android - 编译包含OpenCV header 的JNI库

Question

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我有一个带有cpp文件的Android项目，该文件需要编译。该文件包括OpenCV库的一些头。如您在Android.mk文件中看到的，OpenCV源文件位于jni / include / opencv2文件夹下。当我尝试使用ndk-build文件进行编译时，编译器给出以下错误:

"undefined reference to"

似乎对所有这些文件都是“错误: undefined reference ”问题。

Android.mk文件具有以下内容:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

OPENCV_PACKAGE_DIR := $(LOCAL_PATH)/include

LOCAL_MODULE := iqindex

LOCAL_C_INCLUDES := \
    $(LOCAL_PATH) \
    $(OPENCV_PACKAGE_DIR)

LOCAL_SRC_FILES := \
    main.cpp

LOCAL_SHARED_LIBRARIES := iqindex

LOCAL_LDLIBS := -llog -lz

include $(BUILD_SHARED_LIBRARY)

我对jni / ndk的东西没有足够的经验，我的问题是:

编译需要另一个头文件的.cpp文件是否足以使用ndk-build命令进行编译，并且将全部完成吗？

我尝试编译时出了什么问题？ Android.mk有什么问题？

编辑:控制台错误如下:

C:\MyName\My Project App>ndk-build

C:/MyName/android-ndk-r8e/build/core/add-application.mk:128: Android NDK: WARNING: APP_PLATFORM android-14 is larger than android:minSdkVersion 8 in ./AndroidManifest.xml
SharedLibrary  : libiqindex.so

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o:(.ARM.extab.text.unlikely._ZL6jthrowP7_JNIEnv+0x2c): error: undefined reference to 'typeinfo for cv::Exception'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function cv::Mat::Mat(cv::Mat const&):jni/include/opencv2/core/mat.hpp:125: error: undefined reference to 'cv::Mat::copySize(cv::Mat const&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function cv::Mat::release():jni/include/opencv2/core/mat.hpp:364: error: undefined reference to 'cv::Mat::deallocate()'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function cv::Mat::~Mat():jni/include/opencv2/core/mat.hpp:278: error: undefined reference to 'cv::fastFree(void*)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Mat_submat_1n:jni/include/opencv2/core/mat.hpp:376: error: undefined reference to 'cv::Mat::Mat(cv::Mat const&, cv::Rect_<int> const&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Mat_resize_1n:jni/main.cpp:111: error: undefined reference to 'cv::_InputArray::_InputArray(cv::Mat const&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Mat_resize_1n:jni/main.cpp:111: error: undefined reference to 'cv::_OutputArray::_OutputArray(cv::Mat&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Mat_resize_1n:jni/main.cpp:111: error: undefined reference to 'cv::resize(cv::_InputArray const&, cv::_OutputArray const&, cv::Size_<int>, double, double, int)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Utils_rotateData:jni/main.cpp:124: error: undefined reference to'cv::_InputArray::_InputArray(cv::Mat const&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Utils_rotateData:jni/main.cpp:124: error: undefined reference to'cv::_OutputArray::_OutputArray(cv::Mat&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Utils_rotateData:jni/main.cpp:124: error: undefined reference to'cv::flip(cv::_InputArray const&, cv::_OutputArray const&, int)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_Utils_rotateData:jni/main.cpp:125: error: undefined reference to'cv::Mat::t() const'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_IQLocal_nativeCreate:jni/main.cpp:139: error: undefined reference to 'get_instance()'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_IQLocal_load:jni/main.cpp:156: error: undefined reference to 'IQIndex::load(std::string, std::string)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_IQLocal_match:jni/main.cpp:171: error: undefined reference to 'IQIndex::match(cv::Mat&)'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_IQLocal_train:jni/main.cpp:182: error: undefined reference to 'IQIndex::train()'

C:/MyName/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: ./obj/local/armeabi-v7a/objs/iqindex/main.o: in function Java_project_name_zxing_IQLocal_compute:jni/main.cpp:198: error: undefined reference to 'IQIndex::compute(cv::Mat const&, char const*, char const*)'

collect2: ld returned 1 exit status

make: *** [obj/local/armeabi-v7a/libiqindex.so] Error 1

第二次编辑:现在，Android.mk看起来像这样:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

# OpenCV
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on

include C:/Emil/downloads/OpenCV-2.4.6-android-sdk-r2/OpenCV-2.4.6-android-sdk/sdk    /native/jni/OpenCV.mk

LOCAL_MODULE := iqindex

LOCAL_SRC_FILES := \
    main.cpp

LOCAL_C_INCLUDES := \
    $(LOCAL_PATH)/iqindex.h

LOCAL_LDLIBS := -llog -lz

include $(BUILD_SHARED_LIBRARY)

Answer 1

我想您忘记了将OpenCV库添加到您的项目中。因此，链接器找不到与OpenCV相关的功能。

From OpenCV documentation:

If your application project doesn’t have a JNI part, just copy the corresponding OpenCV native libs from /sdk/native/libs/ to your project directory to folder libs/.

In case of the application project with a JNI part, instead of manual libraries copying you need to modify your Android.mk file: add the following two code lines after the "include $(CLEAR_VARS)" and before "include path_to_OpenCV-2.4.6-android-sdk/sdk/native/jni/OpenCV.mk OPENCV_CAMERA_MODULES:=on OPENCV_INSTALL_MODULES:=on

因此，Android.mk中应包含以下几行:

include $(CLEAR_VARS)
# OpenCV
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
include ../../sdk/native/jni/OpenCV.mk