Android10.0 BroadcastCast广播机制原理
原文地址：https://skytoby.github.io/2019/BroadcastCast%E5%B9%BF%E6%92%AD%E6%9C%BA%E5%88%B6%E5%8E%9F%E7%90%86/
基于Android10.0，分析广播机制的原理
一、概述
广播（BroadcastCast）用于进程/线程间的通信，广播有发送广播和接收广播两部分组成，其中广播接收者BroadcastReceiver是四大组件之一。
BroadcastReceiver分为两类：
-
静态广播：通过AndroidManifeset.xml的标签来注册BroadcastReceiver。
-
动态广播：通过AMS.registeredReceiver方式注册BroadcastReceiver，动态注册相对静态注册更加的灵活，在不需要时通过unregisteredReceiver来取消注册。
从广播的发送方式分为四种：
-
普通广播：完全异步的广播，在广播发出之后，所有的广播接收器几乎在同一时刻接收到这条广播消息，接收的先后顺序是随机的。通过Context.sendBroadcast发送。
-
有序广播：同步执行的广播。在广播发出去之后，同一时刻只有一个广播接收器能够收到这条广播消息，当这个广播接收器中的逻辑处理完成后，广播才可以继续传递。这种广播的接收顺序通过优先级(priority)设置，高的优先级先会收到广播。有序广播可以被接收者截断，使得后面的广播无法收到它。通过Context.sendOrderedBroadcast发送。
-
粘性广播：这种广播会一直滞留，当有匹配该广播的接收器被注册后，该接收器就会收到这个广播。粘性广播如果被销毁，下一次重建时会重新接收到消息数据。这种方式一般用来确保重要状态改变后的信息被持久的保存，并且能随时广播给新的广播接收器，比如：耗电量的改变。通过Context.sendStickyBroadcast发送。Android系统已经 @Deprecated该广播方式。
-
本地广播：发送处理的广播只能够在应用程序的内部进行传递，并且广播接收器也只能接收本应用程序发出的广播。通过LocalBroadcastManager.sendBroadcast发送。（基本原理是Handler，所以在AMS中没有本地广播的处理）
广播在系统中通过BroadcastRecord来记录。
/**
* An active intent broadcast.
*/
final class BroadcastRecord extends Binder {
final Intent intent; // the original intent that generated us
final ComponentName targetComp; // original component name set on the intent
final ProcessRecord callerApp; // process that sent this
final String callerPackage; // who sent this
final int callingPid; // the pid of who sent this
final int callingUid; // the uid of who sent this
final boolean callerInstantApp; // caller is an Instant App?
final boolean ordered; // serialize the send to receivers?
final boolean sticky; // originated from existing sticky data?
final boolean initialSticky; // initial broadcast from register to sticky?
final int userId; // user id this broadcast was for
final String resolvedType; // the resolved data type
final String[] requiredPermissions; // permissions the caller has required
final int appOp; // an app op that is associated with this broadcast
final BroadcastOptions options; // BroadcastOptions supplied by caller
//包括动态注册的BroadcastFilter和静态注册的ResolveInfo
final List receivers; // contains BroadcastFilter and ResolveInfo
//广播的分发状态
final int[] delivery; // delivery state of each receiver
IIntentReceiver resultTo; // who receives final result if non-null
//入队列时间
long enqueueClockTime; // the clock time the broadcast was enqueued
//分发时间
long dispatchTime; // when dispatch started on this set of receivers
//分发时间
long dispatchClockTime; // the clock time the dispatch started
//接收时间
long receiverTime; // when current receiver started for timeouts.
//广播完成时间
long finishTime; // when we finished the broadcast.
}
二、注册广播
注册广播一般可以在Activity/Service中调用registerReceiver方法，而这两者间接集成Context，其实现是ContextImpl。
2.1 CI.registerReceiver
[->ContextImpl.java]
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), 0);
}
其中broadcastPermission表示广播的权限，scheduler表示接收广播时onReceive执行的线程，当scheduler==null时代表在主线程中执行，大部分情况是不会指令scheduler。getOuterContext可以获取最外层调用者。
2.2 CI.registerReceiverInternal
[->ContextImpl.java]
private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
IntentFilter filter, String broadcastPermission,
Handler scheduler, Context context, int flags) {
IIntentReceiver rd = null;
if (receiver != null) {
if (mPackageInfo != null && context != null) {
if (scheduler == null) {
//主线程Handler赋予scheduler
scheduler = mMainThread.getHandler();
}
//见2.3节，获取IIntentReceiver
rd = mPackageInfo.getReceiverDispatcher(
receiver, context, scheduler,
mMainThread.getInstrumentation(), true);
} else {
if (scheduler == null) {
scheduler = mMainThread.getHandler();
}
//context为空，新建ReceiverDispatcher对象（见2.3.1节），并获取IIntentReceiver
rd = new LoadedApk.ReceiverDispatcher(
receiver, context, scheduler, null, true).getIIntentReceiver();
}
}
try {
//通过Binder调用AMS.registerReceiver
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();
}
}
2.3 LA.getReceiverDispatcher
[->LoadedApk.java]
public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
Context context, Handler handler,
Instrumentation instrumentation, boolean registered) {
synchronized (mReceivers) {
LoadedApk.ReceiverDispatcher rd = null;
ArrayMap map = null;
//已经注册
if (registered) {
map = mReceivers.get(context);
if (map != null) {
rd = map.get(r);
}
}
if (rd == null) {
//广播分发者为空，创建ReceiverDispatcher
rd = new ReceiverDispatcher(r, context, handler,
instrumentation, registered);
if (registered) {
if (map == null) {
map = new ArrayMap();
mReceivers.put(context, map);
}
map.put(r, rd);
}
} else {
//验证广播分发者的context和handler是否一致
rd.validate(context, handler);
}
rd.mForgotten = false;
return rd.getIIntentReceiver();
}
}
mReceivers定义为final ArrayMap
mReceivers是以Context为key,以ArrayMap为value的ArrayMap。
2.3.1 创建ReceiverDispatcher
[->LoadedApk.java]
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();
}
mActivityThread为前面传过来的Handler。
2.3.2 创建InnerReceiver
[->LoadedApk.java]
final static class InnerReceiver extends IIntentReceiver.Stub {
final WeakReference mDispatcher;
final LoadedApk.ReceiverDispatcher mStrongRef;
InnerReceiver(LoadedApk.ReceiverDispatcher rd, boolean strong) {
//弱引用
mDispatcher = new WeakReference(rd);
mStrongRef = strong ? rd : null;
}
...
}
InnerReceiver继承于IIntentReceiver.Stub，是一个服务器端，广播分发者通过getReceiverDispatcher可以获取该Binder服务端对象InnerReceiver，用于IPC通信。
2.4 AMS.registerReceiver
[->ActivityManagerService.java]
public Intent registerReceiver(IApplicationThread caller, String callerPackage,
IIntentReceiver receiver, IntentFilter filter, String permission, int userId,
int flags) {
enforceNotIsolatedCaller("registerReceiver");
ArrayList stickyIntents = null;
ProcessRecord callerApp = null;
final boolean visibleToInstantApps
= (flags & Context.RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
int callingUid;
int callingPid;
boolean instantApp;
synchronized(this) {
if (caller != null) {
//查询调用者的进程信息
callerApp = getRecordForAppLocked(caller);
if (callerApp == null) {
throw new SecurityException(
"Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when registering receiver " + receiver);
}
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();
}
//是否是即时应用
instantApp = isInstantApp(callerApp, callerPackage, callingUid);
userId = mUserController.handleIncomingUser(callingPid, callingUid, userId, true,
ALLOW_FULL_ONLY, "registerReceiver", callerPackage);
//获取InterFilter中的Action
Iterator actions = filter.actionsIterator();
if (actions == null) {
ArrayList noAction = new ArrayList(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) {
//从mStickyBroadcasts中查看用户的sticky intent
ArrayMap> stickies = mStickyBroadcasts.get(id);
if (stickies != null) {
ArrayList intents = stickies.get(action);
if (intents != null) {
if (stickyIntents == null) {
stickyIntents = new ArrayList();
}
//将sticky intent加入队列
stickyIntents.addAll(intents);
}
}
}
}
}
ArrayList 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);
//即时应用跳过
// Don't provided intents that aren't available to instant apps.
if (instantApp &&
(intent.getFlags() & Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS) == 0) {
continue;
}
//查询匹配到的sticky广播，见2.4.2节
// 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();
}
//匹配成功，则将该intent添加到allSticky队列
allSticky.add(intent);
}
}
}
//返回第一个stick intent
// The first sticky in the list is returned directly back to the client.
Intent sticky = allSticky != null ? allSticky.get(0) : null;
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Register receiver " + filter + ": " + sticky);
if (receiver == null) {
return sticky;
}
synchronized (this) {
if (callerApp != null && (callerApp.thread == null
|| callerApp.thread.asBinder() != caller.asBinder())) {
// Original caller already died
//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) {
//每个应用最多只能注册1000个接收者
final int totalReceiversForApp = rl.app.receivers.size();
if (totalReceiversForApp >= MAX_RECEIVERS_ALLOWED_PER_APP) {
throw new IllegalStateException("Too many receivers, total of "
+ totalReceiversForApp + ", registered for pid: "
+ rl.pid + ", callerPackage: " + callerPackage);
}
//新创建的接收者队列，添加到已注册队列
rl.app.receivers.add(rl);
} else {
try {
//服务停止后重连
receiver.asBinder().linkToDeath(rl, 0);
} catch (RemoteException e) {
return sticky;
}
rl.linkedToDeath = true;
}
mRegisteredReceivers.put(receiver.asBinder(), rl);
} else if (rl.uid != callingUid) {
throw new IllegalArgumentException(
"Receiver requested to register for uid " + callingUid
+ " was previously registered for uid " + rl.uid
+ " callerPackage is " + callerPackage);
} else if (rl.pid != callingPid) {
throw new IllegalArgumentException(
"Receiver requested to register for pid " + callingPid
+ " was previously registered for pid " + rl.pid
+ " callerPackage is " + callerPackage);
} else if (rl.userId != userId) {
throw new IllegalArgumentException(
"Receiver requested to register for user " + userId
+ " was previously registered for user " + rl.userId
+ " callerPackage is " + callerPackage);
}
//创建BroadcastFilter队列，并添加到接收者队列
BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,
permission, callingUid, userId, instantApp, visibleToInstantApps);
if (rl.containsFilter(filter)) {
Slog.w(TAG, "Receiver with filter " + filter
+ " already registered for pid " + rl.pid
+ ", callerPackage is " + callerPackage);
} else {
rl.add(bf);
if (!bf.debugCheck()) {
Slog.w(TAG, "==> For Dynamic broadcast");
}
//新创建的广播过滤对象，添加到mReceiverResolver队列
mReceiverResolver.addFilter(bf);
}
//所有匹配该filter的stick广播执行入队操作
// Enqueue broadcasts for all existing stickies that match
// this filter.
