Question

我试图建立OpenALPR example project for Android几天。它构建并启动，但在调用本机方法识别它后会产生异常：

java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
at java.util.concurrent.FutureTask.run(FutureTask.java:239)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
at java.lang.Thread.run(Thread.java:838)

Caused by: java.lang.UnsatisfiedLinkError: Native method not found: org.openalpr.AlprJNIWrapper.recognizeWithCountryRegionNConfig:(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;I)Ljava/lang/String;
at org.openalpr.AlprJNIWrapper.recognizeWithCountryRegionNConfig(Native Method)
at org.openalpr.app.AlprFragment$AlprTask.doInBackground(AlprFragment.java:78)
at org.openalpr.app.AlprFragment$AlprTask.doInBackground(AlprFragment.java:1)
at android.os.AsyncTask$2.call(AsyncTask.java:287)
at java.util.concurrent.FutureTask.run(FutureTask.java:234)
... 4 more

我什么都做不了，它总是出现。

Application.mk

APP_ABI := armeabi-v7a
APP_CPPFLAGS := -frtti -fexceptions
APP_STL := gnustl_static

所有尝试后

Android.mk

LOCAL_PATH := $(call my-dir)
LIB_PATH := $(LOCAL_PATH)/../libs/armeabi-v7a

include $(CLEAR_VARS)

LOCAL_MODULE := leptonica
LOCAL_SRC_FILES := 3rdparty/liblept.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := tesseract
LOCAL_SRC_FILES := 3rdparty/libtess.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := simpleini
LOCAL_SRC_FILES := 3rdparty/libsimpleini.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := support
LOCAL_SRC_FILES := 3rdparty/libsupport.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := openalpr
LOCAL_SRC_FILES := 3rdparty/libopenalpr-static.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)

OPENCV_INSTALL_MODULES:=on
OPENCV_CAMERA_MODULES:=off

include d:\Other\robovisor_mobile\OpenCV-android-sdk\sdk\native\jni\OpenCV.mk

LOCAL_MODULE := openalpr-native
SOURCE_LIST := $(wildcard $(LOCAL_PATH)/*.cpp)
HEADER_LIST := $(wildcard $(LOCAL_PATH)/*.h)
LOCAL_SRC_FILES := AlprJNIWrapper.cpp
LOCAL_SRC_FILES += $(HEADER_LIST:$(LOCAL_PATH)/%=%)
LOCAL_SRC_FILES += $(SOURCE_LIST:$(LOCAL_PATH)/%=%)
LOCAL_EXPORT_C_INCLUDES += /home/sujay/builds/src/openalpr/src/openalpr
LOCAL_EXPORT_C_INCLUDES += /home/sujay/builds/src/OpenCV-2.4.9-android-sdk/sdk/native/include
FILE_LIST := $(foreach dir, $(LOCAL_EXPORT_C_INCLUDES), $(wildcard $(dir)/*.cpp))
LOCAL_SRC_FILES := $(FILE_LIST:$(LOCAL_PATH)/%=%)

LOCAL_C_INCLUDES += /home/sujay/builds/src/openalpr/src/openalpr
LOCAL_C_INCLUDES += /home/sujay/builds/src/OpenCV-2.4.9-android-sdk/sdk/native/include
LOCAL_C_INCLUDES += /home/sujay/tools/android-ndk-r10/platforms/android-19/arch-arm/usr/include
LOCAL_SHARED_LIBRARIES += tesseract leptonica
LOCAL_STATIC_LIBRARIES += openalpr support simpleini
LOCAL_LDLIBS := -llog

include $(BUILD_SHARED_LIBRARY)

AlprJNIWrapper.cpp包含我原生函数所需

/**
 * Created by sujay on 13/11/14.
 */
#include <string>
#include <sstream>
#include <cstdio>
#include <iostream>

// openCV includes
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

// open alpr includes
#include "support/filesystem.h"
#include "support/timing.h"
#include "alpr.h"
#include "cjson.h"

#include "AlprJNIWrapper.h"
#include "AlprNative.h"

using namespace alpr;

JNIEXPORT jstring JNICALL Java_org_openalpr_AlprJNIWrapper_recognize(JNIEnv *env,
        jobject object, jstring jimgFilePath, jint jtopN)
{
    jstring defaultCountry = env->NewStringUTF("us");
    jstring defaultRegion = env->NewStringUTF("");
    jstring defaultConfigFilePath = env->NewStringUTF(CONFIG_FILE);
    return _recognize(env, object, defaultCountry, defaultRegion, jimgFilePath, defaultConfigFilePath, jtopN);
}

