broadcast receiver_consolidator

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应用调用RegisterReciever，实质是调用的ContextImpl的registerReceiver,接下来跟一下这个流程：

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
    return registerReceiver(receiver, filter, null, null);
}

其中receiver，即应用中自定义的receiver。

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
    String broadcastPermission, Handler scheduler) {
        return registerReceiverInternal(receiver, getUserId(),
               filter, broadcastPermission, scheduler, getOuterContext(), 0);
}

即此处的参数：

参数	值
receiver	即应用中已定义的receiver
filter	应用中的filter
broadcastPermission	null
scheduler	null

该函数中新增了两个参数broadcastPermission和scheduler。

broadcastPermission：对广播者增加了权限控制，只有拥有对应权限的广播者发出的广播才能被此接收者接收；
scheduler：BroacastReceiver对象的onReceive函数可调度到scheduler所在的线程中执行。

接下来是registerReceiverInternal函数：

registerReceiverInternal

  private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
            IntentFilter filter, String broadcastPermission,
            Handler scheduler, Context context, int flags) {
        //创建一个IIntentReciever对象
        IIntentReceiver rd = null;
        if (receiver != null) {
            if (mPackageInfo != null && context != null) {
                if (scheduler == null) { //没有scheduler，则默认使用主线程的Handler
                    scheduler = mMainThread.getHandler();
                }
                rd = mPackageInfo.getReceiverDispatcher(
                    receiver, context, scheduler,
                    mMainThread.getInstrumentation(), true);
            } else {
                if (scheduler == null) {
                    scheduler = mMainThread.getHandler();
                }
                rd = new LoadedApk.ReceiverDispatcher(
                        receiver, context, scheduler, null, true).getIIntentReceiver();
            }
        }
        try {
            final Intent intent = ActivityManager.getService().registerReceiver(
                    mMainThread.getApplicationThread(), mBasePackageName, rd, filter,
                    broadcastPermission, userId, flags);
            if (intent != null) {
                intent.setExtrasClassLoader(getClassLoader());
                intent.prepareToEnterProcess();
            }
            return intent;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

该函数中的参数值：

参数	值
receiver	应用中自定义的receiver
userId	getUserId的返回值
filter	应用中的filter
broadcastPermission	null
scheduler	null
context	getOuterContext()。Context家族中真正干活的是ContextImpl，而其代理对象可以是Application或者Actiivity等，getOuterContext就返回的是这个代理。如果是在Activity中调用的registerReceiver，那此处的context就是Activity.
flags	0

此函数中else中对rd的赋值：

rd = new LoadedApk.ReceiverDispatcher(
                        receiver, context, scheduler, null, true).getIIntentReceiver();

先看LoadedApk.ReceiverDispatcher构造函数

/*参数解读：
   receiver---应用中的receiver
   context---调用registerReceiver的Activity
   activityThread---null
   instrumentation---null
   registered --- true
*/
ReceiverDispatcher(BroadcastReceiver receiver, Context context,
                Handler activityThread, Instrumentation instrumentation,
                boolean registered) {
            if (activityThread == null) {
                throw new NullPointerException("Handler must not be null");
            }

            mIIntentReceiver = new InnerReceiver(this, !registered);
            mReceiver = receiver;
            mContext = context;
            mActivityThread = activityThread;
            mInstrumentation = instrumentation;
            mRegistered = registered;
            mLocation = new IntentReceiverLeaked(null);
            mLocation.fillInStackTrace();
}

注意到其中有个变量mIIntentReceiver：

 final IIntentReceiver.Stub mIIntentReceiver;

IIntentReceiver是个interface，关系图谱：

明朗晨光

由上面的关系图可知：

BrocastReceiver内部有一个PendingResult类，该类是用于异步处理广播信息的。如当BroacastReceiver收到广播时，其onReceive函数被调用，一般都是直接在该函数里处理广播。不过，若广播处理比较耗时，可以采用异步的方式进行处理，即先调用BroadcastReceiver的goAsync函数得到一个PendingResult对象，然后将该对象放到工作线程中去处理，这样onReceive函数就可以立即返回而不至于耽误太长时间。工作线程处理完这条广播后，需要调用PendingResult的finish函数来完成整个广播的处理流程。
广播由AMS发出，而处理却在另一个进程中进行。整个过程一定涉及进程间通信，虽然在BroadcastReceiver定义了了一个广播接收者，但是它与Binder没有任何关系，故其不直接参与进程间通信。与之相反的是，IIntentReceiver接口和Binder密切相关，故可知广播的接收者是由IIntentReceiver接口来完成的。在整个流程中，首先接收到来自AMS的广播的将是该接口的Bn端，即LoadedApk.ReceiverDispatcher.InnerReceiver。

