1# Sensor Development (C/C++) 2 3 4## When to Use 5 6With the sensor module, a device can obtain sensor data. For example, the device can subscribe to data of the orientation sensor to detect its own orientation, and data of the pedometer sensor to learn the number of steps the user walks every day. 7 8For details about the APIs, see [Sensor API Reference](../../reference/apis-sensor-service-kit/_sensor.md). 9 10## Function Description 11 12| Name | Description | 13| ------------------------------------------------------------ | ------------------------------------------------------------ | 14| OH_Sensor_GetInfos(Sensor_Info **infos, uint32_t *count) | Obtains information about all sensors on the device. | 15| OH_Sensor_Subscribe(const Sensor_SubscriptionId *id, const Sensor_SubscriptionAttribute *attribute, const Sensor_Subscriber *subscriber) | Subscribe to sensor data. The system will report sensor data to the subscriber at the specified frequency.<br>To subscribe to data of acceleration sensors, request the **ohos.permission.ACCELEROMETER** permission.<br>To subscribe to data of gyroscope sensors, request the **ohos.permission.GYROSCOPE** permission.<br>To subscribe to data of pedometer-related sensors, request the **ohos.permission.ACTIVITY_MOTION** permission.<br>To subscribe to data of health-related sensors, such as heart rate sensors, request the **ohos.permission.READ_HEALTH_DATA** permission. Otherwise, the subscription fails.<br>You do not need to request any permission to subscribe to data of other types of sensors.| 16| OH_Sensor_Unsubscribe(const Sensor_SubscriptionId *id, const Sensor_Subscriber *subscriber) | Unsubscribes from sensor data.<br>To unsubscribe from data of acceleration sensors, request the **ohos.permission.ACCELEROMETER** permission.<br>To unsubscribe from data of gyroscope sensors, request the **ohos.permission.GYROSCOPE** permission.<br>To unsubscribe from data of pedometer-related sensors, request the **ohos.permission.ACTIVITY_MOTION** permission.<br>To unsubscribe from data of health-related sensors, request the **ohos.permission.READ_HEALTH_DATA** permission. Otherwise, the unsubscription fails.<br>You do not need to request any permission to unsubscribe from data of other types of sensors.| 17| OH_Sensor_CreateInfos(uint32_t count) | Creates an array of instances with the given number. For details, see [Sensor_Info](../../reference/apis-sensor-service-kit/_sensor.md#sensor_info).| 18| OH_Sensor_DestroyInfos(Sensor_Info **sensors, uint32_t count) | Destroys the array of instances and reclaims the memory. For details, see [Sensor_Info](../../reference/apis-sensor-service-kit/_sensor.md#sensor_info).| 19| OH_SensorInfo_GetName(Sensor_Info *sensor, char *sensorName, uint32_t *length) | Obtains the sensor name. | 20| OH_SensorInfo_GetVendorName(Sensor_Info* sensor, char *vendorName, uint32_t *length) | Obtains the sensor's vendor name. | 21| OH_SensorInfo_GetType(Sensor_Info* sensor, Sensor_Type *sensorType) | Obtains the sensor type. | 22| OH_SensorInfo_GetResolution(Sensor_Info* sensor, float *resolution) | Obtains the sensor resolution. | 23| OH_SensorInfo_GetMinSamplingInterval(Sensor_Info* sensor, int64_t *minSamplingInterval) | Obtains the minimum data reporting interval of a sensor. | 24| OH_SensorInfo_GetMaxSamplingInterval(Sensor_Info* sensor, int64_t *maxSamplingInterval) | Obtains the maximum data reporting interval of a sensor. | 25| OH_SensorEvent_GetType(Sensor_Event* sensorEvent, Sensor_Type *sensorType) | Obtains the sensor type. | 26| OH_SensorEvent_GetTimestamp(Sensor_Event* sensorEvent, int64_t *timestamp) | Obtains the timestamp of sensor data. | 27| OH_SensorEvent_GetAccuracy(Sensor_Event* sensorEvent, Sensor_Accuracy *accuracy) | Obtains the accuracy of sensor data. | 28| OH_SensorEvent_GetData(Sensor_Event* sensorEvent, float **data, uint32_t *length) | Obtains sensor data.