/*
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* Copyright (C) 2012 Markus Junginger, greenrobot (http://greenrobot.de)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package de.greenrobot.event;
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import android.os.Looper;
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import android.util.Log;
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import java.lang.reflect.InvocationTargetException;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.CopyOnWriteArrayList;
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import java.util.concurrent.ExecutorService;
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/**
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* EventBus is a central publish/subscribe event system for Android. Events are posted ({@link #post(Object)}) to the
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* bus, which delivers it to subscribers that have a matching handler method for the event type. To receive events,
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* subscribers must register themselves to the bus using {@link #register(Object)}. Once registered,
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* subscribers receive events until {@link #unregister(Object)} is called. By convention, event handling methods must
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* be named "onEvent", be public, return nothing (void), and have exactly one parameter (the event).
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*
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* @author Markus Junginger, greenrobot
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*/
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public class EventBus {
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/** Log tag, apps may override it. */
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public static String TAG = "Event";
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static volatile EventBus defaultInstance;
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private static final EventBusBuilder DEFAULT_BUILDER = new EventBusBuilder();
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private static final Map<Class<?>, List<Class<?>>> eventTypesCache = new HashMap<Class<?>, List<Class<?>>>();
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private final Map<Class<?>, CopyOnWriteArrayList<Subscription>> subscriptionsByEventType;
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private final Map<Object, List<Class<?>>> typesBySubscriber;
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private final Map<Class<?>, Object> stickyEvents;
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private final ThreadLocal<PostingThreadState> currentPostingThreadState = new ThreadLocal<PostingThreadState>() {
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@Override
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protected PostingThreadState initialValue() {
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return new PostingThreadState();
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}
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};
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private final HandlerPoster mainThreadPoster;
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private final BackgroundPoster backgroundPoster;
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private final AsyncPoster asyncPoster;
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private final SubscriberMethodFinder subscriberMethodFinder;
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private final ExecutorService executorService;
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private final boolean throwSubscriberException;
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private final boolean logSubscriberExceptions;
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private final boolean logNoSubscriberMessages;
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private final boolean sendSubscriberExceptionEvent;
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private final boolean sendNoSubscriberEvent;
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private final boolean eventInheritance;
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/** Convenience singleton for apps using a process-wide EventBus instance. */
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public static EventBus getDefault() {
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if (defaultInstance == null) {
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synchronized (EventBus.class) {
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if (defaultInstance == null) {
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defaultInstance = new EventBus();
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}
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}
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}
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return defaultInstance;
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}
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public static EventBusBuilder builder() {
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return new EventBusBuilder();
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}
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/** For unit test primarily. */
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public static void clearCaches() {
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SubscriberMethodFinder.clearCaches();
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eventTypesCache.clear();
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}
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/**
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* Creates a new EventBus instance; each instance is a separate scope in which events are delivered. To use a
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* central bus, consider {@link #getDefault()}.
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*/
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public EventBus() {
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this(DEFAULT_BUILDER);
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}
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EventBus(EventBusBuilder builder) {
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subscriptionsByEventType = new HashMap<Class<?>, CopyOnWriteArrayList<Subscription>>();
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typesBySubscriber = new HashMap<Object, List<Class<?>>>();
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stickyEvents = new ConcurrentHashMap<Class<?>, Object>();
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mainThreadPoster = new HandlerPoster(this, Looper.getMainLooper(), 10);
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backgroundPoster = new BackgroundPoster(this);
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asyncPoster = new AsyncPoster(this);
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subscriberMethodFinder = new SubscriberMethodFinder(builder.skipMethodVerificationForClasses);
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logSubscriberExceptions = builder.logSubscriberExceptions;
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logNoSubscriberMessages = builder.logNoSubscriberMessages;
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sendSubscriberExceptionEvent = builder.sendSubscriberExceptionEvent;
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sendNoSubscriberEvent = builder.sendNoSubscriberEvent;
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throwSubscriberException = builder.throwSubscriberException;
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eventInheritance = builder.eventInheritance;
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executorService = builder.executorService;
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}
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/**
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* Registers the given subscriber to receive events. Subscribers must call {@link #unregister(Object)} once they
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* are no longer interested in receiving events.
