This library contains anything needed to build a backend for UnifiedNlp.

Writing the service

The easy way (Location)

Writing a service is fairly easy. Just create a class that extends org.microg.nlp.api.LocationBackendService, it provides several methods:


You'll most likely want to override this method. It is called every time when an application requests a location.

However, as this method is blocking, you should not do heavy I/O operations (like network) in it. If your backend uses a remote provider for location retrieval, do requests in an additional thread and return null in update(). On request success, use report() to send the new location to the requesting application.

See JavaDoc for additional information.

onOpen()-method and onClose()-method

These might be interesting to override too. onOpen() is called after UnifiedNlp connected to this backend and onClose() is called before connection closure. This is a good place to initialize or respectively destroy whatever you need during update() calls.


You can call this method every time to report the given location as soon as possible.

The easy way (Geocoding)

Providing a Geocoder is even simpler than a LocationProvider. Extend org.microg.nlp.api.GeocoderBackendService and implement the methods getFromLocation and getFromLocationName. Both methods reflect a call to the corresponding method in android.location.Geocoder.

The flexible way

Instead of using the LocationBackendService helper class you can do it by hand. It's important that your service overrides the onBind() method and responds with a Binder to the LocationBackend interface.

Advertise your service

To let UnifiedNlp see your service you need to advertise it by providing the org.microg.nlp.LOCATION_BACKEND action.

For security reasons, you should add an android:permission restriction to android.permission.ACCESS_COARSE_LOCATION. This ensures only application with access to coarse locations will be able to connect to your service.

You may want to set android:icon and android:label to something reasonable, else your applications icon/label are used. If your backend has settings you can advertise it's activity using the org.microg.nlp.BACKEND_SETTINGS_ACTIVITY meta-data so that it is callable from the UnifiedNlp settings.

A service entry for a backend service could be:

    android:label="A very nice Backend">
        <action android:name="org.microg.nlp.LOCATION_BACKEND" />
        android:value="org.microg.nlp.api.sample.SampleActivity" />