Android中的观察者模式与数据同步

Question

public class Observable {

    public interface Observer {
        void notify(List<Object> results);
    }

    private HandlerThread handlerThread;
    private List<Object> results = new ArrayList<>();
    private final Map<Observer, ObserverWrapper> observers = new HashMap<>();

    private void working() {
        //Critial section...

        //modifying results list...

        synchronized (observers) {
            for (ObserverWrapper wrapper : observers.values()) {
                wrapper.notify(results);
            }
        }
    }

    public void register(Observer observer, Handler handler) {
        synchronized (observers) {
            //Create observer wrapper and add to map here...
        }
    }

    public void unregister(Observer observer) {
        synchronized (observers) {
            //Remove observer from the map...
        }
    }

    private static final class ObserverWrapper {
       private final Observer observer;
       private final Handler handler;

       public ObserverWrapper(Observer observer, Handler handler) {
           this.observer = observer;
           this.handler = handler;
       }

       public void notify(final List<Object> results) {
           //The observable thread

           handler.post(new Runnable() {
               void run() {
                   //The observer thread
                   //Critical section...
                   observer.notify(results);
               }
           });
       }
    }
}

Answer 1

我可以想到三个选择：

>

使用results对象作为监视器。这需要最少的更改，但这不是很干净，因为对象本身没有说明要成为监视器。b）考虑到更新每隔几毫秒就来一次，人们担心观察者线程会在更长的时间内锁定生产者线程。生产者和观察者都必须：

同步（结果）{

私有最终对象锁=new Object（）；

已同步（锁定）{//更新结果}

...已同步（锁定）{//读取结果}