Build sample Android NDK on Linux

1. Download Android-NDK (i'm using android-ndk-r8-crystax-1)
2. Create a simple Java wrapper file named NativeLib.java

package com.pt;

/**
 * @author khanh
 *
 */
public class NativeLib {
    static {
        System.loadLibrary("ndk_sample");
    }

    /**
     * Adds two integers, returning their sum
     */
    public native int add(int v1, int v2);

    /**
     * Returns Hello World string
     */
    public native String hello();
}

3. Create C header file by running javah -jni

javah -jni com.pt.NativeLib
mv mv com_pt_NativeLib.h ../jni/

4. Write implement C file for com_pt_NativeLib.h

 #include "com_pt_NativeLib.h"

JNIEXPORT jstring JNICALL Java_com_marakana_NativeLib_hello
  (JNIEnv * env, jobject obj) {
        return (*env)->NewStringUTF(env, "Hello World!");
}

JNIEXPORT jint JNICALL Java_com_marakana_NativeLib_add
  (JNIEnv * env, jobject obj, jint value1, jint value2) {
        return (value1 + value2);
}

5. To build library, create file Android.mk to lead compilers how to build

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := ndk_sample
LOCAL_SRC_FILES := ndk_sample.c

include $(BUILD_SHARED_LIBRARY)

6. Create folder in /apps/ndk_sample/ and create Application.mk

APP_PROJECT_PATH := $(call my-dir)/project
APP_MODULES      := ndk_sample

7. Create symbol link to the project by typing

ln -s ~/home/Android/NDKSampleProj /apps/ndk_demo/project

8. Finally, run make APP=ndk_sample that will generate libs/armeabi/libndk_sample.so
9. Enjoy the coding now with native code.