编写通过JS应用控制LED灯

在本示例将演示如何在系统中添加自定义JS API，达到能通过JS应用关闭灯、开启灯以及翻转灯的状态。希望通过本教程的学习，开发者能掌握如何在OpenHarmony中自定义JS API。

注: 在学习本教程之前，请确保已经完成编写一个点亮LED灯程序实验，因为本实验将依赖编写一个点亮LED灯程序实验中开发的驱动，以下教程篇幅较长，请耐心仔细阅读。

一、JS API接口开发

1. 添加控制LED灯的JS API接口

   修改foundation\ace\ace_engine_lite\frameworks\src\core\modules\app_module.h，加入toggleLed JS API,（"##start##"和"##end##"仅用来标识位置，添加完配置后删除这两行）

   public:
   ACE_DISALLOW_COPY_AND_MOVE(AppModule);
   AppModule() = default;
   ~AppModule() = default;
   static JSIValue GetInfo(const JSIValue thisVal, const JSIValue *args, uint8_t argsNum);
   static JSIValue Terminate(const JSIValue thisVal, const JSIValue *args, uint8_t argsNum);
   ##start##
   static JSIValue ToggleLed(const JSIValue thisVal, const JSIValue* args, uint8_t argsNum);
   ##end##
   #ifdef FEATURE_SCREEN_ON_VISIBLE
       static JSIValue ScreenOnVisible(const JSIValue thisVal, const JSIValue *args, uint8_t argsNum);
   #endif

   void InitAppModule(JSIValue exports)
   {
       JSI::SetModuleAPI(exports, "getInfo", AppModule::GetInfo);
       JSI::SetModuleAPI(exports, "terminate", AppModule::Terminate);
   ##start##
       JSI::SetModuleAPI(exports, "ledcontrol", AppModule::ToggleLed);
   ##end##
   #ifdef FEATURE_SCREEN_ON_VISIBLE
       JSI::SetModuleAPI(exports, "screenOnVisible", AppModule::ScreenOnVisible);
   #endif
   }

2. 编写控制LED灯c++ 业务代码

   在foundation\ace\ace_engine_lite\frameworks\src\core\modules\app_module.cpp中加入控制LED灯c++ 业务代码（"##start##"和"##end##"仅用来标识位置，添加完配置后删除这两行）。

   #include "app_module.h"
   #include "ace_log.h"
   #include "js_app_context.h"
   #ifdef FEATURE_SCREEN_ON_VISIBLE
   #include "js_async_work.h"
   #include "product_adapter.h"
   #endif
   
   ##start##
   #include "hdf_sbuf.h"
   #include "hdf_io_service_if.h"
   
   #define LED_WRITE_READ 1
   #define LED_SERVICE "hdf_led"
   ##end##
   
   namespace OHOS {
   namespace ACELite {
   const char * const AppModule::FILE_MANIFEST = "manifest.json";
   const char * const AppModule::KEY_APP_NAME = "appName";
   const char * const AppModule::KEY_VERSION_NAME = "versionName";
   const char * const AppModule::KEY_VERSION_CODE = "versionCode";
   

   struct AsyncParams : public MemoryHeap {
       ACE_DISALLOW_COPY_AND_MOVE(AsyncParams);
       AsyncParams() : result(nullptr), callback(nullptr), context(nullptr) {}
   
       JSIValue result;
       JSIValue callback;
       JSIValue context;
   };
   #endif
   
   ##start##
   
   static int OnDevEventReceived(void *priv, uint32_t id, struct HdfSBuf *data)
   {
       uint32_t value;
       HdfSbufReadUint32(data, &value);
       HILOG_ERROR(HILOG_MODULE_ACE,"%s: dev event received: %u %u\n", (char *)priv, id, value);
   
       return HDF_SUCCESS;
   }
   
   static int GpioWriteRead(struct HdfIoService *serv, int32_t eventData, int32_t *val)
   {
       int ret = HDF_FAILURE;
       struct HdfSBuf *data = HdfSBufObtainDefaultSize();
       struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
   
       if (data == NULL || reply == NULL) {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to obtain sbuf data\n");
           return ret;
       }
   
       if (!HdfSbufWriteUint8(data, (uint8_t)eventData))
       {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to write sbuf\n");
           HdfSBufRecycle(data);
           HdfSBufRecycle(reply);
           return ret;
       }
   
       ret = serv->dispatcher->Dispatch(&serv->object, LED_WRITE_READ, data, reply);
       if (ret != HDF_SUCCESS)
       {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to send service call\n");
           HdfSBufRecycle(data);
           HdfSBufRecycle(reply);
           return ret;
       }
       if (!HdfSbufReadInt32(reply, val))
       {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to get service call reply\n");
           ret = HDF_ERR_INVALID_OBJECT;
           HdfSBufRecycle(data);
           HdfSBufRecycle(reply);
           return ret;
       }
       HILOG_ERROR(HILOG_MODULE_ACE,"Get reply is: %d\n", val);
   
