Android Studio jni开发 串口通信

公司需求做串口通信,由于开发环境是Android Studio所以配置时出现很多问题.

这个是网上照搬的SerialPort类:

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) 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 777 " + device.getAbsolutePath() + "\n"
+ "exit\n";
/*String cmd = "chmod 777 /dev/s3c_serial0" + "\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);
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);
public native void close();
static {
System.loadLibrary("SerialPort");
}
}

点击"View->Tool Windows->Terminal"，即在Studio中进行终端命令行工具.执行如下命令生成c语言头文件:

src\main\java>javah -jni com.serialport.main.SerialPort

创建c文件

右键>new>Folder>Jni Folder

将java文件夹下生成的com_serialport_main_SerialPort.h文件移动到main文件夹下的jni文件夹下

创建com_serialport_main_SerialPort.c文件,复制下面代码

//根据自己的h文件修改成一样的>>>>重要
#include <com_serialport_main_SerialPort.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 "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)


/*
* Class: android_serialport_SerialPort
* Method: open
* Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
*/
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: cedric_serial_SerialPort
* Method: open
* Signature: (Ljava/lang/String;)V
*/
//根据自己的h文件修改成一样的>>>>重要
JNIEXPORT jobject JNICALL Java_com_serialport_main_SerialPort_open
(JNIEnv *env, jobject thiz, jstring path, jint baudrate)
{
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", path_utf);
fd = open(path_utf, O_RDWR | O_SYNC);
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
*/
//根据自己的h文件修改成一样的>>>>重要
JNIEXPORT void JNICALL Java_com_serialport_main_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);
}

在根目录中的local.properties文件中添加代码

ndk.dir=D\:\\Android\\android-ndk-r10

android-ndk根据要求下载,由于机器要求不同,android-ndk的版本要求也不一样,我下载了4个版本只有这个r10可以用,看网上其他人好像用的版本也是有差异的

在build.gradle中添加代码

在defaultConfig下添加

ndk{
abiFilter "armeabi"
moduleName "SerialPort"
ldLibs "log", "z", "m", "jnigraphics", "android"
}

在android下添加

sourceSets{ //设置.so文件路径
main{
jniLibs.srcDirs = ['libs']
}
}

当有错误提示时:
检查项目属性,设置builders 选项;确保对.c更改自动生成.so文件;具体详见NDK环境搭建
删除项目libs/libserial_port.so文件,如果没有此文件完成第三步会自动生成,否则继续第一步;
修改serialport.c文件,移除fd = open(path_utf, O_RDWR | O_DIRECT | O_SYNC);中的 O_DIRECT选项;保存;//重要,因为我就遇到这个问题,修改后成功

因为是串口通信,所以测试机要有串口,还要root

这个不是类只是代码的使用集合:

FileOutputStream mOutputStream;
FileInputStream mInputStream;
SerialPort sp;


//初始化 需注意要先获取root权限
try {
sp=new SerialPort(new File("/dev/ttyS4"),9600);
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

if(sp != null){
mOutputStream=(FileOutputStream) sp.getOutputStream();
mInputStream=(FileInputStream) sp.getInputStream();
}

//关闭
sp.close();
sp = null;
try {
mOutputStream.close();
mOutputStream = null;
mInputStream.close();
mInputStream = null;
} catch (IOException e) {
e.printStackTrace();
}

//发送
try {
mOutputStream.write("write".getBytes());
mOutputStream.write('\n');
} catch (IOException e) {
e.printStackTrace();
}

//接收
Thread thread = new Thread(){
@Override
public void run() {
while (mInputStream != null){

int size;
try {
int length = mInputStream.available();
if (length > 0) {
byte[] buffer = new byte[length];
size = mInputStream.read(buffer);//该方法会阻塞线程直到接收到数据
stringBuffer.append(new String(buffer, 0, size));
handler.post(dataReceived);
}
} catch (IOException e) {
e.printStackTrace();
}
}
super.run();
}
};
thread.start();


StringBuffer stringBuffer = new StringBuffer();
Handler handler = new Handler();
DataReceived dataReceived = new DataReceived();

private class DataReceived implements Runnable{
@Override
public void run() {
if(stringBuffer.length() != 0){
String msg = stringBuffer.toString();
//对接收的数据进行处理,我这里没有进行处理
//比如一串字符串,会被分成好几个片段接收,像"abcd"可能被分开四次发送,这样接收就是"a","b","c","d"需要自己想办法拼接,做完这个我刚好辞职了,代码给忘记了,哈哈
 stringBuffer.delete(0,stringBuffer.length());
}
}
}