The PositionSource type provides the device's current position. 更多...
| import 语句： | import QtPositioning 5.12 |
| Since: | Qt 5.2 |
The PositionSource type provides information about the user device's current position. The position is available as a Position type, which contains all the standard parameters typically available from GPS and other similar systems, including longitude, latitude, speed and accuracy details.
As different position sources are available on different platforms and devices, these are categorized by their basic type (Satellite, NonSatellite, and AllPositioningMethods). The available methods for the current platform can be enumerated in the supportedPositioningMethods 特性。
To indicate which methods are suitable for your application, set the preferredPositioningMethods property. If the preferred methods are not available, the default source of location data for the platform will be chosen instead. If no default source is available (because none are installed for the runtime platform, or because it is disabled), the valid property will be set to false.
The updateInterval property can then be used to indicate how often your application wishes to receive position updates. The start (), stop () 和 update () methods can be used to control the operation of the PositionSource , as well as the active property, which when set is equivalent to calling start () 或 stop ().
当
PositionSource
is active, position updates can be retrieved either by simply using the
position
property in a binding (as the value of another item's property), or by providing an implementation of the
onPositionChanged
signal-handler.
The following example shows a simple PositionSource used to receive updates every second and print the longitude and latitude out to the console.
PositionSource {
id: src
updateInterval: 1000
active: true
onPositionChanged: {
var coord = src.position.coordinate;
console.log("Coordinate:", coord.longitude, coord.latitude);
}
}
The GeoFlickr example application shows how to use a PositionSource in your application to retrieve local data for users from a REST web service.
另请参阅 QtPositioning::Position and QGeoPositionInfoSource .
|
active : bool |
This property indicates whether the position source is active. Setting this property to false equals calling stop , and setting this property true equals calling start .
|
name : string |
This property holds the unique internal name for the plugin currently providing position information.
Setting the property causes the PositionSource to use a particular positioning provider. If the PositionSource is active at the time that the name property is changed, it will become inactive. If the specified positioning provider cannot be loaded the position source will become invalid.
Changing the name property may cause the updateInterval , supportedPositioningMethods and preferredPositioningMethods properties to change as well.
|
nmeaSource : url |
This property holds the source for NMEA (National Marine Electronics Association) position-specification data (file). One purpose of this property is to be of development convenience.
Setting this property will override any other position source. Currently only files local to the .qml -file are supported. The NMEA source is created in simulation mode, meaning that the data and time information in the NMEA source data is used to provide positional updates at the rate at which the data was originally recorded.
If nmeaSource has been set for a PositionSource object, there is no way to revert back to non-file sources.
|
position : Position |
This property holds the last known positional data. It is a read-only property.
The Position type has different positional member variables, whose validity can be checked with appropriate validity functions (for example sometimes an update does not have speed or altitude data).
However, whenever a
positionChanged
signal has been received, at least position::coordinate::latitude, position::coordinate::longitude, and position::timestamp can be assumed to be valid.
|
preferredPositioningMethods : enumeration |
This property holds the preferred positioning methods of the current source.
|
sourceError : enumeration |
This property holds the error which last occurred with the PositionSource .
|
supportedPositioningMethods : enumeration |
This property holds the supported positioning methods of the current source.
|
updateInterval : int |
This property holds the desired interval between updates (milliseconds).
另请参阅 QGeoPositionInfoSource::updateInterval() .
|
valid : bool |
This property is true if the PositionSource object has acquired a valid backend plugin to provide data. If false, other methods on the PositionSource will have no effect.
Applications should check this property to determine whether positioning is available and enabled on the runtime platform, and react accordingly.
若 update() was called, this signal is emitted if the current position could not be retrieved within a certain amount of time.
若 start() was called, this signal is emitted if the position engine determines that it is not able to provide further regular updates.
This signal was introduced in Qt Positioning 5.5.
另请参阅 QGeoPositionInfoSource::updateTimeout() .
Requests updates from the location source. Uses updateInterval if set, default interval otherwise. If there is no source available, this method has no effect.
另请参阅 stop , update ，和 active .
Stops updates from the location source. If there is no source available or it is not active, this method has no effect.
另请参阅 start , update ，和 active .
A convenience method to request single update from the location source. If there is no source available, this method has no effect.
If the position source is not active, it will be activated for as long as it takes to receive an update, or until the request times out. The request timeout period is source-specific.