Gaunt Face | Matthew Gaunt | Proximity Alerts in Android

Proximity Alerts in Android

4 Jan 2010

I’ve spent probably the best part of a couple of days attempting to get Proximity Alerts working in Android. There are a large number of Google Group threads, all leading to essentially someone saying it still doesn’t work. There was one or two that had working solutions, or some who managed to get it working to a certain degree.

I managed to get a working implementation of proximity alerts by combining the information from a number of threads, this is just a guide through what I learnt and should get you up and running with your own alerts.

Just for the record, I need to learn a great deal more about Intent Filters and Broadcast Receivers as my knowledge of them is fairly vague, so please correct me in the comments if I say anything wrong, or should be implementing things differently.

Lets start of with the basic intent action:

public class EventsMapping extends MapActivity
{
// Proximity Alerts
private String proximityIntentAction = new String("co.uk.gauntface.android.wheresmycontacts.PROXIMITY_ALERT");

This is simply a string I have made up to signify the action of an intent is a proximity alert action (i.e. this identifies the intent as a proximity alert). The usual convention for naming the intent actions is com.some.package.action.ACTION_NAME, notice the action before the action name. This then needs to be applied to an intent filter, which is then applied to a broadcast receiver. This can be done in the AndroidManifest.xml file, however I didn’t have any luck this way (told you I needed to do some learning) so for now I can only show how to achieve this in code.

In your Activity:

IntentFilter intentFilter = new IntentFilter(proximityIntentAction);
registerReceiver(new ProximityAlert(), intentFilter);

ProximityAlert Class:

public class ProximityAlert extends BroadcastReceiver
{
@Override
public void onReceive(Context context, Intent intent)
{
Log.v("SomeTag","Proximity Alert Intent Received");
}
}

It’s worth noting at this point that you only need one broadcast receiver for a number of proximity alerts, since one receiver will pick up any number of intents fired off defined by the intent filter. We’ve got the broadcast receiver with the intent filter applied to it. Now lets define out proximity alerts function.

private void setProximityAlert(double lat, double lon, final long eventID, int requestCode)
{
// 100 meter radius
float radius = 100f;

// Expiration is 10 Minutes
long expiration = 600000;

LocationManager locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

Intent intent = new Intent(proximityIntentAction);

PendingIntent pendingIntent = PendingIntent.getBroadcast(getApplicationContext(), requestCode, intent, PendingIntent.FLAG_CANCEL_CURRENT);

locManager.addProximityAlert(lat, lon, radius, expiration, pendingIntent);

}

Breaking this down, you obviously set radius and expiration to anything you wish, expiration = -1 will mean the alert will never expire. We get the LocationManager as shown, the intent is just an intent using your action string I previously mentioned. In my example I added an extra item, now in the Google Groups there was quite a bit of talk about needing to apply a different extra to the intent, this isn’t necessary, however the VERY IMPORTANT THING to getting multiple proximity alerts working is in the request code in the PendingIntent.getBroadcast. In the java docs for pending intents, it says “Private request code for the sender (currently not used).” So one would assume it doesn’t matter, Wrong, it’s extremely important. You need to send a different request code for each proximity alert so the location manager can identify each of the pending intents as different, otherwise (I think) it caches them and treats them the same, meaning all proximity alerts will have the same extra data (or at least that’s what I found).

So I hope that helps someone, if I have missed anything out let me know, I know my naming for these classes is poor, but I was working on some coursework and refactoring was bottom of the list I’m afraid.

Do as I say, not as I do.

UPDATE: I’ve just made a full example of the code here – http://www.gauntface.co.uk/blog/2010/12/28/how-to-multiple-proximity-alerts-in-android/

Steven says:
February 8, 2010 @ 5:03 pm

Thanks for the article, I’ve been struggling to get multiple proximity alerts working. The request code did the trick for me.

mimi says:
May 27, 2010 @ 10:57 pm

sorry steven but i used the request code but it seem to not work!!! ,you say that it work with you i use different request code but i still have the same problem help please.

Maarten Damen says:
May 13, 2010 @ 10:41 am

Thanks!
Finally got my proximityalert to work!

Steve says:
May 23, 2010 @ 11:18 pm

I’ve been trying everything to get proximity alerts working with the emulator. There’s one small part you left out of your tutorial – the code to trigger the alert. I’ve read articles (and even the source code for LocationManagerService) and can’t get the alerts to trigger the receiver. According to some articles I’ve read, one must disable the GPS provider and use the Network provider as these are the only two that proximity alerts deal with. Given that the network provider is disable in the emulator, you can safely use this provider and inject locations into it (once activated) and triggers the proximity alerts. Seems well and good, only I haven’t had any luck. I also have been trying the receiver tag in the XML file but switched to code to see if that worked – no go, however.

Would you be able to follow up this article with one on how to test this code by injecting locations into the network provider?

Flavio says:
October 5, 2010 @ 12:16 pm

Did you have any luck finding and implementing the code to trigger the alert? I manage to create the alerts but they never get fired. I only tryin in the emulator for now, could you explain to me a bit more what you said about to disable the GPS provider and use the network provider?

Thanks in advance, any source would be appreciated

sampath says:
June 9, 2010 @ 6:44 am

this worked like a charm. thanks

luiz says:
June 22, 2010 @ 3:48 pm

Hi….
My proximity alert is now working fine, but, now I want to remove ALL proximity alerts, I have around 9000 alerts, but the android 2.1 SDK only allow to remove one by one passing the PendingIntent.

Now here comes the BIG problem, I add all alerts dinamically reading one config file. Do I have to keep in an array variable all PendingItents that I’ve create to then remove then one by one, or it is an easier way to do that!?

Tks!