Android Broadcast广播机制分析

基于Android 6.0的源码剖析， 分析android广播的发送与接收流程。

一、概述

广播(Broadcast)机制用于进程/线程间通信，广播分为广播发送和广播接收两个过程，其中广播接收者BroadcastReceiver便是Android四大组件之一。

BroadcastReceiver分为两类：

静态广播接收者：通过AndroidManifest.xml的标签来申明的BroadcastReceiver。动态广播接收者：通过AMS.registerReceiver()方式注册的BroadcastReceiver，动态注册更为灵活，可在不需要时通过unregisterReceiver()取消注册。

从广播发送方式可分为三类：

普通广播：通过Context.sendBroadcast()发送，可并行处理有序广播：通过Context.sendOrderedBroadcast()发送，串行处理Sticky广播：通过Context.sendOrderedBroadcast()发送

二、注册广播

2.1 registerReceiver

广播注册，对于应用开发来说，往往是在Activity/Service中调用registerReceiver()方法，而Activity/Service都间接继承于Context抽象类，真正干活是交给ContextImpl类。另外调用getOuterContext()可获取最外层的调用者Activity/Service。

[ContextImpl.java]

@Overridepublic Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {return registerReceiver(receiver, filter, null, null);}@Overridepublic Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,String broadcastPermission, Handler scheduler) {//【见小节2.2】return registerReceiverInternal(receiver, getUserId(),filter, broadcastPermission, scheduler, getOuterContext());}

当执行两参数的registerReceiver方法，增加两个broadcastPermission=null和scheduler=null调用四参数的注册方法。其中broadcastPermission拥有广播的权限控制，scheduler用于指定接收到广播时onRecive执行线程，当scheduler=null则默认代表在主线程中执行，这也是最常见的用法。 再然后调用6参数的registerReceiverInternal。

2.2 registerReceiverInternal

[ContextImpl.java]

private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,IntentFilter filter, String broadcastPermission,Handler scheduler, Context context) {IIntentReceiver rd = null;if (receiver != null) {if (mPackageInfo != null && context != null) {if (scheduler == null) {//将主线程Handler赋予scheulerscheduler = mMainThread.getHandler();}//获取IIntentReceiver对象【2.3】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 {//调用AMP.registerReceiver 【2.4】return ActivityManagerNative.getDefault().registerReceiver(mMainThread.getApplicationThread(), mBasePackageName,rd, filter, broadcastPermission, userId);} catch (RemoteException e) {return null;}}

ActivityManagerNative.getDefault()返回的是ActivityManagerProxy对象，简称AMP，该方法中参数有mMainThread.getApplicationThread()返回的是ApplicationThread，这是Binder的Bn端，用于system_server进程与该进程的通信。

2.3 LoadedApk.getReceiverDispatcher

[-> LoadedApk.java]

public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,Context context, Handler handler,Instrumentation instrumentation, boolean registered) {synchronized (mReceivers) {LoadedApk.ReceiverDispatcher rd = null;ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> map = null;//此处registered=true，则进入该分支if (registered) {map = mReceivers.get(context);if (map != null) {rd = map.get(r);}}if (rd == null) {//当广播分发者为空，则创建ReceiverDispatcher【2.3.1】rd = new ReceiverDispatcher(r, context, handler,instrumentation, registered);if (registered) {if (map == null) {map = new ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher>();mReceivers.put(context, map);}map.put(r, rd);}} else {//验证广播分发者的context、handler是否一致rd.validate(context, handler);}rd.mForgotten = false;//获取IIntentReceiver对象return rd.getIIntentReceiver();}}

不妨令 以BroadcastReceiver(广播接收者)为key，LoadedApk.ReceiverDispatcher(分发者)为value的ArrayMap 记为A。此处mReceivers是一个以Context为key，以A为value的ArrayMap。对于ReceiverDispatcher(广播分发者)，当不存在时则创建一个。

2.3.1 创建ReceiverDispatcher

ReceiverDispatcher(BroadcastReceiver receiver, Context context,Handler activityThread, Instrumentation instrumentation,boolean registered) {//创建InnerReceiver【2.3.2】mIIntentReceiver = new InnerReceiver(this, !registered);mReceiver = receiver;mContext = context;mActivityThread = activityThread;mInstrumentation = instrumentation;mRegistered = registered;mLocation = new IntentReceiverLeaked(null);mLocation.fillInStackTrace();}

2.3.2 创建InnerReceiver

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;}...}

ReceiverDispatcher(广播分发者)有一个内部类InnerReceiver，该类继承于IIntentReceiver.Stub。显然，这是一个Binder服务端，广播分发者通过rd.getIIntentReceiver()可获取该Binder服务端对象InnerReceiver，用于Binder IPC通信。

2.4 AMP.registerReceiver

[-> ActivityManagerNative.java]

public Intent registerReceiver(IApplicationThread caller, String packageName,IIntentReceiver receiver,IntentFilter filter, String perm, int userId) throws RemoteException{Parcel data = Parcel.obtain();Parcel reply = Parcel.obtain();data.writeInterfaceToken(IActivityManager.descriptor);data.writeStrongBinder(caller != null ? caller.asBinder() : null);data.writeString(packageName);data.writeStrongBinder(receiver != null ? receiver.asBinder() : null);filter.writeToParcel(data, 0);data.writeString(perm);data.writeInt(userId);//Command为REGISTER_RECEIVER_TRANSACTIONmRemote.transact(REGISTER_RECEIVER_TRANSACTION, data, reply, 0);reply.readException();Intent intent = null;int haveIntent = reply.readInt();if (haveIntent != 0) {intent = Intent.CREATOR.createFromParcel(reply);}reply.recycle();data.recycle();return intent;}

这里有两个Binder服务端对象caller和receiver，AMP通过Binder驱动将这些信息发送给system_server进程中的AMS对象，接下来进入AMS.registerReceiver。

