Professional Android 4 Application Development

516 x CHAPTER 13 MAPS, GEOCODING, AND LOCATION-BASED SERVICES
Most GPS systems record track-files using GPX, whereas KML is used extensively
online to define geographic information. You can handwrite your own
KML file or generate one by using Google Earth to find directions between two
locations.
All location changes applied using the DDMS location controls will be applied to the GPS receiver,
which must be enabled and active.
Configuring the Emulator to Test Location-Based Services
The GPS values returned by getLastKnownLocation do not change unless at least one application
requests location updates. As a result, when the Emulator is first started, the result returned from a
call to getLastKnownLocation is likely to be null, as no application has made a request to receive
location updates.
Further, the techniques used to update the mock location described in the previous section are effective
only when at least one application has requested location updates from the GPS.
Listing 13-2 shows how to enable continuous location updates on the Emulator, allowing you to use
DDMS to update the mock location within the Emulator.
LISTING 13-2: Enabling the GPS provider on the Emulator
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER, 0, 0,
new LocationListener() {
public void onLocationChanged(Location location) {}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status,
Bundle extras) {}
}
);
code snippet PA4AD_Ch13_Location/src/MyActivity.java
Note that this code effectively locks the GPS Location Provider into an on state. This is considered
poor practice, as it will quickly drain the battery on a real device; therefore, this technique should
only be used when testing on the Emulator.
SELECTING A LOCATION PROVIDER
Depending on the device, you can use several technologies to determine the current location. Each
technology, available as a Location Provider, offers different capabilities — including differences in
power consumption, accuracy, and the ability to determine altitude, speed, or heading information.