Android NDK预构建共享库使用

Question

I have precompiled shared library (.so), named libxxx.so.3.3. I don't know why the name after compilation was "libxxx.so.3.3". I'd like to use it in my Android app via JNI. For this i've created ndk module xxx_jni:

Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := xxx
LOCAL_SRC_FILES := xxx.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := xxx_jni
LOCAL_SRC_FILES := xxx_wrapper.c
LOCAL_SHARED_LIBRARIES := xxx
LOCAL_C_INCLUDES := /softdev/xxx/host/include/

include $(BUILD_SHARED_LIBRARY)

I had to rename " .so.3.3" to " .so" as ndk-build failed to compile libxxx_jni.so:

Android NDK: ERROR:/Users/user/Documents/dev/src/xxx_jni/jni/Android.xxx: LOCAL_SRC_FILES should point to a file ending with ".so"    
Android NDK: The following file is unsupported: libxxx.so.3.3    

My wrapper class (for JNI):

#include "xxx_wrapper.h"
#include <xxx-c/Index.h> // include "xxx" library header

#ifndef _Included_name_antonsmirnov_android_xxx_wrapper
#define _Included_name_antonsmirnov_android_xxx_wrapper
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     name_antonsmirnov_android_xxx_wrapper
 * Method:    exec_test
 * Signature: (Ljava/lang/String;)I
 */
JNIEXPORT jint JNICALL Java_name_antonsmirnov_android_xxx_1wrapper_exec_1test(JNIEnv *, jobject, jstring)
{
    // using method from "xxx" library
    xxx_method();

    return 7;
}

So after ndk compilation (ndk-build) i have 2 stripped files in "libs/armeabi" folder: libxxx.so and libxxx_jni.so.

Then i try to load libraries in runtime in wrapper class:

public class xxx_wrapper {

    static {
        System.loadLibrary("xxx");
        System.loadLibrary("xxx_jni"); // error here!
    }

error:

at dalvik.system.NativeStart.main(Native Method)
        Caused by: java.lang.UnsatisfiedLinkError: Cannot load library: link_image[1891]:   167 could not load needed library 'libxxx.so.3.3' for 'libxxx_jni.so' (load_library[1093]: Library 'libxxx.so.3.3' not found)

So i'm in stuck what i've missed.. I've tried to leave ".so.3.3" extension and symlink ".so" -> ".so.3.3" but the same result. As far as i understand the problem is that xxx_wrapper lib still wants ".so.3.3" library loaded, but it's ".so".

Answer 1

Is it possible the precompiled library wasn't caompiled using ndk-build ? The Android package manager (and builder!) cannot deal with .so files which have a version number as suffix.

You can overcome this by either:

Recompile the library using ndk-build (it would imply writing a new makefile) if you have the sources.

Or:

Embed the library as an asset in the .apk file. When the app starts, save these assets into the applications data folder. Now you can use

System.load( "/path/to/lib/libxxx.so.3.3" );

which shouldn't fail as it points to a file using a system path, rather than a library that is embedded within the app. It means the application will consume more storage on the device, but if you can't recompile the library (and no one else knows a proper solution!) this might be a workaround.