OpenCV4Android:non-system libraries in linker flags: -lopencv_java错误的解决

最近搞之前的一份老代码，发现OpenCV到2.4.11之后，之前的mk文件不适用了，报一堆一堆的错误。

一是如前文所述，LOCAL_LDLIBS    += -lm -llog这一句+=绝不能错误的写成:=.另外，还会报这样一个错误：

Android NDK: WARNING: APP_PLATFORM android-17 is larger than android:minSdkVersion 16 in ./AndroidManifest.xml
Android NDK: WARNING:jni/Android.mk:ProcessImg: non-system libraries in linker flags: -lopencv_java
Android NDK:     This is likely to result in incorrect builds. Try using LOCAL_STATIC_LIBRARIES
Android NDK:     or LOCAL_SHARED_LIBRARIES instead to list the library dependencies of the
Android NDK:     current module
[armeabi-v7a] Compile++ thumb: ProcessImg <= DetectFace_JNI.cpp
jni/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

尽管so文件生成了，也安装了，但是报一个non-system libraries in linker flags: -lopencv_java的错误，编译出来的so文件只有330KB左右，理论上这个so应该4.5M左右。运行知道发现找不到libopencv.so. 这是产生这个错误的mk文件：

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.mk
else
include $(OPENCV_MK_PATH)
endif
LOCAL_LDLIBS    += -lm -llog
LOCAL_MODULE    := ProcessImg
LOCAL_SRC_FILES := DetectFace_JNI.cpp 					src/copyToAssets.cpp 					src/detectFace.cpp

include $(BUILD_SHARED_LIBRARY)

正确的mk文件应该如下：

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

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

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.mk
else
include $(OPENCV_MK_PATH)
endif

LOCAL_MODULE    := ProcessImg
LOCAL_SRC_FILES := DetectFace_JNI.cpp 					src/copyToAssets.cpp 					src/detectFace.cpp

LOCAL_LDLIBS    += -lm -llog
include $(BUILD_SHARED_LIBRARY)

问题就出在：

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

这三句话，尤其是OPENCV_LIB_TYPE:=STATIC是要害，没这一句编译出来的so还是要依赖libopencv_java.so的。而且这句话必须放在include OpenCV.mk文件之前。切记切记！

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