GetStringUTFChars(env, path, &iscopy);
    LOGD("Opening serial port %s with flags 0x%x", path_utf, O_RdwR | flags);
    fd = open(path_utf, O_RDWR | flags);
    LOGD("open() fd = %d", fd);
    (*env)->ReleaseStringUTFChars(env, path, path_utf);
    if (fd == -1)
    {
      /* Throw an exception */
      LOGE("Cannot open porpythont");
      /* TODO: throw an exception */
      return NULL;
    }
  }

  /* Configure device */
  {
    struct termios cfg;
    LOGD("Configuring serial port");
    if (tcgetattr(fd, &cfg))
    {
      LOGE("tcgetattr() failed");
      close(fd);
      /* TODO: throw an exception */
      return NULL;
    }

    cfmakeraw(&cfg);
    cfsetispeed(&cfg, speed);
    cfsetospeed(&cfg, speed);

    if (tcsetattr(fd, TCSANOW, &cfg))
    {
      LOGE("tcsetattr() failed");
      close(fd);
      /* TODO: throw an exception */
      return NULL;
    }
  }

  /* Create a corresponding file descriptor */
  {
    jclass cFileDescriptor = (*env)->FindClass(env, "java/io/FileDescriptor");
    jmethodID iFileDescriptor = (*env)->GetMethodID(env, cFileDescriptor, "<init>", "()V");
    jfieldID descriptorID = (*env)->GetFieldID(env, cFileDescriptor, "descriptor", "I");
    mFileDescriptor = (*env)->NewObject(env, cFileDescriptor, iFileDescriptor);
    (*env)->SetIntField(env, mFileDescriptor, descriptorID, (jint)fd);
  }

  return mFileDescriptor;
}

/*
* Class:   cedric_serial_SerialPort
* Method:  close
* Signature: ()V
*/
 //这里同样是生成.h文件全称
JNIEXPORT void JNICALL Java_com_***_***_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", "Ljava/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(fd = %d)", descriptor);
close(descriptor);
}

termios.h 具体代码:

#ifndef _TERMIOS_H_
#define _TERMIOS_H_

#include <sys/cdefs.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <stdint.h>
#include <linux/termios.h>

__BEGIN_DECLS

/* Redefine these to match their ioctl number */
#undef TCSANOW
#define TCSANOW  TCSETS

#undef TCSADRAIN
#define TCSADRAIN TCSETSW

#undef TCSAFLUSH
#define TCSAFLUSH TCSETSF

static __inline__ int tcgetattr(int fd, struct termios *s)
{
  return ioctl(fd, TCGETS, s);
}

static __inline__ int tcsetattr(int fd, int __opt, const struct termios *s)
{
  return ioctl(fd, __opt, (void *)s);
}

static __inline__ int tcflow(int fd, int action)
{
  return ioctl(fd, TCXONC, (void *)(intptr_t)action);
}

static __inline__ int tcflush(int fd, int __queue)
{
  return ioctl(fd, TCFLSH, (void *)(intptr_t)__queue);
}

static __inline__ pid_t tcgetsid(int fd)
{
  pid_t _pid;
  return ioctl(fd, TIOCGSID, &_pid) ? (pid_t)-1 : _pid;
}

static __inline__ int tcsendbreak(int fd, int __duration)
{
  return ioctl(fd, TCSBRKP, (void *)(uintptr_t)__duration);
}

static __inline__ speed_t cfgetospeed(const struct termios *s)
{
  return (speed_t)(s->c_cflag & CBAUD);
}

static __inline__ int cfsetospeed(struct termios *s, speed_t speed)
{
  s->c_cflag = (s->c_cflag & ~CBAUD) | (speed & CBAUD);
  return 0;
}

static __inline__ speed_t cfgetispeed(const struct termios *s)
{
  return (speed_t)(s->c_cflag & CBAUD);
}

static __inline__ int cfsetispeed(struct termios *s, speed_t speed)
{
  s->c_cflag = (s->c_cflag & ~CBAUD) | (speed & CBAUD);
 return 0;
}

static __inline__ void cfmakeraw(struct termios *s)
{
  s->c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL|IXON);
  s->c_oflag &= ~OPOST;
  s->c_lflag &= ~(ECHO|ECHONL|ICANON|ISIG|IEXTEN);
  s->c_cflag &= ~(CSIZE|PARENB);
  s->c_cflag |= CS8;
}

