Android之JNI：Android Studio使用Gradle编译C/C++源码

使用Gradle编译C/C++源码步骤 

申明NDK工具类，内部定义native方法

package com.coca.firstdemo;

/**
 * Created by Administrator on 2016/6/6.
 */
public class JniShareUtils {
    public native String getLogCount(String params);
}

定位至项目的app文件夹，调用javah命令生成.h文件：

javah com.coca.firstdemo.JniShareUtils

执行完会在.java文件同目录下生成com_coca_firstdemo_JniShareUtils.h文件，内容如下：

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

#ifndef _Included_com_coca_firstdemo_JniShareUtils
#define _Included_com_coca_firstdemo_JniShareUtils
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_coca_firstdemo_JniShareUtils
 * Method:    getLogCount
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_com_coca_firstdemo_JniShareUtils_getLogCount
  (JNIEnv *, jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

在app文件夹下新建jni目录存放生成的.h文件。新建.c文件，名字随意，内容如下：

#include "com_coca_firstdemo_JniShareUtils.h"

JNIEXPORT jstring JNICALL Java_com_coca_firstdemo_JniShareUtils_getLogCount
        (JNIEnv *env, jobject obj, jstring jstr){
    return (*env)->NewStringUTF(env,"This just a test for Android Studio NDK JNI developer!");
}

在app的build.gradle中添加设置(ABI支持的7种平台： armeabi, armeabi-v7a, x86, x86_64, mips, mips64, arm64-v8a

defaultConfig {
    //...
    ndk{
        moduleName "wangjun_so_jni"          //生成的so名字,名字随意
        abiFilters "armeabi", "armeabi-v7a", "x86" //输出指定三种abi体系结构下的so库。目前可有可无。
    }
}

在JniShareUtils中添加静态初始化代码：

static {
    System.loadLibrary("wangjun_so_jni");//与上述build.gradle中定义的moduleName对应
}

为什么不用建立Android.mk文件？

在app的build.gradle中按住ctrl点击ndk代码块的modelName即可跳转至NdkOptions.java文件

package com.android.build.gradle.internal.dsl;
/**
 * DSL object for NDK-related settings.
 */
public class NdkOptions implements CoreNdkOptions, Serializable {
    private static final long serialVersionUID = 1L;

    private String moduleName;
    private String cFlags;
    private List<String> ldLibs;
    private Set<String> abiFilters;
    private String stl;
    private Integer jobs;
}

即ndk代码块中可设置的参数有5个，代替了Android.mk中的参数设置。

小Tips：

1.提示错误：Error: NDK integration is deprecated in the current plugin. Consider trying the new experimental plugin. For details, see http://tools.android.com/tech-docs/new-build-system/gradle-experimental. Set "android.useDeprecatedNdk=true" in gradle.properties to continue using the current NDK integration.

解决：在gradle.properties中添加android.useDeprecatedNdk=true

来自为知笔记(Wiz)