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);
//根据intent返回前台或者后台广播队列，见2.4.3节
BroadcastQueue queue = broadcastQueueForIntent(intent);
BroadcastRecord r = new BroadcastRecord(queue, intent, null,
null, -1, -1, false, null, null, OP_NONE, null, receivers,
null, 0, null, null, false, true, true, -1);
//该广播加入到并行队列
queue.enqueueParallelBroadcastLocked(r);
//调度广播，发送BROADCAST_INTENT_MSG消息，触发处理广播
queue.scheduleBroadcastsLocked();
}
}
return sticky;
}
}
mReceiverResolver记录着所有已经注册的广播，是以receiver IBinder为key， ReceiverList为value的ArrayMap。
在BroadcastQueue中有两个广播队列mParallelBroadcasts、mOrderedBroadcasts，类型为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，前台和后台的广播分别位于独立的队列。
-
mOrderedBroadcasts：有序广播，同一时间只允许执行一个广播，该队列头部的广播就是活动广播，其他广播必须等待该广播结束才能运行，也是独立区别前台和后台的广播。
2.4.1 AMS.getRecordForAppLocked
[->ActivityManagerService.java]
ProcessRecord getRecordForAppLocked(IApplicationThread thread) {
if (thread == null) {
return null;
}
//从mLruProcesses队列中获取
int appIndex = getLRURecordIndexForAppLocked(thread);
if (appIndex >= 0) {
return mLruProcesses.get(appIndex);
}
//mLruProcesses不存在，再检查一遍
// Validation: if it isn't in the LRU list, it shouldn't exist, but let's
// double-check that.
final IBinder threadBinder = thread.asBinder();
final ArrayMap> pmap = mProcessNames.getMap();
for (int i = pmap.size()-1; i >= 0; i--) {
final SparseArray procs = pmap.valueAt(i);
for (int j = procs.size()-1; j >= 0; j--) {
final ProcessRecord proc = procs.valueAt(j);
if (proc.thread != null && proc.thread.asBinder() == threadBinder) {
Slog.wtf(TAG, "getRecordForApp: exists in name list but not in LRU list: "
+ proc);
return proc;
}
}
}
return null;
}
mLruProcesses 定义为ArrayList mLruProcesses ，ProcessRecord对象中有一个IApplicationThread字段，根据该字段来查找对应的ProcessRecord。
2.4.3 IntentFilter.match
[->IntentFilter.java]
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 categories, String logTag) {
//不存在匹配的action，存在即可以
if (action != null && !matchAction(action)) {
if (false) Log.v(
logTag, "No matching action " + action + " for " + this);
return NO_MATCH_ACTION;
}
//不存在匹配的type或data
int dataMatch = matchData(type, scheme, data);
if (dataMatch < 0) {
if (false) {
if (dataMatch == NO_MATCH_TYPE) {
Log.v(logTag, "No matching type " + type
+ " for " + this);
}
if (dataMatch == NO_MATCH_DATA) {
Log.v(logTag, "No matching scheme/path " + data
+ " for " + this);
}
}
return dataMatch;
}
//不存在匹配的category，需要全部匹配
String categoryMismatch = matchCategories(categories);
if (categoryMismatch != null) {
if (false) {
Log.v(logTag, "No matching category " + categoryMismatch + " for " + this);
}
return NO_MATCH_CATEGORY;
}
// It would be nice to treat container activities as more
// important than ones that can be embedded, but this is not the way...
if (false) {
if (categories != null) {
dataMatch -= mCategories.size() - categories.size();
}
}
return dataMatch;
}
该方法用于匹配Intent的数据是否成功，匹配的数据包括action,type,data,category四项，任何一项匹配不成功都会失败。
2.4.3 AMS.broadcastQueueForIntent
[->ActivityManagerService.java]
BroadcastQueue broadcastQueueForIntent(Intent intent) {
final boolean isFg = (intent.getFlags() & Intent.FLAG_RECEIVER_FOREGROUND) != 0;
if (DEBUG_BROADCAST_BACKGROUND) Slog.i(TAG_BROADCAST,
"Broadcast intent " + intent + " on "
+ (isFg ? "foreground" : "background") + " queue");
return (isFg) ? mFgBroadcastQueue : mBgBroadcastQueue;
}
broadcastQueueForIntent通过判断intent中是否包含FLAG_RECEIVER_FOREGROUND来决定是前台广播还是后台广播
2.5 小结
注册广播：
1.注册广播的参数为广播BroadcastReceiver和过滤添加IntentFilter；
2.创建对象LoadedApk.ReceiverDispatcher.InnerReceiver,该对象集成于IIntentReceiver.Stub；
3.通过AMS把当前进程的ApplicationThread和InnerReceiver对象的代理类，注册到systemserver进程；
4.当广播receiver没有注册时，则创建广播接收者队列ReceiverList,该对象集成于ArrayList，并添加到AMS.mRegisteredReceivers(已注册广播队列)；
5.创建BroadcastFilter队列，并添加到AMS.mReceiverResolver
6.将BroadcastFilter添加到广播接收者的ReceiverList
当注册的广播为Sticky广播：
1.创建BroadcastRecord，并添加到BroadcastQueue中的mParallelBroadcasts，注册后，调用AMS处理该广播
2.根据注册的intent中是否包含FLAG_RECEIVER_FOREGROUND,包含则是mFgBroadcastQueue队列，否则为mBgBroadcastQueue队列。
三、发送广播
和注册广播一样，最后调用的是ContextImpl.sendBroadcast
3.1 CI.sendBroadcast
[->ContextImpl.java]
@Override
public void sendBroadcast(Intent intent) {
//UID如果是SYSTEM_UID则提示警告信息
//"Calling a method in the system process without a qualified user:""
warnIfCallingFromSystemProcess();
String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
try {
intent.prepareToLeaveProcess(this);
//通过binder方式调用AMS.broadcastIntent
ActivityManager.getService().broadcastIntent(
mMainThread.getApplicationThread(), intent, resolvedType, null,
Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false, false,
getUserId());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
3.2 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 bOptions,
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3.2节
int res = broadcastIntentLocked(callerApp,
callerApp != null ? callerApp.info.packageName : null,
intent, resolvedType, resultTo, resultCode, resultData, resultExtras,
requiredPermissions, appOp, bOptions, serialized, sticky,
callingPid, callingUid, userId);
Binder.restoreCallingIdentity(origId);
return res;
}
}
broadcastIntent有两个boolean值参数serialized、sticky共同决定是普通广播，有效广播，还是sticky广播。
| 类型 | serialized | sticky |
|---|---|---|
| sendBroadcast | false | false |
| sendOrderedBroadcast | true | false |
| sendStickyBroadcast | false | true |
3.3 AMS.broadcastIntentLocked
[->ActivityManagerService.java]
@GuardedBy("this")
final int broadcastIntentLocked(ProcessRecord callerApp,
String callerPackage, Intent intent, String resolvedType,
IIntentReceiver resultTo, int resultCode, String resultData,
Bundle resultExtras, String[] requiredPermissions, int appOp, Bundle bOptions,
boolean ordered, boolean sticky, int callingPid, int callingUid, int userId) {
//setp1：设置广播flags
//setp2：广播权限验证
//setp3：处理系统相关广播
//setp4：增加sticky广播
//setp5：查询receivers和registeredReceivers
//setp6：处理并行广播
//setp7：合并registeredReceivers到receivers
//setp8：处理串行广播
return ActivityManager.BROADCAST_SUCCESS;
}
该方法比较长，这里分为8部分进行分析。
3.3.1 设置广播flags
intent = new Intent(intent);
//判断是否是即时应用
final boolean callerInstantApp = isInstantApp(callerApp, callerPackage, callingUid);
//即时应用如果没有设置FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS则不会收到广播
// Instant Apps cannot use FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS
if (callerInstantApp) {
intent.setFlags(intent.getFlags() & ~Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS);
}
//增加flag,广播不会发送给已经停止的package
// By default broadcasts do not go to stopped apps.
intent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);
//系统没有启动完成，不允许启动新进程
// If we have not finished booting, don't allow this to launch new processes.
if (!mProcessesReady && (intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0) {
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
}
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST,
(sticky ? "Broadcast sticky: ": "Broadcast: ") + intent
+ " ordered=" + ordered + " userid=" + userId);
if ((resultTo != null) && !ordered) {
Slog.w(TAG, "Broadcast " + intent + " not ordered but result callback requested!");
}
userId = mUserController.handleIncomingUser(callingPid, callingUid, userId, true,
ALLOW_NON_FULL, "broadcast", callerPackage);
//检查发送广播时的用户状态
// Make sure that the user who is receiving this broadcast or its parent is running.
// If not, we will just skip it. Make an exception for shutdown broadcasts, upgrade steps.
if (userId != UserHandle.USER_ALL && !mUserController.isUserOrItsParentRunning(userId)) {
if ((callingUid != SYSTEM_UID
|| (intent.getFlags() & Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0)
&& !Intent.ACTION_SHUTDOWN.equals(intent.getAction())) {
Slog.w(TAG, "Skipping broadcast of " + intent
+ ": user " + userId + " and its parent (if any) are stopped");
return ActivityManager.BROADCAST_FAILED_USER_STOPPED;
}
}
这个过程主要的工作如下：
1.是否设置FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS标志，如果设置广播对即时应用可见；
2.添加flagFLAG_EXCLUDE_STOPPED_PACKAGES,保证已经停止的app不会收到广播；
3.当系统还没有启动完成，不允许启动新进程；
4.非USER_ALL广播且接收广播的用户没有处于Running的情况下，除非是系统升级广播和关键广播，否则直接返回。
BroadcastReceiver还有其他flag，位于Intent.java常量中：
FLAG_RECEIVER_REGISTERED_ONLY //只允许已经注册的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，只允许已注册的receiver接收广播
FLAG_RECEIVER_BOOT_UPGRADE //升级模式下，允许系统准备就绪前发送广播
FLAG_RECEIVER_INCLUDE_BACKGROUND //允许后台台receiver接收广播
FLAG_RECEIVER_EXCLUDE_BACKGROUND //不允许后台台receiver接收广播
FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS //广播对即时应用可见
3.3.2 广播权限验证
final String action = intent.getAction();
BroadcastOptions brOptions = null;
if (bOptions != null) {
brOptions = new BroadcastOptions(bOptions);
if (brOptions.getTemporaryAppWhitelistDuration() > 0) {
//如果AppWhitelistDuration>0,检查是否有CHANGE_DEVICE_IDLE_TEMP_WHITELIST权限
// See if the caller is allowed to do this. Note we are checking against
// the actual real caller (not whoever provided the operation as say a
// PendingIntent), because that who is actually supplied the arguments.
if (checkComponentPermission(
android.Manifest.permission.CHANGE_DEVICE_IDLE_TEMP_WHITELIST,
Binder.getCallingPid(), Binder.getCallingUid(), -1, true)
!= PackageManager.PERMISSION_GRANTED) {
String msg = "Permission Denial: " + intent.getAction()
+ " broadcast from " + callerPackage + " (pid=" + callingPid
+ ", uid=" + callingUid + ")"
+ " requires "
+ android.Manifest.permission.CHANGE_DEVICE_IDLE_TEMP_WHITELIST;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
}
//检查是否有后台限制
if (brOptions.isDontSendToRestrictedApps()
&& !isUidActiveLocked(callingUid)
&& isBackgroundRestrictedNoCheck(callingUid, callerPackage)) {
Slog.i(TAG, "Not sending broadcast " + action + " - app " + callerPackage
+ " has background restrictions");
return ActivityManager.START_CANCELED;
}
}
//检查受保护的广播只允许系统使用
// Verify that protected broadcasts are only being sent by system code,
// and that system code is only sending protected broadcasts.
final boolean isProtectedBroadcast;
try {
isProtectedBroadcast = AppGlobals.getPackageManager().isProtectedBroadcast(action);
} catch (RemoteException e) {
Slog.w(TAG, "Remote exception", e);
return ActivityManager.BROADCAST_SUCCESS;
}
final boolean isCallerSystem;
switch (UserHandle.getAppId(callingUid)) {
case ROOT_UID:
case SYSTEM_UID:
case PHONE_UID:
case BLUETOOTH_UID:
case NFC_UID:
case SE_UID:
case NETWORK_STACK_UID:
isCallerSystem = true;
break;
default:
isCallerSystem = (callerApp != null) && callerApp.persistent;
break;
}
//非系统发送的广播
// First line security check before anything else: stop non-system apps from
// sending protected broadcasts.
