OpenCV4Android: non-system libraries in linker flags:-lopencv_java error Solution

OpenCV4Android: non-system libraries in linker flags:-lopencv_java error Solution

Recently I made a copy of the old Code and found that after OpenCV to 2.4.11, the previous mk file was not applicable and a bunch of errors were reported.

First, as described above, the LOCAL_LDLIBS + =-lm-llog sentence + = must not be written incorrectly as: =. In addition, the following error will be reported:

Android NDK: WARNING: APP_PLATFORM android-17 is larger than android:minSdkVersion 16 in ./AndroidManifest.xmlAndroid NDK: WARNING:jni/Android.mk:ProcessImg: non-system libraries in linker flags: -lopencv_javaAndroid NDK:     This is likely to result in incorrect builds. Try using LOCAL_STATIC_LIBRARIESAndroid NDK:     or LOCAL_SHARED_LIBRARIES instead to list the library dependencies of theAndroid NDK:     current module[armeabi-v7a] Compile++ thumb: ProcessImg <= DetectFace_JNI.cppjni/DetectFace_JNI.cpp: In function '_jstring* Java_org_yan_processlib_LibProcessImg_processIplImg(JNIEnv*, jobject, jintArray, int, int)':jni/DetectFace_JNI.cpp:97:44: warning: converting 'false' to pointer type for argument 2 of 'jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)' [-Wconversion-null]  cbuf = env->GetIntArrayElements(buf, false);                                            ^jni/DetectFace_JNI.cpp: In function '_jstring* Java_org_yan_processlib_LibProcessImg_processStaticImg(JNIEnv*, jobject, jintArray, int, int)':jni/DetectFace_JNI.cpp:131:44: warning: converting 'false' to pointer type for argument 2 of 'jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)' [-Wconversion-null]  cbuf = env->GetIntArrayElements(buf, false);                                            ^[armeabi-v7a] Compile++ thumb: ProcessImg <= copyToAssets.cpp[armeabi-v7a] Compile++ thumb: ProcessImg <= detectFace.cpp[armeabi-v7a] SharedLibrary  : libProcessImg.so/Users/yanzi/work/android-ndk-r10d/toolchains/arm-linux-androideabi-4.8/prebuilt/darwin-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: warning: hidden symbol '__aeabi_atexit' in /Users/yanzi/work/android-ndk-r10d/sources/cxx-stl/gnu-libstdc++/4.8/libs/armeabi-v7a/thumb/libgnustl_static.a(atexit_arm.o) is referenced by DSO /Users/yanzi/work/OpenCV-android-sdk/sdk/native/jni/../libs/armeabi-v7a/libopencv_java.so[armeabi-v7a] Install        : libProcessImg.so => libs/armeabi-v7a/libProcessImg.so

Although the so file is generated and installed, a non-system libraries in linker flags:-lopencv_java error is reported. The compiled so file is only about KB, in theory, this so should be about 4 MB. The running knows that the libopencv. so cannot be found. This is the mk file that generated this error:

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)ifeq ("$(wildcard $(OPENCV_MK_PATH))","") #try to load OpenCV.mk from default install location #include $(TOOLCHAIN_PREBUILT_ROOT)/user/share/OpenCV/OpenCV.mk include /Users/yanzi/work/OpenCV-android-sdk/sdk/native/jni/OpenCV.mkelse include $(OPENCV_MK_PATH)endifLOCAL_LDLIBS    += -lm -llog LOCAL_MODULE    := ProcessImg LOCAL_SRC_FILES := DetectFace_JNI.cpp \src/copyToAssets.cpp \src/detectFace.cppinclude $(BUILD_SHARED_LIBRARY) 

The correct mk file should be as follows:

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)OpenCV_INSTALL_MODULES:=onOPENCV_CAMERA_MODULES:=offOPENCV_LIB_TYPE:=STATICifeq ("$(wildcard $(OPENCV_MK_PATH))","") #try to load OpenCV.mk from default install location #include $(TOOLCHAIN_PREBUILT_ROOT)/user/share/OpenCV/OpenCV.mk include /Users/yanzi/work/OpenCV-android-sdk/sdk/native/jni/OpenCV.mkelse include $(OPENCV_MK_PATH)endifLOCAL_MODULE    := ProcessImg LOCAL_SRC_FILES := DetectFace_JNI.cpp \src/copyToAssets.cpp \src/detectFace.cppLOCAL_LDLIBS    += -lm -lloginclude $(BUILD_SHARED_LIBRARY) 

The problem lies in:

 

OpenCV_INSTALL_MODULES: = on
OPENCV_CAMERA_MODULES: = off
OPENCV_LIB_TYPE: = STATIC

These three statements, especially OPENCV_LIB_TYPE: = STATIC, are crucial. If this sentence is not compiled, so still depends on libopencv_java.so. This statement must be placed before the include OpenCV. mk file.. Remember!