2.5 AMS.registerReceiver

[-> ActivityManagerService.java]

public Intent registerReceiver(IApplicationThread caller, String callerPackage,IIntentReceiver receiver, IntentFilter filter, String permission, int userId) {//孤立进程不允许注册广播接收者enforceNotIsolatedCaller("registerReceiver");ArrayList<Intent> stickyIntents = null;ProcessRecord callerApp = null;int callingUid;int callingPid;synchronized(this) {if (caller != null) {//从mLruProcesses队列中查找调用者的ProcessRecord 【见2.5.1】callerApp = getRecordForAppLocked(caller);//查询不到目标进程，则抛出异常if (callerApp == null) {throw new SecurityException("");}//非系统进程且包名不等于“android”，同时调用者进程不包括该包名时抛异常if (callerApp.info.uid != Process.SYSTEM_UID &&!callerApp.pkgList.containsKey(callerPackage) &&!"android".equals(callerPackage)) {throw new SecurityException("");}callingUid = callerApp.info.uid;callingPid = callerApp.pid;} else {callerPackage = null;callingUid = Binder.getCallingUid();callingPid = Binder.getCallingPid();}userId = handleIncomingUser(callingPid, callingUid, userId,true, ALLOW_FULL_ONLY, "registerReceiver", callerPackage);//获取IntentFilter中的actionsIterator<String> actions = filter.actionsIterator();if (actions == null) {ArrayList<String> noAction = new ArrayList<String>(1);noAction.add(null);actions = noAction.iterator();}int[] userIds = { UserHandle.USER_ALL, UserHandle.getUserId(callingUid) };while (actions.hasNext()) {String action = actions.next();for (int id : userIds) {//从mStickyBroadcasts中查看用户的sticky IntentArrayMap<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>();}//将sticky Intent加入到队列stickyIntents.addAll(intents);}}}}}ArrayList<Intent> allSticky = null;if (stickyIntents != null) {final ContentResolver resolver = mContext.getContentResolver();for (int i = 0, N = stickyIntents.size(); i < N; i++) {Intent intent = stickyIntents.get(i);//查询匹配的sticky广播 【见2.5.2】if (filter.match(resolver, intent, true, TAG) >= 0) {if (allSticky == null) {allSticky = new ArrayList<Intent>();}//匹配成功，则将给intent添加到allSticky队列allSticky.add(intent);}}}//当IIntentReceiver为空，则直接返回第一个sticky Intent，Intent sticky = allSticky != null ? allSticky.get(0) : null;if (receiver == null) {return sticky;}synchronized (this) {if (callerApp != null && (callerApp.thread == null|| callerApp.thread.asBinder() != caller.asBinder())) {//调用者已经死亡return null;}ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());if (rl == null) {//对于没有注册的广播，则创建接收者队列rl = new ReceiverList(this, callerApp, callingPid, callingUid,userId, receiver);if (rl.app != null) {rl.app.receivers.add(rl);} else {try {//注册死亡通知receiver.asBinder().linkToDeath(rl, 0);} catch (RemoteException e) {return sticky;}rl.linkedToDeath = true;}//新创建的接收者队列，添加到已注册广播队列。mRegisteredReceivers.put(receiver.asBinder(), rl);}...//创建BroadcastFilter对象，并添加到接收者队列BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,permission, callingUid, userId);rl.add(bf);//新创建的广播过滤者，添加到ReceiverResolver队列mReceiverResolver.addFilter(bf);//所有匹配该filter的sticky广播执行入队操作//如果没有使用sendStickyBroadcast，则allSticky=null。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);//当intent为前台广播，则返回mFgBroadcastQueue//当intent为后台广播，则返回mBgBroadcastQueueBroadcastQueue queue = broadcastQueueForIntent(intent);//创建BroadcastRecordBroadcastRecord r = new BroadcastRecord(queue, intent, null,null, -1, -1, null, null, AppOpsManager.OP_NONE, null, receivers,null, 0, null, null, false, true, true, -1);//该广播加入到并行广播队列queue.enqueueParallelBroadcastLocked(r);//调度广播，发送BROADCAST_INTENT_MSG消息，触发处理下一个广播。queue.scheduleBroadcastsLocked();}}return sticky;}}

其中mRegisteredReceivers记录着所有已注册的广播，以receiver IBinder为key, ReceiverList为value为HashMap。另外，这个过程涉及对象ReceiverList，BroadcastFilter，BroadcastRecord的创建。

在BroadcastQueue中有两个广播队列mParallelBroadcasts,mOrderedBroadcasts，数据类型都为ArrayList：

mParallelBroadcasts:并行广播队列，可以立刻执行，而无需等待另一个广播运行完成，该队列只允许动态已注册的广播，从而避免发生同时拉起大量进程来执行广播，前台的和后台的广播分别位于独立的队列。mOrderedBroadcasts：有序广播队列，同一时间只允许执行一个广播，该队列顶部的广播便是活动广播，其他广播必须等待该广播结束才能运行，也是独立区别前台的和后台的广播。

2.5.1 AMS.getRecordForAppLocked

final ProcessRecord getRecordForAppLocked(IApplicationThread thread) {if (thread == null) {return null;}//从mLruProcesses队列中查看int appIndex = getLRURecordIndexForAppLocked(thread);return appIndex >= 0 ? mLruProcesses.get(appIndex) : null;}

mLruProcesses数据类型为ArrayList<ProcessRecord>，而ProcessRecord对象有一个IApplicationThread字段，根据该字段查找出满足条件的ProcessRecord对象。

2.5.2 IntentFilter.match

public final int match(ContentResolver resolver, Intent intent,boolean resolve, String logTag) {String type = resolve ? intent.resolveType(resolver) : intent.getType();return match(intent.getAction(), type, intent.getScheme(),intent.getData(), intent.getCategories(), logTag);}public final int match(String action, String type, String scheme,Uri data, Set<String> categories, String logTag) {//不存在匹配的actionif (action != null && !matchAction(action)) {return NO_MATCH_ACTION; }//不存在匹配的type或dataint dataMatch = matchData(type, scheme, data);if (dataMatch < 0) {return dataMatch; }//不存在匹配的categoryString categoryMismatch = matchCategories(categories);if (categoryMismatch != null) {return NO_MATCH_CATEGORY;}return dataMatch;}

