EventBus 3之原始碼分析
eventbus 2的原始碼分析:https://blog.csdn.net/qq_35559358/article/details/74295870
請看本篇的朋友先看2從更基礎更詳細的地方理解,篇末將加入2個版本原始碼中最大不同實現的對比,新人菜鳥,請不要罵太凶。
本篇的分析和eventbus 2有很多相同的,借用原作者的部落格,說明大部分邏輯。
轉載自:
https://xudeveloper.github.io/2018/01/20/EventBus%203.1.1%20%E6%BA%90%E7%A0%81%E8%A7%A3%E6%9E%90/
一、本文需要解決的問題
我研究EventBus原始碼的目的是解決以下幾個我在使用過程中所思考的問題:
- 這個框架涉及到一種設計模式叫做觀察者模式,什麼是觀察者模式?
- 事件如何進行定義,有沒有相關限制?
- 觀察者繫結觀察事件的時候,繫結方法的命名有限制嗎?
- 事件傳送和接收的原理?
二、初步使用
為了研究原始碼的方便,我寫了一個簡單的demo。
定義事件
TestEvent.java:
public class TestEvent {
private String msg;
public String getMsg() {
return msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
}
主Activity
MainActivity.java:
public class MainActivity extends AppCompatActivity { private Button button; private TextView textView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = findViewById(R.id.button); textView = findViewById(R.id.text); EventBus.getDefault().register(this); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { TestEvent event = new TestEvent(); event.setMsg("已接收到事件!"); EventBus.getDefault().post(event); } }); } @Subscribe(threadMode = ThreadMode.MAIN) public void onTestEvent(TestEvent event) { textView.setText(event.getMsg()); } @Override protected void onDestroy() { EventBus.getDefault().unregister(this); super.onDestroy(); } }
執行效果
三、原始碼分析
關於觀察者模式
- 簡介:觀察者模式是設計模式中的一種。它是為了定義物件間的一種一對多的依賴關係,即當一個物件的狀態發生改變時,所有依賴於它的物件都得到通知並被自動更新。
- 如何使用:這裡傳送門有相關的demo,這裡不再詳述。
- 重點:在這個模式中主要包含兩個重要的角色:釋出者和訂閱者(又稱觀察者)。對應EventBus來說,釋出者即傳送訊息的一方(即呼叫EventBus.getDefault().post(event)的一方),訂閱者即接收訊息的一方(即呼叫EventBus.getDefault().register()的一方)。
我們已經解決了第一個問題~
關於事件
這裡指的事件其實是一個泛泛的統稱,指的是一個概念上的東西(當時我還以為一定要以啥Event命名…),通過查閱官方文件,我知道事件的命名格式並沒有任何要求,你可以定義一個物件作為事件,也可以傳送基本資料型別如int,String等作為一個事件。後續的原始碼分析我也會再次證明一下。
具體分析
從函式入口開始分析:
1.EventBus#getDefault():
public static EventBus getDefault() {
if (defaultInstance == null) {
synchronized (EventBus.class) {
if (defaultInstance == null) {
defaultInstance = new EventBus();
}
}
}
return defaultInstance;
}
這裡就是採用雙重校驗並加鎖的單例模式生成EventBus例項。
public void register(Object subscriber) {
Class<?> subscriberClass = subscriber.getClass();
List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriberClass);
synchronized (this) {
for (SubscriberMethod subscriberMethod : subscriberMethods) {
subscribe(subscriber, subscriberMethod);
}
}
}
由於我們傳入的為this,即MainActivity的例項,所以第一行程式碼獲取了訂閱者的class物件,然後會找出所有訂閱的方法。我們看一下第二行的邏輯。
SubscriberMethodFinder#findSubscriberMethods():
List<SubscriberMethod> findSubscriberMethods(Class<?> subscriberClass) {
List<SubscriberMethod> subscriberMethods = METHOD_CACHE.get(subscriberClass);
if (subscriberMethods != null) {
return subscriberMethods;
}
if (ignoreGeneratedIndex) {