if (!isCallerSystem) {
//是保护广播，则抛出异常
if (isProtectedBroadcast) {
String msg = "Permission Denial: not allowed to send broadcast "
+ action + " from pid="
+ callingPid + ", uid=" + callingUid;
Slog.w(TAG, msg);
throw new SecurityException(msg);
} else if (AppWidgetManager.ACTION_APPWIDGET_CONFIGURE.equals(action)
|| AppWidgetManager.ACTION_APPWIDGET_UPDATE.equals(action)) {
//限制广播只发送自己
// Special case for compatibility: we don't want apps to send this,
// but historically it has not been protected and apps may be using it
// to poke their own app widget. So, instead of making it protected,
// just limit it to the caller.
if (callerPackage == null) {
String msg = "Permission Denial: not allowed to send broadcast "
+ action + " from unknown caller.";
Slog.w(TAG, msg);
throw new SecurityException(msg);
} else if (intent.getComponent() != null) {
// They are good enough to send to an explicit component... verify
// it is being sent to the calling app.
if (!intent.getComponent().getPackageName().equals(
callerPackage)) {
String msg = "Permission Denial: not allowed to send broadcast "
+ action + " to "
+ intent.getComponent().getPackageName() + " from "
+ callerPackage;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
} else {
// Limit broadcast to their own package.
intent.setPackage(callerPackage);
}
}
}
if (action != null) {
//如果允许后台应用接收广播，则添加FLAG_RECEIVER_INCLUDE_BACKGROUND
if (getBackgroundLaunchBroadcasts().contains(action)) {
if (DEBUG_BACKGROUND_CHECK) {
Slog.i(TAG, "Broadcast action " + action + " forcing include-background");
}
intent.addFlags(Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND);
}
主要工作如下：
1.如果TemporaryAppWhitelistDuration>0,检查是否有CHANGE_DEVICE_IDLE_TEMP_WHITELIST权限，没有抛出异常
2.检查是否后台限制发送广播，如果限制，则后台应用将不能发送广播
3.callingUid为 ROOT_UID， SYSTEM_UID，PHONE_UID，BLUETOOTH_UID，NFC_UID，SE_UID，NETWORK_STACK_UID和persistent进程时，可以发送受保护广播
4.为非系统应用发送广播时：当发送的是受保护的广播，则抛出异常；当action为ACTION_APPWIDGET_CONFIGURE或ACTION_APPWIDGET_UPDATE时，限制该广播只发送给自己，否则抛出异常。
5.如果允许后台应用接收广播，则添加FLAG_RECEIVER_INCLUDE_BACKGROUND
3.3.3 处理系统相关广播
switch (action) {
case Intent.ACTION_UID_REMOVED://uid移除
case Intent.ACTION_PACKAGE_REMOVED://package移除
case Intent.ACTION_PACKAGE_CHANGED://改变package
case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE://外部设备不可用
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE:
case Intent.ACTION_PACKAGES_SUSPENDED:
case Intent.ACTION_PACKAGES_UNSUSPENDED:
// Handle special intents: if this broadcast is from the package
// manager about a package being removed, we need to remove all of
// its activities from the history stack.
if (checkComponentPermission(
android.Manifest.permission.BROADCAST_PACKAGE_REMOVED,
callingPid, callingUid, -1, true)
!= PackageManager.PERMISSION_GRANTED) {
String msg = "Permission Denial: " + intent.getAction()
+ " broadcast from " + callerPackage + " (pid=" + callingPid
+ ", uid=" + callingUid + ")"
+ " requires "
+ android.Manifest.permission.BROADCAST_PACKAGE_REMOVED;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
switch (action) {
case Intent.ACTION_UID_REMOVED:
final int uid = getUidFromIntent(intent);
if (uid >= 0) {
mBatteryStatsService.removeUid(uid);
mAppOpsService.uidRemoved(uid);
}
break;
case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE:
// If resources are unavailable just force stop all those packages
// and flush the attribute cache as well.
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(
ApplicationThreadConstants.EXTERNAL_STORAGE_UNAVAILABLE,
list, userId);
}
break;
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE:
mRecentTasks.cleanupLocked(UserHandle.USER_ALL);
break;
case Intent.ACTION_PACKAGE_REMOVED:
case Intent.ACTION_PACKAGE_CHANGED:
Uri data = intent.getData();
String ssp;
if (data != null && (ssp=data.getSchemeSpecificPart()) != null) {
boolean removed = Intent.ACTION_PACKAGE_REMOVED.equals(action);
final boolean replacing =
intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);
final boolean killProcess =
!intent.getBooleanExtra(Intent.EXTRA_DONT_KILL_APP, false);
final boolean fullUninstall = removed && !replacing;
if (removed) {
if (killProcess) {
forceStopPackageLocked(ssp, UserHandle.getAppId(
intent.getIntExtra(Intent.EXTRA_UID, -1)),
false, true, true, false, fullUninstall, userId,
removed ? "pkg removed" : "pkg changed");
}
final int cmd = killProcess
? ApplicationThreadConstants.PACKAGE_REMOVED
: ApplicationThreadConstants.PACKAGE_REMOVED_DONT_KILL;
sendPackageBroadcastLocked(cmd,
new String[] {ssp}, userId);
if (fullUninstall) {
mAppOpsService.packageRemoved(
intent.getIntExtra(Intent.EXTRA_UID, -1), ssp);
// Remove all permissions granted from/to this package
removeUriPermissionsForPackageLocked(ssp, userId, true,
false);
mRecentTasks.removeTasksByPackageName(ssp, userId);
mServices.forceStopPackageLocked(ssp, userId);
mAppWarnings.onPackageUninstalled(ssp);
mCompatModePackages.handlePackageUninstalledLocked(ssp);
mBatteryStatsService.notePackageUninstalled(ssp);
}
} else {
if (killProcess) {
killPackageProcessesLocked(ssp, UserHandle.getAppId(
intent.getIntExtra(Intent.EXTRA_UID, -1)),
userId, ProcessList.INVALID_ADJ,
false, true, true, false, "change " + ssp);
}
cleanupDisabledPackageComponentsLocked(ssp, userId, killProcess,
intent.getStringArrayExtra(
Intent.EXTRA_CHANGED_COMPONENT_NAME_LIST));
}
}
break;
case Intent.ACTION_PACKAGES_SUSPENDED:
case Intent.ACTION_PACKAGES_UNSUSPENDED:
final boolean suspended = Intent.ACTION_PACKAGES_SUSPENDED.equals(
intent.getAction());
final String[] packageNames = intent.getStringArrayExtra(
Intent.EXTRA_CHANGED_PACKAGE_LIST);
final int userHandle = intent.getIntExtra(
Intent.EXTRA_USER_HANDLE, UserHandle.USER_NULL);
synchronized(ActivityManagerService.this) {
mRecentTasks.onPackagesSuspendedChanged(
packageNames, suspended, userHandle);
}
break;
}
break;
case Intent.ACTION_PACKAGE_REPLACED:
{
final Uri data = intent.getData();
final String ssp;
if (data != null && (ssp = data.getSchemeSpecificPart()) != null) {
ApplicationInfo aInfo = null;
try {
aInfo = AppGlobals.getPackageManager()
.getApplicationInfo(ssp, STOCK_PM_FLAGS, userId);
} catch (RemoteException ignore) {}
if (aInfo == null) {
Slog.w(TAG, "Dropping ACTION_PACKAGE_REPLACED for non-existent pkg:"
+ " ssp=" + ssp + " data=" + data);
return ActivityManager.BROADCAST_SUCCESS;
}
mStackSupervisor.updateActivityApplicationInfoLocked(aInfo);
mServices.updateServiceApplicationInfoLocked(aInfo);
sendPackageBroadcastLocked(ApplicationThreadConstants.PACKAGE_REPLACED,
new String[] {ssp}, userId);
}
break;
}
case Intent.ACTION_PACKAGE_ADDED:
{
// Special case for adding a package: by default turn on compatibility mode.
Uri data = intent.getData();
String ssp;
if (data != null && (ssp = data.getSchemeSpecificPart()) != null) {
final boolean replacing =
intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);
mCompatModePackages.handlePackageAddedLocked(ssp, replacing);
try {
ApplicationInfo ai = AppGlobals.getPackageManager().
getApplicationInfo(ssp, STOCK_PM_FLAGS, 0);
mBatteryStatsService.notePackageInstalled(ssp,
ai != null ? ai.versionCode : 0);
} catch (RemoteException e) {
}
}
break;
}
case Intent.ACTION_PACKAGE_DATA_CLEARED:
{
Uri data = intent.getData();
String ssp;
if (data != null && (ssp = data.getSchemeSpecificPart()) != null) {
mCompatModePackages.handlePackageDataClearedLocked(ssp);
mAppWarnings.onPackageDataCleared(ssp);
}
break;
}
case Intent.ACTION_TIMEZONE_CHANGED:
// If this is the time zone changed action, queue up a message that will reset
// the timezone of all currently running processes. This message will get
// queued up before the broadcast happens.
mHandler.sendEmptyMessage(UPDATE_TIME_ZONE);
break;
case Intent.ACTION_TIME_CHANGED:
// EXTRA_TIME_PREF_24_HOUR_FORMAT is optional so we must distinguish between
// the tri-state value it may contain and "unknown".
// For convenience we re-use the Intent extra values.
final int NO_EXTRA_VALUE_FOUND = -1;
final int timeFormatPreferenceMsgValue = intent.getIntExtra(
Intent.EXTRA_TIME_PREF_24_HOUR_FORMAT,
NO_EXTRA_VALUE_FOUND /* defaultValue */);
// Only send a message if the time preference is available.
if (timeFormatPreferenceMsgValue != NO_EXTRA_VALUE_FOUND) {
Message updateTimePreferenceMsg =
mHandler.obtainMessage(UPDATE_TIME_PREFERENCE_MSG,
timeFormatPreferenceMsgValue, 0);
mHandler.sendMessage(updateTimePreferenceMsg);
}
BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();
synchronized (stats) {
stats.noteCurrentTimeChangedLocked();
}
break;
case Intent.ACTION_CLEAR_DNS_CACHE: //清除DNS cache
mHandler.sendEmptyMessage(CLEAR_DNS_CACHE_MSG);
break;
case Proxy.PROXY_CHANGE_ACTION: //网络代理改变
mHandler.sendMessage(mHandler.obtainMessage(UPDATE_HTTP_PROXY_MSG));
break;
case android.hardware.Camera.ACTION_NEW_PICTURE:
case android.hardware.Camera.ACTION_NEW_VIDEO:
// In N we just turned these off; in O we are turing them back on partly,
// only for registered receivers. This will still address the main problem
// (a spam of apps waking up when a picture is taken putting significant
// memory pressure on the system at a bad point), while still allowing apps
// that are already actively running to know about this happening.
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
break;
case android.security.KeyChain.ACTION_TRUST_STORE_CHANGED:
mHandler.sendEmptyMessage(HANDLE_TRUST_STORAGE_UPDATE_MSG);
break;
case "com.android.launcher.action.INSTALL_SHORTCUT":
// As of O, we no longer support this broadcasts, even for pre-O apps.