该方法用于匹配发起的Intent数据是否匹配成功，匹配项共有4项action, type, data, category，任何一项匹配不成功都会失败。

小结

注册广播的过程，主要功能：

创建ReceiverList(接收者队列)，并添加到AMS.mRegisteredReceivers(已注册广播队列)；创建BroadcastFilter(广播过滤者)，并添加到AMS.mReceiverResolver(接收者的解析人)；当注册的是Sticky广播，则创建BroadcastRecord，并添加到BroadcastQueue的mParallelBroadcasts(并行广播队列)，注册后调用AMS来尽快处理该广播。

三、 发送广播

发送广播，同样往往是在Activity/Service中调用registerReceiver()方法，而Activity/Service都间接继承于Context抽象类，真正干活是交给ContextImpl类。

3.1 sendBroadcast

[ContextImpl.java]

@Overridepublic void sendBroadcast(Intent intent) {warnIfCallingFromSystemProcess();String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());try {intent.prepareToLeaveProcess();// 调用AMP.broadcastIntent 【见3.2】ActivityManagerNative.getDefault().broadcastIntent(mMainThread.getApplicationThread(), intent, resolvedType, null,Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false, false,getUserId());} catch (RemoteException e) {throw new RuntimeException("Failure from system", e);}}

3.2 AMP.broadcastIntent

[-> ActivityManagerNative.java]

public int broadcastIntent(IApplicationThread caller,Intent intent, String resolvedType, IIntentReceiver resultTo,int resultCode, String resultData, Bundle map,String[] requiredPermissions, int appOp, Bundle options, boolean serialized,boolean sticky, int userId) throws RemoteException{Parcel data = Parcel.obtain();Parcel reply = Parcel.obtain();data.writeInterfaceToken(IActivityManager.descriptor);data.writeStrongBinder(caller != null ? caller.asBinder() : null);intent.writeToParcel(data, 0);data.writeString(resolvedType);data.writeStrongBinder(resultTo != null ? resultTo.asBinder() : null);data.writeInt(resultCode);data.writeString(resultData);data.writeBundle(map);data.writeStringArray(requiredPermissions);data.writeInt(appOp);data.writeBundle(options);data.writeInt(serialized ? 1 : 0);data.writeInt(sticky ? 1 : 0);data.writeInt(userId);//Command为BROADCAST_INTENT_TRANSACTIONmRemote.transact(BROADCAST_INTENT_TRANSACTION, data, reply, 0);reply.readException();int res = reply.readInt();reply.recycle();data.recycle();return res;}

3.3 AMS.broadcastIntent

[-> ActivityManagerService.java]

public final int broadcastIntent(IApplicationThread caller,Intent intent, String resolvedType, IIntentReceiver resultTo,int resultCode, String resultData, Bundle resultExtras,String[] requiredPermissions, int appOp, Bundle options,boolean serialized, boolean sticky, int userId) {enforceNotIsolatedCaller("broadcastIntent");synchronized(this) {//验证广播intent是否有效intent = verifyBroadcastLocked(intent);//获取调用者进程记录对象final ProcessRecord callerApp = getRecordForAppLocked(caller);final int callingPid = Binder.getCallingPid();final int callingUid = Binder.getCallingUid();final long origId = Binder.clearCallingIdentity();//【见小节3.4】int res = broadcastIntentLocked(callerApp,callerApp != null ? callerApp.info.packageName : null,intent, resolvedType, resultTo, resultCode, resultData, resultExtras,requiredPermissions, appOp, null, serialized, sticky,callingPid, callingUid, userId);Binder.restoreCallingIdentity(origId);return res;}}

broadcastIntent()方法有两个布尔参数serialized和sticky来共同决定是普通广播，有序广播，还是Sticky广播，参数如下：

3.4 AMS.broadcastIntentLocked

private final int broadcastIntentLocked(ProcessRecord callerApp,String callerPackage, Intent intent, String resolvedType,IIntentReceiver resultTo, int resultCode, String resultData,Bundle resultExtras, String[] requiredPermissions, int appOp, Bundle options,boolean ordered, boolean sticky, int callingPid, int callingUid, int userId) {//part 1: 设置flag//part 2: 广播权限验证//part 3: 处理系统相关广播//part 4: 增加sticky广播//part 5: 查询receivers和registeredReceivers//part 6: 处理并行广播//part 7: 合并registeredReceivers到receivers//part 8: 处理串行广播return ActivityManager.BROADCAST_SUCCESS;}

broadcastIntentLocked方法比较长，这里划分为8个部分来分别说明。

part 1: 设置广播flag

intent = new Intent(intent);//增加该flag，则广播不会发送给已停止的packageintent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);//当没有启动完成时，不允许启动新进程if (!mProcessesReady && (intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0) {intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);}userId = handleIncomingUser(callingPid, callingUid, userId,true, ALLOW_NON_FULL, "broadcast", callerPackage);//检查发送广播时用户状态if (userId != UserHandle.USER_ALL && !isUserRunningLocked(userId, false)) {if ((callingUid != Process.SYSTEM_UID|| (intent.getFlags() & Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0)&& !Intent.ACTION_SHUTDOWN.equals(intent.getAction())) {return ActivityManager.BROADCAST_FAILED_USER_STOPPED;}}

这个过程最重要的工作是：

添加flag=FLAG_EXCLUDE_STOPPED_PACKAGES，保证已停止app不会收到该广播；当系统还没有启动完成，则不允许启动新进程，，即只有动态注册receiver才能接受广播当非USER_ALL广播且当前用户并没有处于Running的情况下，除非是系统升级广播或者关机广播，否则直接返回。

BroadcastReceiver还有其他flag，位于Intent.java常量:

