ndk build library outside main project source tree

Question

I wants to build a 3rd party library avahi using ndk. avahi has android port already (with valid Android.mk).

What I have done: I have successfully created a proje

Answer 1

You are right, this is not the case of Import Module. The way you reference the avihi library from your native code will still be as LOCAL_SHARED_LIBRARIES (see NDK sample module-exports). But in your jni/Android.mk file, you may use include command to another file. This command is very similar to #include statement in C. This file needs not to be inside your project tree. Taking the same sample, here is how it can work:

Original Android.mk from samples/module-exports/jni:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := foo
LOCAL_SRC_FILES := foo/foo.c
LOCAL_CFLAGS := -DFOO=2
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/foo
LOCAL_EXPORT_CFLAGS := -DFOO=1
LOCAL_EXPORT_LDLIBS := -llog
include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := bar
LOCAL_SRC_FILES := bar/bar.c
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/bar
LOCAL_STATIC_LIBRARIES := foo
include $(BUILD_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := zoo
LOCAL_SRC_FILES := zoo/zoo.c
LOCAL_SHARED_LIBRARIES := bar
include $(BUILD_SHARED_LIBRARY)

The changed file will look as follows:

ZOO_LOCAL_PATH := $(call my-dir)
include ~/projects/bar/jni/Android.mk
LOCAL_PATH := $(ZOO_LOCAL_PATH)

include $(CLEAR_VARS)
LOCAL_MODULE := zoo
LOCAL_SRC_FILES := zoo/zoo.c
LOCAL_SHARED_LIBRARIES := bar
include $(BUILD_SHARED_LIBRARY)

And the external bar/jni/Android.mk as follows:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := foo
LOCAL_SRC_FILES := foo/foo.c
LOCAL_CFLAGS := -DFOO=2
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/foo
LOCAL_EXPORT_CFLAGS := -DFOO=1
LOCAL_EXPORT_LDLIBS := -llog
include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := bar
LOCAL_SRC_FILES := bar/bar.c
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/bar
LOCAL_STATIC_LIBRARIES := foo
include $(BUILD_SHARED_LIBRARY)

Now, both files bar.c and foo.c may be kept outside the tree of the zoo project!