使用Android NDK构建本机OpenCV提供了“对'cv :: String :: deallocate（）的未定义引用”

Question

I'm attempting to use OpenCV with the NDK in Android Studio. As you may notice I'm using another native library called GStreamer.

My build.gradle:

apply plugin: 'com.android.application'

def getNdkCommandLine(ndkRoot, target) {
    def gstRoot
    def opencvRoot
    gstRoot = 'C:/local/gstreamer-1.0-android-arm-1.8.0'
    opencvRoot = 'C:/local/OpenCV-3.1.0-android-sdk/OpenCV-android-sdk'

    if (ndkRoot == null)
        throw new GradleException('NDK not configured')

    return ["$ndkRoot/ndk-build.cmd",
            'NDK_PROJECT_PATH=build',
            'APP_BUILD_SCRIPT=src/main/jni/Android.mk',
            'NDK_APPLICATION_MK=src/main/jni/Application.mk',
            'GSTREAMER_JAVA_SRC_DIR=src/main/java',
            "GSTREAMER_ROOT_ANDROID=$gstRoot",
            "OPENCV_ROOT_ANDROID=$opencvRoot",
            "$target"]
}

android {
    compileSdkVersion 19
    buildToolsVersion "23.0.2"

    sourceSets {
        main {
            // Avoid using the built in JNI generation plugin
            jni.srcDirs = []
            jniLibs.srcDirs = ['build/libs']
        }
    }

    defaultConfig {
        applicationId "com.mytestcom.mytestapp"
        minSdkVersion 19
        targetSdkVersion 19
        compileOptions {
            sourceCompatibility JavaVersion.VERSION_1_7
            targetCompatibility JavaVersion.VERSION_1_7
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
            signingConfig signingConfigs.release
        }
    }

    // Before compiling our app, prepare NDK code
    tasks.withType(JavaCompile) {
        compileTask -> compileTask.dependsOn ndkBuild
    }

    // Need to call clean on NDK ourselves too
    clean.dependsOn 'ndkClean'

    // Build native code using mk files like on Eclipse
    task ndkBuild(type: Exec, description: 'Compile JNI source via NDK') {
        commandLine getNdkCommandLine(android.ndkDirectory, 'TARGET_ARCH_ABI=armeabi-v7a')
    }

    task ndkClean(type: Exec, description: 'Clean JNI code built via NDK') {
        commandLine getNdkCommandLine(android.ndkDirectory, 'clean')
    }

    //Renames APK to current versionName found in Android Manifest
    applicationVariants.all { variant ->
        variant.outputs.each { output ->
            def outputFile = output.outputFile
            if (outputFile != null && outputFile.name.endsWith('.apk')) {
                def fileName = "My_Test_App-${versionName}.apk"
                output.outputFile = new File(outputFile.parent, fileName)
            }
        }
    }
}

dependencies {
    compile 'com.android.support:support-v4:19.1.0'
    compile project(':openCVLibrary310')
}

Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := gstplayer
LOCAL_SRC_FILES := player.cpp
LOCAL_C_INCLUDES := $(OPENCV_ROOT_ANDROID)/sdk/native/jni/include

LOCAL_SHARED_LIBRARIES := gstreamer_android
LOCAL_LDLIBS := -llog -landroid
include $(BUILD_SHARED_LIBRARY)

ifeq ($(TARGET_ARCH_ABI),armeabi)
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_ARM)
else ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_ARMV7)
else ifeq ($(TARGET_ARCH_ABI),arm64-v8a)
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_ARM64)
else ifeq ($(TARGET_ARCH_ABI),x86)
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_X86)
else ifeq ($(TARGET_ARCH_ABI),x86_64)
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_X86_64)
else
$(error Target arch ABI not supported)
endif

ifndef GSTREAMER_ROOT
ifndef GSTREAMER_ROOT_ANDROID
$(error GSTREAMER_ROOT_ANDROID is not defined!)
endif
GSTREAMER_ROOT        := $(GSTREAMER_ROOT_ANDROID)
endif

