EventBus/src/org/greenrobot/eventbus/EventBus.java
public void cancelEventDelivery(Object event) {
        PostingThreadState postingState = currentPostingThreadState.get();
        if (!postingState.isPosting) {
            throw new EventBusException(
                    "This method may only be called from inside event handling methods on the posting thread");
        } else if (event == null) {
            throw new EventBusException("Event may not be null");
        } else if (postingState.event != event) {
            throw new EventBusException("Only the currently handled event may be aborted");
        } else if (postingState.subscription.subscriberMethod.threadMode != ThreadMode.POSTING) {
            throw new EventBusException(" event handlers may only abort the incoming event");
        }

        postingState.canceled = true;
    }
public void cancelEventDelivery(Object event) {
        PostingThreadState postingState = currentPostingThreadState.get();
        if (!postingState.isPosting) {
            throw new EventBusException(
                    "This method may only be called from inside event handling methods on the posting thread");
        } else if (event == null) {
            throw new EventBusException("Event may not be null");
        } else if (postingState.event != event) {
            throw new EventBusException("Only the currently handled event may be aborted");
        } else if (postingState.subscription.subscriberMethod.threadMode != ThreadMode.POSTING) {
            throw new EventBusException(" event handlers may only abort the incoming event");
        }

        postingState.canceled = true;
    }
Called from a subscriber's event handling method, further event delivery will be canceled. Subsequent
subscribers
won't receive the event. Events are usually canceled by higher priority subscribers (see
{@link Subscribe#priority()}). Canceling is restricted to event handling methods running in posting thread
{@link ThreadMode#POSTING}.