EventBus getDefault()入口
除了注解，其他都和EventBus这个类有关系了
我们先从getDefault()方法开始分析
入口分析
这里的getDefault()静态方法，很容易看出，是一个
线程加锁的懒汉单例
具体通过new EventBus() 来创建实例
public static EventBus getDefault() {
if (defaultInstance == null) {
synchronized (EventBus.class) {
if (defaultInstance == null) {
defaultInstance = new EventBus();
}
}
}
return defaultInstance;
}
具体EventBus()构造
我们可以发现，具体的构造，其实是
初始化一些Map值，引用类，EventBusBuilder中的实现传递给EventBus类
其他的类，慢慢分析
EventBus(EventBusBuilder builder) {
subscriptionsByEventType = new HashMap<>();
typesBySubscriber = new HashMap<>();
stickyEvents = new ConcurrentHashMap<>();
mainThreadPoster = new HandlerPoster(this, Looper.getMainLooper(), 10);
backgroundPoster = new BackgroundPoster(this);
asyncPoster = new AsyncPoster(this);
indexCount = builder.subscriberInfoIndexes != null ? builder.subscriberInfoIndexes.size() : 0;
subscriberMethodFinder = new SubscriberMethodFinder(builder.subscriberInfoIndexes,
builder.strictMethodVerification, builder.ignoreGeneratedIndex);
logSubscriberExceptions = builder.logSubscriberExceptions;
logNoSubscriberMessages = builder.logNoSubscriberMessages;
sendSubscriberExceptionEvent = builder.sendSubscriberExceptionEvent;
sendNoSubscriberEvent = builder.sendNoSubscriberEvent;
throwSubscriberException = builder.throwSubscriberException;
eventInheritance = builder.eventInheritance;
executorService = builder.executorService;
}
这里EventBusBuilder，只是一个 饿汉单例
在类创建之前，就已经创建出来了
private static final EventBusBuilder DEFAULT_BUILDER = new EventBusBuilder();
而构造的赋值，只是把 Builder中的值传递到本类中
对应的EventBusBuilder对象
我们观察下面对应的EventBusBuilder类
有1个默认的线程池，管理线程
有很多boolean类型的变量，存储默认boolean属性
有2个List，分别存储Class<?>类型 和
EventBusBuilder
public class EventBusBuilder {
private final static ExecutorService DEFAULT_EXECUTOR_SERVICE = Executors.newCachedThreadPool();
boolean logSubscriberExceptions = true;
boolean logNoSubscriberMessages = true;
boolean sendSubscriberExceptionEvent = true;
boolean sendNoSubscriberEvent = true;
boolean throwSubscriberException;
boolean eventInheritance = true;
boolean ignoreGeneratedIndex;
boolean strictMethodVerification;
ExecutorService executorService = DEFAULT_EXECUTOR_SERVICE;
List<Class<?>> skipMethodVerificationForClasses;
List<SubscriberInfoIndex> subscriberInfoIndexes;
EventBusBuilder() {
}
/** Default: true */
public EventBusBuilder logSubscriberExceptions(boolean logSubscriberExceptions) {
this.logSubscriberExceptions = logSubscriberExceptions;
return this;
}
/** Default: true */
public EventBusBuilder logNoSubscriberMessages(boolean logNoSubscriberMessages) {
this.logNoSubscriberMessages = logNoSubscriberMessages;
return this;
}
/** Default: true */
public EventBusBuilder sendSubscriberExceptionEvent(boolean sendSubscriberExceptionEvent) {
this.sendSubscriberExceptionEvent = sendSubscriberExceptionEvent;
return this;
}
/** Default: true */
public EventBusBuilder sendNoSubscriberEvent(boolean sendNoSubscriberEvent) {
this.sendNoSubscriberEvent = sendNoSubscriberEvent;
return this;
}
/**
* Fails if an subscriber throws an exception (default: false).
* <p/>
* Tip: Use this with BuildConfig.DEBUG to let the app crash in DEBUG mode (only). This way, you won't miss
* exceptions during development.
*/
public EventBusBuilder throwSubscriberException(boolean throwSubscriberException) {
this.throwSubscriberException = throwSubscriberException;
return this;
}
/**
* By default, EventBus considers the event class hierarchy (subscribers to super classes will be notified).
* Switching this feature off will improve posting of events. For simple event classes extending Object directly,
* we measured a speed up of 20% for event posting. For more complex event hierarchies, the speed up should be
* >20%.
* <p/>
* However, keep in mind that event posting usually consumes just a small proportion of CPU time inside an app,
* unless it is posting at high rates, e.g. hundreds/thousands of events per second.
