在公司主要做VC++ 方面开发，最近公司新模块开发，主要用串口通讯，而且要求二次开发包，要VC、Linux和Android 三个平台的，但是由于Android 方面不关我事。但是，小弟是个新手，目前正在学习Android 开发（准备往这方面发展），于是乎，就自己私底下搞搞学习学习。因此，记录这一个多星期的一些收获，以后可以看看。

1、开发环境

(1) Android Studio 2.2.2 (2) JDK 1.8 (3) NDK android-ndk-r10e (一般使用这个版本，低于这个版本的我调试都报错)

(4) 最重要的谷歌开源的串口类android-serialport-api 下载地址： http://code.google.com/p/android-serialport-api/ 这个地址需要，也可以到GitHub或则百度大把。下载源码之后发现源码可以在ADT使用。

2、创建SerialPortNDK工程

(1) 这个工程主要用户生成SerialPort类的动态连接库libserial_port.so文件。

(2) 选择编译SDK版本 API19

3、导入下载SerialPort类和SerialPortFinder类（文章末尾有两个类的源码）

4、使用javah 命令生成JNI的 .h头文件

（1）使用windows自带的命令行或则使用Android Studio打开 Terminal（View -> Tool Windows -> Terminal），进入JNI工程的根目录下，

使用执行javah -classpath . -jni SerialPort

这个步骤很容易出现找不到类文件的情况，如：

a、

b、

出现第一种，就是没有找到jni的根目录，第二种就是没有指定路径

记住通用格式——

javah -classpath . -jni 类路径.JNI类

这个步骤需要注意的地方是什么才算工程的根目录，请看下面图的解释：

看文字可能有点难理解，举个例子，那我当前的工程目录来说：

E:\androidcode\SerialPortNDK\app\src\main\java\com\serialport

则根目录就是E:\androidcode\SerialPortNDK\app\src\main\java ---》 java就是根目录

其实，还有个窍门，直接看.java类文件的包名也可以知道，如：查看SerialPort.java 文件

上图中包名为 com.serialport 则包名的上一层目录就是根目录。

因此，执行在java目录，执行javah -classpath . -jni com.serialport.SerialPort 如图：

可以看到在java 目录下出现jni 头文件：

PC文件夹下：

5、在工程中建立JNI文件夹，添加.c文件

(1) 在工程的java文件下右键 jni 文件夹，如图
(2) 将右键菜单中选择New -> C/C++ Source File创建与 .h 文件同名的 .c 文件

com_serialport_SerialPort.h 文件移动到jni目录下，并且生成同名的.c文件( com_serialport_SerialPort.c )

如图：

特别需要注意的地方是： （3）在.c文件中，open和close 名字必须与.h文件的名字一样如图：

（4）并且#include "xxx.h"名字必须和jni.h文件名一样，否则编译将不通过。

上面两个注意的地方可以去查看c/c++的规则
6、修改和配置相关文件生成动态库.so 文件 (1) 在工程目录下的 local.properties文件，添加 ndk 路径, 如图，我的ndk路径

Android-ndk的版本至少要 r9d 以上的版本，如果等于或低于该版本，运行时会提示No rule to make target的错误。我使用的是 r10e 的版本。

(2) 在 module 的 build.gradle 中添加 ndk 配置在 defaultConfig 节点下添加：

        ndk{            //abiFilter "armeabi"           //过滤器，生成相关平台的.so文件， 不写，则生成每种平台相关的.so文件            moduleName "serial_port"        // 生成so的名称            ldLibs "log", "z", "m", "jnigraphics", "android"        }

如图：

(3) 在工程的gradle.properties 文件中添加

android.useDeprecatedNdk=true

否则 sync 时会提示错误 NDK integration is deprecated in the current plugin.

(4) Sync Project with Gradle Files 或则Rebuild Project整个工程，则可以生成我们需要的libserial_port.so动态库了。生成的libserial_port.so 目录在E:\androidcode\SerialPortNDK\app\build\intermediates\ndk\debug\lib

终于成功了，初学什么都不懂，整整搞了一个星期，每天下班后都在弄，皇天不负有心人。。。。。

后记：由于api 19 之后的 termios.h 里面的函数有调整，因此调试过程中，有可能出现
java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "tcgetattr" referenced by "libserialport.so"...

