线程模型
在EventBus3.0框架中执行线程的快速切换，通过ThreadMode来指定线程在哪个线程中执行;
在EventBus3.0框架线程模型有个PendingPost 类负责数据的传递;
final class PendingPost {
private final static List<PendingPost> pendingPostPool = new ArrayList<PendingPost>();
Object event;
Subscription subscription;
PendingPost next;
private PendingPost(Object event, Subscription subscription) {
this.event = event;
this.subscription = subscription;
}
}PendingPost 类中维护了3个字段，其中event为事件类的实例，subscription是监听回调信息封装，next 的类型也是一个PendingPost ，通过next可以构建一个列表;
在类的内部也维护着一个静态的PendingPost 对象的对象池，当需要PendingPost 实例时，首先从对象池中获取，当获取不到时在进行对象的new创建;
ThreadMode.MAIN 当调用线程不是主线程时，需要把事件执行推送到主线程中，在EventBus3.0框架中的EventBus类中维护着一个HandlerPoster对象来进行主线程数据的处理;HandlerPoster类是一个Handler,监听事件函数的执行应该在主线程回调的handleMessage 方法中,在源码中也确实是在handleMessage方法执行：
eventBus.invokeSubscriber(pendingPost); ThreadMode.Background 与ThreadMode.AsyncPoster 执行的方式差不多相同，都是从后台线程池中取出线程进行执行;在EventBus类中初始化了BackgroundPoster与AsyncPoster来对这2种线程模型进行处理，这2个类都继承了Runnable 接口;
final class BackgroundPoster implements Runnable {
private final PendingPostQueue queue;
private final EventBus eventBus;
private volatile boolean executorRunning;
BackgroundPoster(EventBus eventBus) {
this.eventBus = eventBus;
queue = new PendingPostQueue();
}
public void enqueue(Subscription subscription, Object event) {
PendingPost pendingPost = PendingPost.obtainPendingPost(subscription, event);
synchronized (this) {
queue.enqueue(pendingPost);
if (!executorRunning) {
executorRunning = true;
eventBus.getExecutorService().execute(this);
}
}
}
}在BackgroundPoster 类中PendingPostQueue 是一个存储了PendingPost类型的队列，eventBus对应的就是EventBus类的实例,在BackgroundPoster 类中enqueue方法是在EventBus分发Post方法内部进行调用的;
eventBus.getExecutorService()获取EventBus类中的ExecutorService,在源码我们可以发现ExecutorService=Executors.newCachedThreadPool();
当执行eventBus.getExecutorService().execute(this);代码时,就跳转到BackgroundPoster 的run方法中
@Override
public void run() {
try {
try {
while (true) {
PendingPost pendingPost = queue.poll();
if (pendingPost == null) {
synchronized (this) {
// Check again, this time in synchronized
pendingPost = queue.poll();
if (pendingPost == null) {
executorRunning = false;
return;
}
}
}
eventBus.invokeSubscriber(pendingPost);
}
} catch (InterruptedException e) {
Log.w("Event", Thread.currentThread().getName() + " was interruppted", e);
}
} finally {
executorRunning = false;
}
}
从run方法中可以看出，最终执行的还是eventBus.invokeSubscriber(pendingPost) 方法;