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Map Applications

Map Applications. Location Service. Two main LBS elements Location Manager: Provides hooks to the location-based services Location Providers: Each of these represents a different location-finding technology used to determine the device’s current location Location Manager

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Map Applications

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  1. Map Applications

  2. Location Service • Two main LBS elements • Location Manager: Provides hooks to the location-based services • Location Providers: Each of these represents a different location-finding technology used to determine the device’s current location • Location Manager • Obtain current location • Track movement • Set proximity alerts for areas • Find available Location Providers • Location Providers • Various location-finding technologies (GPS, Cellular network)

  3. Android Software Stack

  4. Global Positioning System (GPS)

  5. Cell Tower Triangulation • An alternative method to determine the location of a cell phone is to estimate its distance to three nearby cell towers. • Distance of the phone to each antenna could be estimated based upon the lag time between the moment the tower sends a ping to the phone and receives the answering ping back. • Quite similar to the 2D-Trilateration Method.

  6. Latitude & Longitude • Latitude in GPS-Decimal notation: +90.00000 (North) to -90.000000 (South) • • Longitude GPS-Decimal notation: +180.000000 (East) to -180.000000 (West)

  7. Latitude & Longitude

  8. Android Location Classes • The Android API provides Location data based on a variety of methods including: Cell Tower Triangulation, and most commonly GPS chip readings. GPS is the most common location provider on the Android based phones. It offers the most accuracy. Picture: Epson Infineon GPS (2.8 x 2.9mm)

  9. Android Location Classes

  10. Location Class • A class representing a geographic location sensed at a particular time. • A location consists of a latitude and longitude, a UTC timestamp and optionally information on altitude, speed, and bearing. • Information specific to a particular provider or class of providers may be communicated to the application using getExtras, which returns a Bundle of key/value pairs. • Each provider will only provide those entries for which information is available.

  11. Location Values Format • The three common formats: There are sixty seconds in a minute (60" = 1') and There are sixty minutes in a degree (60' = 1°).

  12. Location Manager • This class provides access to the system location services. • These services allow applications • To obtain periodic updates of the device's geographical location, • or to fire an application-specified Intent when the device enters the proximity of a given geographical location. String service_name = Context.LOCATION_SERVICE; LocationManagerlocationManager = (LocationManager) getSystemService(service_name)

  13. LocationProvider Class • An abstract superclass for location providers. • A location provider supplies periodic reports on the geographical location of the device. • Each provider has a set of criteria under which it may be used; for example, • some providers require GPS hardware and visibility to a number of satellites; • others require the use of the cellular radio, • or access to a specific carrier's network, • or access to the internet. • They may also have different battery consumption characteristics or monetary costs to the user. • The Criteria class allows providers to be selected based on userspecified criteria.

  14. LocationProvider Class • Provider Reference String providerName = LocationManager.GPS_PROVIDER; LocationProvidergpsProvider; gpsProvider = locationManager.getProvider(providerName); • Common Location Providers: • LocationManager.GPS_PROVIDER • LocationManager.NETWORK_PROVIDER • Getting list of all providers booleanenabledOnly = true; List<String> providers = locationManager.getProviders(enabledOnly);

  15. Finding Location Providers Using Criteria • Provider with specific requirements Criteria criteria = new Criteria(); criteria.setAccuracy(Criteria.ACCURACY_COARSE); criteria.setPowerRequirement(Criteria.POWER_LOW); criteria.setAltitudeRequired(false); criteria.setBearingRequired(false); criteria.setSpeedRequired(false); criteria.setCostAllowed(true); String bestProvider = locationManager.getBestProvider(criteria, true); • To get all matching Providers List<String> matchingProviders = locationManager.getProviders(criteria, false);

  16. LocationListener Class • Used for receiving notifications from the LocationManagerwhen the location has changed. • These methods are called if the LocationListenerhasbeen registered with the location manager service using the method: requestLocationUpdates (Provider, minTime, minDistance, LocationListener)

  17. LocationListener String provider = LocationManager.GPS_PROVIDER; int t = 5000; // milliseconds int distance = 5; // meters LocationListenermyLocationListener = new LocationListener() { public void onLocationChanged(Location location) { // Update application based on new location. } public void onProviderDisabled(String provider) { // Update application if provider disabled. } public void onProviderEnabled(String provider) { // Update application if provider enabled.} public void onStatusChanged(String provider, int status, Bundle extras) {// Update application if provider hardware status changed.} }; locationManager.requestLocationUpdates(provider, t, distance, myLocationListener);