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* <p/>
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* Subscribers have event handling methods that are identified by their name, typically called "onEvent". Event
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* handling methods must have exactly one parameter, the event. If the event handling method is to be called in a
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* specific thread, a modifier is appended to the method name. Valid modifiers match one of the {@link ThreadMode}
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* enums. For example, if a method is to be called in the UI/main thread by EventBus, it would be called
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* "onEventMainThread".
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*/
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public void register(Object subscriber) {
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register(subscriber, false, 0);
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}
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/**
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* Like {@link #register(Object)} with an additional subscriber priority to influence the order of event delivery.
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* Within the same delivery thread ({@link ThreadMode}), higher priority subscribers will receive events before
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* others with a lower priority. The default priority is 0. Note: the priority does *NOT* affect the order of
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* delivery among subscribers with different {@link ThreadMode}s!
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*/
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public void register(Object subscriber, int priority) {
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register(subscriber, false, priority);
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}
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/**
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* Like {@link #register(Object)}, but also triggers delivery of the most recent sticky event (posted with
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* {@link #postSticky(Object)}) to the given subscriber.
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*/
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public void registerSticky(Object subscriber) {
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register(subscriber, true, 0);
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}
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/**
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* Like {@link #register(Object, int)}, but also triggers delivery of the most recent sticky event (posted with
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* {@link #postSticky(Object)}) to the given subscriber.
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*/
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public void registerSticky(Object subscriber, int priority) {
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register(subscriber, true, priority);
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}
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private synchronized void register(Object subscriber, boolean sticky, int priority) {
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List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriber.getClass());
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for (SubscriberMethod subscriberMethod : subscriberMethods) {
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subscribe(subscriber, subscriberMethod, sticky, priority);
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}
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}
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// Must be called in synchronized block
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private void subscribe(Object subscriber, SubscriberMethod subscriberMethod, boolean sticky, int priority) {
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Class<?> eventType = subscriberMethod.eventType;
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CopyOnWriteArrayList<Subscription> subscriptions = subscriptionsByEventType.get(eventType);
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Subscription newSubscription = new Subscription(subscriber, subscriberMethod, priority);
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if (subscriptions == null) {
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subscriptions = new CopyOnWriteArrayList<Subscription>();
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subscriptionsByEventType.put(eventType, subscriptions);
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} else {
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if (subscriptions.contains(newSubscription)) {
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throw new EventBusException("Subscriber " + subscriber.getClass() + " already registered to event "
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+ eventType);
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}
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}
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// Starting with EventBus 2.2 we enforced methods to be public (might change with annotations again)
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// subscriberMethod.method.setAccessible(true);
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int size = subscriptions.size();
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for (int i = 0; i <= size; i++) {
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if (i == size || newSubscription.priority > subscriptions.get(i).priority) {
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subscriptions.add(i, newSubscription);
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break;
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}
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}
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List<Class<?>> subscribedEvents = typesBySubscriber.get(subscriber);
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if (subscribedEvents == null) {
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subscribedEvents = new ArrayList<Class<?>>();
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typesBySubscriber.put(subscriber, subscribedEvents);
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}
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subscribedEvents.add(eventType);
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if (sticky) {
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Object stickyEvent;
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synchronized (stickyEvents) {
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stickyEvent = stickyEvents.get(eventType);
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}
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if (stickyEvent != null) {
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// If the subscriber is trying to abort the event, it will fail (event is not tracked in posting state)
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// --> Strange corner case, which we don't take care of here.
