Tuesday, April 30, 2013

Android Tip - Monitor a Location

Your application wants to monitor a particular location and when the device is near that location, you want to perform some actions. This is very useful if you are writing an application that reminds you when you are near to some places of interests.
One very cool feature of the LocationManager class is its ability to monitor a specific location. This is achieved using the addProximityAlert() method.

The following code snippet shows how to monitor a particular location so that if the user is within a five-meter radius of that location, your application will fire a PendingIntent object to launch the web browser:

import android.app.Activity;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Bundle;

public class MainActivity extends Activity {
    LocationManager lm;
    PendingIntent pendingIntent;

    public void onCreate(Bundle savedInstanceState) {

        //---use the LocationManager class to obtain
        // locations data---
        lm = (LocationManager)

    public void onResume() {
        //---PendingIntent to launch activity if the user
        // is within the proximity of some locations---
        pendingIntent = PendingIntent.getActivity(
            this, 0, new
                   Uri.parse("http://www.amazon.com")), 0);

        lm.addProximityAlert(37.422006, -122.084095,
                             5, -1, pendingIntent);

    public void onDestroy() {

The addProximityAlert() method takes five arguments: latitude, longitude, radius (in meters), expiration (time for the proximity alert to be valid, after which it will be deleted; -1 for no expiration), and the PendingIntent object.

Note that if the Android device’s screen goes to sleep, the proximity is also checked once every four minutes in order to preserve the battery life of the device. Also, your app would need the
android.permission.ACCESS_FINE_LOCATION permission.

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