FLAG_RECEIVER_REGISTERED_ONLY //只允许已注册receiver接收广播FLAG_RECEIVER_REPLACE_PENDING //新广播会替代相同广播FLAG_RECEIVER_FOREGROUND //只允许前台receiver接收广播FLAG_RECEIVER_NO_ABORT //对于有序广播，先接收到的receiver无权抛弃广播FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT //Boot完成之前，只允许已注册receiver接收广播FLAG_RECEIVER_BOOT_UPGRADE //升级模式下，允许系统准备就绪前可以发送广播

part 2: 广播权限验证

int callingAppId = UserHandle.getAppId(callingUid);if (callingAppId == Process.SYSTEM_UID || callingAppId == Process.PHONE_UID|| callingAppId == Process.SHELL_UID || callingAppId == Process.BLUETOOTH_UID|| callingAppId == Process.NFC_UID || callingUid == 0) {//直接通过} else if (callerApp == null || !callerApp.persistent) {try {if (AppGlobals.getPackageManager().isProtectedBroadcast(intent.getAction())) {//不允许发送给受保护的广播throw new SecurityException(msg);} else if (AppWidgetManager.ACTION_APPWIDGET_CONFIGURE.equals(intent.getAction())) {//这个case是出于兼容性考虑，限制只允许发送给自己。...}} catch (RemoteException e) {return ActivityManager.BROADCAST_SUCCESS;}}

主要功能：

对于callingAppId为SYSTEM_UID，PHONE_UID，SHELL_UID，BLUETOOTH_UID，NFC_UID之一或者callingUid == 0时都畅通无阻；否则对于调用者进程为空并且不是persistent进程的情况下： 当发送的是受保护广播mProtectedBroadcasts(只允许系统使用)，则抛出异常；当action为ACTION_APPWIDGET_CONFIGURE时，虽然不希望该应用发送这种广播，处于兼容性考虑，限制该广播只允许发送给自己，否则抛出异常。

part 3: 处理系统相关广播

final String action = intent.getAction();if (action != null) {switch (action) {case Intent.ACTION_UID_REMOVED:mBatteryStatsService.removeUid(uid);mAppOpsService.uidRemoved(uid);break;case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE:String list[] = intent.getStringArrayExtra(Intent.EXTRA_CHANGED_PACKAGE_LIST);if (list != null && list.length > 0) {for (int i = 0; i < list.length; i++) {forceStopPackageLocked(list[i], -1, false, true, true,false, false, userId, "storage unmount");}mRecentTasks.cleanupLocked(UserHandle.USER_ALL);sendPackageBroadcastLocked(IApplicationThread.EXTERNAL_STORAGE_UNAVAILABLE, list,userId);}break;case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLEmRecentTasks.cleanupLocked(UserHandle.USER_ALL);break;case Intent.ACTION_PACKAGE_REMOVED:case Intent.ACTION_PACKAGE_CHANGED:Uri data = intent.getData();boolean removed = Intent.ACTION_PACKAGE_REMOVED.equals(action);boolean fullUninstall = removed && !intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);final boolean killProcess = !intent.getBooleanExtra(Intent.EXTRA_DONT_KILL_APP, false);if (killProcess) {forceStopPackageLocked(ssp, UserHandle.getAppId(intent.getIntExtra(Intent.EXTRA_UID, -1)),false, true, true, false, fullUninstall, userId,removed ? "pkg removed" : "pkg changed");}if (removed) {sendPackageBroadcastLocked(IApplicationThread.PACKAGE_REMOVED,new String[] {ssp}, userId);if (fullUninstall) {mAppOpsService.packageRemoved(intent.getIntExtra(Intent.EXTRA_UID, -1), ssp);removeUriPermissionsForPackageLocked(ssp, userId, true);removeTasksByPackageNameLocked(ssp, userId);mBatteryStatsService.notePackageUninstalled(ssp);}} else {cleanupDisabledPackageComponentsLocked(ssp, userId, killProcess,intent.getStringArrayExtra(Intent.EXTRA_CHANGED_COMPONENT_NAME_LIST));}break;case Intent.ACTION_PACKAGE_ADDED:Uri data = intent.getData();final boolean replacing =intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);mCompatModePackages.handlePackageAddedLocked(ssp, replacing);ApplicationInfo ai = AppGlobals.getPackageManager().getApplicationInfo(ssp, 0, 0);break;case Intent.ACTION_TIMEZONE_CHANGED:mHandler.sendEmptyMessage(UPDATE_TIME_ZONE);break;case Intent.ACTION_TIME_CHANGED:final int is24Hour = intent.getBooleanExtra(Intent.EXTRA_TIME_PREF_24_HOUR_FORMAT, false) ? 1: 0;mHandler.sendMessage(mHandler.obtainMessage(UPDATE_TIME, is24Hour, 0));BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();synchronized (stats) {stats.noteCurrentTimeChangedLocked();}break;case Intent.ACTION_CLEAR_DNS_CACHE: mHandler.sendEmptyMessage(CLEAR_DNS_CACHE_MSG);break;case Proxy.PROXY_CHANGE_ACTION:ProxyInfo proxy = intent.getParcelableExtra(Proxy.EXTRA_PROXY_INFO);mHandler.sendMessage(mHandler.obtainMessage(UPDATE_HTTP_PROXY_MSG, proxy));break;}}