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postToSubscription(newSubscription, stickyEvent, Looper.getMainLooper() == Looper.myLooper());
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}
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}
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}
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public synchronized boolean isRegistered(Object subscriber) {
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return typesBySubscriber.containsKey(subscriber);
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}
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/** Only updates subscriptionsByEventType, not typesBySubscriber! Caller must update typesBySubscriber. */
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private void unubscribeByEventType(Object subscriber, Class<?> eventType) {
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List<Subscription> subscriptions = subscriptionsByEventType.get(eventType);
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if (subscriptions != null) {
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int size = subscriptions.size();
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for (int i = 0; i < size; i++) {
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Subscription subscription = subscriptions.get(i);
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if (subscription.subscriber == subscriber) {
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subscription.active = false;
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subscriptions.remove(i);
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i--;
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size--;
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}
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}
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}
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}
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/** Unregisters the given subscriber from all event classes. */
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public synchronized void unregister(Object subscriber) {
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List<Class<?>> subscribedTypes = typesBySubscriber.get(subscriber);
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if (subscribedTypes != null) {
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for (Class<?> eventType : subscribedTypes) {
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unubscribeByEventType(subscriber, eventType);
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}
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typesBySubscriber.remove(subscriber);
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} else {
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Log.w(TAG, "Subscriber to unregister was not registered before: " + subscriber.getClass());
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}
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}
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/** Posts the given event to the event bus. */
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public void post(Object event) {
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PostingThreadState postingState = currentPostingThreadState.get();
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List<Object> eventQueue = postingState.eventQueue;
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eventQueue.add(event);
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if (!postingState.isPosting) {
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postingState.isMainThread = Looper.getMainLooper() == Looper.myLooper();
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postingState.isPosting = true;
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if (postingState.canceled) {
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throw new EventBusException("Internal error. Abort state was not reset");
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}
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try {
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while (!eventQueue.isEmpty()) {
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postSingleEvent(eventQueue.remove(0), postingState);
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}
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} finally {
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postingState.isPosting = false;
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postingState.isMainThread = false;
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}
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}
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}
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/**
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* Called from a subscriber's event handling method, further event delivery will be canceled. Subsequent
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* subscribers
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* won't receive the event. Events are usually canceled by higher priority subscribers (see
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* {@link #register(Object, int)}). Canceling is restricted to event handling methods running in posting thread
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* {@link ThreadMode#PostThread}.
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*/
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public void cancelEventDelivery(Object event) {
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PostingThreadState postingState = currentPostingThreadState.get();
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if (!postingState.isPosting) {
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throw new EventBusException(
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"This method may only be called from inside event handling methods on the posting thread");
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} else if (event == null) {
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throw new EventBusException("Event may not be null");
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} else if (postingState.event != event) {
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throw new EventBusException("Only the currently handled event may be aborted");
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} else if (postingState.subscription.subscriberMethod.threadMode != ThreadMode.PostThread) {
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throw new EventBusException(" event handlers may only abort the incoming event");
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}
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postingState.canceled = true;
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}
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/**
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* Posts the given event to the event bus and holds on to the event (because it is sticky). The most recent sticky
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* event of an event's type is kept in memory for future access. This can be {@link #registerSticky(Object)} or
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* {@link #getStickyEvent(Class)}.
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*/
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public void postSticky(Object event) {
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synchronized (stickyEvents) {
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stickyEvents.put(event.getClass(), event);
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}
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// Should be posted after it is putted, in case the subscriber wants to remove immediately
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post(event);
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}
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/**
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* Gets the most recent sticky event for the given type.
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*
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* @see #postSticky(Object)
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*/
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public <T> T getStickyEvent(Class<T> eventType) {
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synchronized (stickyEvents) {
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return eventType.cast(stickyEvents.get(eventType));
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}
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}
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/**
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* Remove and gets the recent sticky event for the given event type.
