NDK开发模块的时候，如果涉及到网络请求，类似json数据传递的时候，有现成的第三方json库可以移植，后台C++开发中使用的比较多的是jsoncpp，今天记录一下jsoncpp移植到Android平台的过程
cmake编译
此方法并非标准的NDK项目
采用的是cmake交叉编译生成
jsoncpp地址
https://github.com/open-source-parsers/jsoncpp
先将源码克隆下来
新建文件夹libjson
将jsoncpp源码中的include文件夹复制到该目录，然后进入src/lib_json目录复制
部分文件到libjson目录下的src目录中，如下
json_reader.cpp
json_tool.h
json_value.cpp
json_valueiterator.inl
json_writer.cpp
version.h.in
在libjson目录新建文件CMakeLists.txt
内容如下
CMAKE_MINIMUM_REQUIRED(VERSION 3.5)
PROJECT(Jpp)
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
#ARCHS集合
SET(ARCHS "arm" "arm64" "x86" "x86_64" "mips" "mips64")
#PLATFORM集合
SET(PLATFORM "arm-linux-androideabi" "aarch64-linux-android" "i686-linux-android" "x86_64-linux-android" "mipsel-linux-android" "mips64el-linux-android")
SET(JSONCPP_INCLUDE_DIR include)
INCLUDE_DIRECTORIES(${JSONCPP_INCLUDE_DIR})
SET(PUBLIC_HEADERS
${JSONCPP_INCLUDE_DIR}/json/config.h
${JSONCPP_INCLUDE_DIR}/json/forwards.h
${JSONCPP_INCLUDE_DIR}/json/features.h
${JSONCPP_INCLUDE_DIR}/json/value.h
${JSONCPP_INCLUDE_DIR}/json/reader.h
${JSONCPP_INCLUDE_DIR}/json/writer.h
${JSONCPP_INCLUDE_DIR}/json/assertions.h
${JSONCPP_INCLUDE_DIR}/json/version.h
)
SOURCE_GROUP("Public API" FILES ${PUBLIC_HEADERS})
SET(jsoncpp_sources
src/json_tool.h
src/json_reader.cpp
src/json_valueiterator.inl
src/json_value.cpp
src/json_writer.cpp
src/version.h.in)
#INDEX=0 "arm"
#INDEX=1 "arm64"
#INDEX=2 "x86"
#INDEX=3 "x86_64"
#INDEX=4 "mips"
#INDEX=5 "mips64"
SET(INDEX 0)
list(GET ARCHS ${INDEX} TARGET_ARCH)
list(GET PLATFORM ${INDEX} TARGET_PLATFORM)
MESSAGE("ARCH= " ${TARGET_ARCH})
MESSAGE("PLATFORM= " ${TARGET_PLATFORM})
SET(CMAKE_C_COMPILER "$ENV{HOME}/android-toolchain/${TARGET_ARCH}/bin/${TARGET_PLATFORM}-gcc")
SET(CMAKE_CXX_COMPILER "$ENV{HOME}/android-toolchain/${TARGET_ARCH}/bin/${TARGET_PLATFORM}-g++")
SET(EXECUTABLE_OUTPUT_PATH ${PROJECT_BINARY_DIR}/bin)
SET(LIBRARY_OUTPUT_PATH ${PROJECT_BINARY_DIR}/lib)
ADD_LIBRARY(${TARGET_ARCH}_share SHARED ${PUBLIC_HEADERS} ${jsoncpp_sources})
SET_TARGET_PROPERTIES(${TARGET_ARCH}_share PROPERTIES OUTPUT_NAME ${TARGET_ARCH})
ADD_LIBRARY(${TARGET_ARCH}_static STATIC ${PUBLIC_HEADERS} ${jsoncpp_sources})
SET_TARGET_PROPERTIES(${TARGET_ARCH}_static PROPERTIES OUTPUT_NAME ${TARGET_ARCH})
编译之前确认已安装cmake
如果没有，请先安装
sudo apt-get install cmake
目录结构如下
准备工作做好之后可以进行编译了
cmake .
make
笔者目前只编译了arm平台的，如果有需要其他平台的，只需要改动上述CMakeLists.txt中的编号即可
SET(INDEX 0)
NDK原生编译
测试
下面简单测试一下，就不建Android项目了
新建文件夹JNI
将刚才生成的libarm.a和include文件夹放入进去，新建文件Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE:= jsoncpp
LOCAL_SRC_FILES := libarm.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE:= main
LOCAL_C_INCLUDES := $(LOCAL_PATH)/include/json
LOCAL_SRC_FILES := main.cpp
LOCAL_CPPFLAGS := -fexceptions
LOCAL_STATIC_LIBRARIES := jsoncpp
LOCAL_CFLAGS += -pie -fPIE
LOCAL_LDFLAGS += -pie -fPIE
LOCAL_LDLIBS := -llog
include $(BUILD_EXECUTABLE)
新建Application.mk文件
APP_ABI := armeabi
APP_PLATFORM := 12
APP_STL := gnustl_static
APP_CPPFLAGS := -fexceptions -frtti
APP_CPPFLAGS += -std=gnu++11
APP_CPPFLAGS += -fpermissive
新建main.cpp
#include <jni.h>
#include <iostream>
#include "include/json/json.h"
using namespace std;
void JsonTest();
int main(){
JsonTest();
return 0;
}
void JsonTest(){
Json::Value root;
Json::Value array;
Json::Value item;
for (int i = 0; i < 2; i ++)
{
item["id"] = i;
item["name"] = "name";
array.append(item);
}
root["username"] = "andy";
root["age"] = 18;
root["array"] = array;
string out = root.toStyledString();
cout << out << endl;
}
然后编译
ndk-build
然后将生成的main执行文件上传到手机中测试，手机需要root权限
笔者一般丢在/data/local目录下测试
./main