// Apps should now be using ShortcutManager.pinRequestShortcut().
Log.w(TAG, "Broadcast " + action
+ " no longer supported. It will not be delivered.");
return ActivityManager.BROADCAST_SUCCESS;
}
if (Intent.ACTION_PACKAGE_ADDED.equals(action) ||
Intent.ACTION_PACKAGE_REMOVED.equals(action) ||
Intent.ACTION_PACKAGE_REPLACED.equals(action)) {
final int uid = getUidFromIntent(intent);
if (uid != -1) {
final UidRecord uidRec = mActiveUids.get(uid);
if (uidRec != null) {
uidRec.updateHasInternetPermission();
}
}
}
}
该过程主要系统广播，主要是package、时间、网络相关的广播，并对这些广播进行相应的处理。
3.3.4 增加sticky广播
// Add to the sticky list if requested.
if (sticky) {
//检查是否有BROADCAST_STICKY权限
if (checkPermission(android.Manifest.permission.BROADCAST_STICKY,
callingPid, callingUid)
!= PackageManager.PERMISSION_GRANTED) {
String msg = "Permission Denial: broadcastIntent() requesting a sticky broadcast from pid="
+ callingPid + ", uid=" + callingUid
+ " requires " + android.Manifest.permission.BROADCAST_STICKY;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
if (requiredPermissions != null && requiredPermissions.length > 0) {
Slog.w(TAG, "Can't broadcast sticky intent " + intent
+ " and enforce permissions " + Arrays.toString(requiredPermissions));
return ActivityManager.BROADCAST_STICKY_CANT_HAVE_PERMISSION;
}
//发送指定组件，抛出异常
if (intent.getComponent() != null) {
throw new SecurityException(
"Sticky broadcasts can't target a specific component");
}
//当非USER_ALL广播和USER_ALL冲突
// We use userId directly here, since the "all" target is maintained
// as a separate set of sticky broadcasts.
if (userId != UserHandle.USER_ALL) {
// But first, if this is not a broadcast to all users, then
// make sure it doesn't conflict with an existing broadcast to
// all users.
ArrayMap> stickies = mStickyBroadcasts.get(
UserHandle.USER_ALL);
if (stickies != null) {
ArrayList list = stickies.get(intent.getAction());
if (list != null) {
int N = list.size();
int i;
for (i=0; i> stickies = mStickyBroadcasts.get(userId);
if (stickies == null) {
stickies = new ArrayMap<>();
mStickyBroadcasts.put(userId, stickies);
}
ArrayList 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))) {
// This sticky already exists, replace it.
list.set(i, new Intent(intent));
break;
}
}
if (i >= stickiesCount) {
list.add(new Intent(intent));
}
}
这个过程主要是检查sticky广播，将sticky广播放入到mStickyBroadcasts，并增加到list
3.3.5 查询receivers和registeredReceivers
//发送广播的user
int[] users;
if (userId == UserHandle.USER_ALL) {
// Caller wants broadcast to go to all started users.
users = mUserController.getStartedUserArray();
} else {
// Caller wants broadcast to go to one specific user.
users = new int[] {userId};
}
//查询哪些广播将会接受广播
// Figure out who all will receive this broadcast.
List receivers = null;
List registeredReceivers = null;
// Need to resolve the intent to interested receivers...
//当允许静态接收者处理广播时，则通过PKMS根据intent查询静态receivers
if ((intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY)
== 0) {
receivers = collectReceiverComponents(intent, resolvedType, callingUid, users);
}
if (intent.getComponent() == null) {
if (userId == UserHandle.USER_ALL && callingUid == SHELL_UID) {
// Query one target user at a time, excluding shell-restricted users
for (int i = 0; i < users.length; i++) {
if (mUserController.hasUserRestriction(
UserManager.DISALLOW_DEBUGGING_FEATURES, users[i])) {
continue;
}
//查询动态注册广播
List registeredReceiversForUser =
mReceiverResolver.queryIntent(intent,
resolvedType, false /*defaultOnly*/, users[i]);
if (registeredReceivers == null) {
registeredReceivers = registeredReceiversForUser;
} else if (registeredReceiversForUser != null) {
registeredReceivers.addAll(registeredReceiversForUser);
}
}
} else {
registeredReceivers = mReceiverResolver.queryIntent(intent,
resolvedType, false /*defaultOnly*/, userId);
}
}
主要工作如下：
1.根据userId判断发送的是全部的接收者还是指定的userId
2.查询广播，并将其放入到两个列表：
registeredReceivers：来匹配当前intent的所有动态注册的广播接收者（mReceiverResolver见2.4节）
receivers：记录当前intent的所有静态注册的广播接收者
private List collectReceiverComponents(Intent intent, String resolvedType,
int callingUid, int[] users) {
...
//调用PKMS的queryIntentReceivers，可以获取AndroidManifeset中注册的接收信息
List newReceivers = AppGlobals.getPackageManager()
.queryIntentReceivers(intent, resolvedType, pmFlags, user).getList();
...
return receivers;
}
3.3.6 处理并行广播
//用于标识是否需要用新的intent替换旧的intent
final boolean replacePending =
(intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueueing broadcast: " + intent.getAction()
+ " replacePending=" + replacePending);
//处理并行广播
int NR = registeredReceivers != null ? registeredReceivers.size() : 0;
//发送的不是有序广播
if (!ordered && NR > 0) {
// If we are not serializing this broadcast, then send the
// registered receivers separately so they don't wait for the
// components to be launched.
//检查系统发送的广播
if (isCallerSystem) {
checkBroadcastFromSystem(intent, callerApp, callerPackage, callingUid,
isProtectedBroadcast, registeredReceivers);
}
//根据intent的flag来判断前台队列还是后台队列，见2.4.3节
final BroadcastQueue queue = broadcastQueueForIntent(intent);
//创建BroadcastRecord
BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
callerPackage, callingPid, callingUid, callerInstantApp, resolvedType,
requiredPermissions, appOp, brOptions, registeredReceivers, resultTo,
resultCode, resultData, resultExtras, ordered, sticky, false, userId);
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueueing parallel broadcast " + r);
final boolean replaced = replacePending
&& (queue.replaceParallelBroadcastLocked(r) != null);
// Note: We assume resultTo is null for non-ordered broadcasts.
if (!replaced) {
//将BroadcastRecord加入到并行广播队列
queue.enqueueParallelBroadcastLocked(r);
//处理广播，见4.1节
queue.scheduleBroadcastsLocked();
}
//动态注册的广播接收者处理完成，则将该变量设置为空
registeredReceivers = null;
NR = 0;
}
广播队列中有一个mParallelBroadcasts变量，类型为ArrayList，记录所有的并行广播
public void enqueueParallelBroadcastLocked(BroadcastRecord r) {
mParallelBroadcasts.add(r);
enqueueBroadcastHelper(r);
}
3.3.7 合并registeredReceivers到receivers
// Merge into one list.
int ir = 0;
if (receivers != null) {
//防止应用监听广播，在安装时直接运行
// A special case for PACKAGE_ADDED: do not allow the package
// being added to see this broadcast. This prevents them from
// using this as a back door to get run as soon as they are
// installed. Maybe in the future we want to have a special install
// broadcast or such for apps, but we'd like to deliberately make
// this decision.
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= curt.priority) {
// Insert this broadcast record into the final list.
receivers.add(it, curr);
ir++;
curr = null;
it++;
NT++;
} else {
// Skip to the next ResolveInfo in the final list.
it++;
curt = null;
}
}
}
while (ir < NR) {
if (receivers == null) {
receivers = new ArrayList();
}
receivers.add(registeredReceivers.get(ir));
ir++;
}
//检查系统发送的广播
if (isCallerSystem) {
checkBroadcastFromSystem(intent, callerApp, callerPackage, callingUid,
isProtectedBroadcast, receivers);
}
这里主要是将动态注册的registeredReceivers（如果发送的广播不是有序广播则registeredReceivers = null）全部合并到receivers，再统一按照串行方式处理。
3.3.8 处理串行广播
if ((receivers != null && receivers.size() > 0)
|| resultTo != null) {
//根据intent的flag判断是前台队列还是后台队列，见2.4.3节
BroadcastQueue queue = broadcastQueueForIntent(intent);
//创建BroadcastRecord
BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
callerPackage, callingPid, callingUid, callerInstantApp, resolvedType,
requiredPermissions, appOp, brOptions, receivers, resultTo, resultCode,
resultData, resultExtras, ordered, sticky, false, userId);
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueueing ordered broadcast " + r
+ ": prev had " + queue.mOrderedBroadcasts.size());
if (DEBUG_BROADCAST) Slog.i(TAG_BROADCAST,
"Enqueueing broadcast " + r.intent.getAction());
final BroadcastRecord oldRecord =
replacePending ? queue.replaceOrderedBroadcastLocked(r) : null;
if (oldRecord != null) {
// Replaced, fire the result-to receiver.
if (oldRecord.resultTo != null) {
final BroadcastQueue oldQueue = broadcastQueueForIntent(oldRecord.intent);
try {
oldQueue.performReceiveLocked(oldRecord.callerApp, oldRecord.resultTo,
oldRecord.intent,
Activity.RESULT_CANCELED, null, null,
false, false, oldRecord.userId);
} catch (RemoteException e) {
Slog.w(TAG, "Failure ["
+ queue.mQueueName + "] sending broadcast result of "
+ intent, e);
}
}
} else {
//将BroadcastRecord加入到有序广播队列
queue.enqueueOrderedBroadcastLocked(r);
//处理广播，见4.1节
queue.scheduleBroadcastsLocked();
}
} else {
// There was nobody interested in the broadcast, but we still want to record
// that it happened.
if (intent.getComponent() == null && intent.getPackage() == null
&& (intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY) == 0) {
// This was an implicit broadcast... let's record it for posterity.