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*
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* @see #postSticky(Object)
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*/
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public <T> T removeStickyEvent(Class<T> eventType) {
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synchronized (stickyEvents) {
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return eventType.cast(stickyEvents.remove(eventType));
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}
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}
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/**
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* Removes the sticky event if it equals to the given event.
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*
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* @return true if the events matched and the sticky event was removed.
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*/
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public boolean removeStickyEvent(Object event) {
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synchronized (stickyEvents) {
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Class<?> eventType = event.getClass();
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Object existingEvent = stickyEvents.get(eventType);
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if (event.equals(existingEvent)) {
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stickyEvents.remove(eventType);
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return true;
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} else {
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return false;
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}
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}
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}
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/**
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* Removes all sticky events.
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*/
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public void removeAllStickyEvents() {
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synchronized (stickyEvents) {
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stickyEvents.clear();
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}
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}
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public boolean hasSubscriberForEvent(Class<?> eventClass) {
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List<Class<?>> eventTypes = lookupAllEventTypes(eventClass);
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if (eventTypes != null) {
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int countTypes = eventTypes.size();
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for (int h = 0; h < countTypes; h++) {
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Class<?> clazz = eventTypes.get(h);
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CopyOnWriteArrayList<Subscription> subscriptions;
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synchronized (this) {
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subscriptions = subscriptionsByEventType.get(clazz);
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}
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if (subscriptions != null && !subscriptions.isEmpty()) {
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return true;
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}
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}
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}
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return false;
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}
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private void postSingleEvent(Object event, PostingThreadState postingState) throws Error {
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Class<?> eventClass = event.getClass();
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boolean subscriptionFound = false;
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if (eventInheritance) {
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List<Class<?>> eventTypes = lookupAllEventTypes(eventClass);
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int countTypes = eventTypes.size();
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for (int h = 0; h < countTypes; h++) {
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Class<?> clazz = eventTypes.get(h);
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subscriptionFound |= postSingleEventForEventType(event, postingState, clazz);
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}
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} else {
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subscriptionFound = postSingleEventForEventType(event, postingState, eventClass);
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}
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if (!subscriptionFound) {
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if (logNoSubscriberMessages) {
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Log.d(TAG, "No subscribers registered for event " + eventClass);
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}
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if (sendNoSubscriberEvent && eventClass != NoSubscriberEvent.class &&
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eventClass != SubscriberExceptionEvent.class) {
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post(new NoSubscriberEvent(this, event));
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}
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}
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}
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private boolean postSingleEventForEventType(Object event, PostingThreadState postingState, Class<?> eventClass) {
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CopyOnWriteArrayList<Subscription> subscriptions;
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synchronized (this) {
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subscriptions = subscriptionsByEventType.get(eventClass);
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}
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if (subscriptions != null && !subscriptions.isEmpty()) {
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for (Subscription subscription : subscriptions) {
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postingState.event = event;
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postingState.subscription = subscription;
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boolean aborted = false;
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try {
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postToSubscription(subscription, event, postingState.isMainThread);
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aborted = postingState.canceled;
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} finally {
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postingState.event = null;
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postingState.subscription = null;
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postingState.canceled = false;
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}
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if (aborted) {
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break;
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}
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}
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return true;
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}
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return false;
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}
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private void postToSubscription(Subscription subscription, Object event, boolean isMainThread) {
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switch (subscription.subscriberMethod.threadMode) {
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case PostThread:
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invokeSubscriber(subscription, event);
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break;
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case MainThread:
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if (isMainThread) {
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invokeSubscriber(subscription, event);
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} else {
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mainThreadPoster.enqueue(subscription, event);
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}
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break;
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case BackgroundThread:
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if (isMainThread) {
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backgroundPoster.enqueue(subscription, event);
