unsatisfied link error in android native call

Question

I am trying to call a native function from an android activity class, which results in a unsatisfied link error. Here is the activity.

package com.example.rockboos;
import android.os.Bundle;

import android.app.Activity;
import android.widget.Button;
import android.widget.Toast;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity {


    public native void hello();
    private void boostMe() 
    {
        hello();
    }

    private VolumeController volumeController;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.volumeController = new VolumeController(this);
        Button btn = (Button)findViewById(R.id.btn0);
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                    //volumeController.boost();
                boostMe();




            }
        });
    }
    static {
        System.loadLibrary("hellomodule");

    }

}

native.h

#include <jni.h>

JNIEXPORT void JNICALL Java_com_example_rockboost_MainActivity_hello(JNIEnv *, jobject);

native.c:

#include "mp3gain/mp3gain.h"

#include "native.h"

JNIEXPORT void JNICALL Java_com_example_rockboost_MainActivity_hello(JNIEnv *jniEnv, jobject thiz)
{
    //changeGain("/sdcard0/test.mp3", 10, 10);
    int x = 0;
    x++;
}

catlogs

08-03 17:58:54.040: D/dalvikvm(4007): Trying to load lib /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70

08-03 17:58:54.050: D/dalvikvm(4007): Added shared lib /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70

08-03 17:58:54.050: D/dalvikvm(4007): No JNI_OnLoad found in /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70, skipping init

08-03 17:58:55.700: D/gralloc_goldfish(4007): Emulator without GPU emulation detected. 08-03 17:59:15.040: W/dalvikvm(4007): No implementation found for native Lcom/example/rockboost/MainActivity;.hello:()V

08-03 17:59:15.050: D/AndroidRuntime(4007): Shutting down VM 08-03 17:59:15.050: W/dalvikvm(4007): threadid=1: thread exiting with uncaught exception (group=0xb1a4ed70)

08-03 17:59:15.130: E/AndroidRuntime(4007): FATAL EXCEPTION: main

08-03 17:59:15.130: E/AndroidRuntime(4007): Process: com.example.rockboost, PID: 4007

08-03 17:59:15.130: E/AndroidRuntime(4007): java.lang.UnsatisfiedLinkError: Native method not found: com.example.rockboost.MainActivity.hello:()V

08-03 17:59:15.130: E/AndroidRuntime(4007): at com.example.rockboost.MainActivity.hello(Native Method) 08-03 17:59:15.130: E/AndroidRuntime(4007): at com.example.rockboost.MainActivity.boostMe(MainActivity.java:17) 08-03 17:59:15.130: E/AndroidRuntime(4007): at com.example.rockboost.MainActivity.access$0(MainActivity.java:15) 08-03 17:59:15.130: E/AndroidRuntime(4007): at com.example.rockboost.MainActivity$1.onClick(MainActivity.java:35) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.view.View.performClick(View.java:4450) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.view.View$PerformClick.run(View.java:18600) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.os.Handler.handleCallback(Handler.java:733) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.os.Handler.dispatchMessage(Handler.java:95) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.os.Looper.loop(Looper.java:136) 08-03 17:59:15.130: E/AndroidRuntime(4007): at android.app.ActivityThread.main(ActivityThread.java:5026) 08-03 17:59:15.130: E/AndroidRuntime(4007): at java.lang.reflect.Method.invokeNative(Native Method) 08-03 17:59:15.130: E/AndroidRuntime(4007): at java.lang.reflect.Method.invoke(Method.java:515) 08-03 17:59:15.130: E/AndroidRuntime(4007): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777) 08-03 17:59:15.130: E/AndroidRuntime(4007): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602) 08-03 17:59:15.130: E/AndroidRuntime(4007): at dalvik.system.NativeStart.main(Native Method) 08-03 18:04:16.680: I/Process(4007): Sending signal. PID: 4007 SIG: 9 08-03 18:24:16.030: D/dalvikvm(5266): Trying to load lib /data/app-lib/com.example.rockboost-2/libhellomodule.so 0xb1c89f18 08-03 18:24:16.410: D/dalvikvm(5266): Added shared lib /data/app-lib/com.example.rockboost-2/libhellomodule.so 0xb1c89f18 08-03 18:24:16.410: D/dalvikvm(5266): No JNI_OnLoad found in /data/app-lib/com.example.rockboost-2/libhellomodule.so 0xb1c89f18, skipping init 08-03 18:24:17.330: D/gralloc_goldfish(5266): Emulator without GPU emulation detected.

08-03 17:58:54.040: D/dalvikvm(4007): Trying to load lib /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70 08-03 17:58:54.050: D/dalvikvm(4007): Added shared lib /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70 08-03 17:58:54.050: D/dalvikvm(4007): No JNI_OnLoad found in /data/app-lib/com.example.rockboost-1/libhellomodule.so 0xb1c88e70, skipping init 08-03 17:59:15.040: W/dalvikvm(4007): No implementation found for native Lcom/example/rockboost/MainActivity;.hello:()V

The library compiles. I can see in the logs that the shared library could be loaded. However the native call didn't work and caused a unsatified link error

The naming convention seem fine as far as i can see. I can start the application the error only happens when calling the native function. I also made sure that the library is built for the correct cpu/architecture,

Update

I ran objdump -t to check the symbol table:

$ objdump.exe -t libhellomodule.so

libhellomodule.so:     file format elf32-little

SYMBOL TABLE:
no symbols

So the function is not in the library but I don't know why. Here is my Android.mk file:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_LDLIBS := -llog

LOCAL_MODULE    := hellomodule
LOCAL_SRC_FILES := mp3gain mp3gain/mpglibDBL  

LOCAL_C_INCLUDE :=  mp3gain mp3gain/mpglibDBL native.h


APP_ABI := armeabi

include $(BUILD_SHARED_LIBRARY)

There's probably something wrong with that but i'm not sure where.

Update 2

Fixed my Android.mk and used another library

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := mp3lame
LOCAL_SRC_FILES := bitstream.c fft.c id3tag.c mpglib_interface.c presets.c quantize.c reservoir.c tables.c util.c VbrTag.c encoder.c gain_analysis.c lame.c newmdct.c psymodel.c quantize_pvt.c set_get.c takehiro.c vbrquantize.c version.c native.c   


include $(BUILD_SHARED_LIBRARY)

Compiles fine but with the same result, program cannot find the function in the library. Altough nm shows that the symbol is there:

$ nm -D ../libs/armeabi/libmp3lame.so | grep hello
0001c4e9 T Java_com_example_rockboost_MainActivity_hello

Answer 1

LOCAL_SRC_FILES should be a list of C files. In your case, it seems to be

LOCAL_SRC_FILES = native.c

When you run ndk-build, you will see it compiled.

There are other mistakes in your Android.mk.

APP_ABI is irrelevant there; put it in Application.mk or on command line.

LOCAL_C_INCLUDE is misspelled; it reads LOCAL_C_INCLUDES. This lists directories where to look for header files. In your case, it may be path from your project to mp3gain directory.