Android EventBus源码解析

项目地址：https://github.com/greenrobot/EventBus

这个项目个人感觉就是为了解决回调事件过多的，比方说A函数在做完以后要调用b类的c函数，那我们通常的做法就是定义一个接口然后再A函数所属的类里面注册这个接口。

然后a函数做完以后直接调用这个接口即可。但是这种方法写多了以后确实很麻烦，于是EventBus就是用来解决这种场景的。

和以往一样，我们只解析他的源码，如果你要学习他的用法请自行谷歌。

我们就从register函数开始说起。

1  private synchronized void register(Object subscriber, boolean sticky, int priority) {
2         //这个list就是方法的集合
3         List<SubscriberMethod> subscriberMethods = subscriberMethodFinder.findSubscriberMethods(subscriber.getClass());
4         //这个循环的目的就是为了用  方法对象 来构造 Subscription对象
5         for (SubscriberMethod subscriberMethod : subscriberMethods) {
6             subscribe(subscriber, subscriberMethod, sticky, priority);
7         }
8     }

首先来看一下SubscriberMethod这个类，

 1 /*
 2  * Copyright (C) 2012 Markus Junginger, greenrobot (http://greenrobot.de)
 3  *
 4  * Licensed under the Apache License, Version 2.0 (the "License");
 5  * you may not use this file except in compliance with the License.
 6  * You may obtain a copy of the License at
 7  *
 8  *      http://www.apache.org/licenses/LICENSE-2.0
 9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package de.greenrobot.event;
17 
18 import java.lang.reflect.Method;
19 
20 import android.util.Log;
21 
22 /**
23  * 这个类就是描述方法用的
24  */
25 final class SubscriberMethod {
26     final Method method;
27     final ThreadMode threadMode;
28     final Class<?> eventType;
29     /** Used for efficient comparison */
30     /**
31      * 这个methodString 实际上就是用来描述SubscriberMethod对象的，尤其是在重写的equals方法里 起到关键的作用
32      * 就类似于这种结构
33      * com.example.administrator.eventbustest.ItemDetailFragment#onEventMainThread(com.example.administrator.eventbustest.Item
34      *其实也很好理解就是 包名+类名#方法名(参数的类型
35      * 注意这里参数的类型也是全路径名 包名+类名
36      */
37     String methodString;
38 
39     SubscriberMethod(Method method, ThreadMode threadMode, Class<?> eventType) {
40         this.method = method;
41         this.threadMode = threadMode;
42         this.eventType = eventType;
43     }
44 
45     @Override
46     public boolean equals(Object other) {
47         if (other instanceof SubscriberMethod) {
48             checkMethodString();
49             SubscriberMethod otherSubscriberMethod = (SubscriberMethod) other;
50             otherSubscriberMethod.checkMethodString();
51             // Don't use method.equals because of http://code.google.com/p/android/issues/detail?id=7811#c6
52             return methodString.equals(otherSubscriberMethod.methodString);
53         } else {
54             return false;
55         }
56     }
57 
58     private synchronized void checkMethodString() {
59         if (methodString == null) {
60             // Method.toString has more overhead, just take relevant parts of the method
61             StringBuilder builder = new StringBuilder(64);
62             builder.append(method.getDeclaringClass().getName());
63             builder.append('#').append(method.getName());
64             builder.append('(').append(eventType.getName());
65             methodString = builder.toString();
66         }
67     }
68 
69     @Override
70     public int hashCode() {
71         return method.hashCode();
72     }
73 }

