QGeoPositionInfoSource Class

The QGeoPositionInfoSource class is an abstract base class for the distribution of positional updates. More...

Header:	#include <QGeoPositionInfoSource>
qmake:	QT += positioning
Since:	Qt 5.2
Inherits:	QObject
Inherited By:	QNmeaPositionInfoSource

This class was introduced in Qt 5.2.

• List of all members, including inherited members

Public Types

enum	Error { AccessError, ClosedError, NoError, UnknownSourceError }
enum	PositioningMethod { NoPositioningMethods, SatellitePositioningMethods, NonSatellitePositioningMethods, AllPositioningMethods }
flags	PositioningMethods

Properties

• minimumUpdateInterval : const int
• sourceName : const QString
• updateInterval : int

Public Functions

	QGeoPositionInfoSource(QObject *parent)
virtual	~QGeoPositionInfoSource()
QVariant	backendProperty(const QString &name) const
virtual QGeoPositionInfoSource::Error	error() const = 0
virtual QGeoPositionInfo	lastKnownPosition(bool fromSatellitePositioningMethodsOnly = ...) const = 0
virtual int	minimumUpdateInterval() const = 0
QGeoPositionInfoSource::PositioningMethods	preferredPositioningMethods() const
bool	setBackendProperty(const QString &name, const QVariant &value)
virtual void	setPreferredPositioningMethods(QGeoPositionInfoSource::PositioningMethods methods)
virtual void	setUpdateInterval(int msec)
QString	sourceName() const
virtual QGeoPositionInfoSource::PositioningMethods	supportedPositioningMethods() const = 0
int	updateInterval() const

Public Slots

virtual void	requestUpdate(int timeout = ...) = 0
virtual void	startUpdates() = 0
virtual void	stopUpdates() = 0

Signals

void	error(QGeoPositionInfoSource::Error positioningError)
void	positionUpdated(const QGeoPositionInfo &update)
void	supportedPositioningMethodsChanged()
void	updateTimeout()

Static Public Members

QStringList	availableSources()
QGeoPositionInfoSource *	createDefaultSource(QObject *parent)
QGeoPositionInfoSource *	createDefaultSource(const QVariantMap &parameters, QObject *parent)
QGeoPositionInfoSource *	createSource(const QString &sourceName, QObject *parent)
QGeoPositionInfoSource *	createSource(const QString &sourceName, const QVariantMap &parameters, QObject *parent)

Detailed Description

The static function QGeoPositionInfoSource::createDefaultSource() creates a default position source that is appropriate for the platform, if one is available. Otherwise, QGeoPositionInfoSource will check for available plugins that implement the QGeoPositionInfoSourceFactory interface.

Users of a QGeoPositionInfoSource subclass can request the current position using requestUpdate(), or start and stop regular position updates using startUpdates() and stopUpdates(). When an update is available, positionUpdated() is emitted. The last known position can be accessed with lastKnownPosition().

If regular position updates are required, setUpdateInterval() can be used to specify how often these updates should be emitted. If no interval is specified, updates are simply provided whenever they are available. For example:

// Emit updates every 10 seconds if available
QGeoPositionInfoSource *source = QGeoPositionInfoSource::createDefaultSource(0);
if (source)
    source->setUpdateInterval(10000);

To remove an update interval that was previously set, call setUpdateInterval() with a value of 0.

Note that the position source may have a minimum value requirement for update intervals, as returned by minimumUpdateInterval().

Member Type Documentation

enum QGeoPositionInfoSource::Error

The Error enumeration represents the errors which can occur.

Constant	Value	Description
QGeoPositionInfoSource::AccessError	0	The connection setup to the remote positioning backend failed because the application lacked the required privileges.
QGeoPositionInfoSource::ClosedError	1	The remote positioning backend closed the connection, which happens for example in case the user is switching location services to off. As soon as the location service is re-enabled regular updates will resume.
QGeoPositionInfoSource::NoError	3	No error has occurred.
QGeoPositionInfoSource::UnknownSourceError	2	An unidentified error occurred.

enum QGeoPositionInfoSource::PositioningMethodflags QGeoPositionInfoSource::PositioningMethods

Defines the types of positioning methods.

