Android-NDK “java.lang.UnsatisfiedLinkError”

Question

I am new to NDK.

I have a cpp file which has the following function

/* This is a trivial JNI example where we use a native method
 * to return a new VM String. See the corresponding Java source
 * file located at:
 *
 *   apps/samples/hello-jni/project/src/com/example/hellojni/HelloJni.java
 */
JNIEXPORT jstring JNICALL
Java_com_some_player_MainActivity_stringFromJNI( JNIEnv* env,
                                                  jobject thiz )
{
    return env->NewStringUTF("Hello from JNI!");
}

The Java class that calls it

package com.some.player;
public class MainActivity extends Activity {
    public native String stringFromJNI();
    static {
        System.loadLibrary("hello-jni");
    }

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

       TextView tv = (TextView) findViewById(R.id.textView);
       tv.setText(stringFromJNI());
    }
}

The make file

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

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

include $(BUILD_SHARED_LIBRARY)

The problem is that when I call the native function I got the

07-28 23:42:34.256: E/AndroidRuntime(32398): java.lang.UnsatisfiedLinkError: stringFromJNI

take a look at http://stackoverflow.com/questions/4813336/java-lang-unsatisfiedlinkerror — user827992, Jul 28 '12 at 21:54

score 6 · Accepted Answer · answered Jul 28 '12 at 22:11

6

Actually I figured out that I need to add

extern "C" {
    JNIEXPORT jstring JNICALL Java_com_some_player_MainActivity_stringFromJNI( JNIEnv* env, jobject thiz )
};

answered Jul 28 '12 at 22:11

mohamede1945

7,092
6
47
61

score 0 · Answer 2 · answered Jul 28 '12 at 22:07

0

There is error in native code in method paremers

return env->NewStringUTF("Hello from JNI!");

replace

return (*env)->NewStringUTF(env, "Hello from JNI !");

answered Jul 28 '12 at 22:07

InflexCZE

722
1
14
30

Thanks. This is just a copy paste error from another project. But this wasn't the error. – mohamede1945 Jul 28 '12 at 22:10

score 0 · Answer 3 · answered Apr 25 '17 at 06:41

To use c calling conventions in cpp you can surround methods with

extern "C" { /*methods*/ };

Eg:

#include <jni.h>
#include <string>
extern "C" {
JNIEXPORT jstring JNICALL
Java_com_test_ndk_ndktest_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}
JNIEXPORT jint JNICALL
Java_com_test_ndk_ndktest_MainActivity_add(JNIEnv *env, jobject instance, jint a, jint b) {
    return (a + b);
}
};

Android-NDK “java.lang.UnsatisfiedLinkError”

3 Answers3

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