what's "a null update"?

[popways]

in the help file:

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

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.


my question is how to determine the return value is availbale. what's "a null update"? sample code is prefered.

Thank you!

[treinio]

Hi,

If no last known position is available, it'll return an instance of QGeoPositionInfo that was created using a default constructor, i.e. with none of the attributes set. In this case, QGeoPositionInfo::isValid() will return false.

[popways]

I see.
Thank you!


I have another question, please refer to the position getted by QGeoPositionInfoSource not accurate .