android 串口开发第二篇:利用jni完成android和串口通讯

二:代码完毕

  我的费用环境是android studio 2.3.3
串口开发自己创设一个协理c++项目,然后在cpp目录下,制造一个nateve-lib.cpp的次第,将串口打开,串口关闭的程序复制进去即可,native-lib程序中艺术的命名规则须要依照你实在意况,稍作修改,cpp中艺术名格式为,Java_包名_调用jni方法的类名_方法名,如Java_com_serialportdemo_SerialPort_open,此处一定要注意,android
studio生成的是cpp程序,不是c程序,那八个有局部区其余,比如:

我对c也不熟悉,以下语法有误请指出

*.c的语法
变量定义
jstring jstr2 = (*env) -> NewStringUTF(env, cstr);
方法定义
JNIEXPORT jstring JNICALL Java_com_serialportdemo_MainActivity_encode()
JNIEXPORT jstring JNICALL Java_com_serialportdemo_MainActivity_decode()


*.cpp的语法
jstring jstr2 =env->NewStringUTF(hello.c_str());

extern "C"  //如果这里不写extern "C",程序编译不会错,但android无法调用该方法,错误日志是找不到该方法
JNIEXPORT jstring JNICALL Java_com_serialportdemo_MainActivity_encode()

extern "C"
JNIEXPORT jstring JNICALL Java_com_serialportdemo_MainActivity_decode()

 

串口打开,串口关闭代码如下:

//获取波特率
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;
    }
}


//打开串口程序
extern "C"
JNIEXPORT jobject JNICALL
Java_com_serialportdemo_SerialPort_open(JNIEnv *env, jobject thiz, jstring path,jint baudrate) {
    int fd;
    speed_t speed;
    jobject mFileDescriptor;

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

    LOGD("init native Opening device!");
    /* Opening device */
    {
        jboolean iscopy;
        const char *path_utf = env->GetStringUTFChars(path, &iscopy);
        LOGD("Opening serial port %s", path_utf);
//      fd = open(path_utf, O_RDWR | O_DIRECT | O_SYNC);
        fd = open(path_utf, O_RDWR | O_NOCTTY | O_NONBLOCK | O_NDELAY);
        LOGD("open() fd = %d", fd);
        env->ReleaseStringUTFChars(path, path_utf);
        if (fd == -1) {
            /* Throw an exception */
            LOGE("Cannot open port %d",baudrate);
            /* TODO: throw an exception */
            return NULL;
        }
    }

    LOGD("init native Configure device!");
    /* Configure device */
    {
        struct termios cfg;
        if (tcgetattr(fd, &cfg)) {
            LOGE("Configure device tcgetattr() failed 1");
            close(fd);
            return NULL;
        }

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

        if (tcsetattr(fd, TCSANOW, &cfg)) {
            LOGE("Configure device tcsetattr() failed 2");
            close(fd);
            /* TODO: throw an exception */
            return NULL;
        }
    }

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

    return mFileDescriptor;
}

//关闭串口程序
  extern "C"
JNIEXPORT jint JNICALL
Java_com_serialportdemo_SerialPort_close(JNIEnv * env, jobject thiz)
{
    jclass SerialPortClass = env->GetObjectClass(thiz);
    jclass FileDescriptorClass = env->FindClass("java/io/FileDescriptor");

    jfieldID mFdID = env->GetFieldID(SerialPortClass, "mFd", "Ljava/io/FileDescriptor;");
    jfieldID descriptorID = env->GetFieldID(FileDescriptorClass, "descriptor", "I");

    jobject mFd = env->GetObjectField(thiz, mFdID);
    jint descriptor = env->GetIntField(mFd, descriptorID);

    LOGD("close(fd = %d)", descriptor);
    close(descriptor);
    return 1;
}

  android
方法就几乎多了,首先来看串口操作类,在那几个类中开辟串口,测试没有做关闭串口的操作,jni的open方法,再次来到一个java.io.FileDescriptor对像,串口操作类通过该对像,获取文件的读写流操作对像.

//加载so文件
 static {
        System.loadLibrary("native-lib");
    }

/**
     * @param  path 串口文件路径
     * @param baudrate 波特率,不同设备波特率有区别
     * */
    public SerialPort(String path, int baudrate) throws SecurityException, IOException {
        File device = new File(path);
        Logger.d(serialPortMsg());
        if(!device.canRead() || !device.canWrite()) {
            try {
                Process 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.getMessage();
            }

        }

        mFd = open(device.getAbsolutePath(), baudrate);
        Logger.d(TAG+"open commplete");
        if (mFd == null) {
            Logger.e(TAG, "native open returns null");
            throw new IOException();
        }

        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }


 //定义本地方法
public native FileDescriptor open(String path, int baudrate); 
public native void close(); 

接下去须求定义一个读取串口音信的线程,用于获取串口发送给android的音信

class ReadSerialPortMsgThread implements  Runnable{
        @Override
        public void run() {
            int size;
            byte buff[] = new byte[1024];
           final SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
            while (true){
               try {
                   if(mInputStream==null){
                       return;
                   }
                   size = mInputStream.read(buff);
                   if(size<=0){
                       continue;
                   }
                   final String message = new String(buff,0,size);
                   Logger.d(TAG+"接收到串口回调  "+message);
                   seriapPortMsg.append(message);
                   if(buff[size - 1] == '\n'){
                       log.post(new Runnable() {
                           @Override
                           public void run() {
                               log.setText(sdf.format(new Date())+"接收到串口发送的指令  "+message);
                           }
                       });
                   }
               }catch (Exception e){
                   e.printStackTrace();
               }finally {
                   try {
                       Thread.sleep(1000);
                   } catch (InterruptedException e) {
                       e.printStackTrace();
                   }
               }
            }
        }
    }

上述代码落成了对串口的读操作,串口写操作对比简单,就是获取串口的OutputStream,然后调用writer方法即可,代码如下:

  

 @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.sendMsg:
                String msg = serMsg.getText().toString()+"\r\n";
                if(msg!=null&&!msg.equals("")){
                    byte [] buff = msg.getBytes();
                    try {
                        mOutputStream.write(buff,0,buff.length);
                        Logger.d(TAG+"msg 输出完成");
                    } catch (IOException e) {
                        e.printStackTrace();
                        Logger.e(TAG+e.getMessage());
                    }
                }
        }
    }

到此停止,读写操作的代码全体已毕,我的测试串口设备一向在向android发送新闻,如下图

图片 1

三:注意事项

   String SERIALPORT_NO3 = “/dev/ttyS3″,int BAUDRATE=115200;
 那是自身设备定义的串口文件路径和波特率,那一个新闻地点须求基于实际情状作修改。

   

完整demo代码:https://github.com/jlq023/serialport

 

一:串口通讯简介

  由于串口开发涉及到jni,所以开发环境必要协理ndk开发,纵然未配备ndk配置的爱侣,或者对jni不熟谙的情人,请查看上一篇小说,android
串口开发第一篇:搭建ndk开发环境以及第四个jni调用程序 
,串口通讯和java操作io类似,先打开串口,然后向串口发送或者读取数据,最终关闭串口,所以基本思路就是:

  1.对串口文件进行配置(波特率等),选取串口文件,打开串口,设备差距,可以读写的串口也不相同.

  2.读写串口 ,读串口须要开一个子线程,然后死循环读取串口发送的数量

  3.闭馆串口文件

       其中打开,关闭串口是在jni方法执行,读写操作是android程序执行。

相关文章