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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 project and copied all the source code in to jni/ folder and run ndk-build. It builds libavahi.so
What I wants to do: Instead of copying all the source code into jni/ folder, I'd like to store it in a folder outside project source tree. What shall I do? I have looked into NDK DOCUMENTATION/Import Module but nothing is similar to my case.
Newbie in ndk, and any suggestion is welcomed.
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The ndk-build file lives in the top level the NDK installation directory. To run it from the command line, invoke it while in or under your application project directory. For example: In this example, <project> points to your project’s root directory, and <ndk> is the directory where you installed the NDK.
The ndk-build file is a shell script introduced in Android NDK r4. Its purpose is to invoke the right NDK build script.
You need GNU Make 4 to use ndk-build or the NDK in general. The NDK includes its own copy of GNU Make and will use that unless you've set the $GNUMAKE environment variable to point to an unsuitable make. In NDK r18 and newer, ndk-build can generate a JSON compilation database.
In NDK r18 and newer, ndk-build can generate a JSON compilation database. You can either use ndk-build compile_commands.json to generate the database without building your code, or ndk-build GEN_COMPILE_COMMANDS_DB=true if you want to build and generate the database as a side-effect. Last updated 2020-08-17 UTC.
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!
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