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.SecondLibAndroidStudioProjects/SecondNdkTest/ndklibrary/src/main$ lsAndroidManifest.xml  java  jni  resAndroidStudioProjects/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 __cplusplusextern "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.MainActivityError: no classes specifiedbash: ../../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