Android Studio NDK 学习之接受Java传入的Int数组

本博客是基于Android Studio 1.3 preview版本，且默认你已经安装了Android SDK， Android NDK。

用Android Studio新建一个工程叫AndroidJNI_IntArray，其目录结构如下：

├── AndroidJNI_IntArray.iml

├── app

│ ├── app.iml

│ ├── build

│ ├── build.gradle

│ ├── libs

│ ├── proguard-rules.pro

│ └── src

├── build

│ └── intermediates

├── build.gradle

├── gradle

│ └── wrapper

├── gradle.properties

├── gradlew

├── gradlew.bat

├── local.properties

└── settings.gradle

切换到android视图，可见如下目录：

Android Studio NDK 学习之接受Java传入的Int数组

第一步，编写JNI代码：

1、新建jni文件夹，在jni文件夹下创建logger.h，用来打印输出日志的，其内容如下：

#ifndef ANDROIDJNI_INTARRAY_LOGGER_H

#define ANDROIDJNI_INTARRAY_LOGGER_H

#include <jni.h>

#include <android/log.h>

/**

 * 定义log标签

 */

#define TAG "jni_logger"

/**

 * 定义info信息

 */

#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)

/**

 * 定义debug信息

 */

#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__)

/**

 * 定义error信息

 */

#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, TAG, __VA_ARGS__)

#endif //ANDROIDJNI_INTARRAY_LOGGER_H

2、接着创建intarray_jni.c主要用来注册绑定java函数和native函数，以及java函数在c中相应函数的具体实现，内容如下：

#include "logger.h"

#ifndef NULL

#define NULL ((void *) 0)

#endif

/**

 * 获取数组大小

 */

#define NELEM(x) ((int)(sizeof(x) / sizeof((x)[0])))

/**

 * 指定要注册的类，对应完整的java类名

 */

#define JNIREG_CLASS "com/ndk/clarck/MainActivity"

/**

 * 返回数组中元素的和

 */

JNIEXPORT jint JNICALL native_sumArray(JNIEnv *env, jobject obj, jintArray arr) {

    jint *carr;

    jint i, sum = ;

    carr = (*env)->GetIntArrayElements(env, arr, NULL);

    if (carr == NULL) {

        return ;

    }

    for (i = ; i < ; i++) {

        sum += carr[i];

    }

    (*env)->ReleaseIntArrayElements(env, arr, carr, );

    return sum;

}

/**

 * Java和JNI函数绑定

 */

static JNINativeMethod method_table[] = {

        {"sumArray", "([I)I", (void *)native_sumArray},

};

/**

 * 注册native方法到java中

 */

static int registerNativeMethods(JNIEnv *env, const char* className,

        JNINativeMethod* gMethods, int numMethods) {

    jclass clazz;

    clazz = (*env)->FindClass(env, className);

    if (clazz == NULL) {

        return JNI_FALSE;

    }

    if ((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < ) {

        return JNI_FALSE;

    }

    return JNI_TRUE;

}

/**

 * 调用注册方法

 */

int register_ndk_load(JNIEnv *env) {

    return registerNativeMethods(env, JNIREG_CLASS, method_table, NELEM(method_table));

}

JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved) {

    JNIEnv *env = NULL;

    jint result = -;

    if ((*vm)->GetEnv(vm, (void**)&env, JNI_VERSION_1_4) != JNI_OK) {

        return result;

    }

    register_ndk_load(env);

    return JNI_VERSION_1_4;

}

3、java层调用如下：

package com.ndk.clarck;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.Menu;

import android.view.MenuItem;

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        int arr[] = new int[10];

        for (int i = 0; i < 10; i++) {

            arr[i] = i;

        }

        int sum = sumArray(arr);

        Log.d("Test", "sum: " + sum);

    }

    public native int sumArray(int[] arr);

    static {

        System.loadLibrary("intarray_jni");

    }

}

第二步，配置如下环境，执行编译命令：

1、在local.properties配置SDK和NDK路径如下:

　sdk.dir=xxxx

　ndk.dir=xxx

2、打开gradle-wrapper.properties，将其配置修改为使用Gradle 2.5来编译(详情参考:http://www.cnblogs.com/tanlon/p/4731283.html)：

#Mon Aug 17 20:34:50 HKT 2015

distributionBase=GRADLE_USER_HOME

distributionPath=wrapper/dists

zipStoreBase=GRADLE_USER_HOME

zipStorePath=wrapper/dists

distributionUrl=https\://services.gradle.org/distributions/gradle-2.5-all.zip

3、配置Project下面的build.gradle，其内容如下：

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {

    repositories {

        jcenter()

    }

    dependencies {

        classpath 'com.android.tools.build:gradle-experimental:0.2.0'

        // NOTE: Do not place your application dependencies here; they belong

        // in the individual module build.gradle files

    }

}

allprojects {

    repositories {

        jcenter()

