#冲刺创作新星# [七] 写个NAPI子系统 原创 精华

作者：王石

在《[六]第一个hap应用》我们熟悉了如何在OpenHarmony开发hap应用，后期的文章我们会写在hap应用里调用系统库甚至是动态库。此篇文章，我们主要是熟悉下NAPI框架，并一起写一个支持NAPI的子系统，这样以后当我们想在hap应用里加自己功能的时候就可以方便的添加。

NAPI框架简介

NAPI（Native API）组件是一套对外接口基于Node.js N-API规范开发的原生模块扩展开发框架。类似于Android的JNI，NAPI框架实现了应用层ts/ets/js语言编写的代码和OpenHarmony的native代码（c/c++）交互的能力。此框架由Node.js N-API框架扩展而来。

注意：OpenHarmony的标准系统是采用NAPI框架的，轻量系统则是采用jerryscript框架

详细的内容介绍在一下链接内可以看到官方的说明：

参考链接：https://gitee.com/openharmony/arkui_napi

NAPI的使用

graph LR
创建d.ts --> 执行napi_generator --> 建立子系统 --> 引入子系统 --> 编译生成

1. 创建d.ts: @ohos.napitest.d.ts, basic.d.ts

   • @ohos.napitest.d.ts是NAPI的声明文件，在DevEco Studio开发的时候会用到d.ts来检查语法和提供代码帮助；

   import {AsyncCallback} from './basic';
   
   /**
    * Provides interfaces to napitest.
    *
    * @since 7
    */
   declare namespace napitest {
     /**
      * Shuts down the system.
      *
      * <p>This method requires the ohos.permission.SHUTDOWN permission.
      *
      * @param reason Indicates the shutdown reason.
      * @systemapi
      * @since 7
      */
     function shutdownDevice(reason: string): void;
   
     /**
      * Restarts the system.
      *
      * <p>This method requires the ohos.permission.REBOOT permission.
      *
      * @param reason Indicates the restart reason. For example, "updater" indicates entering the updater mode
      * after the restart. If the parameter is not specified, the system enters the normal mode after the restart.
      * @since 7
      */
     function rebootDevice(reason: string): void;
   
     /**
      * Checks whether the screen of a device is on or off.
      *
      * @return Returns true if the screen is on; returns false otherwise.
      * @since 7
      */
     function isScreenOn(callback: AsyncCallback<boolean>): void;
     function isScreenOn(): Promise<boolean>;
   }
   export default napitest;
   

   • basic.d.ts：一些基础方法的声明

   export interface Callback<T> {
       (data: T): void;
   }
     
   export interface ErrorCallback<T extends Error = BusinessError> {
       (err: T): void;
   }
   
   export interface AsyncCallback<T> {
       (err: BusinessError, data: T): void;
   }
   
   export interface BusinessError extends Error {
       code: number;
   }
   

2. 执行napi_generator

   建立个文件夹，将上面建立的两个d.ts和napi_generator放在一起

   //准备环境
   mkdir napitest
   cd napitest
   vim @ohos.napitest.d.ts
   vim basic.d.ts
   //拷贝napi_generator
   cp [路径]/napi_generator-linux .
   chmod +x napi_generator-linux
   //生成napitest代码
   ./napi_generator-linux -f @ohos.napitest.d.ts -o out
   //当看到success则说明烧录成功
   
   //检视out目录
   ├── binding.gyp			//工具中间文件
   ├── BUILD.gn			//之后需要用到的gn文件
   ├── napi_gen.log		//工具log
   ├── napitest.cpp		//自动生成的接口调用的实际代码
   ├── napitest.h			//自动生成的接口调用的实际代码
   ├── napitest_middle.cpp	//自动生成的napi适配代码
   ├── test.sh				//生成js代码的脚本，官方没给说明，试了下不可用
   ├── tool_utility.cpp	//自动生成的napi适配代码
   └── tool_utility.h		//自动生成的napi适配代码
   

