Guava 事件总线 : pause event posting

Question

有什么方法可以暂停 EventBus 从 guava 库中发布事件。

我有一个方法 changeSomething() 发布一个事件(例如 SomethingChangedEvent)。现在这个方法被另一个方法 doStuff() 在循环中调用。问题是 SomethingChangedEvent 会在每次调用 changeSomething() 时发布，即使只有最后一次更改很重要。由于事件处理程序执行一些重量级计算，应用程序的性能会快速下降。

在最后一次 changeSomething() 执行后，我想告诉 guava 恢复事件处理。

有没有办法告诉 Guava 忽略除最后一个之外的所有 SomethingChangedEvent？

Answer 1

我尝试了这种模式，它是使用子类化从毒丸模式派生出来的:

 public class SomethingChangedEvent {

        private final String name;

        public SomethingChangedEvent(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return name;
        }

    }

    public class IgnoreSomethingChangedEvent extends SomethingChangedEvent {
        public IgnoreSomethingChangedEvent(String name) {
            super(name);
        }

    }

    public class HandleSomethingChangedEvent extends SomethingChangedEvent {
        public HandleSomethingChangedEvent(String name) {
            super(name);
        }

    }

    private void eventBusTest() {
        EventBus eventBus = new EventBus();
        eventBus.register(new EventBusSomethingChanged());
        eventBus.post(new SomethingChangedEvent("process this one"));
        eventBus.post(new IgnoreSomethingChangedEvent("ignore"));
        eventBus.post(new SomethingChangedEvent("don't process this one"));
        eventBus.post(new HandleSomethingChangedEvent("handle"));
        eventBus.post(new SomethingChangedEvent("process this one bis"));
    }

    public class EventBusSomethingChanged {
        private boolean ignore;

        @Subscribe
        public void SomethingChanged(SomethingChangedEvent e) {
            if (e instanceof IgnoreSomethingChangedEvent) {
                ignore = true;
                return;
            }
            if (e instanceof HandleSomethingChangedEvent) {
                ignore = false;
                return;
            }
            if (!ignore) {
                System.out.println("processing:" + e);
            }
        }
    }