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Location API gives you the ability to know whether a particular mobile use is within proximity of a particular location. ProximityListener Interface has to be implemented to track the proximity event.

ProximityListener has two methods which have to be overridden.

monitoringStateChanged(boolean isMonitoringActive) :  Called to notify that the state of the proximity monitoring has changed.
proximityEvent(Coordinates coordinates, Location location): This method will have your code for tasks to be done when the user comes into proximity to a particular location.

This listener is registered to LocationProvider by calling its static method addProximityListener().
addProximityListener(ProximityListener listener, Coordinates coordinates, float proximityRadius)

Parameter Description

listener: Class implementing ProximityListener Interface.
coordinates: coordinates for which proximity is checked.
proximityRadius: The radius in meters which forms the arc around the coordinates registered.

The code segment for registration

try {
    		
 	Criteria cr = new Criteria();
 	// Required Accuracy is set to 100 Meters 
	provider = LocationProvider.getInstance(cr);
	// coordinates around which proximity has to be found
	Coordinates myCoordinates = new Coordinates(14.389796709, 50.099850027, 310);
	// Listener registration for above coordinates for proximity of 1000 meters.
	LocationProvider.addProximityListener(this, myCoordinate, 1000.0f);
			
	} catch (LocationException e) {
			
		e.printStackTrace();
	}

Code segment for proximityEvent()

public void proximityEvent(Coordinates arg0, Location arg1) {
	// Display results on form
	resultsForm = new Form("Proximity Result");
	String displayString = "You are presently within 1000 meters radius from Location
	\n\nLat: 14.389796709\nLong: 50.099850027" ;
	resultsForm.append(displayString);
	cmdExit = new Command("Exit", Command.SCREEN, 0); 
	resultsForm.addCommand(cmdExit);
	display.setCurrent(resultsForm);
	resultsForm.setCommandListener(this);
		
}

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