然后我们来看看这个SubscriberMethod对象组成的集合是怎么构造出来的。

 1 List<SubscriberMethod> findSubscriberMethods(Class<?> subscriberClass) {
 2         String key = subscriberClass.getName();
 3         List<SubscriberMethod> subscriberMethods;
 4         synchronized (methodCache) {
 5             subscriberMethods = methodCache.get(key);
 6         }
 7       
 8         if (subscriberMethods != null) {
 9             return subscriberMethods;
10         }
11         subscriberMethods = new ArrayList<SubscriberMethod>();
12         Class<?> clazz = subscriberClass;
13         HashSet<String> eventTypesFound = new HashSet<String>();
14         StringBuilder methodKeyBuilder = new StringBuilder();
15         while (clazz != null) {
16             String name = clazz.getName();
17             //这个地方判断如果是这些类，那么就直接跳出这个while循环
18             //注意name的值 也是包名+类名，所以这里就是过滤掉基础的sdk的那些方法
19             //如果你有引用其他公共lib库的话 你也可以过滤他们的包，
20             if (name.startsWith("java.") || name.startsWith("javax.") || name.startsWith("android.")) {
21                 // Skip system classes, this just degrades performance
22                 break;
23             }
24 
25             // Starting with EventBus 2.2 we enforced methods to be public (might change with annotations again)
26             Method[] methods = clazz.getDeclaredMethods();
27             for (Method method : methods) {
28                 String methodName = method.getName();
29                 Log.e("burning", "methodName == " + methodName);
30                 //只有那些以onEvent开头的方法才是我们需要的
31                 if (methodName.startsWith(ON_EVENT_METHOD_NAME)) {
32                     int modifiers = method.getModifiers();
33                     //注意这个地方判断方法属性的技巧 与 操作
34                     if ((modifiers & Modifier.PUBLIC) != 0 && (modifiers & MODIFIERS_IGNORE) == 0) {
35                         Class<?>[] parameterTypes = method.getParameterTypes();
36                         //如果参数只有一个
37                         if (parameterTypes.length == 1) {
38                             String modifierString = methodName.substring(ON_EVENT_METHOD_NAME.length());
39                             //取ThreadMode
40                             ThreadMode threadMode;
41                             if (modifierString.length() == 0) {
42                                 threadMode = ThreadMode.PostThread;
43                             } else if (modifierString.equals("MainThread")) {
44                                 threadMode = ThreadMode.MainThread;
45                             } else if (modifierString.equals("BackgroundThread")) {
46                                 threadMode = ThreadMode.BackgroundThread;
47                             } else if (modifierString.equals("Async")) {
48                                 threadMode = ThreadMode.Async;
49                             } else {
50                                 if (skipMethodVerificationForClasses.containsKey(clazz)) {
51                                     continue;
52                                 } else {
53                                     throw new EventBusException("Illegal onEvent method, check for typos: " + method);
54                                 }
55                             }
56                             Class<?> eventType = parameterTypes[0];
57                             methodKeyBuilder.setLength(0);
58                             methodKeyBuilder.append(methodName);
59                             methodKeyBuilder.append('>').append(eventType.getName());
60                             //onEventMainThread>java.lang.String
61                             //methodKey就是上面的形式，可以看出来是方法名>参数  的格式
62                             String methodKey = methodKeyBuilder.toString();
64                             //这个地方先去这个hashset里面add这个key，当然了，如果你这个hashset里面已经有这个key
65                             //那必然是add不成功的，只有add成功返回true以后括号内的代码才会得到执行
66                             if (eventTypesFound.add(methodKey)) {
67                                 // Only add if not already found in a sub class
68                                 //这个地方就是构造SubscriberMethod对象放到list里 准备返回
69                                 subscriberMethods.add(new SubscriberMethod(method, threadMode, eventType));
70                             }
71                         }
72                     } else if (!skipMethodVerificationForClasses.containsKey(clazz)) {
73                         Log.d(EventBus.TAG, "Skipping method (not public, static or abstract): " + clazz + "."
74                                 + methodName);
75                     }
76                 }
77             }
78             //这里注意还在大的while循环内，所以你传进去的类自己查完一遍方法以后 还会去找他的父类继续查询方法
79             //一直遍历到父类为 那些java android开头的基类为止！
80             clazz = clazz.getSuperclass();
81 
82         }
83         if (subscriberMethods.isEmpty()) {
84             throw new EventBusException("Subscriber " + subscriberClass + " has no public methods called "
85                     + ON_EVENT_METHOD_NAME);
86         } else {
87             synchronized (methodCache) {
88                 methodCache.put(key, subscriberMethods);
89             }
90             return subscriberMethods;
91         }
92     }