__END_DECLS

#endif /* _TERMIOS_H_ */

生成so文件

首先，在项目（app）的build.gradel中的defaultConfig下添加：

externalNativeBuild {
      cmake {
        cppFlags ""
       // abiFilters "armeabi-v7a", "x86", "arm64-v8a"
      }
    }

然后再在项目（app）的build.gradel 的 android 闭包下添加：

externalNativeBuild {
    cmake {
      path "CMakeLists.txt"
    }
  }

在app下创建一个CMakeLists.txt

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

#设置生成的so动态库最后输出的路径
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI})

add_library( # Sets the name of the library.
    #此处填入library名称，就是生成so文件的名称
    serial_port

    # Sets the library as a shared library.
    SHARED

    # Provides a relative path to your source file(s). c文件或cpp文件的相对路径
    src/main/jni/SerialPort.c
    )
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
    log-lib
    # Specifies the name of the NDK library that
    # you want CMake to locate.
    log)
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
    #此处填入library名称，就是生成so文件的名称
    serial_port
    # Links the target library to the log library
    # included in the NDK.
    ${log-lib})

你现在就可以Make Project 或者 Rebuild Project 一下 ，之后会在这里会生成so库：

把生成的so文件复制到libs下或者jniLibs下
这时so文件我们生成了就需要把build的注释掉不然下次运行还会生成

externalNativeBuild {
      cmake {
        cppFlags ""
       // abiFilters "armeabi-v7a", "x86", "arm64-v8a"
      }
    }


externalNativeBuild {
    cmake {
      path "CMakeLists.txt"
    }
  }

然后我们封装一个SerialPortUtils

import android.util.Log;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
* @author renquan
*/

public class SerialPortUtils {
  private static SerialPortUtils serialPortUtils;
  private final String TAG = "SerialPortUtils";
//  private String path = "/dev/ttyS1";
//  private int baudrate = 9600;
  public boolean serialPortStatus = false; //是否打开串口标志
  public String data_;
  public boolean threadStatus; //线程状态，为了安全终止线程
  public SerialPort serialPort = null;
  public InputStream inputStream = null;
  public OutputStream outputStream = null;
  public ChangeTool changeTool = new ChangeTool();

  public static SerialPortUtils getInstaphpnce() {
    if (null == serialPortUtils){
      serialPortUtils = new SerialPortUtils();
    }
    return serialPortUtils;
  }

  /**
  * 获取状态
  * @return
  */
  public boolean getPortStatus(){
    return serialPortStatus;
  }
  /**
  * 打开串口
  * @return serialPort串口对象
  */
  public SerialPort openSerialPort(String path, int baudrate){
    if (getPortStatus()){
      return serialPort;
    }
    try {
      serialPort = new SerialPort(new File(path),baudrate,0);
      this.serialPortStatus = true;
      threadStatus = false; //线程状态

      //获取打开的串口中的输入输出流，以便于串口数据的收发
      inputStream = serialPort.getInputStream();
      outputStream = serialPort.getOutputStream();


      new ReadThread().start(); //开始线程监控是否有数据要接收
    } catch (IOException e) {
      Log.d(TAG,"打开串口异常");
      Toast.makeText(MyApp.context, "打开串口异常", Toast.LENGTH_SHORT).show();
      isException = true;
      return serialPort;
    }
    Log.d(TAG, "openSerialPort: 打开串口");
    Toast.makeText(MyApp.context, "打开串口", Toast.LENGTH_SHORT).show();

    return serialPort;
  }

  /**
  * 关闭串口
  */
  public void closeSerialPort(){
    if (!getPortStatus()){
      return;
    }
    if (null == inputStream || null == outputStream){
      Log.e(TAG, "closeSerialPort: 关闭串口异常："+"null");