  18. FINDING YOUR LOCATION • Reference Location Manager String service_name = Context.LOCATION_SERVICE; LocationManagerlocationManager = (LocationManager) getSystemService(service_name) • Permissions in Manifest <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> • Last location “fix” String provider = LocationManager.GPS_PROVIDER; Location location = locationManager.getLastKnownLocation(provider);

  19. Example – Obtain Location from GPS • In this example we request GPS services and displaylatitude and longitude values on the UI. • Notes • Observe the GPS chip is not a synchronous device that will immediately respond to a “give me a GPS reading” call. • In order to engineer a good solution that takes into account the potential delays in obtaining location data: • we place the UI in the main activity • and the request for location call in a background service. • Remember the service runs in the same process space as the main activity, therefore for the sake of responsiveness: • we must place the logic for location data request in a separate parallel thread.

  20. Example – Obtain Location from GPS

  21. Geocoding • Geocoding lets you translate between street addresses and longitude/latitude map coordinates. • The geocoding lookups are done on the server, so your applications will require you to include an Internet uses-permission in your manifest, as shown here: <uses-permission android:name="android.permission.INTERNET"/> • The Geocoder class provides access to two geocoding functions: • Forward geocodingFinds the latitude and longitude of an address • Reverse geocodingFinds the street address for a given latitude and longitude

  22. Reverse Geocoding location = locationManager.getLastKnownLocation (LocationManager.GPS_PROVIDER); double latitude = location.getLatitude(); double longitude = location.getLongitude(); List<Address> addresses = null; Geocodergc = new Geocoder(this, Locale.getDefault()); try { addresses = gc.getFromLocation(latitude, longitude, 10); } catch (IOException e) {}

  23. Forward Geocoding GeocoderfwdGeocoder = new Geocoder(this, Locale.US); String streetAddress = "160 Riverside Drive, New York, New York"; List<Address> locations = null; try { locations = fwdGeocoder.getFromLocationName(streetAddress, 10); } catch (IOException e) {}

  24. Emulating GPS Location Use DDMS > Emulator Control

  25. Google Maps External Library • Android uses the Google Maps External Library to add mapping capabilities to your applications. • Google Maps External Library includes the com.google.android.mapspackage. The classes of this package offer built-in downloading, rendering, and caching of Maps tiles, as well as a variety of display options and controls. • The key class in the Maps package is com.google.android.maps.MapView, a subclass of ViewGroup. • The MapView provides an ideal user interface option for presenting geographical data. Road View

  26. MapViews • MapViews support annotation using Overlaysandby pinning Views to geographical locations. • The Maps external library is not part of the standard Android library, so it may not be present on some compliant Android-powered devices. • By default the Android SDK includes the Google APIs add-on, which in turn includes the Maps external library. • MapViews offer full programmatic control of the map display, letting you control the zoom, location, and display modes — including the option to display satellite, street, and traffic views. Aerial View

  27. Google Map Classes • MapViewis the Map View control. • MapActivityis the base class you extend to create a new Activity that can include a Map View. • MapActivityhandles the application life cycle and background service management required for displaying maps. Map Views are used only within MapActivity-derived Activities. • MapControlleris used to control the map, enabling you to set the center location and zoom levels. • Overlay is the class used to annotate your maps. • MyLocationOverlayis a special Overlay that can be used to display the current position and orientation of the device. • ItemizedOverlaysandOverlayItemsare used together to let you create a layer of map markers, displayed using Drawables and associated text.

  28. Creating a Map-Based Activity • Manifest XML <uses-library android:name="com.google.android.maps"/> <uses-permission android:name="android.permission.INTERNET"/> • Layout • <?xml version="1.0" encoding="utf-8"?> • <LinearLayout • xmlns:android="http://schemas.android.com/apk/res/android" • android:orientation="vertical" • android:layout_width="fill_parent" • android:layout_height="fill_parent"> • <com.google.android.maps.MapView • android:id="@+id/map_view" • android:layout_width="fill_parent" • android:layout_height="fill_parent" • android:enabled="true" • android:clickable="true" • android:apiKey="mymapapikey" • /> • </LinearLayout>