3. 建立子系统

   • 在OpenHarmony源码目录下建立foundation/napitest，将之前生成的文件拷贝到文件夹内

   foundation
   ├── ability
   ├── ai
   ├── arkui
   ├── barrierfree
   ├── bundlemanager
   ├── communication
   ├── deviceprofile
   ├── distributeddatamgr
   ├── distributedhardware
   ├── filemanagement
   ├── graphic
   ├── multimedia
   ├── multimodalinput
   ├── napitest
   │   ├── binding.gyp
   │   ├── BUILD.gn
   │   ├── bundle.json
   │   ├── napi_gen.log
   │   ├── napitest.cpp
   │   ├── napitest.h
   │   ├── napitest_middle.cpp
   │   ├── test.sh
   │   ├── tool_utility.cpp
   │   └── tool_utility.h
   ├── resourceschedule
   

   • 在目录里创建bundle.json，使用一下内容

   {
       "name": "@ohos/napitest",
       "description": "napitest provides atomic capabilities",
       "version": "3.1",
       "license": "Apache License 2.0",
       "publishAs": "code-segment",
       "segment": {
         "destPath": "foundation/napitest"
       },
       "dirs": {},
       "scripts": {},
       "component": {
         //部件名称
         "name": "napitest_interface",
         //子系统名称
         "subsystem": "napitest",
         "features": [],
         "adapted_system_type": [
           "standard"
         ],
         "rom": "10000KB",
         "ram": "10000KB",
         "deps": {
           "components": [
             "ace_napi",
             "ipc_core",
             "libhilog"
           ],
           "third_party": [
             "node"
           ]
         },
         "build": {
           "sub_component": [
             "//foundation/napitest:napitest"
           ],
           "inner_kits": [
             {
               "header": {
                 "header_base": "//foundation/napitest",
                 "header_files": [
                   "tool_utility.h",
                   "napitest.h"
                 ]
               },
               "name": "//foundation/napitest:napitest"
             }
           ]
         }
       }
     }
   

   • 为了和bundle.json对应，将BUILD.gn改成如下：

   import("//build/ohos.gni")
   
   ohos_shared_library("napitest")
   {
       sources = [
           "napitest_middle.cpp",
           "napitest.cpp",
           "tool_utility.cpp",
       ]
       include_dirs = [
           ".",
           "//third_party/node/src",
           "//base/hiviewdfx/hilog/interfaces/native/innerkits/include",
       ]
       deps=[
           "//foundation/arkui/napi:ace_napi",
           "//base/hiviewdfx/hilog/interfaces/native/innerkits:libhilog",
       ]
       remove_configs = [ "//build/config/compiler:no_rtti" ]
       cflags=[
       ]
       cflags_cc=[
           "-frtti",
       ]
       ldflags = [
       ]
       
       relative_install_dir = "module"
   	//部件名称
       part_name = "napitest_interface"
   	//子系统名称
       subsystem_name = "napitest"
   }
   

4. 引入子系统

   • 增加子系统，修改build/subsystem_config.json

     //在文件后增加
     {
       //前面省略的内容
     	...
       //新增内容
       "napitest": {
         "path": "foundation/napitest",
         "name": "napitest"
       }
     }
     

   • 增加编译入口（已目前的master版本为基础，3.2后改过编译路径）

     //修改 vendor/hihope/[PRODUCT_NAME]/config.json 文件增加如下行
     {
     	"subsystem": "napitest",
     	"components": [
     	{
     		"component": "napitest_interface",
     		"features": []
     	}
     	]
     },
     

5. 编译生成

   ./build.sh --product-name PRODUCT_NAME
   //看到success则为编译成功，可以通过find out/[PRODUCT_NAME] -name *napitest.z.so查看生成文件,比如我的文件路径如下：
   ./out/rk3568/lib.unstripped/napitest/napitest_interface/libnapitest.z.so
   ./out/rk3568/napitest/napitest_interface/libnapitest.z.so
   ./out/rk3568/innerkits/ohos-arm/napitest_interface/napitest/libnapitest.z.so
   ./out/rk3568/packages/phone/system/lib/module/libnapitest.z.so
   //最后一个路径就是系统镜像的路径，所以两种办法
   //1,直接copy到板子的/system/lib路径；参考《 [二]第一个OpenHarmony程序》
   //2,烧录镜像；参考《 [一]运行OpenHarmony》
   
   
   

总结

这样我们就有了自己的subsystem和napi接口，后面的章节我们会讲如何在hap应用里调用系统库

参考链接：https://gitee.com/openharmony/napi_generator/tree/master