/**
* 第一步：通过subscriptionsByEventType得到该事件类型所有订阅者信息队列，根据优先级将当前订阅者信息插入到订阅者队列subscriptionsByEventType中；
* 第二步：在typesBySubscriber中得到当前订阅者订阅的所有事件队列，将此事件保存到队列typesBySubscriber中，用于后续取消订阅； 第三步：检查这个事件是否是
* Sticky 事件，如果是则从stickyEvents事件保存队列中取出该事件类型最后一个事件发送给当前订阅者。
*
* @param subscriber
* @param subscriberMethod
* @param sticky
* @param priority
*/
private void subscribe(
Object subscriber, SubscriberMethod subscriberMethod, boolean sticky, int priority) {
Class<?> eventType = subscriberMethod.eventType;
CopyOnWriteArrayList<Subscription> subscriptions =
subscriptionsByEventType.get(eventType); // 通过subscriptionsByEventType得到该事件类型所有订阅者信息队列
Subscription newSubscription = new Subscription(subscriber, subscriberMethod, priority);
// 根据当前的eventType，在subscriptionsByEventType生成对应的key-value（没有则加入，有则跳过次处理）
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);
// 根据优先级将当前订阅者信息插入到订阅者队列subscriptionsByEventType中；
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;
}
}
// 在typesBySubscriber中得到当前订阅者订阅的所有事件队列，将此事件保存到队列typesBySubscriber中，用于后续取消订阅；
List<Class<?>> subscribedEvents = typesBySubscriber.get(subscriber);
if (subscribedEvents == null) {
subscribedEvents = new ArrayList<Class<?>>();
typesBySubscriber.put(subscriber, subscribedEvents);
}
subscribedEvents.add(eventType);
// 检查这个事件是否是 Sticky 事件，如果是，则从stickyEvents事件保存队列中取出该事件类型最后一个事件发送给当前订阅者。
if (sticky) {
if (eventInheritance) {
// Existing sticky events of all subclasses of eventType have to be considered.
// Note: Iterating over all events may be inefficient with lots of sticky events,
// thus data structure should be changed to allow a more efficient lookup
// (e.g. an additional map storing sub classes of super classes: Class -> List<Class>).
Set<Map.Entry<Class<?>, Object>> entries = stickyEvents.entrySet();
for (Map.Entry<Class<?>, Object> entry : entries) {
Class<?> candidateEventType = entry.getKey();
if (eventType.isAssignableFrom(
candidateEventType)) { // 是用来判断一个类Class1和另一个类Class2是否相同或是另一个类的超类或接口
Object stickyEvent = entry.getValue();
checkPostStickyEventToSubscription(newSubscription, stickyEvent);
}
}
} else {
Object stickyEvent = stickyEvents.get(eventType);
checkPostStickyEventToSubscription(newSubscription, stickyEvent);
}
}
}