Constant	Value	Description
QGeoPositionInfoSource::NoPositioningMethods	0x00000000	None of the positioning methods.
QGeoPositionInfoSource::SatellitePositioningMethods	0x000000ff	Satellite-based positioning methods such as GPS or GLONASS.
QGeoPositionInfoSource::NonSatellitePositioningMethods	0xffffff00	Other positioning methods such as 3GPP cell identifier or WiFi based positioning.
QGeoPositionInfoSource::AllPositioningMethods	0xffffffff	Satellite-based positioning methods as soon as available. Otherwise non-satellite based methods.

The PositioningMethods type is a typedef for QFlags<PositioningMethod>. It stores an OR combination of PositioningMethod values.

Member Function Documentation

QGeoPositionInfoSource::QGeoPositionInfoSource(QObject *parent)

Creates a position source with the specified parent.

[signal] void QGeoPositionInfoSource::error(QGeoPositionInfoSource::Error positioningError)

This signal is emitted after an error occurred. The positioningError parameter describes the type of error that occurred.

This signal is not emitted when an updateTimeout() has occurred.

Note: Signal error is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(geoPositionInfoSource, QOverload<QGeoPositionInfoSource::Error>::of(&QGeoPositionInfoSource::error),
    [=](QGeoPositionInfoSource::Error positioningError){ /* ... */ });

[signal] void QGeoPositionInfoSource::positionUpdated(const QGeoPositionInfo &update)

If startUpdates() or requestUpdate() is called, this signal is emitted when an update becomes available.

The update value holds the value of the new update.

[pure virtual slot] void QGeoPositionInfoSource::requestUpdate(int timeout = ...)

Attempts to get the current position and emit positionUpdated() with this information. If the current position cannot be found within the given timeout (in milliseconds) or if timeout is less than the value returned by minimumUpdateInterval(), updateTimeout() is emitted.

If the timeout is zero, the timeout defaults to a reasonable timeout period as appropriate for the source.

This does nothing if another update request is in progress. However it can be called even if startUpdates() has already been called and regular updates are in progress.

If the source uses multiple positioning methods, it tries to get the current position from the most accurate positioning method within the given timeout.

[pure virtual slot] void QGeoPositionInfoSource::startUpdates()

Starts emitting updates at regular intervals as specified by setUpdateInterval().

If setUpdateInterval() has not been called, the source will emit updates as soon as they become available.

An updateTimeout() signal will be emitted if this QGeoPositionInfoSource subclass determines that it will not be able to provide regular updates. This could happen if a satellite fix is lost or if a hardware error is detected. Position updates will recommence if the data becomes available later on. The updateTimeout() signal will not be emitted again until after the periodic updates resume.

On iOS, starting from version 8, Core Location framework requires additional entries in the application's Info.plist with keys NSLocationAlwaysUsageDescription or NSLocationWhenInUseUsageDescription and a string to be displayed in the authorization prompt. The key NSLocationWhenInUseUsageDescription is used when requesting permission to use location services while the app is in the foreground. The key NSLocationAlwaysUsageDescription is used when requesting permission to use location services whenever the app is running (both the foreground and the background). If both entries are defined, NSLocationWhenInUseUsageDescription has a priority in the foreground mode.

[pure virtual slot] void QGeoPositionInfoSource::stopUpdates()

Stops emitting updates at regular intervals.

[signal] void QGeoPositionInfoSource::supportedPositioningMethodsChanged()

This signal is emitted when the supported positioning methods changed. The cause for a change could be a user turning Location services on/off or restricting Location services to certain types (e.g. GPS only). Note that changes to the supported positioning methods cannot be detected on all platforms. supportedPositioningMethods() provides an overview of the current platform support.

This function was introduced in Qt 5.12.

[signal] void QGeoPositionInfoSource::updateTimeout()

If requestUpdate() was called, this signal will be emitted if the current position could not be retrieved within the specified timeout.

If startUpdates() has been called, this signal will be emitted if this QGeoPositionInfoSource subclass determines that it will not be able to provide further regular updates. This signal will not be emitted again until after the regular updates resume.

While the triggering of this signal may be considered an error condition, it does not imply the emission of the error() signal. Only the emission of updateTimeout() is required to indicate a timeout.

[virtual] QGeoPositionInfoSource::~QGeoPositionInfoSource()

Destroys the position source.

[static] QStringList QGeoPositionInfoSource::availableSources()

Returns a list of available source plugins. This includes any default backend plugin for the current platform.