JNIEXPORT jstring JNICALL Java_org_openalpr_AlprJNIWrapper_recognizeWithCountryNRegion(
        JNIEnv *env, jobject object, jstring jcountry,
        jstring jregion, jstring jimgFilePath, jint jtopN)
{
    jstring defaultConfigFilePath = env->NewStringUTF(CONFIG_FILE);
    return _recognize(env, object, jcountry, jregion, jimgFilePath, defaultConfigFilePath, jtopN);
}

JNIEXPORT jstring JNICALL Java_org_openalpr_AlprJNIWrapper_recognizeWithCountryRegionNConfig
  (JNIEnv *env, jobject object, jstring jcountry, jstring jregion,
          jstring jimgFilePath, jstring jconfigFilePath, jint jtopN)
{
    return _recognize(env, object, jcountry, jregion, jimgFilePath, jconfigFilePath, jtopN);
}

jstring _recognize(JNIEnv *env, jobject object,
        jstring jcountry, jstring jregion, jstring jimgFilePath,
        jstring jconfigFilePath, jint jtopN)
{

    const char* countryChars = env->GetStringUTFChars(jcountry, NULL);

    std::string country(countryChars);

    env->ReleaseStringUTFChars(jcountry, countryChars);

    if(country.empty())
    {
        country = "us";
    }

    const char* configFilePathChars = env->GetStringUTFChars(jconfigFilePath, NULL);

    std::string configFilePath(configFilePathChars);

    env->ReleaseStringUTFChars(jconfigFilePath, configFilePathChars);

    if(configFilePath.empty())
    {
        configFilePath = "/etc/openalpr/openalpr.conf";
    }

    const char* imgFilePath = env->GetStringUTFChars(jimgFilePath, NULL);

    int topN = jtopN;

    std::string response = "";

    cv::Mat frame;
    Alpr alpr(country, configFilePath);

    const char* regionChars = env->GetStringUTFChars(jregion, NULL);

    std::string region(regionChars);

    env->ReleaseStringUTFChars(jregion, regionChars);

    if(region.empty())
    {
        alpr.setDetectRegion(true);
        alpr.setDefaultRegion(region);
    }


    alpr.setTopN(topN);

    if (alpr.isLoaded() == false) {
        env->ReleaseStringUTFChars(jimgFilePath, imgFilePath);
        response = errorJsonString("Error initializing Open Alpr");
        return env->NewStringUTF(response.c_str());
    }

    if(fileExists(imgFilePath))
    {
        frame = cv::imread(imgFilePath);
        response = detectandshow(&alpr, frame, "");
    }
    else
    {
        response = errorJsonString("Image file not found");
    }
    env->ReleaseStringUTFChars(jimgFilePath, imgFilePath);
    return env->NewStringUTF(response.c_str());
}

JNIEXPORT jstring JNICALL Java_org_openalpr_AlprJNIWrapper_version
  (JNIEnv *env, jobject object)
{
    return env->NewStringUTF(Alpr::getVersion().c_str());
}

std::string detectandshow(Alpr* alpr, cv::Mat frame, std::string region) 
{
    std::vector < uchar > buffer;
    std::string resultJson = "";
    cv::imencode(".bmp", frame, buffer);

    std::vector < char > buffer1;

    for(std::vector < uchar >::iterator i = buffer.begin(); i < buffer.end(); i++) {
        buffer1.push_back(*i);
    }

    timespec startTime;
    getTimeMonotonic(&startTime);

    //std::vector < AlprResults > results = alpr->recognize(buffer);
    AlprResults results = alpr->recognize(buffer1);

    timespec endTime;
    getTimeMonotonic(&endTime);
    double totalProcessingTime = diffclock(startTime, endTime);

    //if (results.size() > 0)
    {
        resultJson = alpr->toJson(results/*, totalProcessingTime*/);
    }

    return resultJson;
}

std::string errorJsonString(std::string msg) 
{
    cJSON *root;
    root = cJSON_CreateObject();
    cJSON_AddTrueToObject(root, "error");
    cJSON_AddStringToObject(root, "msg", msg.c_str());

    char *out;
    out = cJSON_PrintUnformatted(root);

    cJSON_Delete(root);

    std::string response(out);

    free(out);
    return response;
}

AlprJNIWrapper.java调用本机方法

/**
 * 
 */
package org.openalpr;