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 {
METHOD_CACHE.put(subscriberClass, subscriberMethods);
return subscriberMethods;
}
}
分析:
- 如果快取中有對應class的訂閱方法列表,則直接返回,這裡我們是第一次建立,所以此時subscriberMethods為空;
- 接下來會有一個引數判斷,通過檢視前面的建立過程,ignoreGeneratedIndex預設為false,進入else程式碼塊,後面生成subscriberMethods成功的話會加入到快取中,失敗的話會throw異常。
2.SubscriberMethodFinder#findUsingInfo():
private List<SubscriberMethod> findUsingInfo(Class<?> subscriberClass) {
// 2.1
FindState findState = prepareFindState();
findState.initForSubscriber(subscriberClass);
// 2.2
while (findState.clazz != null) {
findState.subscriberInfo = getSubscriberInfo(findState);
if (findState.subscriberInfo != null) {
SubscriberMethod[] array = findState.subscriberInfo.getSubscriberMethods();
for (SubscriberMethod subscriberMethod: array) {
if (findState.checkAdd(subscriberMethod.method, subscriberMethod.eventType)) {
findState.subscriberMethods.add(subscriberMethod);
}
}
} else {
// 2.3
findUsingReflectionInSingleClass(findState);
}
findState.moveToSuperclass();
}
// 2.4
return getMethodsAndRelease(findState);
}
2.1 SubscriberMethodFinder#prepareFindState():
private static final FindState[] FIND_STATE_POOL = new FindState[POOL_SIZE];
private FindState prepareFindState() {
synchronized(FIND_STATE_POOL) {
for (int i = 0; i < POOL_SIZE; i++) {
FindState state = FIND_STATE_POOL[i];
if (state != null) {
FIND_STATE_POOL[i] = null;
return state;
}
}
}
return new FindState();
}
這個方法是建立一個新的FindState類,通過兩種方法獲取,一種是從FIND_STATE_POOL即FindState池中取出可用的FindState,如果沒有的話,則通過第二種方式:直接new一個新的FindState物件。
FindState#initForSubscriber():
static class FindState {
// 省略程式碼
void initForSubscriber(Class<?> subscriberClass) {
this.subscriberClass = clazz = subscriberClass;
skipSuperClasses = false;
subscriberInfo = null;
}
// 省略程式碼
}
FindState類是SubscriberMethodFinder的內部類,這個方法主要做一個初始化的工作。
2.2 SubscriberMethodFinder#getSubscriberInfo():
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;
}
這裡由於初始化的時候,findState.subscriberInfo和subscriberInfoIndexes為空,所以這裡直接返回null,後續我們可以再回到這裡看看subscriberInfo有什麼作用。
2.3 SubscriberMethodFinder#findUsingReflectionInSingleClass():
private void findUsingReflectionInSingleClass(FindState findState) {
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;
}
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");
}
}
}
這個方法的邏輯是:通過反射的方式獲取訂閱者類中的所有宣告方法,然後在這些方法裡面尋找以@Subscribe作為註解的方法進行處理(!!!部分的程式碼),先經過一輪檢查,看看findState.subscriberMethods是否存在,如果沒有的話,將方法名,threadMode,優先順序,是否為sticky方法封裝為SubscriberMethod物件,新增到subscriberMethods列表中。
什麼是sticky event?
sticky event,中文名為粘性事件。普通事件是先註冊,然後傳送事件才能收到;而粘性事件,在傳送事件之後再訂閱該事件也能收到。此外,粘性事件會儲存在記憶體中,每次進入都會去記憶體中查詢獲取最新的粘性事件,除非你手動解除註冊。
在這裡我們解決了第二個和第三個問題,方法的命名並沒有任何要求,只是加上@Subscribe註解即可!同時事件的命名也沒有任何要求!
