Android JNI学习之二 demo

主要参考了文章http://www.cnblogs.com/wmj/archivse/2010/07/25/1784872.html

1. 建立android工程，两个类，一个是activity，一个包含声明native方法的类

package org.simon;

 

import android.app.Activity;

import android.os.Bundle;

 

public class JNITest extends Activity {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        Nadd nadd = new Nadd();

        this.setTitle("100 + 20 = " + nadd.nadd(100, 20));

    }

}

package org.simon;

 

public class Nadd {

    static {

       System.loadLibrary("Nadd");

    }

    

    public native int nadd(int a, int b);

 

}

2. 用JDK自带的javah生成.h头文件。

具体办法参见前一篇文章

http://www.cnblogs.com/simoncook/archive/2010/09/25/1834750.html

3. 编辑.c文件实现native方法。

com_hello_jnitest_Nadd.c文件：
#include <stdlib.h>
#include "com_hello_jnitest_Nadd.h"
JNIEXPORT jint JNICALL Java_com_hello_jnitest_Nadd_nadd(JNIEnv * env, jobject c, jint a, jint b)
{
   return (a+b);
}

4. 下载工具链，并安装

在这里

http://www.codesourcery.com/gnu_toolchains/arm/download.html

Windows: http://www.codesourcery.com/gnu_toolchains/arm/portal/package3400/public/arm-none-linux-gnueabi/arm-2008q3-41-arm-none-linux-gnueabi.exe

Linux: http://www.codesourcery.com/gnu_toolchains/arm/portal/package3399/public/arm-none-linux-gnueabi/arm-2008q3-41-arm-none-linux-gnueabi.bin

我当时用的是ubuntu(10.4)平台

所以是linux那个链接

5. 编译。c文件产生so文件

root@ubuntu:~/project/JNI/JNItest# /root/CodeSourcery/Sourcery_G++_Lite/bin/arm-none-linux-gnueabi-gcc -I /home/tools/jdk1.6.0_21/include -I /home/tools/jdk1.6.0_21/include/linux -fpic -c org_simon_Nadd.c

root@ubuntu:~/project/JNI/JNItest# /root/CodeSourcery/Sourcery_G++_Lite/bin/arm-none-linux-gnueabi-ld -T /root/CodeSourcery/Sourcery_G++_Lite/arm-none-linux-gnueabi/lib/ldscripts/armelf_linux_eabi.xsc -share -o libNadd.so org_simon_Nadd.o

6. 将so文件push进模器

root@ubuntu:/home/tools/android-sdk-linux_x86-1.5_r1/tools# ./adb remount

remount succeeded

root@ubuntu:/home/tools/android-sdk-linux_x86-1.5_r1/tools# ./adb push /root/project/JNI/JNItest/libNadd.so /system/lib

28 KB/s (1969 bytes in 0.068s)

7. 运行工程，测试。