这个过程代码较长，主要处于系统相关的广播，如下10个case：

case Intent.ACTION_UID_REMOVED: //uid移除case Intent.ACTION_PACKAGE_REMOVED: //package移除，case Intent.ACTION_PACKAGE_CHANGED: //package改变case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE: //外部设备不可用时，强制停止所有波及的应用并清空cache数据case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE: //外部设备可用case Intent.ACTION_PACKAGE_ADDED: //增加package，处于兼容考虑case Intent.ACTION_TIMEZONE_CHANGED: //时区改变，通知所有运行中的进程case Intent.ACTION_TIME_CHANGED: //时间改变，通知所有运行中的进程case Intent.ACTION_CLEAR_DNS_CACHE: //dns缓存清空case Proxy.PROXY_CHANGE_ACTION: //网络代理改变

part 4：增加sticky广播

if (sticky) {if (checkPermission(android.Manifest.permission.BROADCAST_STICKY,callingPid, callingUid)!= PackageManager.PERMISSION_GRANTED) {throw new SecurityException("");}if (requiredPermissions != null && requiredPermissions.length > 0) {return ActivityManager.BROADCAST_STICKY_CANT_HAVE_PERMISSION;}if (intent.getComponent() != null) {//当sticky广播发送给指定组件，则throw Exception}if (userId != UserHandle.USER_ALL) {//当非USER_ALL广播跟USER_ALL广播出现冲突,则throw Exception}ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(userId);if (stickies == null) {stickies = new ArrayMap<>();mStickyBroadcasts.put(userId, stickies);}ArrayList<Intent> list = stickies.get(intent.getAction());if (list == null) {list = new ArrayList<>();stickies.put(intent.getAction(), list);}final int stickiesCount = list.size();int i;for (i = 0; i < stickiesCount; i++) {if (intent.filterEquals(list.get(i))) {//替换已存在的sticky intentlist.set(i, new Intent(intent));break;}}//新的intent追加到listif (i >= stickiesCount) {list.add(new Intent(intent));}}

这个过程主要是将sticky广播增加到list，并放入mStickyBroadcasts里面。

part 5：查询receivers和registeredReceivers

int[] users;if (userId == UserHandle.USER_ALL) {users = mStartedUserArray; //广播给所有已启动用户} else {users = new int[] {userId}; //广播给指定用户}List receivers = null;List<BroadcastFilter> registeredReceivers = null;//找出所有能接收该广播的receiversif ((intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY) == 0) {//根据intent查找相应的receiversreceivers = collectReceiverComponents(intent, resolvedType, callingUid, users);}if (intent.getComponent() == null) {if (userId == UserHandle.USER_ALL && callingUid == Process.SHELL_UID) {UserManagerService ums = getUserManagerLocked();for (int i = 0; i < users.length; i++) {//shell用户是否开启允许debug功能if (ums.hasUserRestriction(UserManager.DISALLOW_DEBUGGING_FEATURES, users[i])) {continue;}// 查询动态注册的广播List<BroadcastFilter> registeredReceiversForUser =mReceiverResolver.queryIntent(intent,resolvedType, false, users[i]);if (registeredReceivers == null) {registeredReceivers = registeredReceiversForUser;} else if (registeredReceiversForUser != null) {registeredReceivers.addAll(registeredReceiversForUser);}}} else {// 查询动态注册的广播registeredReceivers = mReceiverResolver.queryIntent(intent,resolvedType, false, userId);}}

receivers：记录着匹配当前intent的所有静态注册广播接收者；registeredReceivers：记录着匹配当前的所有动态注册的广播接收者。

其中，mReceiverResolver是AMS的成员变量，记录着已注册的广播接收者的resolver.

AMS.collectReceiverComponents：

private List<ResolveInfo> collectReceiverComponents(Intent intent, String resolvedType,int callingUid, int[] users) {List<ResolveInfo> receivers = null;for (int user : users) {//调用PKMS.queryIntentReceivers，可获取AndroidManifest.xml声明的接收者信息List<ResolveInfo> newReceivers = AppGlobals.getPackageManager().queryIntentReceivers(intent, resolvedType, STOCK_PM_FLAGS, user);if (receivers == null) {receivers = newReceivers;} else if (newReceivers != null) {...//将所用户的receiver整合到receivers}}return receivers;}

part 6：处理并行广播

//用于标识是否需要用新intent替换旧的intent。final boolean replacePending = (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;//处理并行广播int NR = registeredReceivers != null ? registeredReceivers.size() : 0;if (!ordered && NR > 0) {final BroadcastQueue queue = broadcastQueueForIntent(intent);//创建BroadcastRecord对象BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,callerPackage, callingPid, callingUid, resolvedType, requiredPermissions,appOp, brOptions, registeredReceivers, resultTo, resultCode, resultData,resultExtras, ordered, sticky, false, userId);final boolean replaced = replacePending && queue.replaceParallelBroadcastLocked(r);if (!replaced) {//将BroadcastRecord加入到并行广播队列queue.enqueueParallelBroadcastLocked(r);//处理广播【见小节4.1】queue.scheduleBroadcastsLocked();}registeredReceivers = null;NR = 0;}

广播队列中有一个成员变量mParallelBroadcasts，类型为ArrayList，记录着所有的并行广播。

part 7：合并registeredReceivers到receivers

int ir = 0;if (receivers != null) {//防止应用监听该广播，在安装时直接运行。String skipPackages[] = null;if (Intent.ACTION_PACKAGE_ADDED.equals(intent.getAction())|| Intent.ACTION_PACKAGE_RESTARTED.equals(intent.getAction())|| Intent.ACTION_PACKAGE_DATA_CLEARED.equals(intent.getAction())) {Uri data = intent.getData();if (data != null) {String pkgName = data.getSchemeSpecificPart();if (pkgName != null) {skipPackages = new String[] { pkgName };}}} else if (Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE.equals(intent.getAction())) {skipPackages = intent.getStringArrayExtra(Intent.EXTRA_CHANGED_PACKAGE_LIST);}//将skipPackages相关的广播接收者从receivers列表中移除if (skipPackages != null && (skipPackages.length > 0)) {for (String skipPackage : skipPackages) {if (skipPackage != null) {int NT = receivers.size();for (int it=0; it<NT; it++) {ResolveInfo curt = (ResolveInfo)receivers.get(it);if (curt.activityInfo.packageName.equals(skipPackage)) {receivers.remove(it);it--;NT--;}}}}}//前面part6有一个处理动态广播的过程，处理完后再执行将动态注册的registeredReceivers合并到receiversint NT = receivers != null ? receivers.size() : 0;int it = 0;ResolveInfo curt = null;BroadcastFilter curr = null;while (it < NT && ir < NR) {if (curt == null) {curt = (ResolveInfo)receivers.get(it);}if (curr == null) {curr = registeredReceivers.get(ir);}if (curr.getPriority() >= curt.priority) {receivers.add(it, curr);ir++;curr = null;it++;NT++;} else { it++;curt = null;}}}while (ir < NR) {if (receivers == null) {receivers = new ArrayList();}receivers.add(registeredReceivers.get(ir));ir++;}