之後這個while迴圈會繼續檢查父類,當然遇到系統相關的類時會自動跳過,以提升效能。
2.4 SubscriberMethodFinder#getMethodsAndRelease
private List<SubscriberMethod> getMethodsAndRelease(FindState findState) {
List<SubscriberMethod> subscriberMethods = new ArrayList<>(findState.subscriberMethods);
findState.recycle();
synchronized(FIND_STATE_POOL) {
for (int i = 0; i < POOL_SIZE; i++) {
if (FIND_STATE_POOL[i] == null) {
FIND_STATE_POOL[i] = findState;
break;
}
}
}
return subscriberMethods;
}
這裡將subscriberMethods列表直接返回,同時會把findState做相應處理,儲存在FindState池中,方便下一次使用,提高效能。
- EventBus#subscribe():返回subscriberMethods之後,register方法的最後會呼叫subscribe方法:
public void register(Object subscriber) {
Class<?> subscriberClass = subscriber.getClass();
List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriberClass);
synchronized (this) {
for (SubscriberMethod subscriberMethod : subscriberMethods) {
subscribe(subscriber, subscriberMethod);
}
}
}
private void subscribe(Object subscriber, SubscriberMethod subscriberMethod) {
Class<?> eventType = subscriberMethod.eventType;
Subscription newSubscription = new Subscription(subscriber, subscriberMethod);
CopyOnWriteArrayList<Subscription> subscriptions = subscriptionsByEventType.get(eventType);
if (subscriptions == null) {
subscriptions = new CopyOnWriteArrayList <> ();
subscriptionsByEventType.put(eventType, subscriptions);
} else {
if (subscriptions.contains(newSubscription)) {
throw new EventBusException("Subscriber " + subscriber.getClass() + " already registered to event " + eventType);
}
}
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);
}
}
}
分析:
- 首先,根據subscriberMethod.eventType(在Demo裡面指的是TestEvent),在subscriptionsByEventType去查詢一個CopyOnWriteArrayList ,如果沒有則建立一個新的CopyOnWriteArrayList;
- 然後將這個CopyOnWriteArrayList放入subscriptionsByEventType中,這裡的subscriptionsByEventType是一個Map,key為eventType,value為CopyOnWriteArrayList,這個Map非常重要,後續還會用到它;
- 接下來,就是新增newSubscription,它屬於Subscription類,裡面包含著subscriber和subscriberMethod等資訊,同時這裡有一個優先順序的判斷,說明它是按照優先順序新增的。優先順序越高,會插到在當前List靠前面的位置;
- typesBySubscriber這個類也是一個Map,key為subscriber,value為subscribedEvents,即所有的eventType列表,這個類我找了一下,發現在EventBus#isRegister()方法中有用到,應該是用來判斷這個Subscriber是否已被註冊過。然後將當前的eventType新增到subscribedEvents中;
- 最後,判斷是否是sticky。如果是sticky事件的話,到最後會呼叫checkPostStickyEventToSubscription()方法。
這裡其實就是將所有含@Subscribe註解的訂閱方法最終儲存在subscriptionsByEventType中。
- EventBus#checkPostStickyEventToSubscription():
private void checkPostStickyEventToSubscription(Subscription newSubscription, Object stickyEvent) { if (stickyEvent != null) { // If the subscriber is trying to abort the event, it will fail (event is not tracked in posting state) // --> Strange corner case, which we don't take care of here. postToSubscription(newSubscription, stickyEvent, isMainThread()); } }
接下來,我們重點看post()和postToSubscription()方法。post事件相當於把事件傳送出去,我們看看訂閱者是如何接收到事件的。
private void checkPostStickyEventToSubscription(Subscription newSubscription, Object stickyEvent) {
if (stickyEvent != null) {
// If the subscriber is trying to abort the event, it will fail (event is not tracked in posting state)
// --> Strange corner case, which we don't take care of here.
