// Objective-C(NSString) -> C++(std::string)
NSString * ocString = @"Hello World,OC";
std::string cppString = [ocString UTF8String];
std::cout<<cppString<<std::endl;
// C++(std::string) -> Objective-C(NSString)
std::string cppString2 = "Hello World,C++";
NSString *ocString2= [NSString stringWithCString:cppString2.c_str() encoding:[NSString defaultCStringEncoding]];
NSLog(@"%@",ocString2);

#include <JavaVM/jni.h>
#ifndef _Included_cn_taoweiji_nativemodule_NativeDemo
#define _Included_cn_taoweiji_nativemodule_NativeDemo
#ifdef __cplusplus
extern "C" {
#endif
 JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add
 (JNIEnv *, jclass, jint, jint);
 JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_say
 (JNIEnv *, jclass, jstring);
 JNIEXPORT jstring JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_getInfo
 (JNIEnv *, jclass);

 JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_nativeToJava
 (JNIEnv *, jclass, jobject);

#ifdef __cplusplus
}
#endif
#endif

#include "cn_taoweiji_nativemodule_NativeDemo.h"
#include <string>
JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint param1, jint param2)
{
 jint result = param1 + param2;
 return result;
}
JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_say(JNIEnv *env, jclass, jstring param)
{
 // std::string -> jstring
 const char *param_char = env->GetStringUTFChars(param, NULL);
 std::string str = param_char;
}
JNIEXPORT jstring JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_getInfo(JNIEnv *env, jclass)
{
 // jstring -> std::string
 std::string str = "Hi,I am C++.";
 jstring result = env->NewStringUTF(str.c_str());
 return result;
}
JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_nativeToJava(JNIEnv * env, jclass, jobject obj)
{
 // 调用Java方法
 jclass cls = env->FindClass("cn/taoweiji/nativemodule/NativeDemo");
 //int subtract(int param1, int param2) -> (II)I
 jmethodID mid = env->GetMethodID(cls, "subtract", "(II)I");
 int result = (int) env->CallIntMethod(obj, mid, 10, 2);
// std::cout<<result<<std::endl;
 //常见类型转换例子
 //String getInfo();
 //-> ()Ljava/lang/String;

 //PackageInfo getPackageInfo(String packageName, int flags);
 //-> (Ljava/lang/String;I)Landroid/content/pm/PackageInfo;;

}

package cn.taoweiji.nativemodule;
/**
 * 包名和类名称一定要和前面的C++头文件对应
 * cn_taoweiji_nativemodule_NativeDemo.h
 */
public class NativeDemo {
 public static native int add(int param1, int param2);
 public static native void say(String name);
 public static native String getInfo();
 public static native void nativeToJava(NativeDemo nativeDemo);
 public int subtract(int param1, int param2) {
 System.out.println("NativeDemo:" + String.format("%s - %s = %s", param1, param2, param1 - param2));
 return param1 - param2;
 }
}

public class Main {
 static {
 System.load("/Users/Wiki/Library/Developer/Xcode/DerivedData/DEMO_MAC_JNI-clxymnzifegyfaajsaattzgxqfbr/Build/Products/Debug/DEMO_MAC_JNI");
 }
 public static void main(String[] args) {
 System.out.println("Hello World!");
 int result = NativeDemo.add(1, 2);
 System.out.println("1+2=" + String.valueOf(result));
 NativeDemo.say("Hello,I am Java.");
 System.out.println("getInfo:" + NativeDemo.getInfo());
 NativeDemo.nativeToJava(new NativeDemo());
 }
}

gradle配置（NativeModule）
apply plugin: 'com.android.library'
android {
 compileSdkVersion 23
 buildToolsVersion "24.0.0 rc2"
 defaultConfig {
 minSdkVersion 14
 targetSdkVersion 23
 versionCode 1
 versionName "1.0"
 }
 buildTypes {
 release {
  minifyEnabled false
  proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
  ndk {
  moduleName "joyrun"
  stl "stlport_static"
  ldLibs "log"//用于解决__android_log_print
  abiFilters "armeabi", "armeabi-v7a", "x86", "x86_64", "arm64-v8a"
  //add -fexceptions to allow throw error
  //add -w to "format not a string literal and no format arguments [-Werror=format-security"
  cFlags "-w -fexceptions"
  }
 }
 }
}
dependencies {
 compile fileTree(dir: 'libs', include: ['*.jar'])
}

// NativeDemo.java
package cn.taoweiji.nativemodule;
public class NativeDemo {
 public static native int add(int param1, int param2);
}

// cn_taoweiji_nativemodule_NativeDemo.h
#include <jni.h>
#ifndef _Included_cn_taoweiji_nativemodule_NativeDemo
#define _Included_cn_taoweiji_nativemodule_NativeDemo
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class: cn_taoweiji_nativemodule_NativeDemo
 * Method: add
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint, jint);
#ifdef __cplusplus
}
#endif
#endif