而InnerReceiver类的具体实现：

final static class InnerReceiver extends IIntentReceiver.Stub {
            final WeakReference<LoadedApk.ReceiverDispatcher> mDispatcher;
            final LoadedApk.ReceiverDispatcher mStrongRef;

            InnerReceiver(LoadedApk.ReceiverDispatcher rd, boolean strong) {
                mDispatcher = new WeakReference<LoadedApk.ReceiverDispatcher>(rd);
                mStrongRef = strong ? rd : null;
            }

            @Override
            public void performReceive(Intent intent, int resultCode, String data,
                    Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
                final LoadedApk.ReceiverDispatcher rd;
                if (intent == null) {
                    Log.wtf(TAG, "Null intent received");
                    rd = null;
                } else {
                    rd = mDispatcher.get();
                }
                if (ActivityThread.DEBUG_BROADCAST) {
                    int seq = intent.getIntExtra("seq", -1);
                    Slog.i(ActivityThread.TAG, "Receiving broadcast " + 
                          intent.getAction()
                          + " seq=" + seq + " to " + (rd != null ? rd.mReceiver : null));
                }
                if (rd != null) {
                    rd.performReceive(intent, resultCode, data, extras,
                            ordered, sticky, sendingUser);
                } else {
                    // The activity manager dispatched a broadcast to a registered
                    // receiver in this process, but before it could be delivered the
                    // receiver was unregistered.  Acknowledge the broadcast on its
                    // behalf so that the system's broadcast sequence can continue.
                    if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
                            "Finishing broadcast to unregistered receiver");
                    IActivityManager mgr = ActivityManager.getService();
                    try {
                        if (extras != null) {
                            extras.setAllowFds(false);
                        }
                        mgr.finishReceiver(this, resultCode, data, extras, false, 
                                                              intent.getFlags());                 
                    } catch (RemoteException e) {
                        throw e.rethrowFromSystemServer();
                    }
               }
         }
}

而rd =new LoadedApk.ReceiverDispatcher(receiver, context, scheduler, null, true).getIIntentReceiver();中的getIIntentReceiver就是返回的mIIntentReceiver变量。

小结

registerReceiverInternal函数主要完成了2个工作：

创建了一个IIntentReceiver对象
调用AMS的registerReceiver函数

接下来看AMS的registerReceiver函数：

AMS.registerReceiver

//ContextImpl.java
final Intent intent = ActivityManager.getService().registerReceiver(
                    mMainThread.getApplicationThread(), mBasePackageName, rd, filter,
                    broadcastPermission, userId, flags);

//ActivityManagerService.java
public Intent registerReceiver(IApplicationThread caller, String callerPackage,
            IIntentReceiver receiver, IntentFilter filter, String permission, int userId,
            int flags) {
        //....
}

由上可知，传入AMS.registerReceiver的参数表：

参数	值
caller	应用主线程的ApplicationThread
callerPackage	进程创建时new ContextImpl时的package
receiver	即IIntentReceiver，接收来自AMS的Bn端
filter	应用传入的filter
permission	null
userId	进程的userId

public Intent registerReceiver(IApplicationThread caller, String callerPackage,
            IIntentReceiver receiver, IntentFilter filter, String permission, int userId,
            int flags) {
         enforceNotIsolatedCaller("registerReceiver");
         ArrayList<Intent> stickyIntents = null;
         ProcessRecord callerApp = null;
         ...
         int callingUid;
         int callingPid;
         synchronized(this) {
            if (caller != null) {
                callerApp = getRecordForAppLocked(caller);
                if (callerApp == null) { //系统不允许未注册的进程注册动态receiver
                    throw new SecurityException(
                            "Unable to find app for caller " + caller
                            + " (pid=" + Binder.getCallingPid()
                            + ") when registering receiver " + receiver);
                }
                //检查调用进程是否有callerPackage信息，如果没有，抛出异常
                if (callerApp.info.uid != SYSTEM_UID &&
                        !callerApp.pkgList.containsKey(callerPackage) &&
                        !"android".equals(callerPackage)) {
                    throw new SecurityException("Given caller package " + callerPackage
                            + " is not running in process " + callerApp);
                }
                callingUid = callerApp.info.uid;
                callingPid = callerApp.pid;
            } else {
                callerPackage = null;
                callingUid = Binder.getCallingUid();
                callingPid = Binder.getCallingPid();
            }

            ....//instantApp的处理
            //从系统的Sticky Intent中查询匹配IntentFilter的intent，结果保存到allSticky中
            Iterator<String> actions = filter.actionsIterator();
            if (actions == null) {
                ArrayList<String> noAction = new ArrayList<String>(1);
                noAction.add(null);
                actions = noAction.iterator();
            }

