本文小编为大家详细介绍“Android如何实现串口通信”，内容详细，步骤清晰，细节处理妥当，希望这篇“Android如何实现串口通信”文章能帮助大家解决疑惑，下面跟着小编的思路慢慢深入，一起来学习新知识吧。
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
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_ */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;
}
}
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>
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
读到这里，这篇“Android如何实现串口通信”文章已经介绍完毕，想要掌握这篇文章的知识点还需要大家自己动手实践使用过才能领会，如果想了解更多相关内容的文章，欢迎关注亿速云行业资讯频道。
免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
