Equivalent of iOS NSNotificationCenter in Android?

Question

Is there an equivalent of the iOS class NSNotificationCenter in Android ? Are there any libraries or useful code available to me ?

Answer 1

If you don't want to use Observer - it can be problematic in cases you want a Fragment to be your Observer cause you can't extend more then one class- You can use google's Guava Library (https://code.google.com/p/guava-libraries/) for "Function" and "Multimap" - although you can use as well HashMap> for the subscibersCollection

and implement something like this:

    import java.util.Collection;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.base.Function;

public class EventService {

    ArrayListMultimap> subscibersCollection;

    private static EventService instance = null;

    private static final Object locker = new Object();

    private EventService() {
        subscibersCollection = ArrayListMultimap.create();
    }

    public static EventService getInstance() {
        if (instance == null) {
            synchronized (locker) {
                if (instance == null) {
                    instance = new EventService();
                }
            }
        }
        return instance;
    }

    /**
     * Subscribe to the notification, and provide the callback functions in case
     * notification is raised.
     * 
     * @param notification
     *            - notification name
     * @param func
     *            - function to apply when notification is raised
     */
    public void addSubscription(String notification, Function func) {
        synchronized (subscibersCollection) {
            if (!subscibersCollection.containsEntry(notification, func)) {
                subscibersCollection.put(notification, func);
            }
        }
    }

    /**
     * Remove subscription from notification
     */
    public void removeSubscription(String notification,
            Function func) {
        synchronized (subscibersCollection) {
            subscibersCollection.remove(notification, func);
        }
    }

    /**
     * raise notification for all its subscribers
     * 
     * @param notification
     *            - notification name
     * @param data
     *            - update data
     */
    public void publish(String notification, Object data) {
        Collection> observableList = subscibersCollection
                .get(notification);
        for (Function func : observableList) {
            func.apply(data);
        }
    }
}