EventBus源码解析04-取消订阅

取消订阅会调用unregister()

public synchronized void unregister(Object subscriber) {    //根据subscriber获取eventType集合    List<Class<?>> subscribedTypes = typesBySubscriber.get(subscriber);    if (subscribedTypes != null) {        //遍历eventType集合        for (Class<?> eventType : subscribedTypes) {            unsubscribeByEventType(subscriber, eventType);        }        typesBySubscriber.remove(subscriber);    } else {        Log.w(TAG, "Subscriber to unregister was not registered before: " + subscriber.getClass());    }}  

可以看到，这里会根据subscriber获取eventType集合，再遍历这个集合逐个调用unsubscribeByEventType

private void unsubscribeByEventType(Object subscriber, Class<?> eventType) {    //根据eventType获取Subscription(被观察者)集合    List<Subscription> subscriptions = subscriptionsByEventType.get(eventType);    if (subscriptions != null) {        int size = subscriptions.size();        //遍历subscriptions集合        for (int i = 0; i < size; i++) {            Subscription subscription = subscriptions.get(i);            //判断subscriber是否相同            if (subscription.subscriber == subscriber) {                subscription.active = false;                //移除被观察者                subscriptions.remove(i);                i--;                size--;            }        }    }}  

这里，会根据eventType获取Subscription(被观察者)集合，在遍历subscriptions集合，找到和传入的subscriber相同的对象，将其从subscriptions集合中移除，从而取消订阅。

总结

EventBus的取消订阅主要就是根据传入的subscriber，把相应的被观察者(Subscription)从subscriptions集合(之前注册的时候所存放的集合)中移除。

final class Subscription {    //@Subscribe所在的类    final Object subscriber;    //@Subscribe注解的方法    final SubscriberMethod subscriberMethod; }