快速上手

注册方法：

反注册方法：

接收回调：

发送事件：

package com.lzy.evbusdemo;public class MyEvent {private String msg;public MyEvent(String msg) {this.msg = msg;}public String getMsg() {return msg;}
}

其他两个主文件

package com.lzy.evbusdemo;import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.widget.TextView;public class MainActivity extends Activity {private TextView tvShowTextView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);tvShowTextView = (TextView) findViewById(R.id.tvShow);EventBus.getDefault().register(this);// 订阅}public void jumpTo(View view) {startActivity(new Intent(this, OtherActivity.class));}@Overrideprotected void onDestroy() {super.onDestroy();EventBus.getDefault().unregister(this);}/*** 接收* */@Subscribepublic void onEvent(MyEvent event) {Log.i("Main", "Main - onEvent: " + event.getMsg());}@Subscribepublic void onEventAsync(MyEvent event) {Log.i("Main", "Main - onEventAsync: " + event.getMsg());}@Subscribepublic void onEventBackgroundThread(MyEvent event) {Log.i("Main", "Main - onEventBackgroundThread: " + event.getMsg());}@Subscribepublic void onEventMainThread(MyEvent event) {Log.i("Main", "Main - onEventMainThread: " + event.getMsg());tvShowTextView.setText(event.getMsg());}
}

package com.lzy.evbusdemo;import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.TextView;public class OtherActivity extends Activity {private TextView textView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_other);EventBus.getDefault().register(this);textView = new TextView(this);textView.setText(getResources().getString(R.string.Text_Other_Activity));addContentView(textView, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));textView.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {EventBus.getDefault().post(new MyEvent("LD"));// 发布}});}@Overrideprotected void onDestroy() {super.onDestroy();EventBus.getDefault().unregister(this);}/*** 接收* */@Subscribepublic void onEvent(MyEvent event) {Log.i("Other", "Other - onEvent: " + event.getMsg());}@Subscribepublic void onEventAsync(MyEvent event) {Log.i("Other", "Other - onEventAsync: " + event.getMsg());}@Subscribepublic void onEventBackgroundThread(MyEvent event) {Log.i("Other", "Other - onEventBackgroundThread: " + event.getMsg());}@Subscribepublic void onEventMainThread(MyEvent event) {Log.i("Other", "Other - onEventMainThread: " + event.getMsg());textView.setText(event.getMsg());}
}

通过以上我们就实现了订阅与分发，只要是订阅者，在发送的时候就都能收到了。不过这几个方法我们应该使用哪个呢，还有他们是怎么调用的呢？上述代码调试信息如下

04-08 06:18:47.657: I/Main(1570): Main - onEvent
04-08 06:18:47.657: I/Main(1570): Main - onEventAsync
04-08 06:18:47.661: I/Main(1570): Main - onEventBackgroundThread
04-08 06:18:47.661: I/Main(1570): Main - onEventMainThread
04-08 06:18:47.661: I/Other(1570): Other - onEvent
04-08 06:18:47.661: I/Other(1570): Other - onEventAsync
04-08 06:18:47.661: I/Other(1570): Other - onEventBackgroundThread
04-08 06:18:47.661: I/Other(1570): Other - onEventMainThread

怎么都执行了呢？？？？？我们注意到注解中有“@Subscribe”，我们了解过注解（ http://blog.csdn.net/zhangweiwtmdbf/article/details/30246149）这是在回调中去找EvetBus的接收者，这应该不是，那只有里面的参数了，对试试~  我尝试创建了另外三个事件MyEvent1 ，MyEvent2 ，MyEvent3，代码和MyEvent处理一样。然后分发不同的消息，这四个回调分别去接收不同的消息，最终代码变成如此：

package com.lzy.evbusdemo;import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.widget.TextView;public class MainActivity extends Activity {private TextView tvShowTextView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);tvShowTextView = (TextView) findViewById(R.id.tvShow);EventBus.getDefault().register(this);// 订阅}public void jumpTo(View view) {startActivity(new Intent(this, OtherActivity.class));}@Overrideprotected void onDestroy() {super.onDestroy();EventBus.getDefault().unregister(this);}/*** 接收* */@Subscribepublic void onEvent(MyEvent event) {Log.i("Main", "Main - onEvent: " + event.getMsg());}@Subscribepublic void onEventAsync(MyEvent1 event) {Log.i("Main", "Main - onEventAsync: " + event.getMsg());}@Subscribepublic void onEventBackgroundThread(MyEvent2 event) {Log.i("Main", "Main - onEventBackgroundThread: " + event.getMsg());}@Subscribepublic void onEventMainThread(MyEvent3 event) {Log.i("Main", "Main - onEventMainThread: " + event.getMsg());tvShowTextView.setText(event.getMsg());}
}

package com.lzy.evbusdemo;import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.TextView;public class OtherActivity extends Activity {private TextView textView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_other);EventBus.getDefault().register(this);textView = new TextView(this);textView.setText(getResources().getString(R.string.Text_Other_Activity));addContentView(textView, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));textView.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {EventBus.getDefault().post(new MyEvent("LD"));// 发布EventBus.getDefault().post(new MyEvent1("DCM"));EventBus.getDefault().post(new MyEvent2("HY"));EventBus.getDefault().post(new MyEvent3("JSM"));}});}@Overrideprotected void onDestroy() {super.onDestroy();EventBus.getDefault().unregister(this);}/*** 接收* */@Subscribepublic void onEvent(MyEvent event) {Log.i("Other", "Other - onEvent: " + event.getMsg());}@Subscribepublic void onEventAsync(MyEvent3 event) {Log.i("Other", "Other - onEventAsync: " + event.getMsg());}@Subscribepublic void onEventBackgroundThread(MyEvent1 event) {Log.i("Other", "Other - onEventBackgroundThread: " + event.getMsg());}@Subscribepublic void onEventMainThread(MyEvent2 event) {Log.i("Other", "Other - onEventMainThread: " + event.getMsg());textView.setText(event.getMsg());}
}

