Android实现串口通信

本文实例为大家分享了Android实现串口通信的具体代码,供大家参考,具体内容如下

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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