      Toast.makeText(MyApp.context, "关闭串口异常", Toast.LENGTH_SHORT).show();
      isException = true;
      return;
    }
    try {
      inputStream.close();
      outputStream.close();

      this.serialPortStatus = false;
      this.threadStatus = true; //线程状态
      serialPort.close();
    } catch (IOException e) {
      Log.e(TAG, "closeSerialPort: 关闭串口异常："+e.toString());
      Toast.makeText(MyApp.context, "关闭串口异常", Toast.LENGTH_SHORT).show();
      isException = true;
      return;
    }
    Log.d(TAG, "closeSerialPort: 关闭串口成功");
    Toast.makeText(MyApp.context, "关闭串口", Toast.LENGTH_SHORT).show();
  }

  /**
  * 发送串口指令（字符串）
  * @param data String数据指令
  */
  public void sendSerialPort(String data){
    Log.d(TAG, "sendSerialPort: 发送数据"+data);
    if (null == outputStream){
      Log.e(TAG, "sendSerialPort: 串口数据发送失败："+"null");
      Toast.makeText(MyApp.context, "串口数据发送失败", Toast.LENGTH_SHORT).show();
      return;
    }
    try {
      byte[] sendData = data.getBytes(); //string转byte[]
      this.data_ = new String(sendData); //byte[]转string
      if (sendData.length > 0) http://www.cppcns.com{
        outputStream.write(sendData);
//        outputStream.write('\n');
//        outputStream.write('\r'+'\n');
        outputStream.write('\r');
        outputStream.flush();
        Log.d(TAG, "sendSerialPort: 串口数据发送成功");
      }
    } catch (IOException e) {
      Log.e(TAG, "sendSerialPort: 串口数据发送失败："+e.toString());
      Toast.makeText(MyApp.context, "串口数据发送失败", Toast.LENGTH_SHORT).show();
    }

  }

  /**
  * 单开一线程，来读数据
  */
  private class ReadThread extends Thread {
    @Override
    public void run() {
      super.run();
      //判断进程是否在运行，更安全的结束进程
      while (!threadStatus){
        Log.d(TAG, "进入线程run");
        //64  1024
        byte[] buffer = new byte[64];
        int size; //读取数据的大小
        try {
          size = inputStream.read(buffer);
          if (size > 0){
            Log.d(TAG, "run: 接收到了数据：" + changeTool.ByteArrToHex(buffer));
            Log.d(TAG, "run: 接收到了数据大小：" + String.valueOf(size));
//            onDataReceiveListener.onDataReceive(buffer,size);
          }
        } catch (IOException e) {
          Log.e(TAG, "run: 数据读取异常：" +e.toString());
        }
      }

    }
  }

  //数据回调
  public OnDataReceiveListener onDataReceiveListener = null;
  public static interface OnDataReceiveListener {
    public void onDataReceive(byte[] buffer, int size);
  }
  public void setOnDataReceiveListener(OnDataReceiveListener dataReceiveListener) {
    onDataReceiveListener = dataReceiveListener;
  }

}

常见bug

这说明我们生成的so文件有问题 那么就从头执行一次
或者说我们并没有实现so的open方法这时需要看SerialPort.java
或者打个log看看so文件内的SerialPort和我们创建的SerialPort包名是否一致

如果我们走到了这里抛出异常
说明我们的Android机器并没有root无法访问权限这时我们需要找到厂商改下系统
或者系统给了权限但是我们并没有添加

<!--往sdcard中写入数据的权限 -->
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
  <!--在sdcard中创建/删除文件的权限 -->
  <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"></uses-permission>

*注意

由于设备不同文件路径有不同
这里默认的是/system/bin/su
有的机型路径是/system/xbin/su

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。