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} else {
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invokeSubscriber(subscription, event);
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}
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break;
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case Async:
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asyncPoster.enqueue(subscription, event);
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break;
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default:
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throw new IllegalStateException("Unknown thread mode: " + subscription.subscriberMethod.threadMode);
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}
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}
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/** Looks up all Class objects including super classes and interfaces. Should also work for interfaces. */
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private List<Class<?>> lookupAllEventTypes(Class<?> eventClass) {
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synchronized (eventTypesCache) {
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List<Class<?>> eventTypes = eventTypesCache.get(eventClass);
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if (eventTypes == null) {
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eventTypes = new ArrayList<Class<?>>();
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Class<?> clazz = eventClass;
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while (clazz != null) {
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eventTypes.add(clazz);
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addInterfaces(eventTypes, clazz.getInterfaces());
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clazz = clazz.getSuperclass();
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}
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eventTypesCache.put(eventClass, eventTypes);
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}
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return eventTypes;
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}
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}
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/** Recurses through super interfaces. */
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static void addInterfaces(List<Class<?>> eventTypes, Class<?>[] interfaces) {
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for (Class<?> interfaceClass : interfaces) {
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if (!eventTypes.contains(interfaceClass)) {
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eventTypes.add(interfaceClass);
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addInterfaces(eventTypes, interfaceClass.getInterfaces());
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}
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}
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}
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/**
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* Invokes the subscriber if the subscriptions is still active. Skipping subscriptions prevents race conditions
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* between {@link #unregister(Object)} and event delivery. Otherwise the event might be delivered after the
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* subscriber unregistered. This is particularly important for main thread delivery and registrations bound to the
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* live cycle of an Activity or Fragment.
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*/
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void invokeSubscriber(PendingPost pendingPost) {
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Object event = pendingPost.event;
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Subscription subscription = pendingPost.subscription;
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PendingPost.releasePendingPost(pendingPost);
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if (subscription.active) {
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invokeSubscriber(subscription, event);
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}
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}
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void invokeSubscriber(Subscription subscription, Object event) {
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try {
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subscription.subscriberMethod.method.invoke(subscription.subscriber, event);
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} catch (InvocationTargetException e) {
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handleSubscriberException(subscription, event, e.getCause());
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} catch (IllegalAccessException e) {
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throw new IllegalStateException("Unexpected exception", e);
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}
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}
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private void handleSubscriberException(Subscription subscription, Object event, Throwable cause) {
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if (event instanceof SubscriberExceptionEvent) {
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if (logSubscriberExceptions) {
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// Don't send another SubscriberExceptionEvent to avoid infinite event recursion, just log
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Log.e(TAG, "SubscriberExceptionEvent subscriber " + subscription.subscriber.getClass()
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+ " threw an exception", cause);
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SubscriberExceptionEvent exEvent = (SubscriberExceptionEvent) event;
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Log.e(TAG, "Initial event " + exEvent.causingEvent + " caused exception in "
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+ exEvent.causingSubscriber, exEvent.throwable);
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}
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} else {
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if (throwSubscriberException) {
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throw new EventBusException("Invoking subscriber failed", cause);
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}
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if (logSubscriberExceptions) {
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Log.e(TAG, "Could not dispatch event: " + event.getClass() + " to subscribing class "
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+ subscription.subscriber.getClass(), cause);
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}
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if (sendSubscriberExceptionEvent) {
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SubscriberExceptionEvent exEvent = new SubscriberExceptionEvent(this, cause, event,
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subscription.subscriber);
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post(exEvent);
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}
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}
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}
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/** For ThreadLocal, much faster to set (and get multiple values). */
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final static class PostingThreadState {
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final List<Object> eventQueue = new ArrayList<Object>();
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boolean isPosting;
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boolean isMainThread;
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Subscription subscription;
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Object event;
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boolean canceled;
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}
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ExecutorService getExecutorService() {
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return executorService;
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}
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// Just an idea: we could provide a callback to post() to be notified, an alternative would be events, of course...
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/* public */interface PostCallback {
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void onPostCompleted(List<SubscriberExceptionEvent> exceptionEvents);
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}
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}
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