EventBus的简单使用与原理

EventBus是一款针对Android优化的发布/订阅事件总线。主要功能是替代Intent,Handler,BroadCast在Fragment，Activity，Service，线程之间传递消息.优势是开销小，代码更优雅。以及将发送者和接收者解耦。

部分源码：

//经过反射，获取到订阅者的全部方法
			Method[] methods = clazz.getMethods();
			for (Method method : methods) { String methodName = method.getName(); //只找以onEvent开头的方法 if (methodName.startsWith(eventMethodName)) { int modifiers = method.getModifiers(); //判断订阅者是不是public的,而且是否有修饰符，看来订阅者只能是public的，而且不能被final，static等修饰 if ((modifiers & Modifier.PUBLIC) != 0 && (modifiers & MODIFIERS_IGNORE) == 0) { //得到订阅函数的参数 Class<?>[] parameterTypes = method.getParameterTypes(); //看了参数的个数只能是1个 if (parameterTypes.length == 1) { //获取onEvent后面的部分 String modifierString = methodName.substring(eventMethodName.length()); ThreadMode threadMode; if (modifierString.length() == 0) { //订阅函数为onEvnet //记录线程模型为PostThread,意义就是发布事件和接收事件在同一个线程执行，详细能够参考我对于四个订阅函数不一样点分析 threadMode = ThreadMode.PostThread; } else if (modifierString.equals("MainThread")) { //对应onEventMainThread threadMode = ThreadMode.MainThread; } else if (modifierString.equals("BackgroundThread")) { //对应onEventBackgrondThread threadMode = ThreadMode.BackgroundThread; } else if (modifierString.equals("Async")) { //对应onEventAsync threadMode = ThreadMode.Async; } else { if (skipMethodVerificationForClasses.containsKey(clazz)) { continue; } else { throw new EventBusException("Illegal onEvent method, check for typos: " + method); } } //获取参数类型，其实就是接收事件的类型 Class<?> eventType = parameterTypes[0]; methodKeyBuilder.setLength(0); methodKeyBuilder.append(methodName); methodKeyBuilder.append('>').append(eventType.getName()); String methodKey = methodKeyBuilder.toString(); if (eventTypesFound.add(methodKey)) { // Only add if not already found in a sub class //封装一个订阅方法对象，这个对象包含Method对象，threadMode对象，eventType对象 subscriberMethods.add(new SubscriberMethod(method, threadMode, eventType)); } } } else if (!skipMethodVerificationForClasses.containsKey(clazz)) { Log.d(EventBus.TAG, "Skipping method (not public, static or abstract): " + clazz + "." + methodName); } } } //看了还会遍历父类的订阅函数 clazz = clazz.getSuperclass(); } //最后加入缓存，第二次使用直接从缓存拿 if (subscriberMethods.isEmpty()) { throw new EventBusException("Subscriber " + subscriberClass + " has no public methods called " + eventMethodName); } else { synchronized (methodCache) { methodCache.put(key, subscriberMethods); } return subscriberMethods; } }

更多源码见：http://www.tuicool.com/articles/jUvyUjB