如何在RxJava Android中订阅和事件

Question

I'm building an Android app, and new to Rxjava, having a beginner's question: How can i subscribe to an event on activity starts, and close the subscription on activity stops?

I confused how to implement it.

Answer 1

You have to create an instance of PublishSubject and subscribe to it. and when you want to send and event you need to call onNext() of the PublishSubject instance.

Note: you have to hold one instance for each type of subscriptions.

First of all you must create EventSubscription class to hold specific PublishSubject instance:

EventSubscription.java:

public class EventSubscription {
    private static EventSubscription instance;

    private PublishSubject<String> subject = PublishSubject.create();

    /**
     * Singleton
     */
    public static EventSubscription getInstance() {
        if (instance == null) {
            instance = new EventSubscription();
        }
        return instance;
    }

    /**
     * Pass any event down to event listeners.
     */
    public void setString(String eventName) {
        subject.onNext(eventName);
    }

    /**
     * Subscribe to this Observable. On event
     */
    public Observable<String> getEvents() {
        return subject;
    }
}

And in your activity you also need to hold a subscription instance to be able to unsubscribe it on activity stop. see the following activity class:

public class MyActivity extends Activity {

    private Subscription mMySubscription;

    @Override
    public void onStart(){

        // Start the subscription
        mMySubscription = EventSubscription.getInstance().getEvents()
                .subscribe(new Action1<String>() {

                    @Override
                    public void call(String eventName){

                        // Handle new event
                    }
                });
    }

    @Override
    public void onStop(){

        if(mMySubscription != null && ! mMySubscription.isUnsubscribed()){

            // if your subscription already unsubscribed
            mMySubscription.unsubscribe();
        }
    }

}