addBroadcastStatLocked(intent.getAction(), callerPackage, 0, 0, 0);
}
}
广播队列中有一个mOrderedBroadcasts变量，类型为ArrayList，记录所有的有序广播
//串行广播加入到mOrderedBroadcasts队列
public void enqueueOrderedBroadcastLocked(BroadcastRecord r) {
mOrderedBroadcasts.add(r);
enqueueBroadcastHelper(r);
}
3.4 小结
发送广播的过程：
1.默认不发送给已停止的（FLAG_EXCLUDE_STOPPED_PACKAGES）应用和即时应用（需要添加该FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS标记才可以）
2.对广播进行权限验证，是否是受保护的广播，是否允许后台接收广播，是否允许后台发送广播
3.处理系统广播，主要是package、时间、网络相关的广播
4.当为粘性广播时，将sticky广播增加到list，并放入mStickyBroadcasts队列
5.当广播的intent没有设置FLAG_RECEIVER_REGISTERED_ONLY，则允许静态广播接收者来处理该广播；创建BroadcastRecord对象，并将该对象加入到相应的广播队列，然后调用BroadcastQueue的scheduleBroadcastsLocked方法来完成不同广播的处理。
不同广播的处理方式：
1.sticky广播：广播注册过程中处理AMS.registerReceiver，开始处理粘性广播，见2.4节
- 创建BroadcastRecord对象
- 添加到mParallelBroadcasts队列
- 然后执行 queue.scheduleBroadcastsLocked()
2.并行广播：广播发送处理过程见3.3.6节
- 只有动态注册的registeredReceivers才会进行并行处理
- 创建BroadcastRecord对象
- 添加到mParallelBroadcasts队列
- 然后执行 queue.scheduleBroadcastsLocked()
3.串行广播：广播发送处理过程见3.3.8节
- 所有静态注册的receivers以及动态注册的registeredReceivers（发送的广播是有序广播）合并到一张表处理
- 创建BroadcastRecord对象
- 添加到mOrderedBroadcasts队列
- 然后执行 queue.scheduleBroadcastsLocked()
从上面可以看出，不管哪种广播方式，都是通过broadcastQueueForIntent来根据intent的flag判段是前台队列还是后台队列广播，然后再调用对应广播队列的scheduleBroadcastsLocked方法来处理广播。
四、接收广播
在发送广播的过程会执行scheduleBroadcastsLocked方法来处理广播
4.1 BQ.scheduleBroadcastsLocked
[->BroadcastQueue.java]
public void scheduleBroadcastsLocked() {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Schedule broadcasts ["
+ mQueueName + "]: current="
+ mBroadcastsScheduled);
//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;
}
4.1.1 BroadcastHandler
[->BroadcastQueue.java]
private final class BroadcastHandler extends Handler {
public BroadcastHandler(Looper looper) {
super(looper, null, true);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case BROADCAST_INTENT_MSG: {
if (DEBUG_BROADCAST) Slog.v(
TAG_BROADCAST, "Received BROADCAST_INTENT_MSG");
//见4.2节
processNextBroadcast(true);
} break;
case BROADCAST_TIMEOUT_MSG: {
synchronized (mService) {
broadcastTimeoutLocked(true);
}
} break;
}
}
}
发送BROADCAST_INTENT_MSG消息后，BroadcastHandler进行处理，其初始化在构造函数中创建，而BroadcastQueue是在AMS初始化，从源码中可以看出handler采用的是"ActivityManagerService"线程的loop。
BroadcastQueue(ActivityManagerService service, Handler handler,
String name, long timeoutPeriod, boolean allowDelayBehindServices) {
mService = service;
//创建BroadcastHandler
mHandler = new BroadcastHandler(handler.getLooper());
mQueueName = name;
mTimeoutPeriod = timeoutPeriod;
mDelayBehindServices = allowDelayBehindServices;
}
public ActivityManagerService(Context systemContext) {
...
//名为ActivityManagerService的线程
mHandlerThread = new ServiceThread(TAG,
THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
mHandler = new MainHandler(mHandlerThread.getLooper());
//创建BroadcastQueue对象
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", BROADCAST_FG_TIMEOUT, false);
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", BROADCAST_BG_TIMEOUT, true);
//android10.0新增加的一个分流队列，目前仅处理BOOT_COMPLETED广播
// Convenient for easy iteration over the queues. Foreground is first
// so that dispatch of foreground broadcasts gets precedence.
final BroadcastQueue[] mBroadcastQueues = new BroadcastQueue[2];
...
}
//广播超时时间定义
// How long we allow a receiver to run before giving up on it.
static final int BROADCAST_FG_TIMEOUT = 10*1000;
static final int BROADCAST_BG_TIMEOUT = 60*1000;
4.2 BQ.processNextBroadcast
[->BroadcastQueue.java]
final void processNextBroadcast(boolean fromMsg) {
//同步mService
synchronized (mService) {
processNextBroadcastLocked(fromMsg, false);
}
}
此次mService为AMS，整个流程比较长，全程持有AMS锁，所以广播效率低下的情况下，直接会严重影响手机的性能和流畅度，这里是否应考虑细化同步锁的粒度。
final void processNextBroadcastLocked(boolean fromMsg, boolean skipOomAdj) {
//setp1：处理并行广播
//setp2：处理串行广播
//setp3：获取下条有序广播
//setp4：处理下条有序广播
}
整个处理的过程比较长，将分为四个部分进行分析。
4.2.1 处理并行广播
BroadcastRecord r;
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "processNextBroadcast ["
+ mQueueName + "]: "
+ mParallelBroadcasts.size() + " parallel broadcasts, "
+ mOrderedBroadcasts.size() + " ordered broadcasts");
//更新cpu统计信息
mService.updateCpuStats();
//方法传进来的是true，将mBroadcastsScheduled重置为false
if (fromMsg) {
mBroadcastsScheduled = false;
}
// 处理并行队列
// First, deliver any non-serialized broadcasts right away.
while (mParallelBroadcasts.size() > 0) {
r = mParallelBroadcasts.remove(0);
r.dispatchTime = SystemClock.uptimeMillis();
r.dispatchClockTime = System.currentTimeMillis();
if (Trace.isTagEnabled(Trace.TRACE_TAG_ACTIVITY_MANAGER)) {
Trace.asyncTraceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER,
createBroadcastTraceTitle(r, BroadcastRecord.DELIVERY_PENDING),
System.identityHashCode(r));
Trace.asyncTraceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER,
createBroadcastTraceTitle(r, BroadcastRecord.DELIVERY_DELIVERED),
System.identityHashCode(r));
}
final int N = r.receivers.size();
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST, "Processing parallel broadcast ["
+ mQueueName + "] " + r);
for (int i=0; i通过while循环，每次取出一个，一次性分发完所有的并发广播后，将分发完成的添加到历史广播队列。
4.2.2 处理串行广播
// Now take care of the next serialized one...
// If we are waiting for a process to come up to handle the next
// broadcast, then do nothing at this point. Just in case, we
// check that the process we're waiting for still exists.
if (mPendingBroadcast != null) {
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST,
"processNextBroadcast [" + mQueueName + "]: waiting for "
+ mPendingBroadcast.curApp);
boolean isDead;
if (mPendingBroadcast.curApp.pid > 0) {
synchronized (mService.mPidsSelfLocked) {
//从mPidsSelfLocked获取正在处理的广播进程，判断进程是否死亡
ProcessRecord proc = mService.mPidsSelfLocked.get(
mPendingBroadcast.curApp.pid);
isDead = proc == null || proc.crashing;
}
} else {
//从mProcessNames获取正在处理的广播进程，判断进程是否死亡
final ProcessRecord proc = mService.mProcessNames.get(
mPendingBroadcast.curApp.processName, mPendingBroadcast.curApp.uid);
isDead = proc == null || !proc.pendingStart;
}
if (!isDead) {
// 如果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
// It's still alive, so keep waiting
return;
} else {
Slog.w(TAG, "pending app ["
+ mQueueName + "]" + mPendingBroadcast.curApp
+ " died before responding to broadcast");
mPendingBroadcast.state = BroadcastRecord.IDLE;
mPendingBroadcast.nextReceiver = mPendingBroadcastRecvIndex;
mPendingBroadcast = null;
}
}
boolean looped = false;
do {
if (mOrderedBroadcasts.size() == 0) {
// No more broadcasts pending, so all done!
//所有的串行广播处理完成，则调度执行gc
mService.scheduleAppGcsLocked();
if (looped) {
// If we had finished the last ordered broadcast, then
// make sure all processes have correct oom and sched
// adjustments.
mService.updateOomAdjLocked();
}
return;
}
r = mOrderedBroadcasts.get(0);
boolean forceReceive = false;
// Ensure that even if something goes awry with the timeout
// detection, we catch "hung" broadcasts here, discard them,
// and continue to make progress.
//
// This is only done if the system is ready so that PRE_BOOT_COMPLETED
// receivers don't get executed with timeouts. They're intended for
// one time heavy lifting after system upgrades and can take
// significant amounts of time.
//所有有序广播的接收者
int numReceivers = (r.receivers != null) ? r.receivers.size() : 0;
//系统进程已经准备好
if (mService.mProcessesReady && r.dispatchTime > 0) {
long now = SystemClock.uptimeMillis();
if ((numReceivers > 0) &&
(now > r.dispatchTime + (2*mTimeoutPeriod*numReceivers))) {
Slog.w(TAG, "Hung broadcast ["
+ mQueueName + "] discarded after timeout failure:"
+ " now=" + now
+ " dispatchTime=" + r.dispatchTime
+ " startTime=" + r.receiverTime
+ " intent=" + r.intent
+ " numReceivers=" + numReceivers
+ " nextReceiver=" + r.nextReceiver
+ " state=" + r.state);
//广播超时，强制结束这条广播
broadcastTimeoutLocked(false); // forcibly finish this broadcast
forceReceive = true;
r.state = BroadcastRecord.IDLE;
}
}
if (r.state != BroadcastRecord.IDLE) {
if (DEBUG_BROADCAST) Slog.d(TAG_BROADCAST,
"processNextBroadcast("
+ mQueueName + ") called when not idle (state="
+ r.state + ")");
return;
}
if (r.receivers == null || r.nextReceiver >= numReceivers
|| r.resultAbort || forceReceive) {
// No more receivers for this broadcast! Send the final
// result if requested...
if (r.resultTo != null) {
try {
if (DEBUG_BROADCAST) Slog.i(TAG_BROADCAST,
"Finishing broadcast [" + mQueueName + "] "
+ r.intent.getAction() + " app=" + r.callerApp);
//处理广播消息，调用到onReceive()
performReceiveLocked(r.callerApp, r.resultTo,
new Intent(r.intent), r.resultCode,
r.resultData, r.resultExtras, false, false, r.userId);
// Set this to null so that the reference
// (local and remote) isn't kept in the mBroadcastHistory.
r.resultTo = null;
} catch (RemoteException e) {
r.resultTo = null;
Slog.w(TAG, "Failure ["
+ mQueueName + "] sending broadcast result of "
+ r.intent, e);
}
}
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Cancelling BROADCAST_TIMEOUT_MSG");
//取消BROADCAST_TIMEOUT_MSG消息
cancelBroadcastTimeoutLocked();
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST,
"Finished with ordered broadcast " + r);
// 添加到队列消息记录
// ... and on to the next...
addBroadcastToHistoryLocked(r);
if (r.intent.getComponent() == null && r.intent.getPackage() == null
&& (r.intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY) == 0) {
// This was an implicit broadcast... let's record it for posterity.
mService.addBroadcastStatLocked(r.intent.getAction(), r.callerPackage,
r.manifestCount, r.manifestSkipCount, r.finishTime-r.dispatchTime);
}
mOrderedBroadcasts.remove(0);
r = null;
looped = true;
continue;
}
} while (r == null);
mTimeoutPeriod，对于前台广播为10s,后台广播为60s。广播超时为2 * mTimeoutPeriod * numReceivers，接收者个数numReceivers越多，则广播超时总时间越大。
4.2.3 获取下条有序广播
//获取下条广播的index
// Get the next receiver...
int recIdx = r.nextReceiver++;
// Keep track of when this receiver started, and make sure there
// is a timeout message pending to kill it if need be.
//记录开始时间
r.receiverTime = SystemClock.uptimeMillis();
if (recIdx == 0) {
r.dispatchTime = r.receiverTime;
r.dispatchClockTime = System.currentTimeMillis();
if (Trace.isTagEnabled(Trace.TRACE_TAG_ACTIVITY_MANAGER)) {
Trace.asyncTraceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER,
createBroadcastTraceTitle(r, BroadcastRecord.DELIVERY_PENDING),
System.identityHashCode(r));
Trace.asyncTraceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER,
createBroadcastTraceTitle(r, BroadcastRecord.DELIVERY_DELIVERED),
System.identityHashCode(r));
}
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST, "Processing ordered broadcast ["
+ mQueueName + "] " + r);
}
if (! mPendingBroadcastTimeoutMessage) {
long timeoutTime = r.receiverTime + mTimeoutPeriod;
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Submitting BROADCAST_TIMEOUT_MSG ["
+ mQueueName + "] for " + r + " at " + timeoutTime);
//发送广播超时
setBroadcastTimeoutLocked(timeoutTime);
}
final BroadcastOptions brOptions = r.options;
final Object nextReceiver = r.receivers.get(recIdx);
if (nextReceiver instanceof BroadcastFilter) {
// Simple case: this is a registered receiver who gets
// a direct call.