GSTREAMER_NDK_BUILD_PATH  := $(GSTREAMER_ROOT)/share/gst-android/ndk-build/

include $(GSTREAMER_NDK_BUILD_PATH)/plugins.mk
GSTREAMER_PLUGINS         := $(GSTREAMER_PLUGINS_CORE) $(GSTREAMER_PLUGINS_PLAYBACK) $(GSTREAMER_PLUGINS_CODECS) $(GSTREAMER_PLUGINS_NET) $(GSTREAMER_PLUGINS_SYS) $(GSTREAMER_PLUGINS_CODECS_RESTRICTED) $(GSTREAMER_CODECS_GPL) $(GSTREAMER_PLUGINS_ENCODING) $(GSTREAMER_PLUGINS_VIS) $(GSTREAMER_PLUGINS_EFFECTS) $(GSTREAMER_PLUGINS_NET_RESTRICTED)
GSTREAMER_EXTRA_DEPS      := gstreamer-player-1.0 gstreamer-video-1.0 glib-2.0

OPENCV_INSTALL_MODULES:=on
OPENCV_CAMERAMODULES:=off
OPENCV_LIB_TYPE:=STATIC

include $(GSTREAMER_NDK_BUILD_PATH)/gstreamer-1.0.mk
include $(OPENCV_ROOT_ANDROID)/sdk/native/jni/OpenCV.mk

Application.mk:

APP_PLATFORM=android-19
APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a

I'm using OpenCV-3.1.0-android-sdk, NDK r10e, Android Studio 2.1, Windows. I've tried using a different version of OpenCV (2.4.11) but it didn't help.

C:\local\OpenCV-3.1.0-android-sdk\OpenCV-android-sdk\sdk\native\jni\include\opencv2\core\cvstd.hpp
Error:(625) undefined reference to 'cv::String::allocate(unsigned int)'
Error:(667) undefined reference to 'cv::String::deallocate()'
Error:(667) undefined reference to 'cv::String::deallocate()'
Error:(667) undefined reference to 'cv::String::deallocate()'
Error:(667) undefined reference to 'cv::String::deallocate()'

C:\local\OpenCV-3.1.0-android-sdk\OpenCV-android-sdk\sdk\native\jni\include\opencv2\core\mat.inl.hpp
Error:(443) undefined reference to 'cv::error(int, cv::String const&, char const*, char const*, int)'
Error:(459) undefined reference to 'cv::error(int, cv::String const&, char const*, char const*, int)'
Error:(682) undefined reference to 'cv::Mat::deallocate()'
Error:(571) undefined reference to 'cv::fastFree(void*)'
Error:(592) undefined reference to 'cv::Mat::copySize(cv::Mat const&)'

Answer 1

I ran into a similar issue a few days ago. Imo, you should try to replace LOCAL_LDLIBS := -llog -landroid with LOCAL_LDLIBS += -llog -landroid .

Answer 2

The explanation for these errors is that the OpenCV code being used in GStreamer doesn't have access to the rest of the library, so it's failing to find basic methods like allocate() and deallocate() .

The solution was to include some prebuilt static libraries in the Android.mk so that these references are defined. So after include $(OPENCV_ROOT_ANDROID)/sdk/native/jni/OpenCV.mk I added these lines to add the relevant libraries:

include $(CLEAR_VARS)
LOCAL_MODULE := opencv-tbb
LOCAL_SRC_FILES := opencvLib/3rdparty/libs/$(TARGET_ARCH_ABI)/libtbb.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := opencv-core
LOCAL_SRC_FILES := opencvLib/$(TARGET_ARCH_ABI)/libopencv_core.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/opencvLib/include/
LOCAL_STATIC_LIBRARIES := opencv-tbb
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := opencv-imgproc
LOCAL_SRC_FILES := opencvLib/$(TARGET_ARCH_ABI)/libopencv_imgproc.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/opencvLib/include/
LOCAL_STATIC_LIBRARIES := opencv-core
include $(PREBUILT_STATIC_LIBRARY)

The LOCAL_EXPORT_C_INCLUDES variable sets the include files that correspond to that library. In this case the include folder works for both libraries.

Now for the GStreamer code to be able to use these libraries we have to add LOCAL_STATIC_LIBRARIES := opencv-core opencv-imgproc to the gstplayer module which references the 2 added OpenCV modules.

Edit:

Also I forgot to mention I changed APP_STL := gnustl_static to APP_STL := gnustl_shared in Application.mk