QCompass

#include <QtSensors/QCompass>

QtSensors

The QCompass class is a convenience wrapper around QSensor.

The only behavioural difference is that this class sets the type properly.

This class also features a reading() function that returns a QCompassReading instead of a QSensorReading.

For details about how the sensor works, see QCompassReading.

See:

QCompassReading

Since:

1.0

Inheritance

QOrientableSensorBase
	QCompass

Public Types Index

Only has inherited public types

enum AxesOrientationMode

FixedOrientation, AutomaticOrientation, UserOrientation

Properties Index

AxesOrientationMode	axesOrientationMode
int	currentOrientation [read-only]
int	userOrientation
bool	active
bool	alwaysOn
QtMobility::qrangelist	availableDataRates [read-only]
bool	busy [read-only]
bool	connectedToBackend [read-only]
int	dataRate
QString	description [read-only]
int	error [read-only]
int	outputRange
QtMobility::qoutputrangelist	outputRanges [read-only]
QSensorReading	reading [read-only]
QByteArray	sensorid
bool	skipDuplicates

Public Static Attributes Index

char const *const

type

Public Functions Index

	QCompass (QObject *parent=0)
virtual	~QCompass ()
QCompassReading *	reading () const
void	addFilter (QSensorFilter *filter)
qrangelist	availableDataRates () const
AxesOrientationMode	axesOrientationMode () const
Q_INVOKABLE bool	connectToBackend ()
int	currentOrientation () const
int	dataRate () const
QString	description () const
int	error () const
QList< QSensorFilter * >	filters () const
QByteArray	identifier () const
bool	isActive () const
bool	isAlwaysOn () const
bool	isBusy () const
bool	isConnectedToBackend () const
int	outputRange () const
qoutputrangelist	outputRanges () const
	QOrientableSensorBase ()
	QSensor (const QByteArray &type, QObject *parent=0)
void	removeFilter (QSensorFilter *filter)
void	setActive (bool active)
void	setAlwaysOn (bool alwaysOn)
void	setAxesOrientationMode (AxesOrientationMode axesOrientationMode)
void	setCurrentOrientation (int currentOrientation)
void	setDataRate (int rate)
void	setIdentifier (const QByteArray &identifier)
void	setOutputRange (int index)
void	setSkipDuplicates (bool skipDuplicates)
void	setUserOrientation (int userOrientation)
bool	skipDuplicates () const
QByteArray	type () const
int	userOrientation () const

Static Public Functions Index

Only has inherited static public functions

QByteArray	defaultSensorForType (const QByteArray &type)
QList< QByteArray >	sensorsForType (const QByteArray &type)
QList< QByteArray >	sensorTypes ()

Protected Functions Index

Only has inherited protected functions

QSensorPrivate *	d_func () const
	QSensor (const QByteArray &type, QSensorPrivate dd, QObject parent=0)

Public Slots Index

Only has inherited public slots

bool	start ()
void	stop ()

Signals Index

void	axesOrientationModeChanged (AxesOrientationMode axesOrientationMode)
void	currentOrientationChanged (int currentOrientation)
void	userOrientationChanged (int userOrientation)
void	activeChanged ()
void	alwaysOnChanged ()
void	availableSensorsChanged ()
void	busyChanged ()
void	dataRateChanged ()
void	readingChanged ()
void	sensorError (int error)
void	skipDuplicatesChanged (bool skipDuplicates)

Public Types

(Only has inherited public types)

AxesOrientationMode

Describes how reading values are affected by the screen orientation.

FixedOrientation No automatic rotation is applied to the reading values.

AutomaticOrientation The reading values are automatically rotated based on the screen orientation.

UserOrientation The reading values are rotated based on the angle of the userOrientation property.

See:

QOrientableSensorBase::axesOrientationMode

FixedOrientation
AutomaticOrientation
UserOrientation

Properties

AxesOrientationMode axesOrientationMode

int currentOrientation[read-only]

int userOrientation

bool active

a value to indicate if the sensor is active.

This is true if the sensor is active (returning values). This is false otherwise.