//对于动态注册的广播接收者
BroadcastFilter filter = (BroadcastFilter)nextReceiver;
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Delivering ordered ["
+ mQueueName + "] to registered "
+ filter + ": " + r);
//处理广播，见4.3节
deliverToRegisteredReceiverLocked(r, filter, r.ordered, recIdx);
if (r.receiver == null || !r.ordered) {
// The receiver has already finished, so schedule to
// process the next one.
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Quick finishing ["
+ mQueueName + "]: ordered="
+ r.ordered + " receiver=" + r.receiver);
r.state = BroadcastRecord.IDLE;
//处理下一个广播
scheduleBroadcastsLocked();
} else {
if (brOptions != null && brOptions.getTemporaryAppWhitelistDuration() > 0) {
scheduleTempWhitelistLocked(filter.owningUid,
brOptions.getTemporaryAppWhitelistDuration(), r);
}
}
return;
}
// Hard case: need to instantiate the receiver, possibly
// starting its application process to host it.
//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);
//下面都是各种检查权限，权限不满足时则跳过
boolean skip = false;
if (brOptions != null &&
(info.activityInfo.applicationInfo.targetSdkVersion
< brOptions.getMinManifestReceiverApiLevel() ||
info.activityInfo.applicationInfo.targetSdkVersion
> brOptions.getMaxManifestReceiverApiLevel())) {
skip = true; //sdk版本，Androidmanifest中设置
}
int perm = mService.checkComponentPermission(info.activityInfo.permission,
r.callingPid, r.callingUid, info.activityInfo.applicationInfo.uid,
info.activityInfo.exported);
//Component权限
if (!skip && perm != PackageManager.PERMISSION_GRANTED) {
if (!info.activityInfo.exported) {
Slog.w(TAG, "Permission Denial: broadcasting "
+ r.intent.toString()
+ " from " + r.callerPackage + " (pid=" + r.callingPid
+ ", uid=" + r.callingUid + ")"
+ " is not exported from uid " + info.activityInfo.applicationInfo.uid
+ " due to receiver " + component.flattenToShortString());
} else {
Slog.w(TAG, "Permission Denial: broadcasting "
+ r.intent.toString()
+ " from " + r.callerPackage + " (pid=" + r.callingPid
+ ", uid=" + r.callingUid + ")"
+ " requires " + info.activityInfo.permission
+ " due to receiver " + component.flattenToShortString());
}
skip = true;
} else if (!skip && info.activityInfo.permission != null) {
final int opCode = AppOpsManager.permissionToOpCode(info.activityInfo.permission);
if (opCode != AppOpsManager.OP_NONE
&& mService.mAppOpsService.noteOperation(opCode, r.callingUid,
r.callerPackage) != AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: broadcasting "
+ r.intent.toString()
+ " from " + r.callerPackage + " (pid="
+ r.callingPid + ", uid=" + r.callingUid + ")"
+ " requires appop " + AppOpsManager.permissionToOp(
info.activityInfo.permission)
+ " due to registered receiver "
+ component.flattenToShortString());
skip = true;
}
}
if (!skip && info.activityInfo.applicationInfo.uid != Process.SYSTEM_UID &&
r.requiredPermissions != null && r.requiredPermissions.length > 0) {
for (int i = 0; i < r.requiredPermissions.length; i++) {
String requiredPermission = r.requiredPermissions[i];
try {
perm = AppGlobals.getPackageManager().
checkPermission(requiredPermission,
info.activityInfo.applicationInfo.packageName,
UserHandle
.getUserId(info.activityInfo.applicationInfo.uid));
} catch (RemoteException e) {
perm = PackageManager.PERMISSION_DENIED;
}
if (perm != PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: receiving "
+ r.intent + " to "
+ component.flattenToShortString()
+ " requires " + requiredPermission
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
break;
}
int appOp = AppOpsManager.permissionToOpCode(requiredPermission);
if (appOp != AppOpsManager.OP_NONE && appOp != r.appOp
&& mService.mAppOpsService.noteOperation(appOp,
info.activityInfo.applicationInfo.uid, info.activityInfo.packageName)
!= AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: receiving "
+ r.intent + " to "
+ component.flattenToShortString()
+ " requires appop " + AppOpsManager.permissionToOp(
requiredPermission)
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
break;
}
}
}
if (!skip && r.appOp != AppOpsManager.OP_NONE
&& mService.mAppOpsService.noteOperation(r.appOp,
info.activityInfo.applicationInfo.uid, info.activityInfo.packageName)
!= AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: receiving "
+ r.intent + " to "
+ component.flattenToShortString()
+ " requires appop " + AppOpsManager.opToName(r.appOp)
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
}
if (!skip) {
skip = !mService.mIntentFirewall.checkBroadcast(r.intent, r.callingUid,
r.callingPid, r.resolvedType, info.activityInfo.applicationInfo.uid);
}
boolean isSingleton = false;
try {
isSingleton = mService.isSingleton(info.activityInfo.processName,
info.activityInfo.applicationInfo,
info.activityInfo.name, info.activityInfo.flags);
} catch (SecurityException e) {
Slog.w(TAG, e.getMessage());
skip = true;
}
if ((info.activityInfo.flags&ActivityInfo.FLAG_SINGLE_USER) != 0) {
if (ActivityManager.checkUidPermission(
android.Manifest.permission.INTERACT_ACROSS_USERS,
info.activityInfo.applicationInfo.uid)
!= PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: Receiver " + component.flattenToShortString()
+ " requests FLAG_SINGLE_USER, but app does not hold "
+ android.Manifest.permission.INTERACT_ACROSS_USERS);
skip = true;
}
}
if (!skip && info.activityInfo.applicationInfo.isInstantApp()
&& r.callingUid != info.activityInfo.applicationInfo.uid) {
Slog.w(TAG, "Instant App Denial: receiving "
+ r.intent
+ " to " + component.flattenToShortString()
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")"
+ " Instant Apps do not support manifest receivers");
skip = true;
}
if (!skip && r.callerInstantApp
&& (info.activityInfo.flags & ActivityInfo.FLAG_VISIBLE_TO_INSTANT_APP) == 0
&& r.callingUid != info.activityInfo.applicationInfo.uid) {
Slog.w(TAG, "Instant App Denial: receiving "
+ r.intent
+ " to " + component.flattenToShortString()
+ " requires receiver have visibleToInstantApps set"
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
}
if (r.curApp != null && r.curApp.crashing) {
// If the target process is crashing, just skip it.
Slog.w(TAG, "Skipping deliver ordered [" + mQueueName + "] " + r
+ " to " + r.curApp + ": process crashing");
skip = true;
}
if (!skip) {
boolean isAvailable = false;
try {
isAvailable = AppGlobals.getPackageManager().isPackageAvailable(
info.activityInfo.packageName,
UserHandle.getUserId(info.activityInfo.applicationInfo.uid));
} catch (Exception e) {
// all such failures mean we skip this receiver
Slog.w(TAG, "Exception getting recipient info for "
+ info.activityInfo.packageName, e);
}
if (!isAvailable) {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Skipping delivery to " + info.activityInfo.packageName + " / "
+ info.activityInfo.applicationInfo.uid
+ " : package no longer available");
skip = true;
}
}
// If permissions need a review before any of the app components can run, we drop
// the broadcast and if the calling app is in the foreground and the broadcast is
// explicit we launch the review UI passing it a pending intent to send the skipped
// broadcast.
if (mService.mPermissionReviewRequired && !skip) {
if (!requestStartTargetPermissionsReviewIfNeededLocked(r,
info.activityInfo.packageName, UserHandle.getUserId(
info.activityInfo.applicationInfo.uid))) {
skip = true;
}
}
// This is safe to do even if we are skipping the broadcast, and we need
// this information now to evaluate whether it is going to be allowed to run.
final int receiverUid = info.activityInfo.applicationInfo.uid;
// If it's a singleton, it needs to be the same app or a special app
if (r.callingUid != Process.SYSTEM_UID && isSingleton
&& mService.isValidSingletonCall(r.callingUid, receiverUid)) {
info.activityInfo = mService.getActivityInfoForUser(info.activityInfo, 0);
}
String targetProcess = info.activityInfo.processName;
ProcessRecord app = mService.getProcessRecordLocked(targetProcess,
info.activityInfo.applicationInfo.uid, false);
if (!skip) {
final int allowed = mService.getAppStartModeLocked(
info.activityInfo.applicationInfo.uid, info.activityInfo.packageName,
info.activityInfo.applicationInfo.targetSdkVersion, -1, true, false, false);
if (allowed != ActivityManager.APP_START_MODE_NORMAL) {
// We won't allow this receiver to be launched if the app has been
// completely disabled from launches, or it was not explicitly sent
// to it and the app is in a state that should not receive it
// (depending on how getAppStartModeLocked has determined that).
if (allowed == ActivityManager.APP_START_MODE_DISABLED) {
Slog.w(TAG, "Background execution disabled: receiving "
+ r.intent + " to "
+ component.flattenToShortString());
skip = true;
} else if (((r.intent.getFlags()&Intent.FLAG_RECEIVER_EXCLUDE_BACKGROUND) != 0)
|| (r.intent.getComponent() == null
&& r.intent.getPackage() == null
&& ((r.intent.getFlags()
& Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND) == 0)
&& !isSignaturePerm(r.requiredPermissions))) {
mService.addBackgroundCheckViolationLocked(r.intent.getAction(),
component.getPackageName());
Slog.w(TAG, "Background execution not allowed: receiving "
+ r.intent + " to "
+ component.flattenToShortString());
skip = true;
}
}
}
if (!skip && !Intent.ACTION_SHUTDOWN.equals(r.intent.getAction())
&& !mService.mUserController
.isUserRunning(UserHandle.getUserId(info.activityInfo.applicationInfo.uid),
0 /* flags */)) {
skip = true;
Slog.w(TAG,
"Skipping delivery to " + info.activityInfo.packageName + " / "
+ info.activityInfo.applicationInfo.uid + " : user is not running");
}
//跳过该广播
if (skip) {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Skipping delivery of ordered [" + mQueueName + "] "
+ r + " for whatever reason");
r.delivery[recIdx] = BroadcastRecord.DELIVERY_SKIPPED;
r.receiver = null;
r.curFilter = null;
r.state = BroadcastRecord.IDLE;
r.manifestSkipCount++;
scheduleBroadcastsLocked();
return;
}
r.manifestCount++;
r.delivery[recIdx] = BroadcastRecord.DELIVERY_DELIVERED;
r.state = BroadcastRecord.APP_RECEIVE;
r.curComponent = component;
r.curReceiver = info.activityInfo;
if (DEBUG_MU && r.callingUid > UserHandle.PER_USER_RANGE) {
Slog.v(TAG_MU, "Updated broadcast record activity info for secondary user, "
+ info.activityInfo + ", callingUid = " + r.callingUid + ", uid = "
+ receiverUid);
}
if (brOptions != null && brOptions.getTemporaryAppWhitelistDuration() > 0) {
scheduleTempWhitelistLocked(receiverUid,
brOptions.getTemporaryAppWhitelistDuration(), r);
}
// Broadcast正在执行，stopped状态设置成false
// Broadcast is being executed, its package can't be stopped.
try {
AppGlobals.getPackageManager().setPackageStoppedState(
r.curComponent.getPackageName(), false, UserHandle.getUserId(r.callingUid));
} catch (RemoteException e) {
} catch (IllegalArgumentException e) {
Slog.w(TAG, "Failed trying to unstop package "
+ r.curComponent.getPackageName() + ": " + e);
}
发送广播超时，如果是动态注册的广播则执行deliverToRegisteredReceiverLocked方法，如果是静态注册的广播，则进行一系列的权限检查，不满足则跳过该广播。
4.2.4 处理下条有序广播
// Is this receiver's application already running?
if (app != null && app.thread != null && !app.killed) {
// 接收广播的进程还在运行
try {
app.addPackage(info.activityInfo.packageName,
info.activityInfo.applicationInfo.versionCode, mService.mProcessStats);
processCurBroadcastLocked(r, app, skipOomAdj);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when sending broadcast to "
+ r.curComponent, e);
} catch (RuntimeException e) {
Slog.wtf(TAG, "Failed sending broadcast to "
+ r.curComponent + " with " + r.intent, e);
// If some unexpected exception happened, just skip
// this broadcast. At this point we are not in the call
// from a client, so throwing an exception out from here
// will crash the entire system instead of just whoever
// sent the broadcast.
logBroadcastReceiverDiscardLocked(r);
finishReceiverLocked(r, r.resultCode, r.resultData,
r.resultExtras, r.resultAbort, false);
scheduleBroadcastsLocked();
//如果启动receiver失败，则重置状态
// We need to reset the state if we failed to start the receiver.
r.state = BroadcastRecord.IDLE;
return;
}
// If a dead object exception was thrown -- fall through to
// restart the application.