运行一下：

04-08 07:18:58.717: I/Main(2008): Main - onEvent: LD ----------------------------------------- MyEvent
04-08 07:18:58.717: I/Other(2008): Other - onEvent: LD ----------------------------------------- MyEvent
04-08 07:18:58.717: I/Main(2008): Main - onEventAsync: DCM ----------------------------------------- MyEvent1
04-08 07:18:58.717: I/Other(2008): Other - onEventBackgroundThread: DCM ----------------------------------------- MyEvent1
04-08 07:18:58.717: I/Main(2008): Main - onEventBackgroundThread: HY ----------------------------------------- MyEvent2
04-08 07:18:58.717: I/Other(2008): Other - onEventMainThread: HY ----------------------------------------- MyEvent2
04-08 07:18:58.717: I/Main(2008): Main - onEventMainThread: JSM ----------------------------------------- MyEvent3
04-08 07:18:58.717: I/Other(2008): Other - onEventAsync: JSM ----------------------------------------- MyEvent3

发现果真如此。

至此，基本使用就是这些，我们继续往下看原理：

上面已经说了回调是通过注解的方式来找到回调的，那肯定要先告诉EventBus谁是接收者吧，也就是注册register方法。

注册即往List<SubscriberMethod> subscriberMethods中添加方法对象，核心在findSubscriberMethods方法，我们先不看他怎么找的，因为在回调的时候也会通过这个来找，我们先看怎么加入的（到注册表中）：subscribe(subscriber, subscriberMethod);

int size = subscriptions.size();for (int i = 0; i <= size; i++) {if (i == size || subscriberMethod.priority > subscriptions.get(i).subscriberMethod.priority) {subscriptions.add(i, newSubscription);break;}}List<Class<?>> subscribedEvents = typesBySubscriber.get(subscriber);if (subscribedEvents == null) {subscribedEvents = new ArrayList<>();typesBySubscriber.put(subscriber, subscribedEvents);}subscribedEvents.add(eventType);if (subscriberMethod.sticky) {if (eventInheritance) {// Existing sticky events of all subclasses of eventType have to be considered.// Note: Iterating over all events may be inefficient with lots of sticky events,// thus data structure should be changed to allow a more efficient lookup// (e.g. an additional map storing sub classes of super classes: Class -> List<Class>).Set<Map.Entry<Class<?>, Object>> entries = stickyEvents.entrySet();for (Map.Entry<Class<?>, Object> entry : entries) {Class<?> candidateEventType = entry.getKey();if (eventType.isAssignableFrom(candidateEventType)) {Object stickyEvent = entry.getValue();checkPostStickyEventToSubscription(newSubscription, stickyEvent);}}} else {Object stickyEvent = stickyEvents.get(eventType);checkPostStickyEventToSubscription(newSubscription, stickyEvent);}}

订阅者方法实体是SubscriberMethod，定义了一系列属性

看到了一个subscribedEvents.add(eventType);注册事件类型它是 Class<?>

所以也就验证了那四个回调是通过什么区分的这一论证；

根据循环找出不同类型的事件分开保存。执行肯定是通过Method的invoke方法：

反注册就很简单了，从Map中根据键remove掉

我们回过头看findSubscriberMethods方法

先从方法池中获取方法：List<SubscriberMethod> subscriberMethods = METHOD_CACHE.get(subscriberClass);然后分两种情况

第一种核心：

private void findUsingReflectionInSingleClass(FindState findState) {Method[] methods;try {// This is faster than getMethods, especially when subscribers are fat classes like Activitiesmethods = findState.clazz.getDeclaredMethods();} catch (Throwable th) {// Workaround for java.lang.NoClassDefFoundError, see https://github.com/greenrobot/EventBus/issues/149methods = findState.clazz.getMethods();findState.skipSuperClasses = true;}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();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");}}}

筛选：

第二种核心

private SubscriberInfo getSubscriberInfo(FindState findState) {if (findState.subscriberInfo != null && findState.subscriberInfo.getSuperSubscriberInfo() != null) {SubscriberInfo superclassInfo = findState.subscriberInfo.getSuperSubscriberInfo();if (findState.clazz == superclassInfo.getSubscriberClass()) {return superclassInfo;}}if (subscriberInfoIndexes != null) {for (SubscriberInfoIndex index : subscriberInfoIndexes) {SubscriberInfo info = index.getSubscriberInfo(findState.clazz);if (info != null) {return info;}}}return null;}

返回符合的：

看一下post方法：

初始化队列并添加事件到队列：

PostingThreadState postingState = currentPostingThreadState.get();
List<Object> eventQueue = postingState.eventQueue;
eventQueue.add(event);

然后就一直在寻找可以接收的接受者：

private boolean postSingleEventForEventType(Object event, PostingThreadState postingState, Class<?> eventClass) {CopyOnWriteArrayList<Subscription> subscriptions;synchronized (this) {subscriptions = subscriptionsByEventType.get(eventClass);}if (subscriptions != null && !subscriptions.isEmpty()) {for (Subscription subscription : subscriptions) {postingState.event = event;postingState.subscription = subscription;boolean aborted = false;try {postToSubscription(subscription, event, postingState.isMainThread);aborted = postingState.canceled;} finally {postingState.event = null;postingState.subscription = null;postingState.canceled = false;}if (aborted) {break;}}return true;}return false;}

将对应事件所有的找到后

根据类型去执行方法，也就是发送给所有符合定义的事件的那四个方法类型：

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