Question

I am trying to run an easy Android ndk app in c, but I get UnsatisfiedLink Error for the stringFromJNI() function.

Any help would be appreciated. I am quite fluent in C, but my java is a little bit rusty. I have been trying a lot of tips from the web concerning naming, but so far no luck. Here are my files:

hello-jni.c:

#include <string.h>
#include <jni.h>


jstring
Java_com_example_hellojni_HelloJni_stringFromJNI( JNIEnv* env,
                                                  jobject thiz )
{
    return (*env)->NewStringUTF(env, "Hello from JNI !");
}

Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := hello-jni
LOCAL_SRC_FILES := hello-jni.c

include $(BUILD_SHARED_LIBRARY)

I compile this with ndk-build and all goes well, it provides me with a libnative.so, that is located in the project directory. I use eclipse for the rest.

NdkFooActivity.java :

package com.narola.Testndk;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;

public class NdkFooActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ndk_foo);

        Log.i("comes at point","hay...");
        Log.d("value is : ",""+stringFromJNI());
    }

    public native String  stringFromJNI();
    public native String  unimplementedStringFromJNI();

    static {
        System.loadLibrary("hello-jni");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_ndk_foo, menu);
        return true;
    }
}

Thank you for any suggestions, been searching for a few hours now!

Answer 1

The problem is in the hello-jni.c file.
You have method signature in c file is Java_com_example_hellojni_HelloJni_stringFromJNI else in your activity the package name is com.narola.Testndk.

The method signature has format like Java_packagename_activityname_methodname (In package name (.)Dot will be replaced by underscore).
In your case try like Java_com_narola_Testndk_NdkFooActivity_stringFromJNI