finally i succeeded:
i created my own android.mk file:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
# OpenCV
OPENCV_INSTALL_MODULES:=on
include path/to/OpenCV-2.4.10-android-sdk/sdk/native/jni/OpenCV.mk
LOCAL_MODULE := glucomesdk
LOCAL_CFLAGS := -I/path tp/OpenCV-2.4.10-android-sdk/sdk/native/jni/include -Wall -Werror
LOCAL_SRC_FILES := \ all my cpp files
LOCAL_C_INCLUDES += /path to/src/main/jni
LOCAL_C_INCLUDES += /path to/src/debug/jni
LOCAL_C_INCLUDES += /path to/OpenCV-2.4.10-android-sdk/sdk/native/jni/include
LOCAL_STATIC_LIBRARIES := /path to/OpenCV-2.4.10-android-sdk/sdk/native/libs/armeabi-v7a/libopencv_core.a
LOCAL_LDLIBS += -llog -ldl
include $(BUILD_SHARED_LIBRARY)
then i use this code in terminal to build the shared library (.so)
/path/to/android-ndk/ndk-build NDK_PROJECT_PATH=/path/to/project APP_BUILD_SCRIPT=/path/to/Android.mk NDK_OUT=/path/to/project/module/build/intermediates/ndk/debug/obj NDK_LIBS_OUT=/path/to/project/module/build/intermediates/ndk/debug/lib APP_STL=stlport_static APP_ABI=armeabi-v7a
after that i use gradle's assemble(debug) to create an aar file that contains both java code and the shared library