}
// Not running -- get it started, to be executed when the app comes up.
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Need to start app ["
+ mQueueName + "] " + targetProcess + " for broadcast " + r);
//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) {
// Ah, this recipient is unavailable. Finish it if necessary,
// and mark the broadcast record as ready for the next.
Slog.w(TAG, "Unable to launch app "
+ info.activityInfo.applicationInfo.packageName + "/"
+ receiverUid + " for broadcast "
+ r.intent + ": process is bad");
//创建失败，直接结束该receiver
logBroadcastReceiverDiscardLocked(r);
finishReceiverLocked(r, r.resultCode, r.resultData,
r.resultExtras, r.resultAbort, false);
//开启下一个广播
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
-
如果是静态广播接收者，且对应进程已经创建，则调用processCurBroadcastLocked处理
-
如果是静态广播接收者，且对应进程未创建，则调用startProcessLocked创建进程
4.3 BQ.deliverToRegisteredReceiverLocked
[->BroadcastQueue.java]
private void deliverToRegisteredReceiverLocked(BroadcastRecord r,
BroadcastFilter filter, boolean ordered, int index) {
boolean skip = false;
//检查发送者是否有BroadcastFilter所需要的权限
if (filter.requiredPermission != null) {
int perm = mService.checkComponentPermission(filter.requiredPermission,
r.callingPid, r.callingUid, -1, true);
if (perm != PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: broadcasting "
+ r.intent.toString()
+ " from " + r.callerPackage + " (pid="
+ r.callingPid + ", uid=" + r.callingUid + ")"
+ " requires " + filter.requiredPermission
+ " due to registered receiver " + filter);
skip = true;
} else {
final int opCode = AppOpsManager.permissionToOpCode(filter.requiredPermission);
if (opCode != AppOpsManager.OP_NONE
&& mService.mAppOpsService.noteOperation(opCode, r.callingUid,
r.callerPackage) != AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: broadcasting "
+ r.intent.toString()
+ " from " + r.callerPackage + " (pid="
+ r.callingPid + ", uid=" + r.callingUid + ")"
+ " requires appop " + AppOpsManager.permissionToOp(
filter.requiredPermission)
+ " due to registered receiver " + filter);
skip = true;
}
}
}
if (!skip && r.requiredPermissions != null && r.requiredPermissions.length > 0) {
for (int i = 0; i < r.requiredPermissions.length; i++) {
String requiredPermission = r.requiredPermissions[i];
int perm = mService.checkComponentPermission(requiredPermission,
filter.receiverList.pid, filter.receiverList.uid, -1, true);
if (perm != PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " requires " + requiredPermission
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
break;
}
int appOp = AppOpsManager.permissionToOpCode(requiredPermission);
if (appOp != AppOpsManager.OP_NONE && appOp != r.appOp
&& mService.mAppOpsService.noteOperation(appOp,
filter.receiverList.uid, filter.packageName)
!= AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " requires appop " + AppOpsManager.permissionToOp(
requiredPermission)
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
break;
}
}
}
if (!skip && (r.requiredPermissions == null || r.requiredPermissions.length == 0)) {
int perm = mService.checkComponentPermission(null,
filter.receiverList.pid, filter.receiverList.uid, -1, true);
if (perm != PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: security check failed when receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
}
}
if (!skip && r.appOp != AppOpsManager.OP_NONE
&& mService.mAppOpsService.noteOperation(r.appOp,
filter.receiverList.uid, filter.packageName)
!= AppOpsManager.MODE_ALLOWED) {
Slog.w(TAG, "Appop Denial: receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " requires appop " + AppOpsManager.opToName(r.appOp)
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
}
if (!mService.mIntentFirewall.checkBroadcast(r.intent, r.callingUid,
r.callingPid, r.resolvedType, filter.receiverList.uid)) {
skip = true;
}
if (!skip && (filter.receiverList.app == null || filter.receiverList.app.killed
|| filter.receiverList.app.crashing)) {
Slog.w(TAG, "Skipping deliver [" + mQueueName + "] " + r
+ " to " + filter.receiverList + ": process gone or crashing");
skip = true;
}
//即时应用检查
// Ensure that broadcasts are only sent to other Instant Apps if they are marked as
// visible to Instant Apps.
final boolean visibleToInstantApps =
(r.intent.getFlags() & Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
if (!skip && !visibleToInstantApps && filter.instantApp
&& filter.receiverList.uid != r.callingUid) {
Slog.w(TAG, "Instant App Denial: receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")"
+ " not specifying FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS");
skip = true;
}
if (!skip && !filter.visibleToInstantApp && r.callerInstantApp
&& filter.receiverList.uid != r.callingUid) {
Slog.w(TAG, "Instant App Denial: receiving "
+ r.intent.toString()
+ " to " + filter.receiverList.app
+ " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")"
+ " requires receiver be visible to instant apps"
+ " due to sender " + r.callerPackage
+ " (uid " + r.callingUid + ")");
skip = true;
}
if (skip) {
r.delivery[index] = BroadcastRecord.DELIVERY_SKIPPED;
return;
}
// If permissions need a review before any of the app components can run, we drop
// the broadcast and if the calling app is in the foreground and the broadcast is
// explicit we launch the review UI passing it a pending intent to send the skipped
// broadcast.
if (mService.mPermissionReviewRequired) {
if (!requestStartTargetPermissionsReviewIfNeededLocked(r, filter.packageName,
filter.owningUserId)) {
r.delivery[index] = BroadcastRecord.DELIVERY_SKIPPED;
return;
}
}
r.delivery[index] = BroadcastRecord.DELIVERY_DELIVERED;
//如果是有序广播
// If this is not being sent as an ordered broadcast, then we
// don't want to touch the fields that keep track of the current
// state of ordered broadcasts.
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) {
// Bump hosting application to no longer be in background
// scheduling class. Note that we can't do that if there
// isn't an app... but we can only be in that case for
// things that directly call the IActivityManager API, which
// are already core system stuff so don't matter for this.
r.curApp = filter.receiverList.app;
filter.receiverList.app.curReceivers.add(r);
mService.updateOomAdjLocked(r.curApp, true);
}
}
try {
if (DEBUG_BROADCAST_LIGHT) Slog.i(TAG_BROADCAST,
"Delivering to " + filter + " : " + r);
if (filter.receiverList.app != null && filter.receiverList.app.inFullBackup) {
// Skip delivery if full backup in progress
// If it's an ordered broadcast, we need to continue to the next receiver.
if (ordered) {
//跳过有序广播
skipReceiverLocked(r);
}
} else {
//处理广播，见4.4节
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;
}
} catch (RemoteException e) {
Slog.w(TAG, "Failure sending broadcast " + r.intent, e);
if (ordered) {
r.receiver = null;
r.curFilter = null;
filter.receiverList.curBroadcast = null;
if (filter.receiverList.app != null) {
filter.receiverList.app.curReceivers.remove(r);
}
}
}
}
这里是检查动态注册的广播的相关权限，如果是有序广播则跳过。最后执行performReceiveLocked处理并行广播。
4.4 BQ.performReceiveLocked
[->BroadcastQueue.java]
void performReceiveLocked(ProcessRecord app, IIntentReceiver receiver,
Intent intent, int resultCode, String data, Bundle extras,
boolean ordered, boolean sticky, int sendingUser) throws RemoteException {
// Send the intent to the receiver asynchronously using one-way binder calls.
//通过binder机制，发送到广播接收者
if (app != null) {
if (app.thread != null) {
// If we have an app thread, do the call through that so it is
// correctly ordered with other one-way calls.
try {
//见4.5节
app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
data, extras, ordered, sticky, sendingUser, app.repProcState);
// TODO: Uncomment this when (b/28322359) is fixed and we aren't getting
// DeadObjectException when the process isn't actually dead.
//} catch (DeadObjectException ex) {
// Failed to call into the process. It's dying so just let it die and move on.
// throw ex;
} catch (RemoteException ex) {
// Failed to call into the process. It's either dying or wedged. Kill it gently.
synchronized (mService) {
Slog.w(TAG, "Can't deliver broadcast to " + app.processName
+ " (pid " + app.pid + "). Crashing it.");
app.scheduleCrash("can't deliver broadcast");
}
throw ex;
}
} else {
//应有进程死亡，则应有不存在
// Application has died. Receiver doesn't exist.
throw new RemoteException("app.thread must not be null");
}
} else {
//调用者进程为空
receiver.performReceive(intent, resultCode, data, extras, ordered,
sticky, sendingUser);
}
}
通过app.thread获取到IApplicationThread代理类，通过这个代理类，访问到ApplicationThread中的方法。
4.5 AT.scheduleRegisteredReceiver
[->ActivityThread.java::ApplicationThread]
// This function exists to make sure all receiver dispatching is
// correctly ordered, since these are one-way calls and the binder driver
// applies transaction ordering per object for such calls.
