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QGeoPositionInfoSource Class

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

头： #include <QGeoPositionInfoSource>
qmake: QT += positioning
Since: Qt 5.2
继承： QObject
继承者：

QNmeaPositionInfoSource

公共类型

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

特性

公共函数

QGeoPositionInfoSource (QObject * parent )
virtual ~QGeoPositionInfoSource ()
virtual Error error () const = 0
virtual QGeoPositionInfo lastKnownPosition (bool fromSatellitePositioningMethodsOnly = false) const = 0
virtual int minimumUpdateInterval () const = 0
PositioningMethods preferredPositioningMethods () const
virtual void setPreferredPositioningMethods (PositioningMethods methods )
virtual void setUpdateInterval (int msec )
QString sourceName () const
virtual PositioningMethods supportedPositioningMethods () const = 0
int updateInterval () const

公共槽

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

信号

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

静态公共成员

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

额外继承成员

详细描述

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

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 接口。

Users of a QGeoPositionInfoSource subclass can request the current position using requestUpdate (), or start and stop regular position updates using startUpdates () 和 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 ().

成员类型文档编制

enum QGeoPositionInfoSource:: Error

The Error enumeration represents the errors which can occur.

常量 值 描述
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 没有出现错误。
QGeoPositionInfoSource::UnknownSourceError 2 发生无法识别的错误。

enum QGeoPositionInfoSource:: PositioningMethod
flags QGeoPositionInfoSource:: PositioningMethods

Defines the types of positioning methods.

常量 值 描述
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.

特性文档编制

minimumUpdateInterval : const int

This property holds the minimum time (in milliseconds) required to retrieve a position update.

This is the minimum value accepted by setUpdateInterval () 和 requestUpdate ().

访问函数：

virtual int minimumUpdateInterval () const = 0

sourceName : const QString

This property holds the unique name of the position source implementation in use.

This is the same name that can be passed to createSource () in order to create a new instance of a particular position source implementation.

访问函数：

QString sourceName () const

updateInterval : int

This property holds the requested interval in milliseconds between each update.

If the update interval is not set (or is set to 0) the source will provide updates as often as necessary.

If the update interval is set, the source will provide updates at an interval as close to the requested interval as possible. If the requested interval is less than the minimumUpdateInterval (), the minimum interval is used instead.

Changes to the update interval will happen as soon as is practical, however the time the change takes may vary between implementations. Whether or not the elapsed time from the previous interval is counted as part of the new interval is also implementation dependent.

The default value for this property is 0.

Note: Subclass implementations must call the base implementation of setUpdateInterval() so that updateInterval() returns the correct value.

访问函数：

int updateInterval () const
virtual void setUpdateInterval (int msec )

成员函数文档编制

QGeoPositionInfoSource:: QGeoPositionInfoSource ( QObject * parent )

Creates a position source with the specified parent .

[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.

[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:: 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.

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

返回最后发生的错误类型。

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

此信号被发射在发生错误之后。 positioningError 参数描述发生错误的类型。

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

注意： 信号 error 在此类中是重载。要使用函数指针句法连接到此信号，必须在静态铸造中指定信号类型，如此范例所示： 

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

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

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

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

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

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

update value holds the value of the new update.

PositioningMethods QGeoPositionInfoSource:: preferredPositioningMethods () const

Returns the positioning methods set by setPreferredPositioningMethods ().

另请参阅 setPreferredPositioningMethods ().

[pure virtual slot] void QGeoPositionInfoSource:: requestUpdate ( int timeout = 0)

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 () 被发射。

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.

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

Sets the preferred positioning methods for this source to methods .

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

若 methods does not include any methods supported by the source, the preferred methods will be set to the set of methods which the source supports.

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

另请参阅 preferredPositioningMethods () 和 supportedPositioningMethods ().

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

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

若 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.

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

Returns the positioning methods available to this source.

另请参阅 setPreferredPositioningMethods ().

[signal] void QGeoPositionInfoSource:: updateTimeout ()

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

若 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.