register/unregister for Intent to be activated if device is within a specific distance of of given lat/long

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1 stolen from: Locations and Maps Build using android.location package and google maps libraries Main component to talk to is LocationManager Location Manager returned from: getsystemservice(context.location_service) get list of all LocationProviders register/unregister for location updates register/unregister for Intent to be activated if device is within a specific distance of of given lat/long Google Maps External Library com.google.android.maps package offer built-in: - downloading - rendering - caching of Maps tiles - variety of display options and controls com.google.android.maps.mapview, a subclass of ViewGroup. When the MapView has focus, it will capture: - keypresses - touch gestures to pan and zoom the map automatically - handle network requests for additional maps tiles. Provides all of the UI elements necessary for users to control the map Use MapView class methods to control the MapView programmatically and draw a number of Overlay types on top of the map. Lets you work with Maps data as you would other types of Views Not part of the standard Android library. To learn more about the Maps external library: Location You can use both GPS and the Network Location Provider, or just one. Challenges: - Integrating GPS, Cell-ID and Wi-Fi - User movement - Varying Accuracy 1

2 Obtaining Location Updates - tell LocationManager who to notify when location changes requestlocationupdates(locationlistener) LocationListener implements the following: - abstract void onlocationchanged(location location) Called when the location has changed. - abstract void onproviderdisabled(string provider) Called when the provider is disabled by the user. - abstract void onproviderenabled(string provider) Called when the provider is enabled by the user. - abstract void onstatuschanged( String provider, int status, Bundle extras) Called when the provider status changes For Example: // Acquire a reference to the system Location Manager LocationManager locationmanager = (LocationManager) this.getsystemservice(context.location_service); // Define a listener that responds to location updates LocationListener locationlistener = new LocationListener() { public void onlocationchanged(location location) { // Called when a new location is found by the network location provider. makeuseofnewlocation(location); public void onstatuschanged(string provider, int status, Bundle extras) { public void onproviderenabled(string provider) { public void onproviderdisabled(string provider) { ; // Register the listener with the Location Manager to receive location updates locationmanager.requestlocationupdates(locationmanager.network_provider, 0, 0, locationlistener); The first parameter in requestlocationupdates() is the type of location provider to use (in this case, the Network Location Provider for cell tower and Wi-Fi based location) You can control the frequency at which your listener receives updates with the second and third parameter the second is the minimum time interval between notifications and the third is the minimum change in distance between notifications setting both to zero requests location notifications as frequently as possible. The last parameter is your LocationListener, which receives callbacks for location updates. To request location updates from the GPS provider, substitute GPS_PROVIDER for NETWORK_PROVIDER. You can also request location updates from both the GPS and the Network Location Provider by calling requestlocationupdates() twice once for NETWORK_PROVIDER and once for GPS_PROVIDER. In order to receive location updates from NETWORK_PROVIDER or GPS_PROVIDER, you must request user permission by declaring either the ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission, respectively, in your Android manifest file. 2

3 Model for Best Performance A) Problems - accuracy not optimal - device moves - multiple ways to obtain location - limited battery life B) Solution Define a model that specifies: - how location is determined - when to start and stop listening for updates - when to use cached information C) Example 1) Start Application 2) After a certain amount of time, start listening for updates on location from chosen providers 3) Maintain a current "best guess" of location 4) Stop listening for updates 5) Remember best guess D) Listening warning: long periods of listening uses battery power - short periods might compromise accuracy - to start listening, call requestlocationupdates() LocationProvider locationprovider = LocationManager.NETWORK_PROVIDER; //get location using network // LocationProvider locationprovider = LocationManager.GPS_PROVIDER; //use GPS location data: locationmanager.requestlocationupdates(locationprovider, 0, 0, locationlistener); //<-- look at APIs - getting cached copy of location: LocationProvider locationprovider = LocationManager.NETWORK_PROVIDER; // Or use LocationManager.GPS_PROVIDER Location lastknownlocation = locationmanager.getlastknownlocation(locationprovider); - to stop listening, call: locationmanager.removeupdates(locationlistener) 3

4 - Making a best guess -- most recent reading is not necessarily the most accurate - your program might: - Check if retrieved location significantly more recent than previous - Check if new location claims significantly better accuracy than previous - Check provider producing new info -- is it trusted more than previous For example: private static final int TWO_MINUTES = 1000 * 60 * 2; /** Determines whether one Location reading is better than the current Location fix location The new Location that you want to evaluate currentbestlocation The current Location fix, to which you want to compare the new one */ protected boolean isbetterlocation(location location, Location currentbestlocation) { if (currentbestlocation == null) { // A new location is always better than no location // Check whether the new location fix is newer or older long timedelta = location.gettime() - currentbestlocation.gettime(); boolean issignificantlynewer = timedelta > TWO_MINUTES; boolean issignificantlyolder = timedelta < -TWO_MINUTES; boolean isnewer = timedelta > 0; // If it's been more than two minutes since the current location, use the new location // because the user has likely moved if (issignificantlynewer) { // If the new location is more than two minutes older, it must be worse else if (issignificantlyolder) { return false; // Check whether the new location fix is more or less accurate int accuracydelta = (int) (location.getaccuracy() - currentbestlocation.getaccuracy()); boolean islessaccurate = accuracydelta > 0; boolean ismoreaccurate = accuracydelta < 0; boolean issignificantlylessaccurate = accuracydelta > 200; // Check if the old and new location are from the same provider boolean isfromsameprovider = issameprovider(location.getprovider(), currentbestlocation.getprovider()); // Determine location quality using a combination of timeliness and accuracy if (ismoreaccurate) { else if (isnewer &&!islessaccurate) { else if (isnewer &&!issignificantlylessaccurate && isfromsameprovider) { return false; //or: return ismoreaccurate // isnewer &&!islessaccurate // isnewer &&!issignificantlylessaccurate && isfromsameprovider; /** Checks whether two providers are the same */ private boolean issameprovider(string provider1, String provider2) { if (provider1 == null) { return provider2 == null; return provider1.equals(provider2); 4

5 return provider1.equals(provider2); To save power, try the following i) Reduce the size of the listening window ii) Get updates less frequently iii) Use fewer providers Testing: Mock Location Data - Eclipse: 1) Make sure a device is selected 2) Window -> Show View -> Other -> Emulator Control now, Enter GPS coordinates, provide a GPX file, or KML file - DDMS: (see: Manually send long/lat data to device or Use GPX file or Use KML file - Use emulator + command line 1) launch your app in Android emulator launch terminal/console in SDKs /tools directory 2) telnet localhost <console-port> 3) Send a geo fix location with longitude, latitude and altitude (see: geo fix