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 port");
            /* 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 getInstance() {
        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) {
                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。