然后我们来看看register函数里面 5-6行那个循环遍历做了什么

首先我们看看这个循环调用的方法：

 1 /**
 2      * @param subscriber       方法所述的类的 包名+类名
 3      * @param subscriberMethod
 4      * @param sticky
 5      * @param priority
 6      */
 7     private void subscribe(Object subscriber, SubscriberMethod subscriberMethod, boolean sticky, int priority) {
 8         //这个eventtype就是方法的参数的类名
 9         Class<?> eventType = subscriberMethod.eventType;
10  
11         CopyOnWriteArrayList<Subscription> subscriptions = subscriptionsByEventType.get(eventType);
12         Subscription newSubscription = new Subscription(subscriber, subscriberMethod, priority);
13         if (subscriptions == null) {
14             subscriptions = new CopyOnWriteArrayList<Subscription>();
15             subscriptionsByEventType.put(eventType, subscriptions);
16         } else {
17             if (subscriptions.contains(newSubscription)) {
18                 throw new EventBusException("Subscriber " + subscriber.getClass() + " already registered to event "
19                         + eventType);
20             }
21         }
22 
23         // Starting with EventBus 2.2 we enforced methods to be public (might change with annotations again)
24         // subscriberMethod.method.setAccessible(true);
25         //这个就是优先级高的位置在前面
26         int size = subscriptions.size();
27         for (int i = 0; i <= size; i++) {
28             if (i == size || newSubscription.priority > subscriptions.get(i).priority) {
29                 subscriptions.add(i, newSubscription);
30                 break;
31             }
32         }
33 
34         List<Class<?>> subscribedEvents = typesBySubscriber.get(subscriber);
35         if (subscribedEvents == null) {
36             subscribedEvents = new ArrayList<Class<?>>();
37             typesBySubscriber.put(subscriber, subscribedEvents);
38         }
39         subscribedEvents.add(eventType);
40 
41         if (sticky) {
42         
43             if (eventInheritance) {
44                 // Existing sticky events of all subclasses of eventType have to be considered.
45                 // Note: Iterating over all events may be inefficient with lots of sticky events,
46                 // thus data structure should be changed to allow a more efficient lookup
47                 // (e.g. an additional map storing sub classes of super classes: Class -> List<Class>).
48                 Set<Map.Entry<Class<?>, Object>> entries = stickyEvents.entrySet();
49                 for (Map.Entry<Class<?>, Object> entry : entries) {
50                     Class<?> candidateEventType = entry.getKey();
51                     if (eventType.isAssignableFrom(candidateEventType)) {
52                         Object stickyEvent = entry.getValue();
53                         checkPostStickyEventToSubscription(newSubscription, stickyEvent);
54                     }
55                 }
56             } else {
57                 Object stickyEvent = stickyEvents.get(eventType);
58                 checkPostStickyEventToSubscription(newSubscription, stickyEvent);
59             }
60         }
61     }

10-13行我们可以看出来这个函数主要是为了构造subscription这个list对象。

  /**
     * 这个map 存储方法的地方 key就是eventType，value就是copyOnWriteArrayList value就是方法的一切
     */
    private final Map<Class<?>, CopyOnWriteArrayList<Subscription>> subscriptionsByEventType;

我们可以看看这个类是什么

 1 /**
 2  * 这个类里面包含有SubscriberMethod类对象，
 3  * subscriber
 4  */
 5 final class Subscription {
 6     //这个实际上就是描述方法所属的类的
 7     final Object subscriber;
 8     //描述方法的类
 9     final SubscriberMethod subscriberMethod;
10     //优先级
11     final int priority;
12     /**
13      * Becomes false as soon as {@link EventBus#unregister(Object)} is called, which is checked by queued event delivery
14      * {@link EventBus#invokeSubscriber(PendingPost)} to prevent race conditions.
15      */
16     volatile boolean active;
17 
18     Subscription(Object subscriber, SubscriberMethod subscriberMethod, int priority) {
19         this.subscriber = subscriber;
20         this.subscriberMethod = subscriberMethod;
21         this.priority = priority;
22         active = true;
23     }
24 
25     @Override
26     public boolean equals(Object other) {
27         if (other instanceof Subscription) {
28             Subscription otherSubscription = (Subscription) other;
29             return subscriber == otherSubscription.subscriber
30                     && subscriberMethod.equals(otherSubscription.subscriberMethod);
31         } else {
32             return false;
33         }
34     }
35 
36     @Override
37     public int hashCode() {
38         return subscriber.hashCode() + subscriberMethod.methodString.hashCode();
39     }
40 }