postToSubscription(newSubscription, stickyEvent, isMainThread());
}
}
接下來,我們重點看post()和postToSubscription()方法。post事件相當於把事件傳送出去,我們看看訂閱者是如何接收到事件的。
- EventBus#post():
/** Posts the given event to the event bus. */ public void post(Object event) { // 5.1 PostingThreadState postingState = currentPostingThreadState.get(); List <Object> eventQueue = postingState.eventQueue; eventQueue.add(event); // 5.2 if (!postingState.isPosting) { postingState.isMainThread = isMainThread(); postingState.isPosting = true; if (postingState.canceled) { throw new EventBusException("Internal error. Abort state was not reset"); } try { while (!eventQueue.isEmpty()) { postSingleEvent(eventQueue.remove(0), postingState); } } finally { postingState.isPosting = false; postingState.isMainThread = false; } } }
5.1 程式碼段分析
- currentPostingThreadState是一個ThreadLocal型別的,裡面儲存了PostingThreadState,而PostingThreadState中包含了一個eventQueue和其他一些標誌位;
- 然後把傳入的event,儲存到了當前執行緒中的一個變數PostingThreadState的eventQueue中。
private final ThreadLocal <PostingThreadState> currentPostingThreadState = new ThreadLocal <PostingThreadState> () { @Override protected PostingThreadState initialValue() { return new PostingThreadState(); } }; /** For ThreadLocal, much faster to set (and get multiple values). */ final static class PostingThreadState { final List <Object> eventQueue = new ArrayList<>(); boolean isPosting; boolean isMainThread; Subscription subscription; Object event; boolean canceled; }
5.2 程式碼段分析
- 這裡涉及到兩個標誌位,第一個是isMainThread,判斷是否為UI執行緒;第二個是isPosting,作用是防止方法多次呼叫。
- 最後呼叫到postSingleEvent()方法
- EventBus#postSingleEvent():
private void postSingleEvent(Object event, PostingThreadState postingState) throws Error { Class<?> eventClass = event.getClass(); boolean subscriptionFound = false; if (eventInheritance) { List<Class<?>> eventTypes = lookupAllEventTypes(eventClass); int countTypes = eventTypes.size(); for (int h = 0; h < countTypes; h++) { Class<?> clazz = eventTypes.get(h); subscriptionFound |= postSingleEventForEventType(event, postingState, clazz); } } else { subscriptionFound = postSingleEventForEventType(event, postingState, eventClass); } if (!subscriptionFound) { if (logNoSubscriberMessages) { logger.log(Level.FINE, "No subscribers registered for event " + eventClass); } if (sendNoSubscriberEvent && eventClass != NoSubscriberEvent.class && eventClass != SubscriberExceptionEvent.class) { post(new NoSubscriberEvent(this, event)); } } } 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; }
- 這裡會首先取出Event的class型別,然後有一個標誌位eventInheritance判斷,預設為true,作用在相關程式碼註釋有說,如果設為true的話,它會拿到Event父類的class型別,設為false,可以在一定程度上提高效能;
- 接下來是lookupAllEventTypes()方法,就是取出Event及其父類和介面的class列表,當然重複取的話會影響效能,所以它也有做一個eventTypesCache的快取,這樣不用都重複呼叫getClass()方法。
- 然後是postSingleEventForEventType()方法,這裡就很清晰了,就是直接根據Event型別從subscriptionsByEventType中取出對應的subscriptions,與之前的程式碼對應,最後呼叫postToSubscription()方法。
- EventBus#postToSubscription():
private void postToSubscription(Subscription subscription, Object event, boolean isMainThread) { switch (subscription.subscriberMethod.threadMode) { case POSTING: invokeSubscriber(subscription, event); break; case MAIN: if (isMainThread) { invokeSubscriber(subscription, event); } else { mainThreadPoster.enqueue(subscription, event); } break; case MAIN_ORDERED: if (mainThreadPoster != null) { mainThreadPoster.enqueue(subscription, event); } else { // temporary: technically not correct as poster not decoupled from subscriber invokeSubscriber(subscription, event); } break; case BACKGROUND: if (isMainThread) { backgroundPoster.enqueue(subscription, event); } else { invokeSubscriber(subscription, event); } break; case ASYNC: asyncPoster.enqueue(subscription, event); break; default: throw new IllegalStateException("Unknown thread mode: " + subscription.subscriberMethod.threadMode); } }
這裡會根據threadMode來判斷應該在哪個執行緒中去執行方法:
- POSTING:執行invokeSubscriber()方法,就是直接反射呼叫;
- MAIN:首先去判斷當前是否在UI執行緒,如果是的話則直接反射呼叫,否則呼叫mainThreadPoster#enqueue(),即把當前的方法加入到佇列之中,然後通過handler去傳送一個訊息,在handler的handleMessage中去執行方法。具體邏輯在HandlerPoster.java中;
- MAIN_ORDERED:與上面邏輯類似,順序執行我們的方法;
- BACKGROUND:判斷當前是否在UI執行緒,如果不是的話直接反射呼叫,是的話通過backgroundPoster.enqueue()將方法加入到後臺的一個佇列,最後通過執行緒池去執行;
- ASYNC:與BACKGROUND的邏輯類似,將任務加入到後臺的一個佇列,最終由Eventbus中的一個執行緒池去呼叫,這裡的執行緒池與BACKGROUND邏輯中的執行緒池用的是同一個。
補充:BACKGROUND和ASYNC有什麼區別呢?