  29. MapActivity

  30. Configuring and Using Map Views • Specifying how the map is displayed. • mapView.setSatellite(true); • mapView.setStreetView(true); • mapView.setTraffic(true); • Querying the Map View. • intmaxZoom = mapView.getMaxZoomLevel(); • GeoPoint center = mapView.getMapCenter(); • intlatSpan = mapView.getLatitudeSpan(); • intlongSpan = mapView.getLongitudeSpan(); • • Optionally display the standard map zoom controls • mapView.setBuiltInZoomControls(true);

  31. Using the Map Controller • Use the Map Controller to pan and zoom a MapView. • getControllerget a reference to a MapView’s controller. • MapControllermapController = mapView.getController(); • Map locations are represented by GeoPoint objects. • Double lat = 37.422006*1E6; • Double lng = -122.084095*1E6; • GeoPoint point = new GeoPoint(lat.intValue(), lng.intValue()); • Re-center and zoom the Map. • mapController.setCenter(point); • mapController.setZoom(1); // 1=widest (or most distant), 21=tightest (nearest) view • ‘‘jump’’ to a new location • mapController.animateTo(point);

  32. Creating and Using Overlays • Overlays enable you to add annotations and click handling to MapViews. • Each Overlay lets you draw 2D primitives, including text, lines, images, etc. • All the Overlays assigned to a Map View are added as layers, with newer layers potentially obscuring older ones. • User clicks are passed through the stack until they are either handled by an Overlay or registered as clicks on the Map View itself.

  33. Creating New Overlays • To add a new Overlay create a new class that extends Overlay. • Override the draw method to draw the annotations you want to add, and override onTapto react to user clicks

  34. The Projection class lets you translate between latitude/longitude coordinates (stored as GeoPoints) and x/y screen pixel coordinates (stored as Points). • A map’s Projection may change between subsequent calls to draw, so it’s good practice to get a new instance each time. Projection projection = mapView.getProjection(); • Use the fromPixel and toPixel methods to translate from GeoPoints to Points and vice versa. Point myPoint = new Point(); // To screen coordinates projection.toPixels(geoPoint, myPoint); // To GeoPoint location coordinates projection.fromPixels(myPoint.x, myPoint.y);

  35. Drawing on the Overlay Canvas

  36. Handling Map Tap Events • The onTap handler receives two parameters: • A GeoPoint that contains the latitude/longitude of the map location tapped • The MapView that was tapped to trigger this event @Override public booleanonTap(GeoPoint point, MapViewmapView) { // Perform hit test to see if this overlay is handling the click if ([ . . . perform hit test . . . ]) { //[ . . . execute on tap functionality . . . ] return true; } // If not handled return false return false; }

  37. Adding and Removing Overlays • Each MapView contains a list of Overlays currently displayed. • List<Overlay> overlays = mapView.getOverlays(); • To add an Overlay onto a Map View, create a new instance of the Overlay and add it to the list • Good practice to call postInvalidateafter you modify the list to update the changes on the map display • List<Overlay> overlays = mapView.getOverlays(); • MyOverlaymyOverlay = new MyOverlay(); • overlays.add(myOverlay); • mapView.postInvalidate(); • projection.fromPixels(myPoint.x, myPoint.y);

  38. My Location Overlay • Special Overlay designed to show your current location and orientation on a MapView. • List<Overlay> overlays = mapView.getOverlays(); • MyLocationOverlaymyLocationOverlay = new MyLocationOverlay(this, mapView); • overlays.add(myLocationOverlay); • Can display both your current location (represented as a flashing blue marker) and your current orientation (shown as a compass on the map display). • myLocationOverlay.enableCompass(); • myLocationOverlay.enableMyLocation(); • Stopping the service • myLocationOverlay.disableCompass(); • myLocationOverlay.disableMyLocation();

  39. Google API Key • To use the Google Map service an API key is needed. The API key can obtained as follows for development/debugging application: • Get debug.keystorefile. You can find the location to the file under “Default debug keystore” from: Windows ➪ Preferences ➪ Android ➪ build. • Use keytooltool to generate Certificate fingerprint (MD5). Use following command on command prompt keytool -list -alias androiddebugkey -keystore <keystore_location>.keystore -storepass android -keypass android • Go to ‘Sign Up for the Android Maps API‘ page. • Put your Certificate fingerprint (MD5) • And get your API key for android GMap application. • Replace “mymapapikey” in MapView layout item with your API key.

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