EventBus源码分析

s###创建EventBus
EventBus.getDefault() 通过这个方法获取一个默认的对象

 public static EventBus getDefault() {        if (defaultInstance == null) {            synchronized (EventBus.class) {                if (defaultInstance == null) {                    defaultInstance = new EventBus();                }            }        }        return defaultInstance;    }

使用单例设计模式来

private static final EventBusBuilder DEFAULT_BUILDER = new EventBusBuilder();  public EventBus() {        this(DEFAULT_BUILDER);    }

默认的是一个Build的内部类。主要看看里面的参数

 EventBus(EventBusBuilder builder) {      //订阅事件集合        subscriptionsByEventType = new HashMap<>();        //粘性事件         stickyEvents = new ConcurrentHashMap<>();           //订阅事件集合        typesBySubscriber = new HashMap<>();//主线程处理事件        mainThreadPoster = new HandlerPoster(this, Looper.getMainLooper(), 10);        //background        backgroundPoster = new BackgroundPoster(this);      //  异步线程        asyncPoster = new AsyncPoster(this);        indexCount = builder.subscriberInfoIndexes != null ? builder.subscriberInfoIndexes.size() : 0;        //订阅者响应函数信息存储和查找类        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;        //线程池对象        executorService = builder.executorService;    }

配置完基本的属性，来看注册

public void register(Object subscriber) {//得到这个注册类的class对象        Class<?> subscriberClass = subscriber.getClass();        //用于搜索这个注册对象所有注册的事件，以及这个事件的一些属性，比如运行线程，优先级，是否粘性。在订阅的类通过注解的方式来设置。        //这个方法返回一个注册方法的集合，        List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriberClass);        synchronized (this) {            for (SubscriberMethod subscriberMethod : subscriberMethods) {                subscribe(subscriber, subscriberMethod);            }        }    }

SubscriberMethodFinder的实现

 List<SubscriberMethod> findSubscriberMethods(Class<?> subscriberClass) { //首先判断缓存里面有没有存在，存在直接获取        List<SubscriberMethod> subscriberMethods = METHOD_CACHE.get(subscriberClass);        if (subscriberMethods != null) {            return subscriberMethods;        }        if (ignoreGeneratedIndex) {        //主要是这个方法，通过反射来获取注册类的数据            subscriberMethods = findUsingReflection(subscriberClass);        } else {            subscriberMethods = findUsingInfo(subscriberClass);        }        if (subscriberMethods.isEmpty()) {            throw new EventBusException("Subscriber " + subscriberClass                    + " and its super classes have no public methods with the @Subscribe annotation");        } else {        //根据类的class 来缓存注册方法            METHOD_CACHE.put(subscriberClass, subscriberMethods);            return subscriberMethods;        }    }

 private List<SubscriberMethod> findUsingReflection(Class<?> subscriberClass) { //        FindState findState = prepareFindState();        findState.initForSubscriber(subscriberClass);        while (findState.clazz != null) {            findUsingReflectionInSingleClass(findState);            findState.moveToSuperclass();        }        return getMethodsAndRelease(findState);    }

最主要的通过注解获取方法

   private void findUsingReflectionInSingleClass(FindState findState) {      //类的方法        Method[] methods;        try {            // This is faster than getMethods, especially when subscribers are fat classes like Activities            methods = findState.clazz.getDeclaredMethods();        } catch (Throwable th) {            // Workaround for java.lang.NoClassDefFoundError, see https://github.com/greenrobot/EventBus/issues/149            methods = findState.clazz.getMethods();            findState.skipSuperClasses = true;        }        //遍历方法        for (Method method : methods) {            int modifiers = method.getModifiers();            if ((modifiers & Modifier.PUBLIC) != 0 && (modifiers & MODIFIERS_IGNORE) == 0) {                Class<?>[] parameterTypes = method.getParameterTypes();                if (parameterTypes.length == 1) {                    Subscribe subscribeAnnotation = method.getAnnotation(Subscribe.class);                    if (subscribeAnnotation != null) {                        Class<?> eventType = parameterTypes[0];                        if (findState.checkAdd(method, eventType)) {                            ThreadMode threadMode = subscribeAnnotation.threadMode();                     //添加方法       findState.subscriberMethods.add(new SubscriberMethod(method, eventType, threadMode,                                    subscribeAnnotation.priority(), subscribeAnnotation.sticky()));                        }                    }                } else if (strictMethodVerification && method.isAnnotationPresent(Subscribe.class)) {                    String methodName = method.getDeclaringClass().getName() + "." + method.getName();                    throw new EventBusException("@Subscribe method " + methodName +                            "must have exactly 1 parameter but has " + parameterTypes.length);                }            } else if (strictMethodVerification && method.isAnnotationPresent(Subscribe.class)) {                String methodName = method.getDeclaringClass().getName() + "." + method.getName();                throw new EventBusException(methodName +                        " is a illegal @Subscribe method: must be public, non-static, and non-abstract");            }        }    }

到此为止SubscriberMethod都已经被保存，通过这个方法getMethodsAndRelease返回， 通过 METHOD_CACHE.put(subscriberClass, subscriberMethods);缓存注解方法。

subscribe()方法的实现

水平太菜实在看不下去了，等以后在慢慢学吧