EventBus事件分发框架解读

最新推荐文章于 2025-04-09 10:54:57 发布

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最新推荐文章于 2025-04-09 10:54:57 发布

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分类专栏：三方开源实现原理文章标签： framework 框架 EventBus Handler Broadcast

本文链接：https://blog.youkuaiyun.com/u011228356/article/details/45055957

全局框架解析：Trinea的EventBus 源码解析

以下是一些具体过程的分析，最好可以先学习上面的链接内容：

下面的方法是注册最终调用的方法：

 private synchronized void register(Object subscriber, boolean sticky, int priority) {
        List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriber.getClass());
        for (SubscriberMethod subscriberMethod : subscriberMethods) {
            subscribe(subscriber, subscriberMethod, sticky, priority);
        }
    }

1.通过以下方法获取当前订阅者（就是注册的当前类）中所有的事件响应方法（这些响应方法就是该类中的onEvent(),onEventMainThread(),onEventBackgroundThread(),onEventAsync()这些方法），遍历该类中的所有方法，并将这些方法封装到一个集合中，然后以订阅者的类名为key，响应事件的方法集合为value存到一个用作缓存的hashmap中。下次遍历的时候会先通过key获得已经缓存的方法集合，存在就不会重新遍历。（具体参考源码流程）

 List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriber.getClass());

2.接着循环第一步找到的所有的事件响应方法的集合，并执行subscribe方法：

 for (SubscriberMethod subscriberMethod : subscriberMethods) {
            subscribe(subscriber, subscriberMethod, sticky, priority);
        }

具体方法流程：

 private void subscribe(Object subscriber, SubscriberMethod subscriberMethod, boolean sticky, int priority) {
        Class<?> eventType = subscriberMethod.eventType;
        CopyOnWriteArrayList<Subscription> subscriptions = subscriptionsByEventType.get(eventType);
        Subscription newSubscription = new Subscription(subscriber, subscriberMethod, priority);
        if (subscriptions == null) {
            subscriptions = new CopyOnWriteArrayList<Subscription>();
            subscriptionsByEventType.put(eventType, subscriptions);
        } else {
            if (subscriptions.contains(newSubscription)) {
                throw new EventBusException("Subscriber " + subscriber.getClass() + " already registered to event "
                        + eventType);
            }
        }

        // Starting with EventBus 2.2 we enforced methods to be public (might change with annotations again)
        // subscriberMethod.method.setAccessible(true);

        int size = subscriptions.size();
        for (int i = 0; i <= size; i++) {
            if (i == size || newSubscription.priority > subscriptions.get(i).priority) {
                subscriptions.add(i, newSubscription);
                break;
            }
        }

        List<Class<?>> subscribedEvents = typesBySubscriber.get(subscriber);
        if (subscribedEvents == null) {
            subscribedEvents = new ArrayList<Class<?>>();
            typesBySubscriber.put(subscriber, subscribedEvents);
        }
        subscribedEvents.add(eventType);

        if (sticky) {
            if (eventInheritanc