所以总结起来，SubscriberMethod 就是对方法的描述，而我们的SubscriberMethod 实际上就是Subscription的子集，Subscription除了有描述方法的对象以外，还有这个方法所属的类，

而我们的register方法总体来说就是先通过findSubscriberMethods方法取得我们注册类（就是你register调用的时候传的this）所需要的的那些方法（注意不是每个方法都需要只选择自己需要的）

然后把这些方法做一个list，最后再通过便利这个list ：用每一个SubscriberMethod 对象和这个方法所需的类（包名+类名）来构造出一个Subscription对象，然后把这个对象

存储在SubscriptionsByEventType里，注意这个map的key 实际上就是eventType，而value则代表方法的list，换句话说。

这个SubscriptionsByEventType 是一个键值对，它的key 实际上就是我们的类名，value则是这个类里面我们需要存储的方法的list！

这就是register的大致流程，我们再来看看post 流程即可。

 1  /**
 2      * Posts the given event to the event bus.
 3      */
 4     public void post(Object event) {
 5         PostingThreadState postingState = currentPostingThreadState.get();
 6         //这个地方可以看出来是每次有人调用post方法的时候 都会从postingState取出这个队列，然后把这个事件放到这个队列里
 7         List<Object> eventQueue = postingState.eventQueue;
 8         eventQueue.add(event);
 9 
10         //这个判断isPosting 主要是为了保证同一时间只能有一个线程在处理括号体里的内容
11         //currentPostingThreadState 是用threadlocal来构造的 所以保证了同步性
12         if (!postingState.isPosting) {
13             postingState.isMainThread = Looper.getMainLooper() == Looper.myLooper();
14             postingState.isPosting = true;
15             if (postingState.canceled) {
16                 throw new EventBusException("Internal error. Abort state was not reset");
17             }
18             try {
19                 while (!eventQueue.isEmpty()) {
20                     //队列不为空就处理
21                     postSingleEvent(eventQueue.remove(0), postingState);
22                 }
23             } finally {
24                 postingState.isPosting = false;
25                 postingState.isMainThread = false;
26             }
27         }
28     }

先看看第5行的postingState是什么

 1  /**
 2      * 静态类,里面除了有一个队列以外,还有几个标志位，以及一个Subscription
 3      */
 4     final static class PostingThreadState {
 5         final List<Object> eventQueue = new ArrayList<Object>();
 6         boolean isPosting;
 7         boolean isMainThread;
 8         Subscription subscription;
 9         Object event;
10         boolean canceled;
11     }

这个地方就能看出来，我们每次调用post 都是往eventQueue里面添加一个事件，而12行开始则是从队列里面

取事件来处理，注意12行开始一次性只能允许一个线程使用~同步的

然后继续看是怎么处理的。

 1  /**
 2      * @param event        方法的参数的类名
 3      * @param postingState
 4      * @throws Error
 5      */
 6     private void postSingleEvent(Object event, PostingThreadState postingState) throws Error {
 7       
 8         Class<?> eventClass = event.getClass();
 9         boolean subscriptionFound = false;
10        
11         if (eventInheritance) {
12             List<Class<?>> eventTypes = lookupAllEventTypes(eventClass);
13             int countTypes = eventTypes.size();
14             for (int h = 0; h < countTypes; h++) {
15                 Class<?> clazz = eventTypes.get(h);
16                 //这个地方就是取出Subscription对象的的所有信息！发消息也是在这个函数里发送的
17                 subscriptionFound |= postSingleEventForEventType(event, postingState, clazz);
18             }
19         } else {
20             subscriptionFound = postSingleEventForEventType(event, postingState, eventClass);
21         }
22         if (!subscriptionFound) {
23             if (logNoSubscriberMessages) {
24                 Log.d(TAG, "No subscribers registered for event " + eventClass);
25             }
26             if (sendNoSubscriberEvent && eventClass != NoSubscriberEvent.class &&
27                     eventClass != SubscriberExceptionEvent.class) {
28                 post(new NoSubscriberEvent(this, event));
29             }
30         }
31     }

