guava EventBus源码阅读

post → @Subscribe 方法流程

1.post 调用EventBus  this.dispatcher.dispatch(event, eventSubscribers);
2.dispatcher = Dispatcher.perThreadDispatchQueue()
3. new Dispatcher.PerThreadQueuedDispatcher() = new PerThreadQueuedDispatcher(queue,dispatching)
4. PerThreadQueuedDispatcher.dispatch = while(nextEvent.subscribers.hasNext()) {
                            ((Subscriber)nextEvent.subscribers.next()).dispatchEvent(nextEvent.event);
                        }
到此 post跟踪完毕  现在就是要知道 nextEvent 是谁 
<ol>
<li>nextEvent  = new Dispatcher.PerThreadQueuedDispatcher.Event(event, subscribers)
继续追 event，subscribers
发现是最开始 post传进来的，
现在我们要明白一件事情  post 就是  调用了 eventSubscribers里面的dispatchEvent，开始追subscribers
2.Iterator<Subscriber> eventSubscribers = this.subscribers.getSubscribers(event);</li>
<li></li>
</ol>
<p>Iterator<Subscriber> getSubscribers(Object event) {
ImmutableSet<Class<?>> eventTypes = flattenHierarchy(event.getClass());
List<Iterator<Subscriber>> subscriberIterators = Lists.newArrayListWithCapacity(eventTypes.size());
UnmodifiableIterator var4 = eventTypes.iterator();</p>
<pre><code>    while(var4.hasNext()) {
        Class&lt;?&gt; eventType = (Class)var4.next();
        CopyOnWriteArraySet&lt;Subscriber&gt; eventSubscribers = (CopyOnWriteArraySet)this.subscribers.get(eventType);
        if (eventSubscribers != null) {
            **subscriberIterators.add(eventSubscribers.iterator());**
        }
    }

    return Iterators.concat(subscriberIterators.iterator());
} 

4. 发现eventSubscribers 是从this.subscribers拿的开始追this.subscribers

void register(Object listener) { Multimap<Class<?>, Subscriber> listenerMethods = this.findAllSubscribers(listener);

    Collection eventMethodsInListener;
    CopyOnWriteArraySet eventSubscribers;
    for(Iterator var3 = listenerMethods.asMap().entrySet().iterator(); var3.hasNext(); eventSubscribers.addAll(eventMethodsInListener)) {
        Entry<Class<?>, Collection<Subscriber>> entry = (Entry)var3.next();
        Class<?> eventType = (Class)entry.getKey();
        eventMethodsInListener = (Collection)entry.getValue();
        eventSubscribers = (CopyOnWriteArraySet)this.subscribers.get(eventType);
        if (eventSubscribers == null) {
            CopyOnWriteArraySet<Subscriber> newSet = new CopyOnWriteArraySet();
            eventSubscribers = (CopyOnWriteArraySet)MoreObjects.firstNonNull(this.subscribers.putIfAbsent(eventType, newSet), newSet);
        }
    }

}

6.发现了，eventSubscribers这个是在register做的初始化 看看我们register传了什么 7. EventBus eventBus = new EventBus(); eventBus.register(new EventListener()); eventBus.post(1); 8.class EventListener { @Subscribe public void listenInteger(Integer param) { System.out.println("EventListener#listenInteger ->" + param); }

@Subscribe
public void listenInteger2(Integer param) {
    System.out.println("EventListener#listenInteger2 ->" + param);
}

@Subscribe
public void listenString(String param) {
    System.out.println("EventListener#listenString ->" + param);
}

} 9.明白明白了，this.subscribers里面就是我们传入的带有Subscribe注解各种方法，

10.并且这些方法在 private Multimap<Class<?>, Subscriber> findAllSubscribers(Object listener) { Multimap<Class<?>, Subscriber> methodsInListener = HashMultimap.create(); Class<?> clazz = listener.getClass(); UnmodifiableIterator var4 = getAnnotatedMethods(clazz).iterator();

    while(var4.hasNext()) {
        Method method = (Method)var4.next();
        Class<?>[] parameterTypes = method.getParameterTypes();
        Class<?> eventType = parameterTypes[0];
        methodsInListener.put(eventType, Subscriber.create(this.bus, listener, method));
    }

    return methodsInListener;
}

包装成了Subscriber 11.现在我们只要看 Subscriber的dispatchEvent就知道到底干了什么了

final void dispatchEvent(final Object event) { this.executor.execute(new Runnable() { public void run() { try { Subscriber.this.invokeSubscriberMethod(event); } catch (InvocationTargetException var2) { Subscriber.this.bus.handleSubscriberException(var2.getCause(), Subscriber.this.context(event)); }

        }
    });
}

@VisibleForTesting
void invokeSubscriberMethod(Object event) throws InvocationTargetException {
    try {
        this.method.invoke(this.target, Preconditions.checkNotNull(event));
    } catch (IllegalArgumentException var3) {
        throw new Error("Method rejected target/argument: " + event, var3);
    } catch (IllegalAccessException var4) {
        throw new Error("Method became inaccessible: " + event, var4);
    } catch (InvocationTargetException var5) {
        if (var5.getCause() instanceof Error) {
            throw (Error)var5.getCause();
        } else {
            throw var5;
        }
    }
}

13.发现这不就是调用自己的method了么，到此全部解析完毕。