/**
 * @author sujay
 *
 */
public class AlprJNIWrapper implements Alpr {

        static { 
            System.loadLibrary("lept");
            System.loadLibrary("tess");
            System.loadLibrary("opencv_java");
            System.loadLibrary("openalpr-native");
        }

    /* (non-Javadoc)
     * @see org.openalpr.Alpr#recognize(java.lang.String, int)
     */
    @Override
    public native String recognize(String imgFilePath, int topN);

    /* (non-Javadoc)
     * @see org.openalpr.Alpr#recognizeWithCountryNRegion(java.lang.String, java.lang.String, java.lang.String, int)
     */
    @Override
    public native String recognizeWithCountryNRegion(String country, String region,
            String imgFilePath, int topN);

    /* (non-Javadoc)
     * @see org.openalpr.Alpr#recognizeWithCountryRegionNConfig(java.lang.String, java.lang.String, java.lang.String, java.lang.String, int)
     */
    @Override
    public native String recognizeWithCountryRegionNConfig(String country,
            String region, String imgFilePath, String configFilePath, int topN);

    /*
     * (non-Javadoc)
     * @see org.openalpr.Alpr#version()
     */
    @Override
    public native String version();
}

被修改

手机上有关于处理器的信息。

Processor       : ARMv7 Processor rev 3 (v7l)
processor       : 0
BogoMIPS        : 1993.93

Features        : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4
idiva idivt
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 3

再次编辑

我尝试在结果.so文件中获取有关函数的信息，我得到了：

Symbol table '.dynsym' contains 6 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 00000000     0 FUNC    GLOBAL DEFAULT  UND __cxa_finalize
     2: 00000000     0 FUNC    GLOBAL DEFAULT  UND __cxa_atexit
     3: 00002004     0 NOTYPE  GLOBAL DEFAULT  ABS _edata
     4: 00002004     0 NOTYPE  GLOBAL DEFAULT  ABS __bss_start
     5: 00002004     0 NOTYPE  GLOBAL DEFAULT  ABS _end

我是从

获得的

<ndk_path>\toolchains\arm-linux-androideabi-4.8\prebuilt\windows\bin>arm-linux-androideabi-readelf.exe 
-Ws <projects_path>\libs\armeabi-v7a\libopenalpr-native.so

我做错了吗？或者.so文件中确实没有我的功能？

Answer 1

可能有几个问题首先，您在不受支持的设备上运行示例，例如，如果为armeabi-v7构建了lib（由于make文件中的APP_ABI := armeabi-v7a设置，它肯定是这样）并且您的设备是intel x86或低于7 armeabi版本等。
可能是lib项目更新后样本已过时，因此某些方法名称已更改或方法已被删除，因为已弃用等。
还编译NDK lib对包敏感，因此如果将JNI类放入不同的包中，它也不会起作用此外，本机库.so文件必须放在项目的正确位置，而不是通常放置jar-libs的libs文件夹。它与android studio有点不同的文件夹：

... \ src \ main \ jniLibs \ aremabi-v7a \ libYourLib.so（适用于aremabi-v7a版本）
... \ src \ main \ jniLibs \ x86 \ libYourLib.so（适用于x86版本等）

<强>更新
不要忘记尊重最低API级别19。应用程序不适用于API级别较低的设备，我的意思是您可以更改项目中的最低API级别 - 不要这样做。
这里的问题是libopenalpr-native.so名称中包含短划线-字符。 Dash是AOS中资源命名的限制字符。所以我用＆＃34; _＆＃34;和app works now 并在此处替换它：

System.loadLibrary("openalpr_native");

我没有使用您的.so版本，但仅包含在项目一中的更新
看看：http://prntscr.com/6w6qfx你的lib只有5kb，相比原来的1.7Mb肯定有些不对劲。它在评论中解释了你的问题：

为什么System.loadLibrary没有错误（＆＃34; openalpr-native＆＃34;）;?一世只是不能理解这种情况 - 创建libopenalpr-native.so 文件，它加载到程序，没有方法。

您可以使用示例项目中包含的原始库吗？只是为了测试。

Answer 2

在库中找不到正确的方法是由于名称不匹配，您应该在C ++代码中用InspectRequestProcessImpl.processRequest()包装JNI函数代码。

Android的不满意的linkerror OpenALPR测试项目

2 个答案: