Loca%on Support in Android. COMP 355 (Muppala) Location Services and Maps 1

Transcription

1 Loca%on Support in Android COMP 355 (Muppala) Location Services and Maps 1

2 Loca%on Services in Android Loca%on capabili%es for applica%ons supported through the classes in android.loca%on package and Google Maps external library Loca%on framework based around the Loca%onManager system service Provides the APIs to determine the loca%on and bearing of the underlying device ABer gecng access to the Loca%onManager service, we can: Query for last know user s loca%on Register for periodic updates of the user s loca%on Proximity triggered Intent (fired when the user is within a given proximity of a specified loca%on) COMP 355 (Muppala) Location Services and Maps 2

3 Loca%on Services in Android GeCng user s loca%on for your applica%on works by means of callback from the framework: Need to register to receive loca%on updates 1. Get a reference to the system Loca%on Manager service 2. Define a listener that responds to loca%on updates 3. Register the listener with the loca%on manager 4. Request for user permissions in the Manifest file: <uses- permission android:name="android.permission.access_fine_location" /> Allows access to both GPS and network based loca%on provider Use ACCESS_COARSE_LOCATION to use only network based provider COMP 355 (Muppala) Location Services and Maps 3

4 Loca%on Services Example // Acquire a reference to the system Loca%on Manager Loca%onManager loca%onmanager = (Loca%onManager) this.getsystemservice(context.location_service); // Define a listener that responds to loca%on updates Loca%onListener loca%onlistener = new Loca%onListener() { public void onloca%onchanged(loca%on loca%on) { // Called when a new loca%on is found by the network loca%on provider. makeuseofnewloca%on(loca%on); } public void onstatuschanged(string provider, int status, Bundle extras) {} public void onproviderenabled(string provider) {} public void onproviderdisabled(string provider) {} }; // Register the listener with the Loca%on Manager to receive loca%on updates loca%onmanager.requestloca%onupdates(loca%onmanager.network_provider, 0, 0, loca%onlistener); Can use GPS_PROVIDER For GPS location data Can simultaneously register listeners for both providers COMP 355 (Muppala) Location Services and Maps 4

5 Loca%on Services in Android Typical flow of procedures for obtaining user s loca%on: 1. Start applica%on (get a reference to loca%on manager) 2. Some%me later, start listening for updates from desired loca%on providers (use requestloca%onupdates()) 3. Maintain a "current best es%mate" of loca%on by filtering out new, but less accurate fixes 4. Stop listening for loca%on updates (use removeupdates()) 5. Take advantage of the last best loca%on es%mate (use getlastknownloca%on()) COMP 355 (Muppala) Location Services and Maps 5

6 Loca%on Services in Android Listening window COMP 355 (Muppala) Location Services and Maps 6

7 Loca%on Services in Android Saving bajery life and data exchange requirements: Reduce the size of the listening window Set the loca%on providers to return updates less frequently (use the parameters of requestloca%onupdates()) Restrict the set of providers: Use only one provider depending on the environment and accuracy requirements of your applica%on COMP 355 (Muppala) Location Services and Maps 7

8 Loca%on Services Usage Scenario Examples Geotagging user- created content: COMP 355 (Muppala) Location Services and Maps 8

9 Loca%on Services Usage Scenario Examples Loca%on based recommenda%ons: Keep polling for loca%on un%l recommenda%ons have stabilized COMP 355 (Muppala) Location Services and Maps 9

10 Proximity Alert Support in Android Android loca%on services framework support the crea%on of proximity alerts: Alerts generated when the user is physically near (or within a close proximity) of a specific loca%on We make use of the following facili%es in Android for this purpose Loca%onManager class, specifically the addproximityalert() method Proximity intent implemented based on PendingIntent Broadcast receiver that is fired when the PendingIntent is triggered Proximity based applica%ons will be the next wave of loca%on based applica%ons COMP 355 (Muppala) Location Services and Maps 10

11 Proximity Alert Support in Android General steps to implement proximity alert support: 1. Get a reference to the loca%on manager 2. Create a Pending Intent incorpora%ng the getbroadcast() method 3. Create a Broadcast Receiver to be triggered when the Pending Intent created above is fired 4. Create an intent filter and register the receiver to be triggered 5. Add a proximity alert to the specific point of interest (use addproximityalert()) The proximity alert requires you to supply the la%tude and longitude of the loca%on of interest, the radius around this loca%on where your intent will be fired when the user is within the region, an expira%on %me for the alert (if required), and the Pending Intent COMP 355 (Muppala) Location Services and Maps 11

