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I with success compile library LibXtract to shared object libxtract.so and want to use is in second project.

In mention project I try to compile it on simple function:

#include <com_androidnative1_NativeClass.h>
#include <android/log.h>
#include "libxtract.h"

JNIEXPORT void JNICALL Java_com_androidnative1_NativeClass_showText
(JNIEnv *env, jclass clazz)
{

    float mean = 0, vector[] = {.1, .2, .3, .4, -.5, -.4, -.3, -.2, -.1}, spectrum[10];
    int n, N = 9;
    float argf[4];

    argf[0] = 8000.f;
    argf[1] = XTRACT_MAGNITUDE_SPECTRUM;
    argf[2] = 0.f;
    argf[3] = 0.f;

    xtract[XTRACT_MEAN]((void *)&vector, N, 0, (void *)&mean);
    __android_log_print(ANDROID_LOG_DEBUG, "LIbXtract", "Button pushe2");
}

I have flat structure:

  • jni/com_androidnative1_NativeClass.c
  • jni/com_androidnative1_NativeClass.hjni/libxtract.h
  • jni/other *.h files from libxtract interface
  • jni/Android.mk
  • jni/Applicatoin.mk

library libxtract.so I put in mainproject/lib folder

my Android.mk file looks like:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := com_androidnative1_NativeClass.c 
LOCAL_MODULE := com_androidnative1_NativeClass
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/
LOCAL_LDLIBS += -llog
LOCAL_SHARE_LIBRARIES := libxtract
NDK_MODULE_PATH += $(LOCAL_PATH)/../lib/
include $(BUILD_SHARED_LIBRARY)

and I still got error:

Compile thumb  : com_androidnative1_NativeClass <= com_androidnative1_NativeClass.c
SharedLibrary  : libcom_androidnative1_NativeClass.so./obj/local/armeabi/objs/com_androidnative1_NativeClass/com_androidnative1_Nativ    eClass.o: In function `Java_com_androidnative1_NativeClass_showText':
/home/jack/Projects/AndroidNative1/jni/com_androidnative1_NativeClass.c:20: undefined reference to `xtract'
collect2: ld returned 1 exit status
make: *** [obj/local/armeabi/libcom_androidnative1_NativeClass.so] Error 1

Code came form example of LibXtract and under C++ compile without problems, any ideas?

Martijn Courteaux
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Jack
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  • How exactly did you compile libxtract.so? Why don't you add its compilation to same Android.mk file, so both shared libraries can built at the same time? – Mārtiņš Možeiko Jun 03 '12 at 22:35
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    I compile it by adopt this solution [link](http://stackoverflow.com/a/7308682/1409501) I just to add shred library to keep it simple – Jack Jun 03 '12 at 22:41
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    This answer sounds like solving your issue. http://stackoverflow.com/questions/10593987/android-ndk-linking/10615769#10615769 – codetiger Jun 04 '12 at 02:36
  • Possible duplicate of [How to link a prebuilt shared Library to an Android NDK project?](https://stackoverflow.com/questions/9870435/how-to-link-a-prebuilt-shared-library-to-an-android-ndk-project) – Ciro Santilli OurBigBook.com Nov 29 '17 at 17:44

3 Answers3

5

Your Android make file should be ... 

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LIB_PATH := $(LOCAL_PATH)/../lib
LOCAL_SRC_FILES := com_androidnative1_NativeClass.c 
LOCAL_MODULE := com_androidnative1_NativeClass
LOCAL_LDLIBS += -llog

LOCAL_LDLIBS += $(LIB_PATH) -lxtract 

LOCAL_SHARE_LIBRARIES := libxtract
include $(BUILD_SHARED_LIBRARY)

Try this make file in your second project, and you can successfully build your code without having any error.

Suvam Roy
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  • I use yours and @FooF solution, my Android.mk looks like: LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := libxtract LOCAL_SRC_FILES := libxtract.so include $(PREBUILT_SHARED_LIBRARY) include $(CLEAR_VARS) LIB_PATH := $(LOCAL_PATH)/../lib/libxtract.so LOCAL_SRC_FILES := com_androidnative1_NativeClass.c LOCAL_MODULE := com_androidnative1_NativeClass LOCAL_LDLIBS += -llog LOCAL_LDLIBS += $(LIB_PATH) LOCAL_SHARE_LIBRARIES := libxtract include $(BUILD_SHARED_LIBRARY) – Jack Jun 04 '12 at 19:56
  • and its build with success, but when I run code where I use it I got error: 06-04 21:58:26.504: E/AndroidRuntime(14792): Caused by: java.lang.UnsatisfiedLinkError: Couldn't load libxtract: findLibrary returned null of course I use System.loadLibrary("libxtract"); – Jack Jun 04 '12 at 20:00
  • Look, use this make file in your second project after successfully building libxtract.so. And LIB_PATH should be correct. And 'LOCAL_LDLIBS += $(LIB_PATH) -lxtract' should be used in your second project make file, otherwise you will get the error that you issued in above. – Suvam Roy Jun 05 '12 at 05:40
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    LOCAL_SHARE_LIBRARIES => LOCAL_SHARED_LIBRARIES – kid May 25 '21 at 02:52
3

In the above answer all is right but exept one.

When we want to link lib we must add -L before LOCAL_LDLIBS dir as below.

LIB_PATH := $(LOCAL_PATH)/../lib

LOCAL_LDLIBS += **-L**$(LIB_PATH) -lxtract

Else it will give error as below

cannot open XXX/../lib: Permission denied

Sattar Hummatli
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    Can you clarify which answer you are referencing? – James Jenkins Jun 03 '14 at 10:44
  • The syntax to include shared libraries in the search path. 1) Must specify path via -L directive and then 2)immediately afterwards the lib to be shared via the -l directive. – drlolly Nov 01 '17 at 14:30
2

You need to tell Android NDK build scripts about your shared library. Check ${NDK}/doc/PREBUILTS.html for instructions how this can be done. They advise to add Android.mk in the same directory where you have your libXtract.so:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libXtract
LOCAL_SRC_FILES := libXtract.so
include $(PREBUILT_SHARED_LIBRARY)

Debugging tip: I guess you are using ndk-build to build your "second project". Try running ndk-build with V=99 (try V=99 ndk-build or ndk-build V=99 - my memory failing). This will show you the the exact failing linking command. You should likely have options -lXtract and -L/path/to/libXtract/library. (Sometimes it is convenient to just copy and paste the linking command to run it manually to find the right options for successful linking, before actually fixing the build settings.)

Update: I now see @codetiger's comment seems to point to a same sort of answer (without mentioning the NDK document which is good reading - so I am not deleting this answer).

FooF
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