<br>The data length and content depend on the sensor type. The format of the sensor data reported is as follows:<br>- SENSOR_TYPE_ACCELEROMETER: data[0], data[1], and data[2], indicating the acceleration around the x, y, and z axes of a device, respectively, in m/s².<br>- SENSOR_TYPE_GYROSCOPE: data[0], data[1], and data[2], indicating the angular velocity of rotation around the x, y, and z axes of a device, respectively, in rad/s.<br>- SENSOR_TYPE_AMBIENT_LIGHT: data[0], indicating the ambient light intensity, in lux. Since API version 12, two extra data records are returned, where **data[1]** indicates the color temperature (in kelvin), and **data[2]** indicates the infrared luminance (in cd/m²).<br> - SENSOR_TYPE_MAGNETIC_FIELD: data[0], data[1], and data[2], indicating the magnetic field strength around the x, y, and z axes of a device, respectively, in μT.<br>- SENSOR_TYPE_BAROMETER: data[0], indicating the atmospheric pressure, in hPa.<br>- SENSOR_TYPE_HALL: data[0], indicating the opening/closing state of the flip cover. The value **0** means that the flip cover is opened, and a value greater than 0 means that the flip cover is closed.<br>- SENSOR_TYPE_PROXIMITY: data[0], indicates the approaching state. The value **0** means the two objects are close to each other, and a value greater than 0 means that they are far away from each other.<br>- SENSOR_TYPE_ORIENTATION: data[0], data[1], and data[2], indicating the rotation angles of a device around the z, x, and y axes, respectively, in degree.<br>- SENSOR_TYPE_GRAVITY: data[0], data[1], and data[2], indicating the gravitational acceleration around the x, y, and z axes of a device, respectively, in m/s².<br>- SENSOR_TYPE_ROTATION_VECTOR: data[0], data[1] and data[2], indicating the rotation angles of a device around the x, y, and z axes, respectively, in degree. data[3] indicates the rotation vector.<br>- SENSOR_TYPE_PEDOMETER_DETECTION: data[0], indicating the pedometer detection status. The value **1** means that the number of detected steps changes.<br>- SENSOR_TYPE_PEDOMETER: data[0], indicating the number of steps a user has walked.<br>- SENSOR_TYPE_HEART_RATE: data[0], indicating the heart rate value.| 29| OH_Sensor_CreateSubscriptionId(void) | Creates a **Sensor_SubscriptionId** instance. | 30| OH_Sensor_DestroySubscriptionId(Sensor_SubscriptionId *id) | Destroys a **Sensor_SubscriptionId** instance and reclaims memory. | 31| OH_SensorSubscriptionId_SetType(Sensor_SubscriptionId* id, const Sensor_Type sensorType) | Sets the sensor type. | 32| OH_Sensor_CreateSubscriptionAttribute(void) | Creates a **Sensor_SubscriptionAttribute** instance. | 33| OH_Sensor_DestroySubscriptionAttribute(Sensor_SubscriptionAttribute *attribute) | Destroys a **Sensor_SubscriptionAttribute** instance and reclaims memory. | 34| OH_SensorSubscriptionAttribute_SetSamplingInterval(Sensor_SubscriptionAttribute* attribute, const int64_t samplingInterval) | Sets the interval for reporting sensor data. | 35| OH_Sensor_CreateSubscriber(void) | Creates a **Sensor_Subscriber** instance. | 36| OH_Sensor_DestroySubscriber(Sensor_Subscriber *subscriber) | Destroys a **Sensor_Subscriber** instance and reclaims memory. | 37| OH_SensorSubscriber_SetCallback(Sensor_Subscriber* subscriber, const Sensor_EventCallback callback) | Sets a callback function to report sensor data. | 38 39 40## How to Develop 41 42The following uses the acceleration sensor as an example to describe the development procedure. 43 441. Create a native C++ project. 45 46  47 482. Configure the acceleration sensor permission. For details, see [Declaring Permissions](../../security/AccessToken/declare-permissions.md). 