*/
public EventBusBuilder eventInheritance(boolean eventInheritance) {
this.eventInheritance = eventInheritance;
return this;
}
/**
* Provide a custom thread pool to EventBus used for async and background event delivery. This is an advanced
* setting to that can break things: ensure the given ExecutorService won't get stuck to avoid undefined behavior.
*/
public EventBusBuilder executorService(ExecutorService executorService) {
this.executorService = executorService;
return this;
}
/**
* Method name verification is done for methods starting with onEvent to avoid typos; using this method you can
* exclude subscriber classes from this check. Also disables checks for method modifiers (public, not static nor
* abstract).
*/
public EventBusBuilder skipMethodVerificationFor(Class<?> clazz) {
if (skipMethodVerificationForClasses == null) {
skipMethodVerificationForClasses = new ArrayList<>();
}
skipMethodVerificationForClasses.add(clazz);
return this;
}
/** Forces the use of reflection even if there's a generated index (default: false). */
public EventBusBuilder ignoreGeneratedIndex(boolean ignoreGeneratedIndex) {
this.ignoreGeneratedIndex = ignoreGeneratedIndex;
return this;
}
/** Enables strict method verification (default: false). */
public EventBusBuilder strictMethodVerification(boolean strictMethodVerification) {
this.strictMethodVerification = strictMethodVerification;
return this;
}
/** Adds an index generated by EventBus' annotation preprocessor. */
public EventBusBuilder addIndex(SubscriberInfoIndex index) {
if(subscriberInfoIndexes == null) {
subscriberInfoIndexes = new ArrayList<>();
}
subscriberInfoIndexes.add(index);
return this;
}
/**
* Installs the default EventBus returned by {@link EventBus#getDefault()} using this builders' values. Must be
* done only once before the first usage of the default EventBus.
*
* @throws EventBusException if there's already a default EventBus instance in place
*/
public EventBus installDefaultEventBus() {
synchronized (EventBus.class) {
if (EventBus.defaultInstance != null) {
throw new EventBusException("Default instance already exists." +
" It may be only set once before it's used the first time to ensure consistent behavior.");
}
EventBus.defaultInstance = build();
return EventBus.defaultInstance;
}
}
/** Builds an EventBus based on the current configuration. */
public EventBus build() {
return new EventBus(this);
}
}
这里，看上去代码很多
大多数都是设置boolean值的方法
一个设置 线程池 ExecutorService的方法
一个 给List 添加 Class<?> 的 skipMethodVerificationFor方法
一个给List添加SubscriberInfoIndex类型对象的 addIndex 方法
另外有 初始化外面EventBus对象的 installDefaultEventBus() 和 build() 方法
总体，就是设置boolean值，添加List对象的一个类
register(Object subscriber) 和 unregister(Object subscriber)
在外部使用的时候，我们最直接的，除了getDefault()这个单例以外
就是 register 和 unregister了
register
public void register(Object subscriber) {
Class<?> subscriberClass = subscriber.getClass();
List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriberClass);
synchronized (this) {
for (SubscriberMethod subscriberMethod : subscriberMethods) {
subscribe(subscriber, subscriberMethod);
}
}
}
代码内容，也很好理解
- 通过传入的类（Activity中，一般写的是this，也就是Activity本身）
- 得到对应的 Class<?> 对象， 再通过 SubscriberMethodFinder对象（下一篇一起分析这个类）去得到 一个 SubscriberMethod的List
- 把对应的List放入到一个容器中（应该用于之后通知的过程中，判断是否响应）
unregister
/** Unregisters the given subscriber from all event classes. */
public synchronized void unregister(Object subscriber) {
List<Class<?>> subscribedTypes = typesBySubscriber.get(subscriber);
if (subscribedTypes != null) {
for (Class<?> eventType : subscribedTypes) {
unsubscribeByEventType(subscriber, eventType);
}
typesBySubscriber.remove(subscriber);
} else {
Log.w(TAG, "Subscriber to unregister was not registered before: " + subscriber.getClass());
}
}
这里也比较好理解，通过容器，拿到对应的Class<?> 的List
也就是某个Activity或者Fragment中，对应的注解类型
循环去遍历，最后在容器Map<Object, List<Class<?>>> typesBySubscriber 中
remove掉对应的key，也就是Activity或者Fragment中所有注解的方法
post方法
我们知道，对应的值，是通过post去完成的
这里 用 ThreadLocal的线程包装类，去完成对应的线程记录和操作
对应的泛型PostingThreadState对象，记录对应的信息，将对应的线程放入一个List中
通过对应的状态，判断Looper.getMainLooper() == Looper.myLooper() 是否是主线程等操作， 将状态存入PostingThreadState的属性中
最后，遍历容器中的Event，
最后通过存储的Subscription中的subscriberMethod的method，反射去invoke调用方法。
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