SensorDispatch

public class SensorDispatch

A SensorDispatch object is used to receive sensor readings. A SensorDispatch object listens for the underlying WearableDeviceEvent notifications indicating that sensor data has been received. It then unpacks the individual values from the data and dispatches each to its appropriate callback block and to its handler (a SensorDispatchHandler object).

An app can have arbitrarily many SensorDispatch objects. This allows multiple handlers inside an app all to listen to the same sensor. Each SensorDispatch automatically registers and deregisters for the appropriate WearableDeviceEvent notifications.

A SensorDispatch object is created with an associated OperationQueue. Specifying the .main queue is suitable for when the app’s user interface should be updated in response to the event. Otherwise, a background OperationQueue can be provided.

When a WearableDeviceEvent.didReceiveSensorData(SensorData) notification is received, the SensorDispatch object does the following on the OperationQueue provided to the SensorDispatch initializer:

• Dispatches the SensorData object to sensorDataCallback and to SensorDispatchHandler.receivedSensorData(_:).
• Each of the values in the SensorData object is dispatched to the appropriate handler:
  • Accelerometer values are dispatched to accelerometerCallback and to SensorDispatchHandler.receivedAccelerometer(vector:accuracy:timestamp:)
  • Gyroscope values are dispatched to gyroscopeCallback and to SensorDispatchHandler.receivedGyroscope(vector:accuracy:timestamp:)
  • Rotation values are dispatched to rotationCallback and to SensorDispatchHandler.receivedRotation(quaternion:accuracy:timestamp:).
  • Game rotation values are dispatched to gameRotationCallback and to SensorDispatchHandler.receivedGameRotation(quaternion:timestamp:).
  • Orientation values are dispatched to orientationCallback and to SensorDispatchHandler.receivedOrientation(vector:accuracy:timestamp:)
  • Magnetometer values are dispatched to magnetometerCallback and to SensorDispatchHandler.receivedMagnetometer(vector:accuracy:timestamp:)
  • Uncalibrated magnetometer values are dispatched to uncalibratedMagnetometerCallback and to SensorDispatchHandler.receivedUncalibratedMagnetometer(vector:bias:timestamp:)

Callbacks are only invoked if they are non-nil. Thus you need only provide callback blocks for sensors you are interested in. Similarly, the SensorDispatchHandler protocol provides default implementation of all of its handler functions. Thus you need only provide implementations for sensors you are interested in. A SensorDispatchHandler and callback blocks can co-exist. Each callback is invoked before the corresponding SensorDispatchHandler function.