49 50 ```json 51 "requestPermissions": [ 52 { 53 "name": "ohos.permission.ACCELEROMETER", 54 }, 55 ] 56 ``` 57 583. Add the dynamic dependency libraries into the **CMakeLists.txt** file. 59 60 ```c 61 target_link_libraries(entry PUBLIC libace_napi.z.so) 62 target_link_libraries(entry PUBLIC libhilog_ndk.z.so) 63 target_link_libraries(entry PUBLIC libohsensor.so) 64 ``` 65 664. Write the **napi_init.cpp** file to import related modules. 67 68 ```c 69 #include "sensors/oh_sensor.h" 70 #include "napi/native_api.h" 71 #include "hilog/log.h" 72 #include <thread> 73 ``` 74 755. Define constants. 76 77 ```c 78 const int GLOBAL_RESMGR = 0xFF00; 79 const char *TAG = "[Sensor]"; 80 constexpr Sensor_Type SENSOR_ID { SENSOR_TYPE_ACCELEROMETER }; 81 constexpr uint32_t SENSOR_NAME_LENGTH_MAX = 64; 82 constexpr int64_t SENSOR_SAMPLE_PERIOD = 200000000; 83 constexpr int32_t SLEEP_TIME_MS = 1000; 84 constexpr int64_t INVALID_VALUE = -1; 85 constexpr float INVALID_RESOLUTION = -1.0F; 86 Sensor_Subscriber *g_user = nullptr; 87 ``` 88 896. Define a callback function to receive sensor data. 90 91 ```c 92 void SensorDataCallbackImpl(Sensor_Event *event) { 93 if (event == nullptr) { 94 OH_LOG_Print(LOG_APP, LOG_INFO, GLOBAL_RESMGR, TAG, "event is null"); 95 return; 96 } 97 int64_t timestamp = INVALID_VALUE; 98 int32_t ret = OH_SensorEvent_GetTimestamp(event, ×tamp); // Obtain the timestamp of sensor data. 99 if (ret != SENSOR_SUCCESS) { 100 return; 101 } 102 Sensor_Type sensorType; 103 ret = OH_SensorEvent_GetType(event, &sensorType); // Obtain the sensor type. 104 if (ret != SENSOR_SUCCESS) { 105 return; 106 } 107 Sensor_Accuracy accuracy = SENSOR_ACCURACY_UNRELIABLE; 108 ret = OH_SensorEvent_GetAccuracy(event, &accuracy); // Obtain the accuracy of sensor data. 109 if (ret != SENSOR_SUCCESS) { 110 return; 111 } 112 float *data = nullptr; 113 uint32_t length = 0; 114 ret = OH_SensorEvent_GetData(event, &data, &length); // Obtain sensor data. 115 if (ret != SENSOR_SUCCESS) { 116 return; 117 } 118 OH_LOG_Print(LOG_APP, LOG_INFO, GLOBAL_RESMGR, TAG, "sensorType:%{public}d, dataLen:%{public}d, accuracy:%{public}d", sensorType, length, accuracy); 119 for (uint32_t i = 0; i < length; ++i) { 120 OH_LOG_Print(LOG_APP, LOG_INFO, GLOBAL_RESMGR, TAG, "data[%{public}d]:%{public}f", i, data[i]); 121 } 122 } 123 ``` 124 1257. Obtain information about all sensors on the device. 126 127 ```c 128 static napi_value GetSensorInfos(napi_env env, napi_callback_info info) 129 { 130 uint32_t count = 0; 131 int32_t ret = OH_Sensor_GetInfos(nullptr, &count); // Obtain the number of all sensors on the device. 132 if (ret != SENSOR_SUCCESS) { 133 return nullptr; 134 } 135 Sensor_Info **sensors = OH_Sensor_CreateInfos(count); // Create an array of instances with the given number. 136 if (sensors == nullptr) { 137 return nullptr; 138 } 139 ret = OH_Sensor_GetInfos(sensors, &count); // Obtain information about all sensors on the device. 140 if (ret != SENSOR_SUCCESS) { 141 return nullptr; 142 } 143 for (uint32_t i = 0; i < count; ++i) { 144 char sensorName[SENSOR_NAME_LENGTH_MAX] = {}; 145 uint32_t length = SENSOR_NAME_LENGTH_MAX; 146 ret = OH_SensorInfo_GetName(sensors[i], sensorName, &length); // Obtain the sensor name. 147 if (ret != SENSOR_SUCCESS) { 148 return nullptr; 149 } 150 char vendorName[SENSOR_NAME_LENGTH_MAX] = {}; 151 length = SENSOR_NAME_LENGTH_MAX; 152 ret = OH_SensorInfo_GetVendorName(sensors[i], vendorName, &length); // Obtain the manufacturer name of the sensor. 153 if (ret != SENSOR_SUCCESS) { 154 return nullptr; 155 } 156 Sensor_Type sensorType; 157 ret = OH_SensorInfo_GetType(sensors[i], &sensorType); // Obtain the sensor type. 158 if (ret != SENSOR_SUCCESS) { 159 return nullptr; 160 } 161 float resolution = INVALID_RESOLUTION; 162 ret = OH_SensorInfo_GetResolution(sensors[i], &resolution); // Obtain the sensor resolution. 