较新的NDK版本是r10b，Android Studio对NDK开发的支持还处于构思阶段，所以很多工作比如用javah生成头文件等工作还要自己做。今天用一个例子来演示AS中的NDK开发。

新建一个项目SecondNdkTest

在此项目中新建一个Module叫ndklibrary，作为so库单独划出来。在library中新建一个java类SecondLib，内容如下：

package com.linc.ndklibrary;

/**
 * Created by linc on 15-3-29.
 */
public class SecondLib {
    // Native implementation  
    static {  
    System.loadLibrary("SecondLib"); 
    } 
    //int array
    public static native int[] intMethod();
    //string array
    public static native String[] stringMethod();
}

Build—>Make Module’ndklibrary’,这样SecondLib就编译完成了，通过SecondLib.class，用javah生成C的头文件，如下：

AndroidStudioProjects/SecondNdkTest/ndklibrary/src/main$ javah -d jni -classpath ../../build/intermediates/classes/debug com.linc.ndklibrary.SecondLib
AndroidStudioProjects/SecondNdkTest/ndklibrary/src/main$ ls
AndroidManifest.xml  java  jni  res
AndroidStudioProjects/SecondNdkTest/ndklibrary/src/main$ ls jni/
com_linc_ndklibrary_SecondLib.h

头文件内容如下：

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_linc_ndklibrary_SecondLib */

#ifndef _Included_com_linc_ndklibrary_SecondLib
#define _Included_com_linc_ndklibrary_SecondLib
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_linc_ndklibrary_SecondLib
 * Method:    intMethod
 * Signature: ()[I
 */
JNIEXPORT jintArray JNICALL Java_com_linc_ndklibrary_SecondLib_intMethod
  (JNIEnv *, jclass);

/*
 * Class:     com_linc_ndklibrary_SecondLib
 * Method:    stringMethod
 * Signature: ()[Ljava/lang/String;
 */
JNIEXPORT jobjectArray JNICALL Java_com_linc_ndklibrary_SecondLib_stringMethod
  (JNIEnv *, jclass);

#ifdef __cplusplus
}
#endif
#endif

Native代码实现

在jni目录中新建c文件SecondLib.c与头文件对应，分别实现上述两个方法，内容如下：

#include "com_linc_ndklibrary_SecondLib.h"

 const static int length=10;

 //int array
 JNIEXPORT jintArray JNICALL Java_com_linc_ndklibrary_SecondLib_intMethod
   (JNIEnv *env, jclass obj)
 {
    jintArray array;
    array=(*env)->NewIntArray(env,10);
    int i=1;
    for(;i<=10;++i)
    {
        (*env)->SetIntArrayRegion(env,array,i-1,1,&i);
    }

    //get array length
    int len=(*env)->GetArrayLength(env,array);

    //array content
    jint* elems=(*env)->GetIntArrayElements(env,array,0);

    return array;
 }

 //string array
 JNIEXPORT jobjectArray JNICALL Java_com_linc_ndklibrary_SecondLib_stringMethod
   (JNIEnv *env, jclass obj)
 {
    jclass class=(*env)->FindClass(env,"java/lang/String");
    jobjectArray string=(*env)->NewObjectArray(env,(jsize)length,
            class,0);
    jstring jstr;
    char* _char[]={"my ","name ","is ",
                    "linc!!","正在","学习",
                    "JNI","和","NDK","技术！"
                    };
    int i=0;
    for(;i<length;++i)
    {
        jstr=(*env)->NewStringUTF(env,_char[i]);
        (*env)->SetObjectArrayElement(env,string,i,jstr);
    }

    return string;
 }

编译

在local.properties中加入ndk路径：

ndk.dir=/opt/ndk/android-ndk-r10b

然后在ndklibrary的build.gradle中defaultConfig中加入ndk定义，如下：

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        ndk{
            moduleName "SecondLib"
        }
    }

这样就可以直接编译了，不用自己编写make文件了。 
Build—>Make Module’ndklibrary’,生成的so如下：

AndroidStudioProjects/SecondNdkTest$ find -name *.so
./ndklibrary/build/intermediates/ndk/debug/lib/armeabi/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/lib/armeabi-v7a/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/lib/mips/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/lib/x86/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/obj/local/armeabi/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/obj/local/armeabi-v7a/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/obj/local/mips/libSecondLib.so
./ndklibrary/build/intermediates/ndk/debug/obj/local/x86/libSecondLib.so

注： 
至于直接在Activity中用native的方法请参考下面的前两个链接。我遇到了问题没有得到解决：

$ javah -d jni -classpath /opt/sdk/platforms/android-5.1/android.jar;../../build/intermediates/classes/debug   com.linc.secondndktest.MainActivity
Error: no classes specified
bash: ../../build/intermediates/classes/debug/: Is a directory

参考： 

http://blog.csdn.net/rznice/article/details/42295215 

http://blog.csdn.net/sodino/article/details/41946607 

http://stackoverflow.com/questions/10483959/javah-error-android-app-activity-not-found 

http://blog.csdn.net/lincyang/article/details/6705143