Locate user of an Android device

Question

I am new to oriented object paradigm and I work on Android using Java project for an internship.
I must be able to locate the user and some around buildings I read stuff about how to setup LocationListener and all, and decided that I better write a class that manage everything for me.

public class NetCampusLocation {
    private Activity activity;
    private LocationManager locationManager;
    private LocationListener locationListener;
    private Location freshLocation;

    public NetCampusLocation(Activity activity) {
        this.activity = activity;
        this.locationManager = (LocationManager) this.activity.getSystemService(Context.LOCATION_SERVICE);
        this.locationListener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {

            }

            @Override
            public void onStatusChanged(String provider, int status, Bundle extras) {

            }

            @Override
            public void onProviderEnabled(String provider) {

            }

            @Override
            public void onProviderDisabled(String provider) {

            }
        };
        this.freshLocation = this.locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (this.freshLocation == null) {
            this.freshLocation = this.locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        }
    }

    public void setLocationUpdate(String provider, int minTimeInterval, int minDistance, LocationListener listener) {
        this.locationManager.requestLocationUpdates(provider, minTimeInterval, minDistance, listener);
    }

    public void stopLocationUpdate() {
        this.locationManager.removeUpdates(this.locationListener);
    }
}

That is the first time I am writing a class on my own (without any pedagogic goal) and I ever seen an example with an interface nested to a class, I am wondering if this is even logical or totally absurd.

I am also wondering if this a good practice to pass my activity to the constructor or the class or not.

All kind of advices would be really good.

Answer 1

It is good practice to mark as many fields as possible as final.

private final Activity activity;
private final LocationManager locationManager;
private final LocationListener locationListener;

I assume that freshLocation will be changed in your locationListener so that one should not be final.

All fields that only get initialized once can be marked final.

---

You seem to only be using your activity inside the constructor, so you don't need to keep that as a field at all.

Also, instead of passing an Activity, it's enough to pass a Context (Activity extends Context so you can still pass an activity). The only method you use on the activity is getSystemService which is part of the Context class. Contexts are often required to pass to various methods in Android, so that is perfectly fine. It is better to pass a Context than an Activity.

---

About this code:

this.locationListener = new LocationListener() {
    @Override
    public void onLocationChanged(Location location) {

It is totally fine to do it this way. This is an anonymous inner class. The alternative is to use an inner class (non-anonymous), this would reduce code from your constructor but that code would be added in other parts of the class instead so which way you go doesn't matter much. This is fine.

Answer 2

This piece of code clutter almost all your method space :

  this.locationListener = new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {

        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {

        }
    };

If you really need an empty implementation of the LocationListener, you can simply omit white-space in method like so.

  this.locationListener = new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {}
        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {}
        @Override
        public void onProviderEnabled(String provider) {}
        @Override
        public void onProviderDisabled(String provider) {}
    };

This will take less space in your method and we still understand that it's an empty implementation. I find it weird that there is no default implementation that you could use, but this is not that much of a problem.