part 8: 处理串行广播

if ((receivers != null && receivers.size() > 0)|| resultTo != null) {BroadcastQueue queue = broadcastQueueForIntent(intent);//创建BroadcastRecordBroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,callerPackage, callingPid, callingUid, resolvedType,requiredPermissions, appOp, brOptions, receivers, resultTo, resultCode,resultData, resultExtras, ordered, sticky, false, userId);boolean replaced = replacePending && queue.replaceOrderedBroadcastLocked(r);if (!replaced) {//将BroadcastRecord加入到有序广播队列queue.enqueueOrderedBroadcastLocked(r);//处理广播【见小节4.1】queue.scheduleBroadcastsLocked(); }}

广播队列中有一个成员变量mOrderedBroadcasts，类型为ArrayList，记录着所有的有序广播。

四、 处理广播

在发送广播过程中会执行scheduleBroadcastsLocked方法来处理相关的广播

4.1 scheduleBroadcastsLocked

[-> BroadcastQueue.java]

public void scheduleBroadcastsLocked() { // 正在处理BROADCAST_INTENT_MSG消息if (mBroadcastsScheduled) {return;}//发送BROADCAST_INTENT_MSG消息mHandler.sendMessage(mHandler.obtainMessage(BROADCAST_INTENT_MSG, this));mBroadcastsScheduled = true;}

在BroadcastQueue对象创建时，mHandler=new BroadcastHandler(handler.getLooper());那么此处交由mHandler的handleMessage来处理：

private final class BroadcastHandler extends Handler {public BroadcastHandler(Looper looper) {super(looper, null, true);}@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case BROADCAST_INTENT_MSG: {processNextBroadcast(true); //【见小节4.2】} break;...}}

4.2 processNextBroadcast

[-> BroadcastQueue.java]

final void processNextBroadcast(boolean fromMsg) {synchronized(mService) {//part 1: 处理并行广播//part 2: 处理有序广播//part 3: 获取下条有序广播//part 4: 处理下条有序广播}}

此处mService为AMS，整个流程还是比较长的，全程持有AMS锁，所以广播效率低的情况下，直接会严重影响这个手机的性能与流畅度，这里应该考虑细化同步锁的粒度。

part 1: 处理并行广播

BroadcastRecord r; mService.updateCpuStats(); //更新CPU统计信息if (fromMsg) mBroadcastsScheduled = false;while (mParallelBroadcasts.size() > 0) {r = mParallelBroadcasts.remove(0);r.dispatchTime = SystemClock.uptimeMillis();r.dispatchClockTime = System.currentTimeMillis();final int N = r.receivers.size();for (int i=0; i<N; i++) {Object target = r.receivers.get(i);//分发广播给已注册的receiver 【见小节4.3】deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false);}addBroadcastToHistoryLocked(r);//将广播添加历史统计}

part 2：处理有序广播

if (mPendingBroadcast != null) {boolean isDead;synchronized (mService.mPidsSelfLocked) {//从mPidsSelfLocked获取正在处理该广播进程，判断该进程是否死亡ProcessRecord proc = mService.mPidsSelfLocked.get(mPendingBroadcast.curApp.pid);isDead = proc == null || proc.crashing;}if (!isDead) {//正在处理广播的进程保持活跃状态，则继续等待其执行完成return;} else {mPendingBroadcast.state = BroadcastRecord.IDLE;mPendingBroadcast.nextReceiver = mPendingBroadcastRecvIndex;mPendingBroadcast = null;}}boolean looped = false;do {if (mOrderedBroadcasts.size() == 0) {//所有串行广播处理完成，则调度执行gcmService.scheduleAppGcsLocked();if (looped) {mService.updateOomAdjLocked();}return;}r = mOrderedBroadcasts.get(0);boolean forceReceive = false;//获取所有该广播所有的接收者int numReceivers = (r.receivers != null) ? r.receivers.size() : 0;if (mService.mProcessesReady && r.dispatchTime > 0) {long now = SystemClock.uptimeMillis();if ((numReceivers > 0) &&(now > r.dispatchTime + (2*mTimeoutPeriod*numReceivers))) {//当广播处理时间超时，则强制结束这条广播broadcastTimeoutLocked(false);forceReceive = true;r.state = BroadcastRecord.IDLE;}}if (r.state != BroadcastRecord.IDLE) {return;}if (r.receivers == null || r.nextReceiver >= numReceivers|| r.resultAbort || forceReceive) {if (r.resultTo != null) {//处理广播消息消息performReceiveLocked(r.callerApp, r.resultTo,new Intent(r.intent), r.resultCode,r.resultData, r.resultExtras, false, false, r.userId);r.resultTo = null;}//取消BROADCAST_TIMEOUT_MSG消息cancelBroadcastTimeoutLocked();addBroadcastToHistoryLocked(r);mOrderedBroadcasts.remove(0);r = null;looped = true;continue;}} while (r == null);

mTimeoutPeriod，对于前台广播则为10s，对于后台广播则为60s，此时广播超时为2*mTimeoutPeriod*numReceivers，接收者越多则广播超时总时长越长。

