问题描述

我正在制作一个应用程序以通过串行端口发送数据.这需要从本地图书馆打电话
我有两个本机方法” open””关闭”我已经使用ndk生成了.so库，然后将它们放入jnilibs文件夹中，但仍然出现一个错误，说”不能重新安置相应的jni函数”

serialport.c

#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;
    }
}

JNIEXPORT jobject JNICALL Java_com_example_richyrony_serial485_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);
        LOGD(" serial port buadrate %s", speed);
//      fd = open(path_utf, O_RDWR | O_DIRECT | O_SYNC);
        fd = open(path_utf,O_RDWR | O_SYNC);               //2011.8.26 
        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;
}

void  Java_com_example_richyrony_serial485_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);
}

serialport.java

package com.example.richyrony.serial485;


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) throws SecurityException, IOException {

    /* Check access permission */
    if (!device.canRead() || !device.canWrite()) {
        try {

            if (!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
static {
    System.loadLibrary("serial_port");

}

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

}

这些是我的Java类和本机文件.请帮助

推荐答案

正如我所解释的那样预先构建的库(即使将其正确复制到 src/main/jnlibs ).

您可以简单地忽略此错误消息:您的APK仍将安装预构建库，并且本机方法将在运行时解决.

您可以为这些方法添加@SuppressWarnings(“JniMissingFunction”)注释，也可以为整个类添加:

@SuppressWarnings("JniMissingFunction")
private native static FileDescriptor open(String path, int baudrate);

@SuppressWarnings("JniMissingFunction")
public native void close();

如果您可以在任何设备，甚至在模拟器上安装APK，并且加载了 Serialport 类，则正确配置了JNI包装器.当系统无法加载本地库时，它将有用的错误消息写入 logcat .

.

让我在上进行一些扩展.在Java中，ClassLoader可以(而不是”应该”)推迟加载类，直到真正有必要为止.因此，仅在APK中将课程放入不会触发其静态构造函数.但是，如果您有一个字段

private SerialPort m_serialPort = new SerialPort();

在您的主进性中，将加载类，即使您实际上没有触摸此 m_serialport ，JNI也将被初始化.请注意，我在 serialport 类中添加了一个无需默认的构造函数:

public SerialPort() {}

这不会测试JNI代码本身，例如参数的转换等.如果您没有可用于测试代码的真实设备，则应设计一些将扮演实际串行端口角色的模拟接口.

以上所述是小编给大家介绍的无法解决相应的jni函数,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对77isp云服务器技术网的支持！