    }

}

4、配置Module下面的build.gradle，其内容如下：

apply plugin: 'com.android.model.application'

model {

    android {

        compileSdkVersion = 22

        buildToolsVersion = "22.0.1"

        defaultConfig.with {

            applicationId = "com.ndk.clarck"

            minSdkVersion.apiLevel    = 15

            targetSdkVersion.apiLevel = 21

        }

    }

    android.ndk {

        moduleName = "intarray_jni"

        ldLibs    += ["log"]

    }

    android.buildTypes {

        release {

            minifyEnabled = false

            proguardFiles += file('proguard-rules.pro')

        }

    }

    android.productFlavors {

        create ("arm7") {

            ndk.abiFilters += "armeabi-v7a"

        }

        create ("arm8") {

            ndk.abiFilters += "arm64-v8a"

        }

        create ("x86-32") {

            ndk.abiFilters += "x86"

        }

        // for detailed abiFilter descriptions, refer to "Supported ABIs" @

        // https://developer.android.com/ndk/guides/abis.html#sa

        // build one including all cpu architectures

        create("all")

    }

}

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile 'com.android.support:appcompat-v7:22.2.0'

}

5、执行Build->Make Project，得到如下输出：

Information:Gradle tasks [:app:assembleAllDebug]

:app:copyArm64-v8aDebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createArm64-v8aDebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileArm64-v8aDebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkArm64-v8aDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsArm64-v8aDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:arm64-v8aDebugAllIntarray_jniSharedLibrary

:app:copyArmeabi-v7aDebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createArmeabi-v7aDebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileArmeabi-v7aDebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkArmeabi-v7aDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsArmeabi-v7aDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:armeabi-v7aDebugAllIntarray_jniSharedLibrary

:app:copyArmeabiDebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createArmeabiDebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileArmeabiDebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkArmeabiDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsArmeabiDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:armeabiDebugAllIntarray_jniSharedLibrary

:app:preBuild UP-TO-DATE

:app:preAllDebugBuild UP-TO-DATE

:app:checkAllDebugManifest

:app:preAllReleaseBuild UP-TO-DATE

:app:preArm7DebugBuild UP-TO-DATE

:app:preArm7ReleaseBuild UP-TO-DATE

:app:preArm8DebugBuild UP-TO-DATE

:app:preArm8ReleaseBuild UP-TO-DATE

:app:preX86-32DebugBuild UP-TO-DATE

:app:preX86-32ReleaseBuild UP-TO-DATE

:app:prepareComAndroidSupportAppcompatV72220Library UP-TO-DATE

:app:prepareComAndroidSupportSupportV42220Library UP-TO-DATE

:app:prepareAllDebugDependencies

:app:compileAllDebugAidl UP-TO-DATE

:app:compileAllDebugRenderscript UP-TO-DATE

:app:generateAllDebugBuildConfig UP-TO-DATE

:app:generateAllDebugAssets UP-TO-DATE

:app:mergeAllDebugAssets UP-TO-DATE

:app:generateAllDebugResValues UP-TO-DATE

:app:generateAllDebugResources UP-TO-DATE

:app:mergeAllDebugResources UP-TO-DATE

:app:processAllDebugManifest UP-TO-DATE

:app:processAllDebugResources UP-TO-DATE

:app:generateAllDebugSources UP-TO-DATE

:app:processAllDebugJavaRes UP-TO-DATE

:app:compileAllDebugJavaWithJavac

:app:copyMips64DebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createMips64DebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileMips64DebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkMips64DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsMips64DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:mips64DebugAllIntarray_jniSharedLibrary

:app:copyMipsDebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createMipsDebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileMipsDebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkMipsDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsMipsDebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:mipsDebugAllIntarray_jniSharedLibrary

:app:copyX86DebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createX86DebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileX86DebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkX86DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsX86DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:x86DebugAllIntarray_jniSharedLibrary

:app:copyX86_64DebugAllIntarray_jniSharedLibraryGdbServer UP-TO-DATE

:app:createX86_64DebugAllIntarray_jniSharedLibraryGdbsetup

:app:compileX86_64DebugAllIntarray_jniSharedLibraryIntarray_jniMainC UP-TO-DATE

:app:linkX86_64DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:stripSymbolsX86_64DebugAllIntarray_jniSharedLibrary UP-TO-DATE

:app:x86_64DebugAllIntarray_jniSharedLibrary

:app:compileAllDebugSources

:app:preDexAllDebug UP-TO-DATE

:app:dexAllDebug

:app:validateDebugSigning

:app:packageAllDebug

:app:zipalignAllDebug

:app:assembleAllDebug

Information:BUILD SUCCESSFUL

Information:Total time: 2.772 secs

Information:0 errors

Information:0 warnings

Information:See complete output in console

6、执行Run，即可运行项目了。

经验：

Error:Cause: com.android.build.gradle.managed.AndroidConfig Impl 原因：
defaultConfig 必须写成 defaultConfig.with

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Android Studio NDK 学习之接受Java传入的Int数组

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