ILocation.Trace()

Description:

The Trace method retrieves periodic updates about +the current location of the device based on a predefined update interval.

This is an asynchronous method.

Syntax:

result = so.ILocation.Trace(criteria, callback);

+ +

Arguments:

criteria:
+ +
This is an object that specifies what type of device location information +is returned and how. For more information about the object properties and +how to define them, see section Criteria for retrieving location information.
+ +
callback:
+ +
The callback argument is the name of the method +that is executed when Trace has results or status information +to return. You must define this method separately. Follow the instructions +in section Defining the callback handler for an asynchronous method to +define the callback method.
+ +

Return value:

The Trace method returns an object that contains +the initial return value for the asynchronous call it started (see the following +table). The actual location information is returned by the callback method in the ReturnValue property of its result object. +The returned information is described in section Returned location information.

+ + + + + + + + + + + + + + + + + + + + + +

**Table:** Return value +properties for Trace
+ Property +	+ Description +	+ Value +
+ `result.TransactionID` +	+ This is a number used as an identification to match transactions started +with the `Trace` call to one or more calls it generates +to `callback`. +
+ `result.ErrorCode` +	+ This is a number that specifies a predefined error code. +	+ See Service API error codes. +
+ `result.ErrorMessage` +	+ This is a text string that describes the error. +	+ See Location Service API error messages. +

Remarks:

Trace retrieves location updates until +cancelled with CancelNotification. +You can therefore have only one Trace call (one instance) +pending or in use at any given time.
The availability of specific location information depends +on the underlying GPS technology. Other factors, such as the number of satellites +available for a location fix, also affect what information can be returned. +You can change the positioning system used by an S60 device from the Settings +> General > Positioning > Positioning methods menu.
It takes time to retrieve the initial position fix. Subsequent +requests are faster.

Example code:

For the complete source of a sample widget +that demonstrates how to use this Service API, see the +full example.

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