12 Proximity Alert Support in Android Example: Intent intent =new Intent(proxalert); PendingIntent opera%on=pendingintent.getbroadcast(this,0,intent, 0); loca%onmanager.addproximityalert(des%na%on.getla%tude(), des%na%on.getlongitude(), 1000, - 1, opera%on); COMP 355 (Muppala) Location Services and Maps 12

13 Geocoding and Reverse Geocoding Supported by the Geocoder class Geocoding: Translate from an address into a la%tude- longitude coordinates Reverse Geocoding: Translate from a la%tude- longitude coordinates into an address Might return only a par%al address Make use of two classes: android.loca%on.geocoder Android.loca%on.Address Geocoding service provided by a backend service Google Maps API provides a client Geocoder service Service needs to be available on the target device COMP 355 (Muppala) Location Services and Maps 13

14 Reverse Geocoding Example List<Address> addresses; try{ Geocoder mgeo = new Geocoder(this, Locale.English); addresses = mgeo.getfromloca%on(mloc.getla%tude(), mloc.getlongitude(),1); if ( addresses!= null ) { Address currentaddr = addresses.get(0); StringBuilder mstrb = new StringBuilder( Address:\n ); for (int i=0;i<currentaddr.getmaxaddresslineindex(); i++) { mstrb.append(currentaddr.getaddressline(i)).append( \n ); } // use the string to update some screen element } } catch(ioexcep%on e) { } COMP 355 (Muppala) Location Services and Maps 14

15 Geocoding Example List<Address> addresses; String myaddress = Clearwater Bay, Hong Kong ; Geocoder mgeo = new Geocoder(this, Locale.English); try{ addresses = mgeo.getfromloca%onname(myaddress, 1); if ( addresses!= null ) { Address currentaddr = addresses.get(0); StringBuilder mstrb = new StringBuilder( Address:\n ); mstrb.append( La%tude: ).append(currentaddr.getla%tude()); mstrb.append( \nlongitude: ).append(currentaddr.getlongitude()); // use the string to update some screen element } } catch(ioexcep%on e) { } COMP 355 (Muppala) Location Services and Maps 15

16 Google Maps Support in Android COMP 355 (Muppala) Location Services and Maps 16

17 Google Maps API Google Maps API supported through the Maps external library includes the com.google.android.maps package offers built- in downloading, rendering, and caching of Maps %les, as well as a variety of display op%ons and controls Not part of the standard Android library Not part of the standard SDK. Need to explicitly install MapView class Subgroup of View class Displays the map with data obtained from Google Maps service Provides all the UI elements necessary to interact with the map Provides user interac%on support through keypresses, touch and zoom controls Overlay support on top of the maps COMP 355 (Muppala) Location Services and Maps 17

18 Google Maps API Need to obtain a valid Maps API key to use the Google Maps service See the documenta%on for details Need the key to use with the MapView class Include MapView in the layout XML file: <com.google.android.maps.mapview xmlns:android="h#p://schemas.android.com/apk/res/android" android:id="@+id/mapview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:clickable="true" android:apikey= Your Maps API Key" /> COMP 355 (Muppala) Location Services and Maps 18

19 Google Maps API Modifica%ons to the Manifest file: Include the following under the applica%on element <uses- library android:name="com.google.android.maps" /> Add the permissions to access Internet and loca%on: <uses- permission android:name="android.permission.internet" /> <uses- permission android:name="android.permission.access_fine_location" /> COMP 355 (Muppala) Location Services and Maps 19

20 Google Maps API To use a Google map in your ac%vity, you should extend the MapAc%vity class, a subclass of Ac%vity Also get a reference to the MapView in the layout. You also need to implement the isroutedisplayed() method. This method is required for some accoun%ng from the Maps service to see if you're currently displaying any route informa%on If you are not using the route display, then you can just implement this method to return false If you are using the emulator to test the applica%on, remember to create a new AVD that support Google Maps API COMP 355 (Muppala) Location Services and Maps 20

21 Google Maps API Adding markers to the map requires the use of an Overlay, supported by the ItemizedOverlay class The class manages a list of OverlayItem elements Create a class that extends the ItemizedOverlay class Also require to override the following methods in ItemizedOverlay: addoverlay(): to add an OverlayItem to the ArrayList. This method also calls populate() which reads the items and prepares it to be drawn createitem(): called by populate() to retrieve an OverlayItem Size(): returns the number of OverlayItem elements in the ArrayList ontap(): callback method which is called when a marker is clicked COMP 355 (Muppala) Location Services and Maps 21