            // Collect stickies of users
            int[] userIds = { UserHandle.USER_ALL, UserHandle.getUserId(callingUid) };
            while (actions.hasNext()) {
                String action = actions.next();
                for (int id : userIds) {
                    ArrayMap<String, ArrayList<Intent>> stickies = 
                                                         mStickyBroadcasts.get(id);
                    if (stickies != null) {
                        ArrayList<Intent> intents = stickies.get(action);
                        if (intents != null) {
                            if (stickyIntents == null) {
                                stickyIntents = new ArrayList<Intent>();
                            }
                            stickyIntents.addAll(intents);
                        }
                    }
                }
            }
        }

        //在stickyIntents中查询和IntentFilter匹配的intent
        ArrayList<Intent> allSticky = null;
        if (stickyIntents != null) {
            final ContentResolver resolver = mContext.getContentResolver();
            // Look for any matching sticky broadcasts...
            for (int i = 0, N = stickyIntents.size(); i < N; i++) {
                Intent intent = stickyIntents.get(i);
                // Don't provided intents that aren't available to instant apps.
                ...//Instant APP的相关处理
                // If intent has scheme "content", it will need to acccess
                // provider that needs to lock mProviderMap in ActivityThread
                // and also it may need to wait application response, so we
                // cannot lock ActivityManagerService here.
                if (filter.match(resolver, intent, true, TAG) >= 0) {
                    if (allSticky == null) {
                        allSticky = new ArrayList<Intent>();
                    }
                    allSticky.add(intent);
                }
            }
        }
         //如果allSticky不为空，则选择第一个Intent作为本函数的返回值
         // The first sticky in the list is returned directly back to the client.
        Intent sticky = allSticky != null ? allSticky.get(0) : null;
        //如果没有设置接收者，则直接返回Sticky的intent
        if (receiver == null) {
            return sticky;
        }
        
        synchronized (this) {
            if (callerApp != null && (callerApp.thread == null
                    || callerApp.thread.asBinder() != caller.asBinder())) {
                // Original caller already died
                //之前的调用者所在进程已经die了
                return null;
            }
            //在mRegisteredReceivers中查询receiver对应的IBinder对象的ReceiverList
            ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
            if (rl == null) {//如果是首次调用，rl = null
                rl = new ReceiverList(this, callerApp, callingPid, callingUid,
                        userId, receiver);
                if (rl.app != null) {
                    rl.app.receivers.add(rl);
                } else {
                    try {
                        //监听广播接收者所在进程的死亡消息
                        receiver.asBinder().linkToDeath(rl, 0);
                    } catch (RemoteException e) {
                        return sticky;
                    }
                    rl.linkedToDeath = true;
                }
                //将rl保存到mRegisterReceivers中
                mRegisteredReceivers.put(receiver.asBinder(), rl);
            } else if (...) {
                ......//其他情况，抛出异常信息
            }
            //新建BroadcastFilter对象
            BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,
                    permission, callingUid, userId, instantApp, visibleToInstantApps);
            //保存到rl中
            rl.add(bf);

            mReceiverResolver.addFilter(bf);

            // Enqueue broadcasts for all existing stickies that match
            // this filter.
            //allSticky不为空，表示有Sticky的intent，需要立即调度广播发送
            if (allSticky != null) {
                ArrayList receivers = new ArrayList();
                receivers.add(bf);

                final int stickyCount = allSticky.size();
                for (int i = 0; i < stickyCount; i++) {
                    Intent intent = allSticky.get(i);
                    BroadcastQueue queue = broadcastQueueForIntent(intent);
                    //为每一个需要发送的广播创建一个BroadcastRecord对象
                    BroadcastRecord r = new BroadcastRecord(queue, intent, null,
                           null, -1, -1, false, null, null, AppOpsManager.OP_NONE, null, 
                           receivers,
                            null, 0, null, null, false, true, true, -1);
                    queue.enqueueParallelBroadcastLocked(r);
                    queue.scheduleBroadcastsLocked();
                }
            }

            return sticky;
        }

这段code中有几个变量需要说明：

mRegisteredReceivers：

    /**
     * Keeps track of all IIntentReceivers that have been registered for broadcasts.
     * Hash keys are the receiver IBinder, hash value is a ReceiverList.
     */
    final HashMap<IBinder, ReceiverList> mRegisteredReceivers = new HashMap<>();

HashMap变量，用于保存IIntentReceiver和对应ReceiverList的关系，即使用接收者（receiver）的IBinder为key，value是receiver对应的ReceiverList（因为一个receiver可能对应多个IntentFilter，所以用List来保存IntentFilter）。

mReceiverResolver

    /**
     * Resolver for broadcast intents to registered receivers.
     * Holds BroadcastFilter (subclass of IntentFilter).
     */
    final IntentResolver<BroadcastFilter, BroadcastFilter> mReceiverResolver
            = new IntentResolver<BroadcastFilter, BroadcastFilter>() {
        ...//实现部分方法
    }

保存receiver设置的过滤条件（IntentFilter）

关联如下：

broadcast receiver_consolidator