Android NDK: Library doesn't build

Question

I am a newbie to NDK Build system, although I know GNU Make quite well.

I am trying to define build system for my project with one Library and a test stub for testing the library.

I have the following setup, which sort of works but I am not happy with it.

--------------jni/Android.mk--------------
# A simple test for the minimal standard c library
LOCAL_PATH := $(call my-dir)
MY_LOCAL_PATH := $(LOCAL_PATH)

include $(CLEAR_VARS)

include $(LOCAL_PATH)/library/Android.mk
---------------jni/Android.mk------------------

-------------jni/library/Android.mk----------------------
# A simple test for the minimal standard c library
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
#LOCAL_CFLAGS := -g -DDEBUG   
LOCAL_C_INCLUDES := $(LOCAL_PATH)/inc
LOCAL_MODULE := lteDiag
LOCAL_SRC_FILES := $(wildcard src/*.c)
include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
#LOCAL_CFLAGS := -g -DDEBUG  
LOCAL_C_INCLUDES := $(LOCAL_PATH)/inc
LOCAL_MODULE := DiagAppf
LOCAL_SRC_FILES := ../test_stub/test.c
LOCAL_STATIC_LIBRARIES := lteDiag
include $(BUILD_EXECUTABLE)

----------------------jni/library/Android.mk-----------

This setup works if I run ndk-build under jni/library, but doesn't work from jni. From jni directory it does not build the library and simply removes the preexisting lib and creates a new empty archive.

I would actually want to do the following.

---------------------jni/Android.mk---------------
# A simple test for the minimal standard c library
LOCAL_PATH := $(call my-dir)
MY_LOCAL_PATH := $(LOCAL_PATH)

include $(CLEAR_VARS)

include $(LOCAL_PATH)/DM_Library/Android.mk

include $(CLEAR_VARS)
#LOCAL_CFLAGS := -g -DDEBUG  
LOCAL_PATH := $(MY_LOCAL_PATH)
LOCAL_C_INCLUDES := $(LOCAL_PATH)/DM_Library/inc
LOCAL_MODULE := DiagAppf
LOCAL_SRC_FILES := test_stub/test.c
LOCAL_STATIC_LIBRARIES := lteDiag
include $(BUILD_EXECUTABLE)

---------------jni/Android.mk---------------

-----------------jni/library/Android.mk-----------------
# A simple test for the minimal standard c library
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
#LOCAL_CFLAGS := -g -DDEBUG   
LOCAL_C_INCLUDES := $(LOCAL_PATH)/inc
LOCAL_MODULE := lteDiag
LOCAL_SRC_FILES := $(wildcard src/*.c)
include $(BUILD_STATIC_LIBRARY)

--------------------jni/library/Android.mk-----------

Thanks in advance for any help. Is there any documentation that I can go through. I am not finding anything that explains in detail building of a complex multiple subdirectory build system.

thanks, Anand

Answer 1

Kindly follow below steps, It may helps you.

1. First Create Android Project.Then Create "jni" folder inside project.

2. Put your c file inside the jni folder and create a new file and name it as Android.mk type the Code.

     LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := samplelib LOCAL_SRC_FILES := sample.c include $(BUILD_SHARED_LIBRARY) 

   samplelib is the library created on libs folder after running project using this u should call inside activity.

sample.c is the c file that contains the JNI Export methods that is important to export to Activity.

3.Paste follwoing codes into sample.c file,

    jint Java_com_example_ndkdemo_ADD (JNIEnv* env, jobject thiz,jint number1,jint number2)
    {
      int value = add(number1,number2);
      return value;
    }

In method "Java_com_example_ndkdemo_ADD" , Java is Keyword com_example_ndkdemo is the package name "com.example.ndkdemo" ADD is the MethodName jint is int value

1. Goto rightclik on project ->properties->builder tab -> select New ->choose Program. window will open ->choose Location ->select Browse FileSystem -> Goto NdkFolder and Select ndk-build file then in Working Directory Choose Browse workspace -> choose your project and select jni folder.