part 3: 获取下条有序广播

//获取下一个receiver的indexint recIdx = r.nextReceiver++;r.receiverTime = SystemClock.uptimeMillis();if (recIdx == 0) {r.dispatchTime = r.receiverTime;r.dispatchClockTime = System.currentTimeMillis();}if (!mPendingBroadcastTimeoutMessage) {long timeoutTime = r.receiverTime + mTimeoutPeriod;//设置广播超时时间，发送BROADCAST_TIMEOUT_MSGsetBroadcastTimeoutLocked(timeoutTime);}final BroadcastOptions brOptions = r.options;//获取下一个广播接收者final Object nextReceiver = r.receivers.get(recIdx);if (nextReceiver instanceof BroadcastFilter) {//对于动态注册的广播接收者，deliverToRegisteredReceiverLocked处理广播BroadcastFilter filter = (BroadcastFilter)nextReceiver;deliverToRegisteredReceiverLocked(r, filter, r.ordered);if (r.receiver == null || !r.ordered) {r.state = BroadcastRecord.IDLE;scheduleBroadcastsLocked();} else {...}return;}//对于静态注册的广播接收者ResolveInfo info = (ResolveInfo)nextReceiver;ComponentName component = new ComponentName(info.activityInfo.applicationInfo.packageName,info.activityInfo.name);...//执行各种权限检测，此处省略，当权限不满足时skip=trueif (skip) {r.receiver = null;r.curFilter = null;r.state = BroadcastRecord.IDLE;scheduleBroadcastsLocked();return;}r.state = BroadcastRecord.APP_RECEIVE;String targetProcess = info.activityInfo.processName;r.curComponent = component;final int receiverUid = info.activityInfo.applicationInfo.uid;if (r.callingUid != Process.SYSTEM_UID && isSingleton&& mService.isValidSingletonCall(r.callingUid, receiverUid)) {info.activityInfo = mService.getActivityInfoForUser(info.activityInfo, 0);}r.curReceiver = info.activityInfo;...//Broadcast正在执行中，stopped状态设置成falseAppGlobals.getPackageManager().setPackageStoppedState(r.curComponent.getPackageName(), false, UserHandle.getUserId(r.callingUid));

part 4： 处理下条有序广播

//该receiver所对应的进程已经运行，则直接处理ProcessRecord app = mService.getProcessRecordLocked(targetProcess,info.activityInfo.applicationInfo.uid, false);if (app != null && app.thread != null) {try {app.addPackage(info.activityInfo.packageName,info.activityInfo.applicationInfo.versionCode, mService.mProcessStats);processCurBroadcastLocked(r, app);return;} catch (RemoteException e) {} catch (RuntimeException e) {finishReceiverLocked(r, r.resultCode, r.resultData, r.resultExtras, r.resultAbort, false);scheduleBroadcastsLocked();r.state = BroadcastRecord.IDLE; //启动receiver失败则重置状态return;}}//该receiver所对应的进程尚未启动，则创建该进程if ((r.curApp=mService.startProcessLocked(targetProcess,info.activityInfo.applicationInfo, true,r.intent.getFlags() | Intent.FLAG_FROM_BACKGROUND,"broadcast", r.curComponent,(r.intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) != 0, false, false))== null) {//创建失败，则结束该receiverfinishReceiverLocked(r, r.resultCode, r.resultData,r.resultExtras, r.resultAbort, false);scheduleBroadcastsLocked();r.state = BroadcastRecord.IDLE;return;}mPendingBroadcast = r;mPendingBroadcastRecvIndex = recIdx;

如果是动态广播接收者，则调用deliverToRegisteredReceiverLocked处理；如果是动态广播接收者，且对应进程已经创建，则调用processCurBroadcastLocked处理；如果是动态广播接收者，且对应进程尚未创建，则调用startProcessLocked创建进程。

4.3 deliverToRegisteredReceiverLocked

[-> BroadcastQueue.java]

private void deliverToRegisteredReceiverLocked(BroadcastRecord r,BroadcastFilter filter, boolean ordered) {...//检查发送者是否有BroadcastFilter所需权限//以及接收者是否有发送者所需的权限等等//当权限不满足要求，则skip=true。if (!skip) {//并行广播ordered = false，只有串行广播才进入该分支if (ordered) {r.receiver = filter.receiverList.receiver.asBinder();r.curFilter = filter;filter.receiverList.curBroadcast = r;r.state = BroadcastRecord.CALL_IN_RECEIVE;if (filter.receiverList.app != null) {r.curApp = filter.receiverList.app;filter.receiverList.app.curReceiver = r;mService.updateOomAdjLocked(r.curApp);}}// 处理广播【见小节4.4】performReceiveLocked(filter.receiverList.app, filter.receiverList.receiver,new Intent(r.intent), r.resultCode, r.resultData,r.resultExtras, r.ordered, r.initialSticky, r.userId);if (ordered) {r.state = BroadcastRecord.CALL_DONE_RECEIVE;}...}}

4.4 deliverToRegisteredReceiverLocked

[-> BroadcastQueue.java]

private static void performReceiveLocked(ProcessRecord app, IIntentReceiver receiver,Intent intent, int resultCode, String data, Bundle extras,boolean ordered, boolean sticky, int sendingUser) throws RemoteException {//通过binder异步机制，向receiver发送intentif (app != null) {if (app.thread != null) {//调用ApplicationThreadProxy类对应的方法 【4.5】app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,data, extras, ordered, sticky, sendingUser, app.repProcState);} else {//应用进程死亡，则Recevier并不存在throw new RemoteException("app.thread must not be null");}} else {//调用者进程为空，则执行该分支receiver.performReceive(intent, resultCode, data, extras, ordered,sticky, sendingUser);}}

4.5 ATP.scheduleRegisteredReceiver

public void scheduleRegisteredReceiver(IIntentReceiver receiver, Intent intent,int resultCode, String dataStr, Bundle extras, boolean ordered,boolean sticky, int sendingUser, int processState) throws RemoteException {Parcel data = Parcel.obtain();data.writeInterfaceToken(IApplicationThread.descriptor);data.writeStrongBinder(receiver.asBinder());intent.writeToParcel(data, 0);data.writeInt(resultCode);data.writeString(dataStr);data.writeBundle(extras);data.writeInt(ordered ? 1 : 0);data.writeInt(sticky ? 1 : 0);data.writeInt(sendingUser);data.writeInt(processState);//command=SCHEDULE_REGISTERED_RECEIVER_TRANSACTIONmRemote.transact(SCHEDULE_REGISTERED_RECEIVER_TRANSACTION, data, null,IBinder.FLAG_ONEWAY);data.recycle();}