继续跟进去

 1 private boolean postSingleEventForEventType(Object event, PostingThreadState postingState, Class<?> eventClass) {
 2         CopyOnWriteArrayList<Subscription> subscriptions;
 3         synchronized (this) {
 4             subscriptions = subscriptionsByEventType.get(eventClass);
 5         }
 6         if (subscriptions != null && !subscriptions.isEmpty()) {
 7             for (Subscription subscription : subscriptions) {
 8                 postingState.event = event;
 9                 postingState.subscription = subscription;
10                 boolean aborted = false;
11                 try {
12                     //这个地方就是真正发消息的地方了
13                     postToSubscription(subscription, event, postingState.isMainThread);
14                     aborted = postingState.canceled;
15                 } finally {
16                     postingState.event = null;
17                     postingState.subscription = null;
18                     postingState.canceled = false;
19                 }
20                 if (aborted) {
21                     break;
22                 }
23             }
24             return true;
25         }
26         return false;
27     }

可以看出来 2-6行就是从我们register流程里存储的键值对里把我们存放的方法给取出来。，

取出来以后就可以反射调用他们的方法了

 1   /**
 2      * 这个类就是反射执行方法 并且是最终执行回调方法的地方
 3      *
 4      * @param subscription
 5      * @param event
 6      * @param isMainThread
 7      */
 8     private void postToSubscription(Subscription subscription, Object event, boolean isMainThread) {
 9         switch (subscription.subscriberMethod.threadMode) {
10             case PostThread:
11                 invokeSubscriber(subscription, event);
12                 break;
13             case MainThread:
14                 if (isMainThread) {
15                     invokeSubscriber(subscription, event);
16                 } else {
17                     mainThreadPoster.enqueue(subscription, event);
18                 }
19                 break;
20             case BackgroundThread:
21                 if (isMainThread) {
22                     backgroundPoster.enqueue(subscription, event);
23                 } else {
24                     invokeSubscriber(subscription, event);
25                 }
26                 break;
27             case Async:
28                 asyncPoster.enqueue(subscription, event);
29                 break;
30             default:
31                 throw new IllegalStateException("Unknown thread mode: " + subscription.subscriberMethod.threadMode);
32         }
33     }

13-18行这个case 如果是主线程，那么就直接反射方法，如果不是的话则要放到主线程handler里执行。

1  private final HandlerPoster mainThreadPoster;

1  //这个就是主线程handler初始化
2         mainThreadPoster = new HandlerPoster(this, Looper.getMainLooper(), 10);

 1 /*
 2  * Copyright (C) 2012 Markus Junginger, greenrobot (http://greenrobot.de)
 3  *
 4  * Licensed under the Apache License, Version 2.0 (the "License");
 5  * you may not use this file except in compliance with the License.
 6  * You may obtain a copy of the License at
 7  *
 8  *      http://www.apache.org/licenses/LICENSE-2.0
 9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package de.greenrobot.event;
17 
18 import android.os.Handler;
19 import android.os.Looper;
20 import android.os.Message;
21 import android.os.SystemClock;
22 
23 final class HandlerPoster extends Handler {
24 
25     private final PendingPostQueue queue;
26     private final int maxMillisInsideHandleMessage;
27     private final EventBus eventBus;
28     private boolean handlerActive;
29 
30     HandlerPoster(EventBus eventBus, Looper looper, int maxMillisInsideHandleMessage) {
31         super(looper);
32         this.eventBus = eventBus;
33         this.maxMillisInsideHandleMessage = maxMillisInsideHandleMessage;
34         queue = new PendingPostQueue();
35     }
36 
37     void enqueue(Subscription subscription, Object event) {
38         PendingPost pendingPost = PendingPost.obtainPendingPost(subscription, event);
39         synchronized (this) {
40             queue.enqueue(pendingPost);
41             if (!handlerActive) {
42                 handlerActive = true;
43                 if (!sendMessage(obtainMessage())) {
44                     throw new EventBusException("Could not send handler message");
45                 }
46             }
47         }
48     }
49 
50     @Override
51     public void handleMessage(Message msg) {
52         boolean rescheduled = false;
53         try {
54             long started = SystemClock.uptimeMillis();
55             while (true) {
56                 PendingPost pendingPost = queue.poll();
57                 if (pendingPost == null) {
58                     synchronized (this) {
59                         // Check again, this time in synchronized
60                         pendingPost = queue.poll();
61                         if (pendingPost == null) {
62                             handlerActive = false;
63                             return;
64                         }
65                     }
66                 }
67                 eventBus.invokeSubscriber(pendingPost);
68                 long timeInMethod = SystemClock.uptimeMillis() - started;
69                 if (timeInMethod >= maxMillisInsideHandleMessage) {
70                     if (!sendMessage(obtainMessage())) {
71                         throw new EventBusException("Could not send handler message");
72                     }
73                     rescheduled = true;
74                     return;
75                 }
76             }
77         } finally {
78             handlerActive = rescheduled;
79         }
80     }
81 }

