Sensors API

Accessing sensor data in a generic fashion

The preferred way to deal with sensor data is via the Reading Classes. However, sometimes this may not be possible. For example, you may be deploying an application to a device that has a new sensor type but no C++ header describing the reading class is available.

Thanks to Qt's property system you can still access the sensor data. You need to know 3 pieces of information in order to do this:

• The sensor type.
• The property name or index.
• The property type or a comparable type.

For example, here is an example of how you can access a property of the accelerometer. This code does not require any compile-time links to QAccelerometer or QAccelerometerReading.

    // start the sensor
    QSensor sensor("QAccelerometer");
    sensor.start();

    // later
    QSensorReading *reading = sensor.reading();
    qreal x = reading->property("x").value<qreal>();
    qreal y = reading->value(1).value<qreal>();

You can discover all of this information at runtime too. The sensor_explorer example shows you information about available sensors.

Front end, back end

The Sensors API has a front end, for application developers to use and a back end, where device implementors write code to access their hardware. As an application developer you do not need to access the back end though it may be useful to understand how it works.

Commands from the application are delivered through QSensor and then down to the device plugin. Data comes back through the QSensorReading class.

More information about the back end can be found in Sensors Backend.

Main Classes

The primary classes that make up the Sensors API.

QSensor	Represents a single hardware sensor
QSensorFilter	Efficient callback facility for asynchronous notifications of sensor changes
QSensorReading	Holds the readings from the sensor

Reading Classes

The best way to access sensor data is via one of these classes.

QAccelerometerReading	Reports on linear acceleration along the X, Y and Z axes
QAmbientLightReading	Represents one reading from the ambient light sensor
QCompassReading	Represents one reading from a compass
QMagnetometerReading	Represents one reading from the magnetometer
QOrientationReading	Represents one reading from the orientation sensor
QProximityReading	Represents one reading from the proximity sensor
QRotationReading	Represents one reading from the rotation sensor
QTapReading	Represents one reading from the tap sensor

Sensor Classes

These classes provide convenience wrappers that reduce the need for casting. Each of these classes represents a sensor type that the Sensors API knows about. Note that additional types may be made available at run-time. See Sensor Types for more information.

QAccelerometer	Convenience wrapper around QSensor
QAmbientLightSensor	Convenience wrapper around QSensor
QCompass	Convenience wrapper around QSensor
QMagnetometer	Convenience wrapper around QSensor
QOrientationSensor	Convenience wrapper around QSensor
QProximitySensor	Convenience wrapper around QSensor
QRotationSensor	Convenience wrapper around QSensor
QTapSensor	Convenience wrapper around QSensor

Filter Classes

As with the sensor classes, these provide convenience wrappers that reduce the need for casting.

QAccelerometerFilter	Convenience wrapper around QSensorFilter
QAmbientLightFilter	Convenience wrapper around QSensorFilter
QCompassFilter	Convenience wrapper around QSensorFilter
QMagnetometerFilter	Convenience wrapper around QSensorFilter
QOrientationFilter	Convenience wrapper around QSensorFilter
QProximityFilter	Convenience wrapper around QSensorFilter
QRotationFilter	Convenience wrapper around QSensorFilter
QTapFilter	Convenience wrapper around QSensorFilter