Note that setting this value to true will not have an immediate effect. Instead, the sensor will be started once the event loop has been reached.

Since:

1.1

bool alwaysOn

a value to indicate if the sensor should remain running when the screen is off.

Some platforms have a policy of suspending sensors when the screen turns off. Setting this property to true will ensure the sensor continues to run.

QtMobility::qrangelist availableDataRates[read-only]

the data rates that the sensor supports.

This is a list of the data rates that the sensor supports. Measured in Hertz.

Entries in the list can represent discrete rates or a continuous range of rates. A discrete rate is noted by having both values the same.

See the sensor_explorer example for an example of how to interpret and use this information.

Note that this information is not mandatory as not all sensors have a rate at which they run. In such cases, the list will be empty.

See:

QSensor::dataRate, qrangelist

Since:

1.0

bool busy[read-only]

a value to indicate if the sensor is busy.

Some sensors may be on the system but unavailable for use. This function will return true if the sensor is busy. You will not be able to start() the sensor.

Note that this function does not return true if you are using the sensor, only if another process is using the sensor.

See:

busyChanged()

Since:

1.0

bool connectedToBackend[read-only]

a value indicating if the sensor has connected to a backend.

A sensor that has not been connected to a backend cannot do anything useful.

Call the connectToBackend() method to force the sensor to connect to a backend immediately. This is automatically called if you call start() so you only need to do this if you need access to sensor properties (ie. to poll the sensor's meta-data before you use it).

Since:

1.0

int dataRate

the data rate that the sensor should be run at.

Measured in Hertz.

The data rate is the maximum frequency at which the sensor can detect changes.

Setting this property is not portable and can cause conflicts with other applications. Check with the sensor backend and platform documentation for any policy regarding multiple applications requesting a data rate.

The default value (0) means that the app does not care what the data rate is. Applications should consider using a timer-based poll of the current value or ensure that the code that processes values can run very quickly as the platform may provide updates hundreds of times each second.

This should be set before calling start() because the sensor may not notice changes to this value while it is running.

Note that there is no mechanism to determine the current data rate in use by the platform.

See:

QSensor::availableDataRates

Since:

1.0

QString description[read-only]

a descriptive string for the sensor.

Since:

1.0

int error[read-only]

the last error code set on the sensor.

Note that error codes are sensor-specific.

Since:

1.0

int outputRange

the output range in use by the sensor.

This value represents the index in the QSensor::outputRanges list to use.

The default value (-1) means that the app does not care what the output range is.

Note that there is no mechanism to determine the current output range in use by the platform.

See:

QSensor::outputRanges

Since:

1.0

QtMobility::qoutputrangelist outputRanges[read-only]

a list of output ranges the sensor supports.

A sensor may have more than one output range. Typically this is done to give a greater measurement range at the cost of lowering accuracy.

Note that this information is not mandatory. This information is typically only available for sensors that have selectable output ranges (such as typical accelerometers).

See:

QSensor::outputRange, qoutputrangelist

Since:

1.0

QSensorReading reading[read-only]

the reading class.

The reading class provides access to sensor readings. The reading object is a volatile cache of the most recent sensor reading that has been received so the application should process readings immediately or save the values somewhere for later processing.

Note that this will return 0 until a sensor backend is connected to a backend.

Also note that readings are not immediately available after start() is called. Applications must wait for the readingChanged() signal to be emitted.

See:

isConnectedToBackend(), start()

Since:

1.0

QByteArray sensorid

the backend identifier for the sensor.

Note that the identifier is filled out automatically when the sensor is connected to a backend. If you want to connect a specific backend, you should call setIdentifier() before connectToBackend().

Since:

1.0

bool skipDuplicates

Indicates whether duplicate reading values should be omitted.

When duplicate skipping is enabled, successive readings with the same or very similar values are omitted and skipped. This helps reducing the amount of processing done, as less sensor readings are made available. As a consequence, readings arrive at an irregular interval.

Duplicate skipping is not just enabled for readings that are exactly the same, but also for readings that are quite similar, as each sensor has a bit of jitter even if the device is not moved.

