SynchronizeEventListener.java

public interface SynchronizeEventListener<T> {

    /**
     * This is called whenever the underlying Synchronizer has new data.
     *
     * @param newData
     */
    void dataUpdated(T newData);

    /**
     *
     * This is called when there is a data conflict.
     *
     * The system will save the returned data.
     *
     * @param clientData
     * @param serverData
     * @return
     */
    T resolveConflicts(T clientData, T serverData);

}

Synchronizer.java

public interface Synchronizer<T> {

    /**
     * A listener listens for data on this synchronizer.
     *
     * @param listener
     */
    public void addListener(SynchronizeEventListener<T> listener);

    /**
     * A listener listens for data on this synchronizer.
     *
     * @param listener
     */
    public void removeListener(SynchronizeEventListener<T> listener);


    /**
     * Does what ever is necessary to start syncing
     */
    public void beginSync(Context appContext);

    /**
     * Sync no more
     */
    public void syncNoMore();

}