51-77行就是我们实际最终调用的地方。

同样的我们在看看20-26行的这个background这个case

 1 final class BackgroundPoster implements Runnable {
 2 
 3     private final PendingPostQueue queue;
 4     private final EventBus eventBus;
 5 
 6     private volatile boolean executorRunning;
 7 
 8     BackgroundPoster(EventBus eventBus) {
 9         this.eventBus = eventBus;
10         queue = new PendingPostQueue();
11     }
12 
13     public void enqueue(Subscription subscription, Object event) {
14         PendingPost pendingPost = PendingPost.obtainPendingPost(subscription, event);
15         synchronized (this) {
16             queue.enqueue(pendingPost);
17             if (!executorRunning) {
18                 executorRunning = true;
19                 eventBus.getExecutorService().execute(this);
20             }
21         }
22     }
23 
24     @Override
25     public void run() {
26         try {
27             try {
28                 while (true) {
29                     PendingPost pendingPost = queue.poll(1000);
30                     if (pendingPost == null) {
31                         synchronized (this) {
32                             // Check again, this time in synchronized
33                             pendingPost = queue.poll();
34                             if (pendingPost == null) {
35                                 executorRunning = false;
36                                 return;
37                             }
38                         }
39                     }
40                     eventBus.invokeSubscriber(pendingPost);
41                 }
42             } catch (InterruptedException e) {
43                 Log.w("Event", Thread.currentThread().getName() + " was interruppted", e);
44             }
45         } finally {
46             executorRunning = false;
47         }
48     }

一看就知道他是runnable对象必然是在后台在子线程内执行，同时他也是一次性只能做一次操作，完成一个事件，

最后我们来看看Async这个case：

 1 /*
 2  * Copyright (C) 2012 Markus Junginger, greenrobot (http://greenrobot.de)
 3  *
 4  * Licensed under the Apache License, Version 2.0 (the "License");
 5  * you may not use this file except in compliance with the License.
 6  * You may obtain a copy of the License at
 7  *
 8  *      http://www.apache.org/licenses/LICENSE-2.0
 9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package de.greenrobot.event;
17 
18 
19 /**
20  * Posts events in background.
21  * 
22  * @author Markus  并发执行任务，在线程池内执行
23  */
24 class AsyncPoster implements Runnable {
25 
26     private final PendingPostQueue queue;
27     private final EventBus eventBus;
28 
29     AsyncPoster(EventBus eventBus) {
30         this.eventBus = eventBus;
31         queue = new PendingPostQueue();
32     }
33 
34     public void enqueue(Subscription subscription, Object event) {
35         PendingPost pendingPost = PendingPost.obtainPendingPost(subscription, event);
36         queue.enqueue(pendingPost);
37         eventBus.getExecutorService().execute(this);
38     }
39 
40     @Override
41     public void run() {
42         PendingPost pendingPost = queue.poll();
43         if(pendingPost == null) {
44             throw new IllegalStateException("No pending post available");
45         }
46         eventBus.invokeSubscriber(pendingPost);
47     }
48 
49 }

这个地方和background相同的就是也是在非主线程，在子线程内执行，但是这个地方是在线程池内执行，可以并发执行多个任务，

而我们的background 则一次性只能执行一个任务，这是2者之间的区别。

posted @ 2015-09-09 11:34 希尔瓦娜斯女神阅读(1050) 评论(1) 编辑收藏举报

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