Communication between Android Services and Activities

Question

I want to develop an Android App with three activities and two services.

The first Service, named WebClientService, calls a REST API every

Answer 1

Use event bus for this communication. EventBus allows publish-subscribe-style communication between components without requiring the components to explicitly register with one another (and thus be aware of each other). It is designed exclusively to replace traditional Java in-process event distribution using explicit registration.

There are a lot of them:

http://square.github.io/otto/

https://github.com/greenrobot/EventBus

This is an example of Otto usage:

Bus bus = new Bus();

bus.post(new AnswerAvailableEvent(42));

@Subscribe public void answerAvailable(AnswerAvailableEvent event) {
    // TODO: React to the event somehow!
}

bus.register(this); // In order to receive events, a class instance needs to register with the bus.

To post from any thread (main or background), in you case a Service and receive events on the main thread:

public class MainThreadBus extends Bus {
  private final Handler mHandler = new Handler(Looper.getMainLooper());

  @Override
  public void post(final Object event) {
    if (Looper.myLooper() == Looper.getMainLooper()) {
      super.post(event);
    } else {
      mHandler.post(new Runnable() {
        @Override
        public void run() {
          MainThreadBus.super.post(event);
        }
      });
    }
  }