163 if (ret != SENSOR_SUCCESS) { 164 return nullptr; 165 } 166 int64_t minSamplePeriod = INVALID_VALUE; 167 ret = OH_SensorInfo_GetMinSamplingInterval(sensors[i], &minSamplePeriod); // Obtain the minimum data reporting interval of a sensor. 168 if (ret != SENSOR_SUCCESS) { 169 return nullptr; 170 } 171 int64_t maxSamplePeriod = INVALID_VALUE; 172 ret = OH_SensorInfo_GetMaxSamplingInterval(sensors[i], &maxSamplePeriod); // Obtain the maximum data reporting interval of a sensor. 173 if (ret != SENSOR_SUCCESS) { 174 return nullptr; 175 } 176 } 177 OH_LOG_Print(LOG_APP, LOG_INFO, GLOBAL_RESMGR, TAG, "GetSensorInfos sucessful"); 178 ret = OH_Sensor_DestroyInfos(sensors, count); // Destroy an array of instances and reclaim the memory. 179 if (ret != SENSOR_SUCCESS) { 180 return nullptr; 181 } 182 } 183 ``` 184 1858. Subscribe to and unsubscribe from sensor data. 186 187 ```c 188 static napi_value Subscriber(napi_env env, napi_callback_info info) 189 { 190 g_user = OH_Sensor_CreateSubscriber(); // Create a Sensor_Subscriber instance. 191 int32_t ret = OH_SensorSubscriber_SetCallback(g_user, SensorDataCallbackImpl); // Set a callback function to report sensor data. 192 if (ret != SENSOR_SUCCESS) { 193 return nullptr; 194 } 195 196 Sensor_SubscriptionId *id = OH_Sensor_CreateSubscriptionId(); // Create a Sensor_SubscriptionId instance. 197 ret = OH_SensorSubscriptionId_SetType(id, SENSOR_ID); // Set the sensor type. 198 if (ret != SENSOR_SUCCESS) { 199 return nullptr; 200 } 201 202 Sensor_SubscriptionAttribute *attr = OH_Sensor_CreateSubscriptionAttribute(); // Create a Sensor_SubscriptionAttribute instance. 203 ret = OH_SensorSubscriptionAttribute_SetSamplingInterval(attr, SENSOR_SAMPLE_PERIOD); // Set the interval for reporting sensor data. 204 if (ret != SENSOR_SUCCESS) { 205 return nullptr; 206 } 207 208 ret = OH_Sensor_Subscribe(id, attr, g_user); // Subscribe to sensor data. 209 if (ret != SENSOR_SUCCESS) { 210 return nullptr; 211 } 212 OH_LOG_Print(LOG_APP, LOG_INFO, GLOBAL_RESMGR, TAG, "Subscriber successful"); 213 std::this_thread::sleep_for(std::chrono::milliseconds(SLEEP_TIME_MS)); 214 ret = OH_Sensor_Unsubscribe(id, g_user); // Unsubscribe from sensor data. 215 if (ret != SENSOR_SUCCESS) { 216 return nullptr; 217 } 218 if (id != nullptr) { 219 OH_Sensor_DestroySubscriptionId(id); // Destroy the Sensor_SubscriptionId instance and reclaim the memory. 220 } 221 if (attr != nullptr) { 222 OH_Sensor_DestroySubscriptionAttribute(attr); // Destroy the Sensor_SubscriptionAttribute instance and reclaim the memory. 223 } 224 if (g_user != nullptr) { 225 OH_Sensor_DestroySubscriber(g_user); // Destroy the Sensor_Subscriber instance and reclaim the memory. 226 g_user = nullptr; 227 } 228 } 229 ``` 230 2319. Add related APIs to the **Init** function. 232 233 ```c 234 static napi_value Init(napi_env env, napi_value exports) 235 { 236 napi_property_descriptor desc[] = { 237 { "getSensorInfos", nullptr, GetSensorInfos, nullptr, nullptr, nullptr, napi_default, nullptr }, 238 { "subscriber", nullptr, Subscriber, nullptr, nullptr, nullptr, napi_default, nullptr } 239 }; 240 napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc); 241 return exports; 242 } 243 EXTERN_C_END 244 ``` 245 24610. Introduce the NAPI APIs to the **index.d.ts** file in **types/libentry**. 247 248 ```c 249 export const getSensorInfos: () => number; 250 export const subscriber: () => number; 251 ``` 252 25311. Delete deprecated functions from the **Index.ets** file. 254 255 ```js 256 .onClick(() => { 257 hilog.info(0x0000, 'testTag', 'Test NAPI 2 + 3 = %{public}d', testNapi.add(2, 3)); 258 }) 259 ``` 260