ATP位于system_server进程，是Binder Bp端通过Binder驱动向Binder Bn端发送消息, ATP所对应的Bn端位于发送广播调用端所在进程的ApplicationThread，即进入AT.scheduleRegisteredReceiver， 接下来说明该方法。

4.6 AT.scheduleRegisteredReceiver

[-> ActivityThread.java]

public void scheduleRegisteredReceiver(IIntentReceiver receiver, Intent intent,int resultCode, String dataStr, Bundle extras, boolean ordered,boolean sticky, int sendingUser, int processState) throws RemoteException {//更新虚拟机进程状态updateProcessState(processState, false);//【见小节4.7】receiver.performReceive(intent, resultCode, dataStr, extras, ordered,sticky, sendingUser);}

此处receiver是注册广播时创建的，见小节[2.3]，可知该receiver=LoadedApk.ReceiverDispatcher.InnerReceiver。

4.7 InnerReceiver.performReceive

[-> LoadedApk.java]

public void performReceive(Intent intent, int resultCode, String data,Bundle extras, boolean ordered, boolean sticky, int sendingUser) {LoadedApk.ReceiverDispatcher rd = mDispatcher.get();if (rd != null) {//【4.8】rd.performReceive(intent, resultCode, data, extras, ordered, sticky, sendingUser);} else {...}}

4.8 ReceiverDispatcher.performReceive

[-> LoadedApk.java]

public void performReceive(Intent intent, int resultCode, String data,Bundle extras, boolean ordered, boolean sticky, int sendingUser) {Args args = new Args(intent, resultCode, data, extras, ordered,sticky, sendingUser);//通过handler消息机制发送args.if (!mActivityThread.post(args)) {if (mRegistered && ordered) {IActivityManager mgr = ActivityManagerNative.getDefault();args.sendFinished(mgr);}}}

其中Args继承于BroadcastReceiver.PendingResult，实现了接口Runnable。这里mActivityThread.post(args) 消息机制，关于Handler消息机制，见Android消息机制1-Handler(Java层)，把消息放入MessageQueue，再调用Args的run()方法。

4.9 Args.run

[-> LoadedApk.java]

public final class LoadedApk {static final class ReceiverDispatcher {final class Args extends BroadcastReceiver.PendingResult implements Runnable {public void run() {final BroadcastReceiver receiver = mReceiver;final boolean ordered = mOrdered;final IActivityManager mgr = ActivityManagerNative.getDefault();final Intent intent = mCurIntent;mCurIntent = null;if (receiver == null || mForgotten) {if (mRegistered && ordered) {sendFinished(mgr);}return;}try {//获取mReceiver的类加载器ClassLoader cl = mReceiver.getClass().getClassLoader();intent.setExtrasClassLoader(cl);setExtrasClassLoader(cl);receiver.setPendingResult(this);//回调广播onReceive方法receiver.onReceive(mContext, intent);} catch (Exception e) {...}if (receiver.getPendingResult() != null) {finish();}}}}

最终调用BroadcastReceiver具体实现类的onReceive()方法。

4.10 PendingResult.finish

[-> BroadcastReceiver.java]

public final void finish() {final IActivityManager mgr = ActivityManagerNative.getDefault();sendFinished(mgr);...}public void sendFinished(IActivityManager am) {synchronized (this) {try {if (mResultExtras != null) {mResultExtras.setAllowFds(false);}if (mOrderedHint) {//串行广播am.finishReceiver(mToken, mResultCode, mResultData, mResultExtras,mAbortBroadcast, mFlags);} else {//并行广播am.finishReceiver(mToken, 0, null, null, false, mFlags);}} catch (RemoteException ex) {}}}

此处AMP.finishReceiver，经过binder调用，进入AMS.finishReceiver方法

4.11 AMS.finishReceiver

public void finishReceiver(IBinder who, int resultCode, String resultData,Bundle resultExtras, boolean resultAbort, int flags) { ...final long origId = Binder.clearCallingIdentity();try {boolean doNext = false;BroadcastRecord r;synchronized(this) {BroadcastQueue queue = (flags & Intent.FLAG_RECEIVER_FOREGROUND) != 0? mFgBroadcastQueue : mBgBroadcastQueue;r = queue.getMatchingOrderedReceiver(who);if (r != null) {doNext = r.queue.finishReceiverLocked(r, resultCode,resultData, resultExtras, resultAbort, true);}}if (doNext) {//处理下一条广播r.queue.processNextBroadcast(false);}trimApplications();} finally {Binder.restoreCallingIdentity(origId);}}

五、总结

未完留坑，后续总结以及增加流程图说明…

附录

本文所涉及的源码：

framework/base/core/java/android/content/BroadcastReceiver.javaframework/base/core/java/android/content/Context.javaframework/base/core/java/android/content/IntentFilter.javaframework/base/core/java/android/app/ContextImpl.javaframework/base/core/java/android/app/LoadedApkframework/base/core/java/android/app/ActivityManagerNative.javaframework/base/core/java/android/app/ApplicationThreadNative.javaframework/base/core/java/android/app/ActivityThread.javaframework/base/services/core/java/com/android/server/ActivityManagerService.javaframework/base/services/core/java/com/android/server/am/BroadcastQueue.javaframework/base/services/core/java/com/android/server/am/BroadcastFilter.javaframework/base/services/core/java/com/android/server/am/BroadcastRecord.javaframework/base/services/core/java/com/android/server/am/ReceiverList.java

原文地址：//06/04/broadcast-receiver/