QVariant QGeoPositionInfoSource::backendProperty(const QString &name) const

Returns the value of the backend-specific property named name, if present. Otherwise, the returned value will be invalid. Supported backend-specific properties are listed and described in Qt Positioning plugins#Default plugins.

This function was introduced in Qt 5.14.

See also setBackendProperty.

[static] QGeoPositionInfoSource *QGeoPositionInfoSource::createDefaultSource(QObject *parent)

Creates and returns a position source with the given parent that reads from the system's default sources of location data, or the plugin with the highest available priority.

Returns 0 if the system has no default position source, no valid plugins could be found or the user does not have the permission to access the current position.

[static] QGeoPositionInfoSource *QGeoPositionInfoSource::createDefaultSource(const QVariantMap &parameters, QObject *parent)

Creates and returns a position source with the given parent that reads from the system's default sources of location data, or the plugin with the highest available priority.

Returns nullptr if the system has no default position source, no valid plugins could be found or the user does not have the permission to access the current position.

This method passes parameters to the factory to configure the source.

This function was introduced in Qt 5.14.

[static] QGeoPositionInfoSource *QGeoPositionInfoSource::createSource(const QString &sourceName, QObject *parent)

Creates and returns a position source with the given parent, by loading the plugin named sourceName.

Returns 0 if the plugin cannot be found.

[static] QGeoPositionInfoSource *QGeoPositionInfoSource::createSource(const QString &sourceName, const QVariantMap &parameters, QObject *parent)

Creates and returns a position source with the given parent, by loading the plugin named sourceName.

Returns nullptr if the plugin cannot be found.

This method passes parameters to the factory to configure the source.

This function was introduced in Qt 5.14.

[pure virtual] QGeoPositionInfoSource::Error QGeoPositionInfoSource::error() const

Returns the type of error that last occurred.

[pure virtual] QGeoPositionInfo QGeoPositionInfoSource::lastKnownPosition(bool fromSatellitePositioningMethodsOnly = ...) const

Returns an update containing the last known position, or a null update if none is available.

If fromSatellitePositioningMethodsOnly is true, this returns the last known position received from a satellite positioning method; if none is available, a null update is returned.

QGeoPositionInfoSource::PositioningMethods QGeoPositionInfoSource::preferredPositioningMethods() const

Returns the positioning methods set by setPreferredPositioningMethods().

See also setPreferredPositioningMethods().

bool QGeoPositionInfoSource::setBackendProperty(const QString &name, const QVariant &value)

Sets the backend-specific property named name to value. Returns true on success, false otherwise. Backend-specific properties can be used to configure the positioning subsystem behavior at runtime. Supported backend-specific properties are listed and described in Qt Positioning plugins#Default plugins.

This function was introduced in Qt 5.14.

See also backendProperty.

[virtual] void QGeoPositionInfoSource::setPreferredPositioningMethods(QGeoPositionInfoSource::PositioningMethods methods)

Sets the preferred positioning methods for this source to methods.

If methods includes a method that is not supported by the source, the unsupported method will be ignored.

If methods does not include a single method available/supported by the source, the preferred methods will be set to the set of methods which the source has available. If the source has no method availabe (e.g. because its Location service is turned off or it does not offer a Location service), the passed methods are accepted as they are.

Note: When reimplementing this method, subclasses must call the base method implementation to ensure preferredPositioningMethods() returns the correct value.

See also preferredPositioningMethods() and supportedPositioningMethods().

[pure virtual] QGeoPositionInfoSource::PositioningMethods QGeoPositionInfoSource::supportedPositioningMethods() const

Returns the positioning methods available to this source. Availability is defined as being usable at the time of calling this function. Therefore user settings like turned off location service or limitations to Satellite-based position providers are reflected by this function. Runtime notifications when the status changes can be obtained via supportedPositioningMethodsChanged().

Not all platforms distinguish the different positioning methods or communicate the current user configuration of the device. The following table provides an overview of the current platform situation:

Platform	Brief Description
Android	Individual provider status and general Location service state are known and communicated when location service is active.
GeoClue	Hardcoced to always return AllPositioningMethods.
GeoClue2	Individual providers are not distinguishable but disabled Location services reflected.
iOS/tvOS	Hardcoced to always return AllPositioningMethods.
macOS	Hardcoced to always return AllPositioningMethods.
Windows (UWP)	Individual providers are not distinguishable but disabled Location services reflected.

See also supportedPositioningMethodsChanged() and setPreferredPositioningMethods().