Android串口通信：串口讀寫實例

在Android串口通信：基本知識梳理（http://gqdy365.iteye.com/admin/blogs/2188846）的基礎上，我結合我項目中使用串口的實例，進行總結；

Android使用jni直接進行串口設備的讀寫網上已經有開源項目了，本文是基於網上的開源項目在實際項目中的使用做的調整和優化；
Google串口開源項目見：https://code.google.com/p/android-serialport-api/

下面是我項目中的相關代碼及介紹：

1、SerialPort.cpp

/*
 * 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.
 */
#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 "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:     cedric_serial_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;)V
 */
JNIEXPORT jobject JNICALL native_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;
}

/*
 * Class:     cedric_serial_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT jint JNICALL native_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;
}

static JNINativeMethod gMethods[] = {
		{ "open", "(Ljava/lang/String;I)Ljava/io/FileDescriptor;",(void*) native_open },
		{ "close", "()I",(void*) native_close },
};

/*
 * 爲某一個類註冊本地方法
 */
static int registerNativeMethods(JNIEnv* env, const char* className,
		JNINativeMethod* gMethods, int numMethods) {
	jclass clazz;
	clazz = env->FindClass(className);
	if (clazz == NULL) {
		return JNI_FALSE;
	}
	if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {
		return JNI_FALSE;
	}

	return JNI_TRUE;
}

/*
 * 爲所有類註冊本地方法
 */
static int registerNatives(JNIEnv* env) {
	const char* kClassName = "com/jerome/serialport/SerialPort"; //指定要註冊的類
	return registerNativeMethods(env, kClassName, gMethods,
			sizeof(gMethods) / sizeof(gMethods[0]));
}

/*
 * System.loadLibrary("lib")時調用
 * 如果成功返回JNI版本, 失敗返回-1
 */
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved) {
	JNIEnv* env = NULL;
	jint result = -1;

	if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
		return -1;
	}
	assert(env != NULL);

	if (!registerNatives(env)) { //註冊
		return -1;
	}
	//成功
	result = JNI_VERSION_1_4;

	return result;
}

在編譯時注意修改const char* kClassName = "com/jerome/serialport/SerialPort";爲你Java層與jni對應得包名；

2、Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

TARGET_PLATFORM := android-3
LOCAL_MODULE    := serial_port
LOCAL_SRC_FILES := SerialPort.cpp
LOCAL_LDLIBS    := -llog

include $(BUILD_SHARED_LIBRARY)

如果要修改生成so文件的名稱，請修改LOCAL_MODULE := serial_port

3、SerialPort.java

package com.jerome.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;

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 {
		mFd = open(device.getAbsolutePath(), baudrate);
		if (mFd == null) {
			throw new IOException();
		}
		mFileInputStream = new FileInputStream(mFd);
		mFileOutputStream = new FileOutputStream(mFd);
	}

	public InputStream getInputStream() {
		return mFileInputStream;
	}

	public OutputStream getOutputStream() {
		return mFileOutputStream;
	}

	private native FileDescriptor open(String path, int baudrate);
	public native int close();

	static {
		System.loadLibrary("serial_port");
	}
}

4、SerialPortUtil.java

package com.jerome.serialport;

import java.io.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;

/**
 * 串口操作類
 * 
 * @author Jerome
 * 
 */
public class SerialPortUtil {
	private String TAG = SerialPortUtil.class.getSimpleName();
	private SerialPort mSerialPort;
	private OutputStream mOutputStream;
	private InputStream mInputStream;
	private ReadThread mReadThread;
	private String path = "/dev/ttyMT1";
	private int baudrate = 115200;
	private static SerialPortUtil portUtil;
	private OnDataReceiveListener onDataReceiveListener = null;
	private boolean isStop = false;

	public interface OnDataReceiveListener {
		public void onDataReceive(byte[] buffer, int size);
	}

	public void setOnDataReceiveListener(
			OnDataReceiveListener dataReceiveListener) {
		onDataReceiveListener = dataReceiveListener;
	}

	public static SerialPortUtil getInstance() {
		if (null == portUtil) {
			portUtil = new SerialPortUtil();
			portUtil.onCreate();
		}
		return portUtil;
	}

	/**
	 * 初始化串口信息
	 */
	public void onCreate() {
		try {
			mSerialPort = new SerialPort(new File(path), baudrate);
			mOutputStream = mSerialPort.getOutputStream();
			mInputStream = mSerialPort.getInputStream();

			mReadThread = new ReadThread();
			isStop = false;
			mReadThread.start();
		} catch (Exception e) {
			e.printStackTrace();
		}
		initBle();
	}

	/**
	 * 發送指令到串口
	 * 
	 * @param cmd
	 * @return
	 */
	public boolean sendCmds(String cmd) {
		boolean result = true;
		byte[] mBuffer = (cmd+"\r\n").getBytes();
//注意：我得項目中需要在每次發送後面加\r\n，大家根據項目項目做修改，也可以去掉，直接發送mBuffer
		try {
			if (mOutputStream != null) {
				mOutputStream.write(mBuffer);
			} else {
				result = false;
			}
		} catch (IOException e) {
			e.printStackTrace();
			result = false;
		}
		return result;
	}

	public boolean sendBuffer(byte[] mBuffer) {
		boolean result = true;
		String tail = "\r\n";
		byte[] tailBuffer = tail.getBytes();
		byte[] mBufferTemp = new byte[mBuffer.length+tailBuffer.length];
		System.arraycopy(mBuffer, 0, mBufferTemp, 0, mBuffer.length);
		System.arraycopy(tailBuffer, 0, mBufferTemp, mBuffer.length, tailBuffer.length);
//注意：我得項目中需要在每次發送後面加\r\n，大家根據項目項目做修改，也可以去掉，直接發送mBuffer
		try {
			if (mOutputStream != null) {
				mOutputStream.write(mBufferTemp);
			} else {
				result = false;
			}
		} catch (IOException e) {
			e.printStackTrace();
			result = false;
		}
		return result;
	}

	private class ReadThread extends Thread {

		@Override
		public void run() {
			super.run();
			while (!isStop && !isInterrupted()) {
				int size;
				try {
					if (mInputStream == null)
						return;
					byte[] buffer = new byte[512];
					size = mInputStream.read(buffer);
					if (size > 0) {
						if(MyLog.isDyeLevel()){
							MyLog.log(TAG, MyLog.DYE_LOG_LEVEL, "length is:"+size+",data is:"+new String(buffer, 0, size));
						}
						if (null != onDataReceiveListener) {
							onDataReceiveListener.onDataReceive(buffer, size);
						}
					}
					Thread.sleep(10);
				} catch (Exception e) {
					e.printStackTrace();
					return;
				}
			}
		}
	}

	/**
	 * 關閉串口
	 */
	public void closeSerialPort() {
		sendShellCommond1();
		isStop = true;
		if (mReadThread != null) {
			mReadThread.interrupt();
		}
		if (mSerialPort != null) {
			mSerialPort.close();
		}
	}

}

5、使用方法：
a、配置ndk開發環境，具體百度一下；
b、工程根目錄下新建jni文件夾，將Android.mk和SerialPort.cpp放進去；
c、ndk中進入jni目錄，編譯生成so文件，默認so生成在libs/armeabi下；
d、新建com.jerom.serialport目錄，將SerialPort和SerialPortUtil放進去；
f、在你要使用的地方初始化SerialPortUtil，實現回調接口OnDataReceiveListener即可接受數據；

[b]
總結：
1、串口發送實質就是向串口設備（類似於文件操作）寫入字節流，串口讀取也是一樣；
2、主要jni與Java native得對應；
[/b]