EventBus分析

private void postToSubscription(Subscription subscription, Object event, boolean isMainThread) {
    switch (subscription.subscriberMethod.threadMode) {
        // 订阅线程跟随发布线程
        case POSTING:
            // 订阅线程和发布线程相同，直接订阅
            invokeSubscriber(subscription, event);
            break;
        // 订阅线程为主线程
        case MAIN:
            if (isMainThread) {
                // 发布线程和订阅线程都是主线程，直接订阅
                invokeSubscriber(subscription, event);
            } else {
                // 发布线程不是主线程，订阅线程切换到主线程订阅
                mainThreadPoster.enqueue(subscription, event);
            }
            break;
        // 订阅线程为后台线程
        case BACKGROUND:
            if (isMainThread) {
                // 发布线程为主线程，切换到后台线程订阅
                backgroundPoster.enqueue(subscription, event);
            } else {
                // 发布线程不为主线程，直接订阅
                invokeSubscriber(subscription, event);
            }
            break;
        // 订阅线程为异步线程
        case ASYNC:
            // 使用线程池线程订阅
            asyncPoster.enqueue(subscription, event);
            break;
        default:
            throw new IllegalStateException("Unknown thread mode: " + subscription.subscriberMethod.threadMode);
    }
}