CODEWITHSUNDEEP
androidandroid-ndkjava-native-interface
MePo
MePo

Reputation: 1074

Passing arguments to JNI giving error java.lang.UnsatisfiedLinkError

I just started to use NDK and i ran Hello_Jni and i know how that works but i wanted to try do something like this and cant get it to work (Im doing this manually)

simple.c

#include "simple.h"
#include <jni.h>

JNIEXPORT jdouble JNICALL
Java_com_example_Test_round_decimals (JNIEnv * env, jobject  obj, jdouble value, jint decimals) {
                  double m = pow (10, decimals);
     return (double) round (value * m) / m;
}

JNIEXPORT jstring JNICALL Java_com_example_Test_hello(JNIEnv* env, jobject javaThis) {
  return (*env)->NewStringUTF(env, "Hello from ME!");
}

simple.h

#include <stdio.h>
#include <stdlib.h>
#include "math.h"
#include <string.h>
#include <jni.h>


JNIEXPORT jdouble JNICALL Java_com_example_Test_round_decimals (JNIEnv * env, jobject  obj,jdouble value, jint decimals);
JNIEXPORT jstring JNICALL Java_com_example_Test_hello(JNIEnv* env, jobject javaThis);

Activity

public class Test{

  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 double test = round_decimals(10.1234,2);
 double test2 = hello();    

         Log.i("Round","Number" + test); // i would like to get this

         Log.i("String","hello? " + test2); // this works it shows "Hello From ME!"

}
public native double round_decimals(double value, int decimals);
public native String hello();

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

}

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := simple
LOCAL_SRC_FILES := simple.c
LOCAL_C_INCLUDES := $(LOCAL_PATH)


include $(BUILD_SHARED_LIBRARY)

android.mk, simple.c and simple.h are in JNI folder of my Activity. And also running Build-ndk in folder of my Activity shows no errors

But when i try to build it on my tablet i get this error.

java.lang.UnsatisfiedLinkError:round_decimals

Upvotes: 0

Views: 583

Answers (3)

ph0b
ph0b

Reputation: 14463

You had an underscore (_) inside your method name and underscores are name delimiters in JNI convention.

Changing the java method name to camel case is a solution but you can also escape underscores using _1 in your native method name, like so: Java_com_example_Test_round_1decimals.

Upvotes: 0

MePo
MePo

Reputation: 1074

i Found the problem it was with Java_com_example_Test_round_decimals had to rename it to Java_com_example_Test_roundDecimals and with that i had to rename public native double round_decimals(double value, int decimals); to public native double roundDecimals(double value, int decimals);

Upvotes: 0

user207421
user207421

Reputation: 310860

You generated the .h file from a version of the .java that had a package statement in it, then you modified the .java file to remove the package statement, then you compiled and ran, and nothing matched up.

There's something else wrong here. The method signature should be (JNIEnv*, jobject, jdouble, jint) if you've generated the files correctly.

Regenerate the .h file and adjust the .c file accordingly.

Upvotes: 1

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