public void scheduleRegisteredReceiver(IIntentReceiver receiver, Intent intent,
int resultCode, String dataStr, Bundle extras, boolean ordered,
boolean sticky, int sendingUser, int processState) throws RemoteException {
//更新进程状态
updateProcessState(processState, false);
//见4.6节，其中receiver为2.3.2节所创建
receiver.performReceive(intent, resultCode, dataStr, extras, ordered,
sticky, sendingUser);
}
receiver是注册广播时创建的，见2.3.3节 receiver=LoadedApk.ReceiverDispatcher.InnerReceiver
4.6 IR.performReceive
[->LoadedApk.java::InnerReceiver]
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) {
//见4.7节
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();
}
}
}
4.7 RD.performReceive
[->LoadedApk.java::ReceiverDispatcher]
public void performReceive(Intent intent, int resultCode, String data,
Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
final Args args = new Args(intent, resultCode, data, extras, ordered,
sticky, sendingUser);
if (intent == null) {
Log.wtf(TAG, "Null intent received");
} else {
if (ActivityThread.DEBUG_BROADCAST) {
int seq = intent.getIntExtra("seq", -1);
Slog.i(ActivityThread.TAG, "Enqueueing broadcast " + intent.getAction()
+ " seq=" + seq + " to " + mReceiver);
}
}
//见4.8节
if (intent == null || !mActivityThread.post(args.getRunnable())) {
//消息post到主线程，则不会走这里
if (mRegistered && ordered) {
IActivityManager mgr = ActivityManager.getService();
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing sync broadcast to " + mReceiver);
args.sendFinished(mgr);
}
}
}
Args继承于BroadcastReceiver.PendingResult，实现了Runnable，其中mActivityThread是当前的主线程，在2.3.1节完成赋值，post消息机制，将消息放入MessageQueue，该消息是Runnable,而后执行该Runnable。
4.8 ReceiverDispatcher.Args.getRunnable
[->LoadedApk.java]
public final Runnable getRunnable() {
return () -> {
final BroadcastReceiver receiver = mReceiver;
final boolean ordered = mOrdered;
if (ActivityThread.DEBUG_BROADCAST) {
int seq = mCurIntent.getIntExtra("seq", -1);
Slog.i(ActivityThread.TAG, "Dispatching broadcast " + mCurIntent.getAction()
+ " seq=" + seq + " to " + mReceiver);
Slog.i(ActivityThread.TAG, " mRegistered=" + mRegistered
+ " mOrderedHint=" + ordered);
}
final IActivityManager mgr = ActivityManager.getService();
final Intent intent = mCurIntent;
if (intent == null) {
Log.wtf(TAG, "Null intent being dispatched, mDispatched=" + mDispatched
+ ": run() previously called at "
+ Log.getStackTraceString(mPreviousRunStacktrace));
}
mCurIntent = null;
mDispatched = true;
mPreviousRunStacktrace = new Throwable("Previous stacktrace");
if (receiver == null || intent == null || mForgotten) {
if (mRegistered && ordered) {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing null broadcast to " + mReceiver);
sendFinished(mgr);
}
return;
}
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastReceiveReg");
try {
//获取mReceiver的类加载器
ClassLoader cl = mReceiver.getClass().getClassLoader();
intent.setExtrasClassLoader(cl);
intent.prepareToEnterProcess();
setExtrasClassLoader(cl);
receiver.setPendingResult(this);
//调用receiver的onReceive回调
receiver.onReceive(mContext, intent);
} catch (Exception e) {
if (mRegistered && ordered) {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing failed broadcast to " + mReceiver);
sendFinished(mgr);
}
if (mInstrumentation == null ||
!mInstrumentation.onException(mReceiver, e)) {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
throw new RuntimeException(
"Error receiving broadcast " + intent
+ " in " + mReceiver, e);
}
}
if (receiver.getPendingResult() != null) {
//见4.9节
finish();
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
};
}
4.9 PendingResult.finish
[->BroadcastReceiver.java::PendingResult]
/* Finish the broadcast. The current result will be sent and the
* next broadcast will proceed.
*/
public final void finish() {
if (mType == TYPE_COMPONENT) {//代表静态注册的广播
final IActivityManager mgr = ActivityManager.getService();
if (QueuedWork.hasPendingWork()) {
// If this is a broadcast component, we need to make sure any
// queued work is complete before telling AM we are done, so
// we don't have our process killed before that. We now know
// there is pending work; put another piece of work at the end
// of the list to finish the broadcast, so we don't block this
// thread (which may be the main thread) to have it finished.
//
// Note that we don't need to use QueuedWork.addFinisher() with the
// runnable, since we know the AM is waiting for us until the
// executor gets to it.
QueuedWork.queue(new Runnable() {
@Override public void run() {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast after work to component " + mToken);
sendFinished(mgr);//见4.9.1节
}
}, false);
} else {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to component " + mToken);
sendFinished(mgr);//见4.9.1节
}
} else if (mOrderedHint && mType != TYPE_UNREGISTERED) { //动态注册的串行广播
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to " + mToken);
final IActivityManager mgr = ActivityManager.getService();
sendFinished(mgr);//见4.9.1节
}
}
主要工作：
1.静态注册的广播接收者:
-
当QueuedWork工作未完成时，则等待完成再执行sendFinished
-
当QueuedWork工作已经完成，直接调用sendFinished方法
2.动态注册的广播接收者：当发送的是串行广播，则直接调用sendFinished
参数说明：
TYPE_COMPONENT：静态注册
TYPE_REGISTERED：动态注册
TYPE_UNREGISTERED：取消注册
4.9.1 PendingResult.sendFinished
[->BroadcastReceiver.java::PendingResult]
/** @hide */
public void sendFinished(IActivityManager am) {
synchronized (this) {
if (mFinished) {
throw new IllegalStateException("Broadcast already finished");
}
mFinished = true;
try {
if (mResultExtras != null) {
mResultExtras.setAllowFds(false);
}
//串行广播，见4.9.2
if (mOrderedHint) {
am.finishReceiver(mToken, mResultCode, mResultData, mResultExtras,
mAbortBroadcast, mFlags);
} else {
// 并行广播，当属于静态注册的广播，需要告知AMS
// This broadcast was sent to a component; it is not ordered,
// but we still need to tell the activity manager we are done.
am.finishReceiver(mToken, 0, null, null, false, mFlags);
}
} catch (RemoteException ex) {
}
}
}
4.9.2 AMS.finishReceiver
[->ActivityManagerService.java]
通过binder机制最后调用到AMS的finishReceiver方法。
public void finishReceiver(IBinder who, int resultCode, String resultData,
Bundle resultExtras, boolean resultAbort, int flags) {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Finish receiver: " + who);
// Refuse possible leaked file descriptors
if (resultExtras != null && resultExtras.hasFileDescriptors()) {
throw new IllegalArgumentException("File descriptors passed in Bundle");
}
final long origId = Binder.clearCallingIdentity();
try {
boolean doNext = false;
BroadcastRecord r;
synchronized(this) {
//属于哪个队列
BroadcastQueue queue = (flags & Intent.FLAG_RECEIVER_FOREGROUND) != 0
? mFgBroadcastQueue : mBgBroadcastQueue;
r = queue.getMatchingOrderedReceiver(who);
if (r != null) {
//见4.9.3节
doNext = r.queue.finishReceiverLocked(r, resultCode,
resultData, resultExtras, resultAbort, true);
}
if (doNext) {
//处理下一条广播
r.queue.processNextBroadcastLocked(/*fromMsg=*/ false, /*skipOomAdj=*/ true);
}
// updateOomAdjLocked() will be done here
trimApplicationsLocked();
}
} finally {
Binder.restoreCallingIdentity(origId);
}
}
4.9.3 BQ.finishReceiverLocked
[->BroadcastQueue.java]
public boolean finishReceiverLocked(BroadcastRecord r, int resultCode,
String resultData, Bundle resultExtras, boolean resultAbort, boolean waitForServices) {
final int state = r.state;
final ActivityInfo receiver = r.curReceiver;
r.state = BroadcastRecord.IDLE;
if (state == BroadcastRecord.IDLE) {
Slog.w(TAG, "finishReceiver [" + mQueueName + "] called but state is IDLE");
}
r.receiver = null;
r.intent.setComponent(null);
if (r.curApp != null && r.curApp.curReceivers.contains(r)) {
r.curApp.curReceivers.remove(r);
}
if (r.curFilter != null) {
r.curFilter.receiverList.curBroadcast = null;
}
r.curFilter = null;
r.curReceiver = null;
r.curApp = null;
mPendingBroadcast = null;
r.resultCode = resultCode;
r.resultData = resultData;
r.resultExtras = resultExtras;
if (resultAbort && (r.intent.getFlags()&Intent.FLAG_RECEIVER_NO_ABORT) == 0) {
r.resultAbort = resultAbort;
} else {
r.resultAbort = false;
}
if (waitForServices && r.curComponent != null && r.queue.mDelayBehindServices
&& r.queue.mOrderedBroadcasts.size() > 0
&& r.queue.mOrderedBroadcasts.get(0) == r) {
ActivityInfo nextReceiver;
if (r.nextReceiver < r.receivers.size()) {
Object obj = r.receivers.get(r.nextReceiver);
nextReceiver = (obj instanceof ActivityInfo) ? (ActivityInfo)obj : null;
} else {
nextReceiver = null;
}
// Don't do this if the next receive is in the same process as the current one.
if (receiver == null || nextReceiver == null
|| receiver.applicationInfo.uid != nextReceiver.applicationInfo.uid
|| !receiver.processName.equals(nextReceiver.processName)) {
// In this case, we are ready to process the next receiver for the current broadcast,
// but are on a queue that would like to wait for services to finish before moving
// on. If there are background services currently starting, then we will go into a
// special state where we hold off on continuing this broadcast until they are done.
if (mService.mServices.hasBackgroundServicesLocked(r.userId)) {
Slog.i(TAG, "Delay finish: " + r.curComponent.flattenToShortString());
r.state = BroadcastRecord.WAITING_SERVICES;
return false;
}
}
}
r.curComponent = null;
// We will process the next receiver right now if this is finishing
// an app receiver (which is always asynchronous) or after we have
// come back from calling a receiver.
return state == BroadcastRecord.APP_RECEIVE
|| state == BroadcastRecord.CALL_DONE_RECEIVE;
}
这个过程主要是设置BroadcastRecord各个参数为null，并判断是否还有广播需要处理。
4.10 小结
接收广播的过程，主要是对并行广播队列和串行广播队列的处理，先处理并行广播队列后处理串行广播队列：
1.处理广播队列，对广播队列进行相应的权限检查处理。无论是并行还是串行，最后调用的都是performReceiveLocked方法。其中串行广播还有时间限制，会调用broadcastTimeoutLocked方法，超时会强制结束广播；
2.通过Binder机制，将消息传递给接收广播的进程进行处理，如果接收广播的进程没起来，还需要启动其进程；
3.最后回调receiver.onReceive的方法，对于串行广播还需要通知AMS已经处理完该条广播，并进行下个广播的处理。
五、总结
发送广播过程的流程如下：
广播机制
1.当发送串行广播（order= true）时
-
静态注册的广播接收者（receivers），采用串行处理
-
动态注册的广播接收者（registeredReceivers），采用串行处理
2.当发送并行广播（order= false）时
-
静态注册的广播接收者（receivers），采用串行处理
-
动态注册的广播接收者（registeredReceivers），采用并行处理
静态注册的receiver都是采用串行处理；动态注册的registeredReceivers处理方式无论是串行还是并行，取决于广播的发送方式（processNextBroadcast）；静态注册的广播由于其所在的进程没有创建，而进程的创建需要耗费系统的资源比较多，所以让静态注册的广播串行化，防止瞬间启动大量的进程。
广播ANR只有在串行广播时才需要考虑，因为接收者是串行处理的，前一个receiver处理慢，会影响后一个receiver；并行广播通过一个循环一次性将所有的receiver分发完，不存在彼此影响的问题，没有广播超时。
串行超时情况：某个广播处理时间>2receiver总个数mTimeoutPeriod，其中mTimeoutPeriod，前后队列为10s,后台队列为60s；某个receiver的执行时间超过mTimeoutPeriod。
附录
源码路径
frameworks/base/services/core/java/com/android/server/am/BroadcastRecord.java
frameworks/base/core/java/android/app/ContextImpl.java
frameworks/base/core/java/android/app/LoadedApk.java
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
frameworks/base/core/java/android/content/IntentFilter.java
frameworks/base/services/core/java/com/android/server/am/BroadcastQueue.java
frameworks/base/core/java/android/content/BroadcastReceiver.java