Android串口通信
吹着空调哼着歌 人气:0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
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