Support for this property depends on the backend. It is disabled by default.

Duplicate skipping can only be changed while the sensor is not active.

Public Static Attributes

char const *const type ()

Public Functions

QCompass (
QObject *parent)

Construct the sensor as a child of parent.

Since:

1.0

virtual~QCompass ()

Destructor.

Stops the sensor if it has not already been stopped.

Since:

1.0

QCompassReading * reading ()

Returns the reading class for this sensor.

See:

QSensor::reading()

Since:

1.0

void addFilter (
QSensorFilter *filter)

Add a filter to the sensor.

The sensor does not take ownership of the filter. QSensorFilter will inform the sensor if it is destroyed.

See:

QSensorFilter

Since:

1.0

qrangelist availableDataRates ()

AxesOrientationMode axesOrientationMode ()

The mode that affects how the screen orientation changes reading values.

When set to FixedOrientation, which is the default mode, no automatic rotation is applied to the reading. This is the only mode available for backends that do not support the QSensor::AxesOrientation feature.

When set to AutomaticOrientation, the reading values are automatically rotated when the screen orientation changes. In effect, the screen orientation is canceled out.

As an example, assume the device is rotated by 180 degrees and therefore the screen orientation also is rotated by 180 degrees from the native orientation. Without automatic axes orientation, the reading values would now be changed: Both the X and the Y values would be negated, forcing an application developer to manually cancel out the negation in application code. Automatic axes orientation does this automatically, in this mode the X and Y values would be the same as with the default screen orientation.

This automatic rotation of the axes is handy is some usecases, for example in a bubble level application that measures how level a surface is by looking at the X axis value of an accelerometer. When the device and screen orientation change by 90 degrees, an application developer does not need to change anything, he can continue using the X axis value even though the device is rotated. Without automatic axes orientation, the application developer would need to look at the Y values instead, thereby adding code to the application that reads from a different axis depending on the screen orientation.

The UserOrientation mode is quite similar to AutomaticOrientation, only that the screen orientation is manually controlled instead of automatically determined. The angle of the userOrientation property is then used for rotating the reading values.

Since the rotation of the reading values is based on the screen orientation, Z values will never change, as the Z axis is perpendicular to the screen. As screen orientation changes in 90 degree steps, rotating the reading values is also done in steps of 90 degrees.

Q_INVOKABLE bool connectToBackend ()

Try to connect to a sensor backend.

Returns true if a suitable backend could be found, false otherwise.

The type must be set before calling this method if you are using QSensor directly.

See:

isConnectedToBackend()

Since:

1.0

int currentOrientation ()

The current orientation that is used for rotating the reading values.

This might not be the same as the screen orientation. For example, in the FixedOrientation mode, the reading values are not rotated, and therefore the property is 0.

In the UserOrientation mode, the readings are rotated based on the userOrientation property, and therefore this property is equal to the userOrientation property.

In the AutomaticOrientation mode, the readings are rotated based on the screen orientation, and therefore this property will be equal to the current screen orientation.

This property is set by the backend.

int dataRate ()

QString description ()

int error ()

QList< QSensorFilter * > filters ()

Returns the filters currently attached to the sensor.

See:

QSensorFilter

Since:

1.2

QByteArray identifier ()

bool isActive ()

bool isAlwaysOn ()

bool isBusy ()

bool isConnectedToBackend ()

int outputRange ()

qoutputrangelist outputRanges ()

QOrientableSensorBase ()

Constructs a QOrientableSensorBase.

QSensor (
const QByteArray &type,
QObject *parent )

Construct the type sensor as a child of parent.

Since:

1.0

void removeFilter (
QSensorFilter *filter)

Remove filter from the sensor.

See:

QSensorFilter

Since:

1.0

void setActive (
boolactive)

void setAlwaysOn (
boolalwaysOn)

void setAxesOrientationMode (
AxesOrientationModeaxesOrientationMode)

void setCurrentOrientation (
intcurrentOrientation)

Sets the current screen orientation to currentOrientation.

