Sensor Type
System sensors are device abstraction concepts that allow applications to access underlying hardware sensors. You can use the Sensor APIs to subscribe to sensor data and develop algorithms based on the data to create various types of applications, such as compass, sports and health, and games.
| Type | Sensor | Description | Usage |
|---|---|---|---|
| ACCELEROMETER | Acceleration sensor | Measures the acceleration (including the gravity acceleration) applied to a device on three physical axes (X, Y, and Z), in the unit of m/s2. | Measures the acceleration of device motion. |
| GYROSCOPE | Gyroscope sensor | Measures the rotation angular velocity of a device on three physical axes (X, Y, and Z), in the unit of rad/s. | Measures the rotation angular velocity. |
| ORIENTATION | Orientation sensor | Measures the orientation angle of the screen around three physical axes (z, x, and y), in rad. | Measures the three orientation angles of the screen. |
Working Principles
The following modules work cooperatively to implement HarmonyOS sensors: Sensor API, Sensor Framework, Sensor Service, and HDF.
Figure 1 HarmonyOS sensors
Sensor API: provides APIs for performing basic operations on sensors, including querying the sensor list, subscribing to or unsubscribing from sensor data, and executing control commands. This module makes application development simpler.
Sensor Framework: manages sensor data subscription, creates and destroys data channels, subscribes to or unsubscribes from sensor data, and implements communication with the Sensor Service module.
Sensor Service: interacts with the HD_IDL module to receive, parse, and distribute data, manages foreground and background policies and sensors of a device, and controls sensor permissions.
HDF layer: selects proper policies based on the hardware first in first out (FIFO) and frequency, and adapts to different devices.
Constraints
To obtain data of the following sensors, you must request the required permissions.
Sensor Permission Sensitivity Description Acceleration sensor, uncalibrated acceleration sensor, and linear acceleration sensor ohos.permission.ACCELEROMETER system_grant The permission allows an application to read data from acceleration sensors, uncalibrated acceleration sensors, and linear acceleration sensors. Gyroscope sensor and uncalibrated gyroscope sensor ohos.permission.GYROSCOPE system_grant The permission allows an application to read data from gyroscope sensors and uncalibrated gyroscope sensors. The on and off APIs work in pairs. If listening for sensor data is no longer needed, call the off API to disable event listening.