Agera Explained - 08.Incrementally Agerifying legacy code

MyListenable.java

public final class MyListenable extends SomeBaseClass implements Observable {

  private final UpdateDispatcher updateDispatcher;

  public MyListenable() {
    // Original constructor code here...
    updateDispatcher = Observables.updateDispatcher(new Bridge());
  }

  // Original class body here... including:
  public void addListener(Listener listener) { … }
  public void removeListener(Listener listener) { … }

  @Override
  public void addUpdatable(Updatable updatable) {
    updateDispatcher.addUpdatable(updatable);
  }

  @Override
  public void removeUpdatable(Updatable updatable) {
    updateDispatcher.removeUpdatable(updatable);
  }

  private final class Bridge implements ActivationHandler, Listener {
    @Override
    public void observableActivated(UpdateDispatcher caller) {
      addListener(this);
    }

    @Override
    public void observableDeactivated(UpdateDispatcher caller) {
      removeListener(this);
    }

    @Override
    public void onEvent() { // Listener implementation
      updateDispatcher.update();
    }
  }
}