This is to be called from the backend whenever the screen orientation or the userOrientation property changes.

void setDataRate (
intrate)

void setIdentifier (
const QByteArray &identifier)

void setOutputRange (
intindex)

void setSkipDuplicates (
boolskipDuplicates)

Sets the duplicate skipping to skipDuplicates.

void setUserOrientation (
intuserOrientation)

bool skipDuplicates ()

QByteArray type ()

int userOrientation ()

The angle used for rotating the reading values in the UserOrientation mode.

When the axesOrientationMode property is set to UserOrientation, the angle for rotating the reading values is taken from this property. In other modes, the property has no effect.

The default is 0. The only valid values are 0, 90, 180 and 270, as those are the only possible screen orientations.

Static Public Functions

(Only has inherited static public functions)

QByteArray defaultSensorForType (
const QByteArray &type)

Returns the default sensor identifier for type.

This is set in a config file and can be overridden if required. If no default is available the system will return the first registered sensor for type.

Note that there is special case logic to prevent the generic plugin's backends from becoming the default when another backend is registered for the same type. This logic means that a backend identifier starting with {generic.} will only be the default if no other backends have been registered for that type or if it is specified in {Sensors.conf}.

See:

{Determining the default sensor for a type}

Since:

1.0

QList< QByteArray > sensorsForType (
const QByteArray &type)

Returns a list of ids for each of the sensors for type.

If there are no sensors of that type available the list will be empty.

Since:

1.0

QList< QByteArray > sensorTypes ()

Returns a list of all sensor types.

Since:

1.0

Protected Functions

(Only has inherited protected functions)

QSensorPrivate * d_func ()

QSensor (
const QByteArray &type,
QSensorPrivate dd,
QObject parent )

Public Slots

(Only has inherited public slots)

bool start ()

Start retrieving values from the sensor.

Returns true if the sensor was started, false otherwise.

The sensor may fail to start for several reasons.

Once an application has started a sensor it must wait until the sensor receives a new value before it can query the sensor's values. This is due to how the sensor receives values from the system. Sensors do not (in general) poll for new values, rather new values are pushed to the sensors as they happen.

For example, this code will not work as intended.

sensor->start(); sensor->reading()->x(); // no data available

To work correctly, the code that accesses the reading should ensure the readingChanged() signal has been emitted.

    connect(sensor, SIGNAL(readingChanged()), this, SLOT(checkReading()));
    sensor->start();
}
void MyClass::checkReading() {
    sensor->reading()->x();

See:

QSensor::busy

Since:

1.0

void stop ()

Stop retrieving values from the sensor.

This releases the sensor so that other processes can use it.

See:

QSensor::busy

Since:

1.0

Signals

void axesOrientationModeChanged (
AxesOrientationModeaxesOrientationMode)

void currentOrientationChanged (
intcurrentOrientation)

void userOrientationChanged (
intuserOrientation)

void activeChanged ()

This signal is emitted when the QSensor::active property has changed.

See:

QSensor::active

Since:

1.1

void alwaysOnChanged ()

This signal is emitted when the alwaysOn property changes.

void availableSensorsChanged ()

This signal is emitted when the list of available sensors has changed.

The sensors available to a program will not generally change over time however some of the avilable sensors may represent hardware that is not permanently connected. For example, a game controller that is connected via bluetooth would become available when it was on and would become unavailable when it was off.

See:

QSensor::sensorTypes(), QSensor::sensorsForType()

Since:

1.2

void busyChanged ()

This signal is emitted when the sensor is no longer busy.

This can be used to grab a sensor when it becomes available.

sensor.start();
if (sensor.isBusy()) {
    // need to wait for busyChanged signal and try again
}

Since:

1.0

void dataRateChanged ()

void readingChanged ()

This signal is emitted when a new sensor reading is received.

The sensor reading can be found in the QSensor::reading property. Note that the reading object is a volatile cache of the most recent sensor reading that has been received so the application should process the reading immediately or save the values somewhere for later processing.

