The starting point for determining device location is the LocationProvider class, which represents
the source of the location information. A LocationProvider object represents a specific way of using a location provider module
to obtain location information. For example, a GPS receiver can be
used for standalone GPS and assisted GPS (separate location providers).
You can create a LocationProvider object in one of
two ways:
Call the LocationProvider.getInstance(Criteria criteria) method. Use the Criteria parameter to specify what kind of
a location provider is accepted. The platform selects the location
provider that best meets the specified criteria. This approach is
supported by all devices that support the Location API.
Call the LocationUtil.getLocationProvider(int[] preferredMethods,
String parameters) method to explicitly specify which
location provider to use. This approach is only supported on Series
40 devices with Java Runtime 1.0.0 for Series 40 or newer.
Both methods return a LocationProvider object
for the selected location provider. Use this object to retrieve the
location information.
The following code snippets shows how to specify the criteria
for selecting a location provider and how to retrieve a location provider
based on those criteria. For a full code example, see the ConfigurationProvider class of the TouristRoute
example MIDlet.
// Specify the criteria for selecting a location provider
Criteria criteria = new Criteria();
criteria.setHorizontalAccuracy(25); // 25m
criteria.setVerticalAccuracy(25); // 25m
criteria.setPreferredResponseTime(Criteria.NO_REQUIREMENT);
criteria.setPreferredPowerConsumption(Criteria.POWER_USAGE_HIGH);
criteria.setCostAllowed(false);
criteria.setSpeedAndCourseRequired(true);
criteria.setAltitudeRequired(true);
criteria.setAddressInfoRequired(true);
// Retrieve a location provider based on the above criteria
LocationProvider provider;
try {
provider = LocationProvider.getInstance(criteria);
if (provider != null) {
// Location provider matching specified criteria found,
// send a selection event
}
} catch(LocationException le) {
// No location providers available,
// handle the exception
}If the device does not have any built-in location
provider modules available or is not connected to an external location
provider module, the LocationProvider.getInstance method throws a LocationException. A return value
other than null indicates that a location provider
was found.
Note: The LocationUtil.getLocationProvider method
is only supported on Series 40 devices with Java Runtime 1.0.0 for
Series 40 or newer. Symbian devices do not support this method.
The LocationUtil.getLocationProvider method
uses the Location class constants (each corresponding
to a specific location-providing method) to specify which location
provider to use. Each location provider corresponds to a specific
bitwise combination of constants:
Location provider |
Definition |
|---|---|
Standalone GPS |
|
Assisted GPS (AGPS) |
|
Online cell ID or WLAN |
|
Offline cell ID |
|
The following code snippet shows how to retrieve a location provider based on standalone GPS.
// Specify the location-providing methods for standalone GPS
int[] methods = {(Location.MTA_UNASSISTED | Location.MTE_SATELLITE | Location.MTY_TERMINALBASED)};
// Retrieve the location provider
LocationProvider provider = LocationUtil.getLocationProvider(methods, null);For more information about cell-ID-based location providers, see section Cell ID positioning.