updating google maps marker from a broadcast sms receiver

Question

I am a newbie to android and java. I am trying to make an application to perform following task.

• receive incoming sms (which will have latitude and longitude information)
• show them on map with markers So every time an sms comes map should get a new marker.

currently I have a map where I can show a point and I have implemented a broadcast receiver to get lattitude and longitude form SMS.

But I am unsure how to update the map from broadcast receiver on receiving a new sms.

Any help or tips will be useful.

Thank you

Answer 1

There are 3 items you need to address:

A. Receive an SMS via a BroadcastReceiver

B. Annotating a MapView using an ItemizedOverlay

C. Communicate the updates from the BroadcastReceiver to the activity showing the map

Item A: Receive SMS

1. Implement your BroadcastReceiver class:

   public class SMSBroadcastReceiver extends BroadcastReceiver
   {
       private static final String SMS_RECEIVED = "android.provider.Telephony.SMS_RECEIVED";
   
       @Override 
       public void onReceive(Context context, Intent intent) 
       {
           if (intent.getAction().equals (SMS_RECEIVED)) 
           {
               Bundle bundle = intent.getExtras();
               if (bundle != null) 
               {
                   Object[] pdusData = (Object[])bundle.get("pdus");
                   for (int i = 0; i < pdus.length; i++) 
                   {
                       SmsMessage message = SmsMessage.createFromPdu((byte[])pdus[i]);
   
                       /* ... extract lat/long from SMS here */
                   }
               }
           }
       }
   }
   

2. Specify your broadcast receiver in the app manifest:

   <manifest ... > 
           <application ... >
                   <receiver 
                           android:name=".SMSBroadcastReceiver"
                           android:enabled="true"
                           android:exported="true">
                           <intent-filter>
                                   <action android:name="android.provider.Telephony.SMS_RECEIVED"></action>
                           </intent-filter>
                   </receiver>
           </application>
   </manifest>
   

(Credits go to the posters in this thread: Android - SMS Broadcast receiver)

Item B: Annotate the Map

1. Create a class derived from ItemizedOverlay, which is used to inform a MapView of any markers which need to be displayed:

   class LocationOverlay extends ItemizedOverlay<OverlayItem>
   {
           public LocationOverlay(Drawable marker) 
           {         
                   /* Initialize this class with a suitable `Drawable` to use as a marker image */
   
                   super( boundCenterBottom(marker));
           }
   
           @Override     
           protected OverlayItem createItem(int itemNumber) 
           {         
                   /* This method is called to query each overlay item. Change this method if
                      you have more than one marker */
   
                   GeoPoint point = /* ... the long/lat from the sms */
                   return new OverlayItem(point, null, null);     
           }
   
      @Override 
      public int size() 
      {
                   /* Return the number of markers here */
                   return 1; // You only have one point to display
      } 
   }
   

2. Now, incorporate the overlay into an activity that displays the actual map:

   public class CustomMapActivity extends MapActivity 
   {     
       MapView map;
       @Override
   
           public void onCreate(Bundle savedInstanceState) 
           {     
               super.onCreate(savedInstanceState);         
               setContentView(R.layout.main);      
   
               /* We're assuming you've set up your map as a resource */
               map = (MapView)findViewById(R.id.map);
   
               /* We'll create the custom ItemizedOverlay and add it to the map */
               LocationOverlay overlay = new LocationOverlay(getResources().getDrawable(R.drawable.icon));
               map.getOverlays().add(overlay);
           }
   }
   

Item C: Communicate the updates

This is the trickiest part (see also Updating an Activity from a BroadcastReceiver). If the app's MapActivity is currently visible, it needs to be notified of the newly received markers. If the MapActivity isn't active, any received points need to be stored somewhere until the user chooses to view the map.

1. Define the private intent (in CustomMapActivity):

   private final String UPDATE_MAP = "com.myco.myapp.UPDATE_MAP"
   

2. Create the private BroadcastReceiver (in CustomMapActivity):

   private  BroadcastReceiver updateReceiver =  new BroadcastReceiver()
   {
       @Override
       public void onReceive(Context context, Intent intent) 
       {
           // custom fields where the marker location is stored
           int longitude = intent.getIntExtra("long");
           int latitude = intent.getIntExtra("lat");
   
           // ... add the point to the `LocationOverlay` ...
           // (You will need to modify `LocationOverlay` if you wish to track more
           // than one location)
   
           // Refresh the map
   
           map.invalidate();
       }
   }
   

3. Register your private BroadcastReceiver when the activity is started (add this to CustomMapActivity.onCreate):

   IntentFilter filter = new IntentFilter();
   filter.addAction(UPDATE_MAP);
   registerReceiver(updateReceiver /* from step 2 */, filter);
   

4. Invoke your private intent from the public BroadcastReceiver (add this to SMSBroadcastReceiver.onReceive):

   Intent updateIntent = new Intent();
   updateIntent.setAction(UPDATE_MAP);
   updateIntent.putExtra("long", longitude);
   updateIntent.putExtra("lat", latitude);
   context.sendBroadcast(updateIntent);
   

Answer 2

It sounds like you are looking for detail on how to communicate between your Activity and the BroadcastReceiver? One approach (there are many different approaches) is to have your map Activity register a temporary BroadcastReceiver that is setup to only listen to private broadcasts from your app, and then have your SMS broadcast receiver generate a new broadcast with the latitude/longitude from the SMS. In your map Activity your receiver will add a new point to the map every time it receives a new private broadcast.