barcode generator visual basic 6 source code Get last-known Location in Java

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Our custom MapViewActivity extends MapActivity B. We ll focus on the MapActivity in more detail in section 11.3, but for now, recognize that this is a special kind of Activity. Within the class, you declare member variables for LocationManager C and LocationProvider D. To acquire the LocationManager, you use the Activity getSystemService (String name) method E. Once you have the LocationManager, you assign the LocationProvider you want to use with the manager s getProvider method F. In this case use the GPS provider. We ll talk more about the LocationProvider class in the next section. Once you have the manager and provider in place, you implement the onCreate method of your Activity to instantiate a MapController and set initial state for the screen G. Section 11.3 covers MapController and the MapView it manipulates. Along with helping you set up the provider you need, LocationManager supplies quick access to the last-known Location H. Use this method if you need a quick fix on the last location, as opposed to the more involved techniques for registering for periodic location updates with a listener; we ll cover that topic in section 11.2.3. Besides the features shown in this listing, LocationManager allows you to directly register for proximity alerts. For example, your app could show a custom message if you pass within a quarter-mile of a store that has a special sale. If you need to fire an Intent based on proximity to a defined location, call the addProximityAlert method. This method lets you set the target location with latitude and longitude, and also lets you specify a radius and a PendingIntent. If the device comes within the range, the PendingIntent is fired. To stop receiving these messages, call removeProximityAlert. Getting back to the main purpose for which you ll use the LocationManager with Wind and Waves, we ll next look more closely at the GPS LocationProvider.

Each implementation responsible for returning location information may be available on different devices and in different circumstances. Available provider implementations depend on the hardware capabilities of the device, such as the presence of a GPS receiver. They also depend on the situation: even if the device has a GPS receiver, can it currently receive data from satellites, or is the user somewhere inaccessible such as an elevator or a tunnel At runtime you ll query for the list of providers available and use the most suitable one. You may select multiple providers to fall back on if your first choice isn t available or enabled. Developers generally prefer using the LocationManager. GPS_PROVIDER provider, which uses the GPS receiver. You ll use this provider for Wind and Waves because of its accuracy and its support in the emulator. Keep in mind that a real device will normally offer multiple providers, including the LocationManager.NETWORK_PROVIDER, which uses cell tower and Wi-Fi access points

to determine location data. To piggyback on other applications requesting location, use LocationManager.PASSIVE_PROVIDER. In listing 11.3 we showed how you can obtain the GPS provider directly using the getProvider(String name) method. Table 11.2 provides alternatives to this approach of directly accessing a particular provider.

List<String> providers = locationManager.getAllProviders(); List<String> enabledProviders = locationManager.getAllProviders(true); locationProvider = locationManager.getProviders(true).get(0); locationProvider = locationManager.getBestProvider( myCriteria, true);

Description Get all of the providers registered on the device. Get all of the currently enabled providers. A shortcut to get the first enabled provider, regardless of type.

An example of getting a LocationProvider using a particular Criteria argument. You can create a Criteria instance and specify whether bearing, altitude, cost, and other metrics are required.

Different providers may support different location-related metrics and have different costs or capabilities. The Criteria class helps define what each provider instance can handle. Available metrics are latitude and longitude, speed, bearing, altitude, cost, and power requirements. Remember to set the appropriate Android permissions. Your manifest needs to include location-related permissions for the providers you want to use. The following listing shows the Wind and Waves manifest XML file, which includes both COARSE- and FINE-grained location-related permissions.