       HdfSBufRecycle(data);
       HdfSBufRecycle(reply);
       return ret;
   }
   
   JSIValue AppModule::ToggleLed(const JSIValue thisVal, const JSIValue *args, uint8_t argsNum)
   {
       HILOG_ERROR(HILOG_MODULE_ACE, "led button pressed.");
   
       struct HdfIoService *serv = HdfIoServiceBind(LED_SERVICE);
       if (serv == NULL)
       {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to get service2 %s\n", LED_SERVICE);
           return JSI::CreateUndefined();
       }
   
       if ((args == nullptr) || (argsNum == 0) || (JSI::ValueIsUndefined(args[0]))) {
           return JSI::CreateUndefined();
       }
   
       JSIValue success = JSI::GetNamedProperty(args[0], CB_SUCCESS);
       JSIValue fail = JSI::GetNamedProperty(args[0], CB_FAIL);
       JSIValue complete = JSI::GetNamedProperty(args[0], CB_COMPLETE);
   
       int32_t num = (int32_t)JSI::GetNumberProperty(args[0], "code");
   
       int32_t replyData = 0;
   
       if (GpioWriteRead(serv, num, &replyData))
       {
           HILOG_ERROR(HILOG_MODULE_ACE,"fail to send event\n");
           JSI::CallFunction(fail, thisVal, nullptr, 0);
           JSI::CallFunction(complete, thisVal, nullptr, 0);
           JSI::ReleaseValueList(success, fail, complete);
           return JSI::CreateUndefined();
       }
   
       JSIValue result = JSI::CreateObject();
       JSI::SetNumberProperty(result, "led_status", replyData);
   
       JSIValue argv[ARGC_ONE] = {result};
       JSI::CallFunction(success, thisVal, argv, ARGC_ONE);
       JSI::CallFunction(complete, thisVal, nullptr, 0);
       JSI::ReleaseValueList(success, fail, complete, result);
   
       HdfIoServiceRecycle(serv);
   
       return JSI::CreateUndefined();
   }
   
   ##end##
   
   JSIValue AppModule::GetInfo(const JSIValue thisVal, const JSIValue *args, uint8_t argsNum)
   {
       JSIValue result = JSI::CreateUndefined();
   
       cJSON *manifest = ReadManifest();
       if (manifest == nullptr) {
           HILOG_ERROR(HILOG_MODULE_ACE, "Fail to get the content of manifest.");
           return result;
       }
   
       cJSON *appName = cJSON_GetObjectItem(manifest, KEY_APP_NAME);
       cJSON *versionName = cJSON_GetObjectItem(manifest, KEY_VERSION_NAME);
       cJSON *versionCode = cJSON_GetObjectItem(manifest, KEY_VERSION_CODE);
   
       result = JSI::CreateObject();
       if (appName != nullptr && appName->type == cJSON_String) {
           JSI::SetStringProperty(result, KEY_APP_NAME, appName->valuestring);
       }
       if (versionName != nullptr && versionName->type == cJSON_String) {
           JSI::SetStringProperty(result, KEY_VERSION_NAME, versionName->valuestring);
       }
       if (versionCode != nullptr && versionCode->type == cJSON_Number) {
           JSI::SetNumberProperty(result, KEY_VERSION_CODE, versionCode->valuedouble);
       }
       cJSON_Delete(manifest);
       manifest = nullptr;
       return result;
   }

3. 配置HDF头文件路径

   在foundation\ace\ace_engine_lite\ace_lite.gni中添加HDF头文件路径。

   ace_lite_include_dirs += [
       "//drivers/framework/ability/sbuf/include",
       "//drivers/framework/include/core",
       "//drivers/framework/include/utils",
       "//drivers/adapter/uhdf/posix/include",
   ]

4. 添加编译依赖

   修改foundation\ace\ace_engine_lite\frameworks\BUILD.gn，在public_deps中添加以下代码

   "//drivers/adapter/uhdf/manager:hdf_core",

   修改foundation\ace\ace_engine_lite\test\ace_test_config.gni，在extra_deps中添加以下代码

   "//drivers/adapter/uhdf/manager:hdf_core",

二、运行结果

示例代码编译、烧录后，参考如何在开发板上安装HAP应用教程安装applications/BearPi/BearPi-HM_Micro/tools/hap_tools/hap_example目录下的LED.hap应用进行测试