Native method not found: com.example.pjtest.JniClass.get_time:()C

Question

I am trying creating simple jni but app is crashing .I am not able to find the mistake I have done .Here is my code :

Example.c

 #include <time.h>
 double My_variable = 3.0;

 int fact(int n) {
     if (n <= 1) return 1;
     else return n*fact(n-1);
 }

 int my_mod(int x, int y) {
     return (x%y);
 }

 char *get_time()
 {
     time_t ltime;
     time(&ltime);
     return ctime(&ltime);
 }

Android.mk

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := example
LOCAL_CFLAGS    := -Werror
LOCAL_SRC_FILES := example.c
LOCAL_LDLIBS    := -llog 

include $(BUILD_SHARED_LIBRARY)

After this I have build the folder using NDK.Files generated in lib is libexample.so.And example.o ,example.o.d in obj folder.when I load lib by name example it is giving error while calling method only but when I load by name l*ibexample* it is giving error while loading lib as well as while calling method.

JNI

package com.example.pjtest;

    public class JniClass {

      public final static native char get_time();
    }

MainActivity

package com.example.pjtest;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        try {
            System.loadLibrary("example");
        } catch (UnsatisfiedLinkError e) {
            e.printStackTrace();
        }
        try{
        System.out.print(JniClass.get_time());
        }
        catch(Exception e )
        {
            e.printStackTrace();
        }

    }
}

Here is log :

04-01 12:32:18.964: E/AndroidRuntime(5325): java.lang.UnsatisfiedLinkError: Native method not found: com.example.pjtest.JniClass.get_time:()C
04-01 12:32:18.964: E/AndroidRuntime(5325):     at com.example.pjtest.JniClass.get_time(Native Method)
04-01 12:32:18.964: E/AndroidRuntime(5325):     at com.example.pjtest.MainActivity.onCreate(MainActivity.java:18)
04-01 12:32:18.964: E/AndroidRuntime(5325):     at android.app.Activity.performCreate(Activity.java:5066)
04-01 12:32:18.964: E/AndroidRuntime(5325):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1101)

Answer 1

You have to load your library in your Activity

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

Make sure your .so file in your lib folder or /system/lib/ in the device where your try to run the application.

Add this to your Example.c

jint Java_com_example_pjtest_get_time(JNIEnv *env)
{
     time_t ltime;
     time(&ltime);
    return ctime(&ltime);

}