BACKGROUND中的任務是一個接著一個的去呼叫,而ASYNC則會即時非同步執行,具體的可以對比AsyncPoster.java和BackgroundPoster.java兩者程式碼實現的區別。
到這裡,我們就解決了第四個問題,事件的傳送和接收,主要是通過subscriptionsByEventType這個非常重要的列表,我們將訂閱即接收事件的方法儲存在這個列表,釋出事件的時候在列表中查詢出相對應的方法並執行~
注意:
不同點:其實整體思路除了在版本3種使用註解獲取事件方法名替代以前的遍歷指定類的onEventXX方法名並存入subscriptionsByEventType map裡之外並無本質上的變化。
不過他的好處在於你指定註解 @Subscribe(threadMode = ThreadMode.MAIN)等註解去解放強制性的方法名繫結,可以試命名更加方便onEvent(),onEventMainThread(),onEventBackgroundThread(),onEventAsync()
版本2:
List<SubscriberMethod> findSubscriberMethods(Class<?> subscriberClass, String eventMethodName) {
String key = subscriberClass.getName() + '.' + eventMethodName;
List<SubscriberMethod> subscriberMethods;
synchronized (methodCache) {
subscriberMethods = methodCache.get(key);
}
if (subscriberMethods != null) {
return subscriberMethods;
}
subscriberMethods = new ArrayList<SubscriberMethod>();
Class<?> clazz = subscriberClass;
HashSet<String> eventTypesFound = new HashSet<String>();
StringBuilder methodKeyBuilder = new StringBuilder();
while (clazz != null) {
String name = clazz.getName();
if (name.startsWith("java.") || name.startsWith("javax.") || name.startsWith("android.")) {
// Skip system classes, this just degrades performance
break;
}
// Starting with EventBus 2.2 we enforced methods to be public (might change with annotations again)
Method[] methods = clazz.getMethods();
for (Method method : methods) {
String methodName = method.getName();
if (methodName.startsWith(eventMethodName)) {
int modifiers = method.getModifiers();
if ((modifiers & Modifier.PUBLIC) != 0 && (modifiers & MODIFIERS_IGNORE) == 0) {
Class<?>[] parameterTypes = method.getParameterTypes();
if (parameterTypes.length == 1) {
String modifierString = methodName.substring(eventMethodName.length());
ThreadMode threadMode;
if (modifierString.length() == 0) {
threadMode = ThreadMode.PostThread;
} else if (modifierString.equals("MainThread")) {
threadMode = ThreadMode.MainThread;
} else if (modifierString.equals("BackgroundThread")) {
threadMode = ThreadMode.BackgroundThread;
} else if (modifierString.equals("Async")) {
threadMode = ThreadMode.Async;
} else {
if (skipMethodVerificationForClasses.containsKey(clazz)) {
continue;
} else {
throw new EventBusException("Illegal onEvent method, check for typos: " + method);
}
}
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
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);
}
}
}
clazz = clazz.getSuperclass();
}
if (subscriberMethods.isEmpty()) {
throw new EventBusException("Subscriber " + subscriberClass + " has no public methods called "
+ eventMethodName);
} else {
synchronized (methodCache) {
methodCache.put(key, subscriberMethods);
}
return subscriberMethods;
}
}
版本3:
private void findUsingReflectionInSingleClass(FindState findState) {
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;
}
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");
}
}
}
其次的不同點,加入了狀態標識和一些快取處理,使得邏輯和效能都有一定的優化……