ROS DefaultNode 监听器的注册和执行

     /***************监听器包EventDispatcher  然后交注册进事件分配器中******************/   public DefaultNode(NodeConfiguration nodeConfiguration, Collection<NodeListener> nodeListeners,      ScheduledExecutorService scheduledExecutorService) {    this.nodeConfiguration = NodeConfiguration.copyOf(nodeConfiguration);//建立DefaultNode监听事件链表    this.nodeListeners = new ListenerGroup<NodeListener>(scheduledExecutorService);    //将监听事件注册到链表中this.nodeListeners.addAll(nodeListeners);    this.scheduledExecutorService = scheduledExecutorService;    masterUri = nodeConfiguration.getMasterUri();    masterClient = new MasterClient(masterUri);    topicParticipantManager = new TopicParticipantManager();    serviceManager = new ServiceManager();    parameterManager = new ParameterManager(scheduledExecutorService);    GraphName basename = nodeConfiguration.getNodeName();    NameResolver parentResolver = nodeConfiguration.getParentResolver();    nodeName = parentResolver.getNamespace().join(basename);    resolver = new NodeNameResolver(nodeName, parentResolver);    slaveServer =        new SlaveServer(nodeName, nodeConfiguration.getTcpRosBindAddress(),            nodeConfiguration.getTcpRosAdvertiseAddress(),            nodeConfiguration.getXmlRpcBindAddress(),            nodeConfiguration.getXmlRpcAdvertiseAddress(), masterClient, topicParticipantManager,            serviceManager, parameterManager, scheduledExecutorService);    slaveServer.start();    NodeIdentifier nodeIdentifier = slaveServer.toNodeIdentifier();    parameterTree =        DefaultParameterTree.newFromNodeIdentifier(nodeIdentifier, masterClient.getRemoteUri(),            resolver, parameterManager);    publisherFactory =        new PublisherFactory(nodeIdentifier, topicParticipantManager,            nodeConfiguration.getTopicMessageFactory(), scheduledExecutorService);    subscriberFactory =        new SubscriberFactory(nodeIdentifier, topicParticipantManager, scheduledExecutorService);    serviceFactory =        new ServiceFactory(nodeName, slaveServer, serviceManager, scheduledExecutorService);    registrar = new Registrar(masterClient, scheduledExecutorService);    topicParticipantManager.setListener(registrar);    serviceManager.setListener(registrar);    scheduledExecutorService.execute(new Runnable() {      @Override      public void run() {        start();      }    });  }    private void start() {    // The Registrar must be started first so that master registration is    // possible during startup.    registrar.start(slaveServer.toNodeIdentifier());    // During startup, we wait for 1) the RosoutLogger and 2) the TimeProvider.    final CountDownLatch latch = new CountDownLatch(2);    log = new RosoutLogger(this);    log.getPublisher().addListener(new DefaultPublisherListener<rosgraph_msgs.Log>() {      @Override      public void onMasterRegistrationSuccess(Publisher<rosgraph_msgs.Log> registrant) {        latch.countDown();      }    });    boolean useSimTime = false;    try {      useSimTime =          parameterTree.has(Parameters.USE_SIM_TIME)              && parameterTree.getBoolean(Parameters.USE_SIM_TIME);    } catch (Exception e) {      signalOnError(e);    }    if (useSimTime) {      ClockTopicTimeProvider clockTopicTimeProvider = new ClockTopicTimeProvider(this);      clockTopicTimeProvider.getSubscriber().addSubscriberListener(          new DefaultSubscriberListener<rosgraph_msgs.Clock>() {            @Override            public void onMasterRegistrationSuccess(Subscriber<rosgraph_msgs.Clock> subscriber) {              latch.countDown();            }          });      timeProvider = clockTopicTimeProvider;    } else {      timeProvider = nodeConfiguration.getTimeProvider();      latch.countDown();    }    try {      latch.await();    } catch (InterruptedException e) {      signalOnError(e);      shutdown();      return;    }     //向事件监听ListenerGroup注册监听事件    signalOnStart();    }      /**   * SignalRunnable all {@link NodeListener}s that the {@link Node} has started.   * <p>   * Each listener is called in a separate thread.   */      /*  任务链结构| nodeListener1—————————————nodeListener2——————————————nodeListener3------------||注册任务1_1            |                             ||注册任务2_1            |                             ||注册任务3_1            |                             ||注册任务4_1            |                             |                      |注册任务1_2                  ||注册任务2_2                  ||注册任务3_2                  ||注册任务4_2                  |                                                                  |注册任务1_3  |注册任务2_3   |注册任务3_3  |注册任务4_3    */  private void signalOnStart() {  //注册参数  DefaultNode ： connectedNode      final ConnectedNode connectedNode = this; //监听任务链 中的每个监听任务 注册SignalRunnable 任务    nodeListeners.signal(new SignalRunnable<NodeListener>() {      @Override      public void run(NodeListener listener) {        listener.onStart(connectedNode);      }    });  }        /***************监听器运行******************/  public Collection<EventDispatcher<T>> addAll(Collection<T> listeners, int limit) {    Collection<EventDispatcher<T>> eventDispatchers = Lists.newArrayList();    for (T listener : listeners) {      eventDispatchers.add(add(listener, limit)); // 注册监听器，并且执行监听    }    return eventDispatchers;  }        public EventDispatcher<T> add(T listener, int queueCapacity) {    EventDispatcher<T> eventDispatcher = new EventDispatcher<T>(listener, queueCapacity);    eventDispatchers.add(eventDispatcher);    //注册监听    executorService.execute(eventDispatcher); //执行监听    return eventDispatcher;  }