解决方法：

将api 19 的 termios.h 拷贝到 jni 目录下
termios.h
详情请查看 http://jp1017.github.io/2016/06/30/jni-%E5%BC%80%E5%8F%91%E9%94%99%E8%AF%AF%E4%B9%8B-java-lang-UnsatisfiedLinkError-dlopen-failed-cannot-locate-symbol-tcgetattr-referenced-by-libserial-port-so/

http://www.eoeandroid.com/thread-914514-1-1.html

上面主要使用到的类：

(1) SerialPort.class

/* * Copyright 2009 Cedric Priscal *  * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at *  * http://www.apache.org/licenses/LICENSE-2.0 *  * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License.  */package com.serialport;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;import android.util.Log;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 {/* 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 666 " + 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 setterspublic InputStream getInputStream() {return mFileInputStream;}public OutputStream getOutputStream() {return mFileOutputStream;}// JNIprivate native static FileDescriptor open(String path, int baudrate, int flags);public native void close();static {System.loadLibrary("serial_port");}}

(2) SerialPortFinder.class

/* * Copyright 2009 Cedric Priscal *  * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at *  * http://www.apache.org/licenses/LICENSE-2.0 *  * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License.  */package com.serialport;import java.io.File;import java.io.FileReader;import java.io.IOException;import java.io.LineNumberReader;import java.util.Iterator;import java.util.Vector;import android.util.Log;public class SerialPortFinder {public class Driver {public Driver(String name, String root) {mDriverName = name;mDeviceRoot = root;}private String mDriverName;private String mDeviceRoot;Vector mDevices = null;public Vector getDevices() {if (mDevices == null) {mDevices = new Vector();File dev = new File("/dev");File[] files = dev.listFiles();int i;for (i=0; i mDrivers = null;Vector getDrivers() throws IOException {if (mDrivers == null) {mDrivers = new Vector();LineNumberReader r = new LineNumberReader(new FileReader("/proc/tty/drivers"));String l;while((l = r.readLine()) != null) {// Issue 3:// Since driver name may contain spaces, we do not extract driver name with split()String drivername = l.substring(0, 0x15).trim();String[] w = l.split(" +");if ((w.length >= 5) && (w[w.length-1].equals("serial"))) {Log.d(TAG, "Found new driver " + drivername + " on " + w[w.length-4]);mDrivers.add(new Driver(drivername, w[w.length-4]));}}r.close();}return mDrivers;}public String[] getAllDevices() {Vector devices = new Vector();// Parse each driverIterator itdriv;try {itdriv = getDrivers().iterator();while(itdriv.hasNext()) {Driver driver = itdriv.next();Iterator itdev = driver.getDevices().iterator();while(itdev.hasNext()) {String device = itdev.next().getName();String value = String.format("%s (%s)", device, driver.getName());devices.add(value);}}} catch (IOException e) {e.printStackTrace();}return devices.toArray(new String[devices.size()]);}public String[] getAllDevicesPath() {Vector devices = new Vector();// Parse each driverIterator itdriv;try {itdriv = getDrivers().iterator();while(itdriv.hasNext()) {Driver driver = itdriv.next();Iterator itdev = driver.getDevices().iterator();while(itdev.hasNext()) {String device = itdev.next().getAbsolutePath();devices.add(device);}}} catch (IOException e) {e.printStackTrace();}return devices.toArray(new String[devices.size()]);}}

(3) com_serialport_SerialPort.h

/* DO NOT EDIT THIS FILE - it is machine generated */#include /* Header for class com_serialport_SerialPort */#ifndef _Included_com_serialport_SerialPort#define _Included_com_serialport_SerialPort#ifdef __cplusplusextern "C" {#endif/* * Class:     com_serialport_SerialPort * Method:    open * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor; */JNIEXPORT jobject JNICALL Java_com_serialport_SerialPort_open  (JNIEnv *, jclass, jstring, jint, jint);/* * Class:     com_serialport_SerialPort * Method:    close * Signature: ()V */JNIEXPORT void JNICALL Java_com_serialport_SerialPort_close  (JNIEnv *, jobject);#ifdef __cplusplus}#endif#endif

(3) com_serialport_SerialPort.c

/* * Copyright 2009-2011 Cedric Priscal * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */#include #include #include #include #include #include #include #include "com_serialport_SerialPort.h.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; */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, "", "()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 */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);}

参考教程（都是大神，所以非常感激）：

http://blog.csdn.net/caojengineer/article/details/51838394

http://blog.csdn.net/u010302327/article/details/50224457

http://blog.csdn.net/doris_d/article/details/53330838

Android(安卓)studio 使用NDK 实现串口动态库

1、开发环境

可以看到在java 目录下出现jni 头文件：

5、在工程中建立JNI文件夹，添加.c文件

com_serialport_SerialPort.h 文件移动到jni目录下，并且生成同名的.c文件( com_serialport_SerialPort.c )

如图：

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Android(安卓)studio 使用NDK 实现串口 动态库

1、开发环境

可以看到在java 目录下出现jni 头文件：

5、在工程中建立JNI文件夹，添加.c文件

com_serialport_SerialPort.h 文件移动到jni目录下，并且生成同名的.c文件( com_serialport_SerialPort.c )

如图：

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Android(安卓)studio 使用NDK 实现串口动态库