// NativeDemo.cpp
#include "cn_taoweiji_nativemodule_NativeDemo.h"
JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint param1, jint param2)
{
 jint result = param1 + param2;
 return result;
}

// 静态加载
static {
 System.loadLibrary("joyrun");
}
//调用
int result = NativeDemo.add(1,2);
Log.i("1+2=",String.valueOf(result));

// 生成so文件的名称
moduleName "joyrun"
// 引入STL标准库
stl "stlport_static"//gnustl_static
//用于解决__android_log_print
ldLibs "log"
abiFilters "armeabi", "armeabi-v7a", "x86", "x86_64", "arm64-v8a" //添加编译的平台
//add -fexceptions to allow throw error
//add -w to "format not a string literal and no format arguments [-Werror=format-security"
cFlags "-w -fexceptions"

#include <android/log.h>
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, "tag_joyrun", __VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, "tag_joyrun", __VA_ARGS__)
LOGE("Hello Logcat");

// std::string -> jstring
std::string str = "Hello World";
jstring result = env->NewStringUTF(str.c_str());
// jstring -> std::string
jstring param;
const char *param_char = env->GetStringUTFChars(param, NULL);
std::string str = param_char;
// jboolean 两个值 JNI_TRUE、JNI_FALSE

public static native void nativeToJava(NativeDemo nativeDemo);
public int subtract(int param1, int param2) {
Log.e("NativeDemo", String.format("%s - %s = %s", param1, param2, param1 - param2));
return param1 - param2;
}

JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_nativeToJava(JNIEnv * env, jclass, jobject obj)
{
 // 调用Java方法
 jclass cls = env->FindClass("cn/taoweiji/nativemodule/NativeDemo");
 jmethodID mid = env->GetMethodID(cls, "subtract", "(II)I");
 int result = (int) env->CallIntMethod(obj, mid, 10, 2);

 //常见类型转换例子
 //String getInfo();
 //-> ()Ljava/lang/String;
 //PackageInfo getPackageInfo(String packageName, int flags);
 //-> (Ljava/lang/String;I)Landroid/content/pm/PackageInfo;;
}

#!/bin/sh
export ProjectPath=$(cd "../$(dirname "$1")"; pwd)
export TargetClassName="co.runner.app.jni.NativeDemo"
export SourceFile="${ProjectPath}/app/src/main/java"
export TargetPath="${ProjectPath}/jni-joyrun/src/main/jni"
cd "${SourceFile}"
javah -d ${TargetPath} -classpath "${SourceFile}" "${TargetClassName}"
echo -d ${TargetPath} -classpath "${SourceFile}" "${TargetClassName}"

// Demo.hpp
#ifndef Demo_hpp
#define Demo_hpp
#include <stdio.h>
#include <string>
class Demo{
public:
 std::string name;
 int age = 0;
 void say();
 static int add(int param1,int param2)
 {
 return param1 + param2;
 }
};
#endif /* Demo_hpp */

// Demo.cpp
#include "Demo.hpp"
#include <iostream>
void Demo::say()
{
 std::cout<<"name = "<<name<<",age = "<<age<<std::endl;
}

//对象创建
Demo d1;
Demo * d2 = new Demo;
// 运算符访问
d1.say();
// 指针访问
d2->say();
//静态函数访问
int result = Demo::add(1,2);
std::cout<<"1 + 2 = "<<result<<std::endl;

//include相关文件
#include <stdio.h>
#include <iostream>
#include <list>
#include "Demo.hpp"
// 链表定义
std::list<Demo> * demos = new std::list<Demo>;
Demo * demo = new Demo;
demo->name = "Wiki";
demo->age = 24;
// 在后面插入数据
demos->push_back(*demo);
demo = new Demo;
demo->name = "Wiki2";
demo->age = 25;
// 在前面插入数据
demos->push_front(*demo);
// 顺序链表遍历
for (std::list<Demo>::iterator iter = demos->begin(); iter != demos->end(); ++iter) {
 iter->say();
}
// 反顺序链表遍历
for (std::list<Demo>::reverse_iterator iter = demos->rbegin(); iter != demos->rend(); ++iter) {
 iter->say();
}
// 获取指定位置元素
std::list<Demo>::iterator iter = demos->begin();
advance(iter, 1);
iter->say();

// 通过指针
void handle1(Demo *p);
// 通过引用
void handle1(Demo& p);
// 通过值
void handle1(Demo *demo);

Demo d1;//栈
Demo * d2 = new Demo;//堆
char c; //栈上分配
char *p = new char[3]; //堆上分配，将地址赋给了p;