Before this signal has been emitted for the first time, the reading object will have uninitialized data.

See:

start()

Since:

1.0

void sensorError (
interror)

This signal is emitted when an error code is set on the sensor.

Note that some errors will cause the sensor to stop working. You should call isActive() to determine if the sensor is still running.

Since:

1.0

void skipDuplicatesChanged (
boolskipDuplicates)

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QCompass

Inheritance

Public Types Index

enum AxesOrientationMode

Properties Index

Public Static Attributes Index

Public Functions Index

Static Public Functions Index

Protected Functions Index

Public Slots Index

Signals Index

Public Types

AxesOrientationMode

Properties

AxesOrientationMode axesOrientationMode

int currentOrientation[read-only]

int userOrientation

bool active

bool alwaysOn

QtMobility::qrangelist availableDataRates[read-only]

bool busy[read-only]

bool connectedToBackend[read-only]

int dataRate

QString description[read-only]

int error[read-only]

int outputRange

QtMobility::qoutputrangelist outputRanges[read-only]

QSensorReading reading[read-only]

QByteArray sensorid

bool skipDuplicates

Public Static Attributes

char const *const type ()

Public Functions

QCompass (QObject *parent)

virtual~QCompass ()

QCompassReading * reading ()

void addFilter (QSensorFilter *filter)

qrangelist availableDataRates ()

AxesOrientationMode axesOrientationMode ()

Q_INVOKABLE bool connectToBackend ()

int currentOrientation ()

int dataRate ()

QString description ()

int error ()

QList< QSensorFilter * > filters ()

QByteArray identifier ()

bool isActive ()

bool isAlwaysOn ()

bool isBusy ()

bool isConnectedToBackend ()

int outputRange ()

qoutputrangelist outputRanges ()

QOrientableSensorBase ()

QSensor (const QByteArray &type, QObject *parent )

void removeFilter (QSensorFilter *filter)

void setActive (boolactive)

void setAlwaysOn (boolalwaysOn)

void setAxesOrientationMode (AxesOrientationModeaxesOrientationMode)

void setCurrentOrientation (intcurrentOrientation)

void setDataRate (intrate)

void setIdentifier (const QByteArray &identifier)

void setOutputRange (intindex)

void setSkipDuplicates (boolskipDuplicates)

void setUserOrientation (intuserOrientation)

bool skipDuplicates ()

QByteArray type ()

int userOrientation ()

Static Public Functions

QByteArray defaultSensorForType (const QByteArray &type)

QList< QByteArray > sensorsForType (const QByteArray &type)

QList< QByteArray > sensorTypes ()

Protected Functions

QSensorPrivate * d_func ()

QSensor (const QByteArray &type, QSensorPrivate *dd, QObject *parent )

Public Slots

bool start ()

void stop ()

Signals

void axesOrientationModeChanged (AxesOrientationModeaxesOrientationMode)

void currentOrientationChanged (intcurrentOrientation)

QCompass (
QObject *parent)

void addFilter (
QSensorFilter *filter)

QSensor (
const QByteArray &type,
QObject *parent )

void removeFilter (
QSensorFilter *filter)

void setActive (
boolactive)

void setAlwaysOn (
boolalwaysOn)

void setAxesOrientationMode (
AxesOrientationModeaxesOrientationMode)

void setCurrentOrientation (
intcurrentOrientation)

void setDataRate (
intrate)

void setIdentifier (
const QByteArray &identifier)

void setOutputRange (
intindex)

void setSkipDuplicates (
boolskipDuplicates)

void setUserOrientation (
intuserOrientation)

QByteArray defaultSensorForType (
const QByteArray &type)

QList< QByteArray > sensorsForType (
const QByteArray &type)

QSensor (
const QByteArray &type,
QSensorPrivate dd,
QObject parent )

void axesOrientationModeChanged (
AxesOrientationModeaxesOrientationMode)

void currentOrientationChanged (
intcurrentOrientation)

void userOrientationChanged (
intuserOrientation)

void sensorError (
interror)

void skipDuplicatesChanged (
boolskipDuplicates)