Finding Your Way - Beginning Java ME Platform - page 488

the LocationProvider instance, you can determine either the current position or the last
known position (which may be null ) by invoking the LocationProvider 's getLocation or
getLastKnownLocation methods, respectively. Many of the LocationManager methods can
throw exceptions—typically LocationException s for location-based failures, or
SecurityException s if the user or platform does not permit the operation.

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Tip Location determination can be a time-consuming process, and the LocationProvider implementa-
tion may block the current thread. For this reason, it's best to invoke getLocation in a thread separate from
the main thread, to avoid stalling the user interface of your application. I show you how to do this in a real
MIDlet later in this chapter, in the “Locating the User” section.

The specific Location instance that the LocationProvider class's getLocation method
returns provides the device's location at a specific instance in time that the implementa-
tion determined using a specific location method. When you invoke getLocation ,you
must pass a number indicating the maximum number of seconds your application is
willing to wait for the positioning request to complete.
From an instance of Location , you can use the following methods to determine more
about the device location:

• isValid : Returns true if the Location is valid with coordinates

• getQualifiedCoordinates : Returns the coordinates of the Location

• getTimestamp : Returns when the location data was collected

• getAddressInfo : Returns the street address (as an AddressInfo object)

• getCourse : Returns the heading in degrees relative to true north

• getSpeed : Returns the device's current ground speed in meters per second at the
measurement time

• getLocationMethod : Returns a bit mask describing how the implementation
determined the location

• getExtraInfo : Returns any additional information about the request

Table 17-2 describes the bit field values that the getLocationMethod uses to report how
the implementation determined the device's location.