Android Context without being in an activity? And other activity-less programming?

Question

I'll try really hard to turn this into one comprehensive question:

I'm writing a method to get a String that contains the name of an Android device's city, as determined by the LocationManager and getLastKnownLocation() and all that.

Then I realized I'd need to do the same thing again in another activity, so why not just make an entirely separate class (LocationFinder) that I could use across my program, instead of writing duplicate code everywhere?

But I've run into problems that confuses me. For instance, if I make this class (LocationFinder), should it extend Activity, even though it is never actually visualized? All this class would do is have a variety of getters like getLastKnownCity() or getCurrentCity() and return strings. I assumed it wouldn't HAVE to extend the Activity class, since it's really not an activity.

But then what Context do I use for:

Geocoder geocoder = new Geocoder(Context context, Locale locale)

?

This made me assume it MUST be an activity. So I extended Activity, and replaced the constructor with

@Override
protected void onCreate(..............

but for some reason, that never ends up getting called, even when I put

String city = new LocationFinder().getLastKnownCity();

My very first line of LocationFinder's onCreate() is

System.out.println("HEY!")

and it never even gets to that. I get a null pointer at android.internal.os.LoggingPrintStream.println() and other stuff.

Plus, there's a bunch of system constants that come from Activity classes. For instance, I need to get at LOCATION_SERVICE, which is a String, which I can't get without extending Activity. Sure, I could cheat and just put in the literal string, but that feels wrong.

Answer 1

EDIT: If possible, use frogmanx's answer. This should only be used when his answer is not possible to use. (ie. singletons that need a context right off the bat.)

Sounds like you should extend Application and not Activity.

Make your Application something like this:

public class MyApplication extends Application {
    private static MyApplication instance;

    public MyApplication() {
        instance = this;
    }

    public static MyApplication getInstance() {
         return instance;
    }

Then add this attribute to the application tag of the manifest:

 <application android:name=".your.package.MyApplication" ... />

After all that, you can get a Context by calling MyApplication.getInstance() from anywhere.

Answer 2

When constructing your class, you can have a constructor that takes in a Context and assigns it a local Context object within your class.

public class LocationFinder {
     private Context myContext;
     private Geocoder geocoder;

     public LocationFinder(Context context)
     {
         myContext = context;
         geocoder = new Geocoder(myContext);
     }

}

And then when you try to access this class, make sure you initialise it like:

public class TestActivity extends Activity {
     protected void onCreate(Bundle savedInstanceState)
     {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
          LocationFinder lFinder = new LocationFinder(getApplication());
     }
}

Of course, you can't access a context from every class that you will be running. So a reference to a View can suffice.

LocationFinder lFinder = new LocationFinder(anyView.getApplication());