基于Android 6.0的源码剖析， 分析android广播的发送与接收流程。
framework/base/services/core/java/com/android/server/
- ActivityManagerService.java
- BroadcastQueue.java
- BroadcastFilter.java
- BroadcastRecord.java
- ReceiverList.java
- ProcessRecord.java
framework/base/core/java/android/content/
- BroadcastReceiver.java
- IntentFilter.java
framework/base/core/java/android/app/
- ActivityManagerNative.java (内含AMP)
- ActivityManager.java
- ApplicationThreadNative.java (内含ATP)
- ActivityThread.java (内含ApplicationThread)
- ContextImpl.java
- LoadedApk
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.sendStickyBroadcast()发送
1.1 BroadcastRecord
广播在系统中以BroadcastRecord对象来记录, 该对象有几个时间相关的成员变量.
final class BroadcastRecord extends Binder {
final ProcessRecord callerApp; //广播发送者所在进程
final String callerPackage; //广播发送者所在包名
final List receivers; // 包括动态注册的BroadcastFilter和静态注册的ResolveInfo
final String callerPackage; //广播发送者
final int callingPid; // 广播发送者pid
final List receivers; // 广播接收者
int nextReceiver; // 下一个被执行的接收者
IBinder receiver; // 当前正在处理的接收者
int anrCount; //广播ANR次数
long enqueueClockTime; //入队列时间
long dispatchTime; //分发时间
long dispatchClockTime; //分发时间
long receiverTime; //接收时间(首次等于dispatchClockTime)
long finishTime; //广播完成时间
}
- enqueueClockTime 伴随着 scheduleBroadcastsLocked
- dispatchClockTime伴随着 deliverToRegisteredReceiverLocked
- finishTime 位于 addBroadcastToHistoryLocked方法内
二、注册广播
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或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或Service。
2.1 registerReceiver
[ContextImpl.java]
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext());
}
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
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scheuler
scheduler = 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();
}
此处mActivityThread便是前面传递过来的当前主线程的Handler.
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_TRANSACTION
mRemote.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，都代表执行注册广播动作所在的进程.
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) {
ArrayList<Intent> stickyIntents = null;
ProcessRecord callerApp = null;
...
synchronized(this) {
if (caller != null) {
//从mLruProcesses查询调用者的进程信息【见2.5.1】
callerApp = getRecordForAppLocked(caller);
...
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actions. 这就是平时所加需要监听的广播action
Iterator<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 Intent
ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(id);
if (stickies != null) {
ArrayList<Intent> intents = stickies.get(action);
if (intents != null) {
if (stickyIntents == null) {
stickyIntents = new ArrayList<Intent>();
}
//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())) {
return null; //调用者已经死亡
}
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 {
receiver.asBinder().linkToDeath(rl, 0); //注册死亡通知
...
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);
//根据intent返回前台或后台广播队列【见2.5.3】
BroadcastQueue queue = broadcastQueueForIntent(intent);
//创建BroadcastRecord
BroadcastRecord 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。
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action
if (action != null && !matchAction(action)) {
return NO_MATCH_ACTION;
}
//不存在匹配的type或data
int dataMatch = matchData(type, scheme, data);
if (dataMatch < 0) {
return dataMatch;
}
//不存在匹配的category
String 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。
2.5.3 AMS.broadcastQueueForIntent
BroadcastQueue broadcastQueueForIntent(Intent intent) {
final boolean isFg = (intent.getFlags() & Intent.FLAG_RECEIVER_FOREGROUND) != 0;
return (isFg) ? mFgBroadcastQueue : mBgBroadcastQueue;
}
broadcastQueueForIntent(Intent intent)通过判断intent.getFlags()是否包含FLAG_RECEIVER_FOREGROUND 来决定是前台或后台广播，进而返回相应的广播队列mFgBroadcastQueue或者mBgBroadcastQueue。
- 当Intent的flags包含FLAG_RECEIVER_FOREGROUND，则返回mFgBroadcastQueue；
- 当Intent的flags不包含FLAG_RECEIVER_FOREGROUND，则返回mBgBroadcastQueue；
2.6 广播注册小结
注册广播：
- 传递的参数为广播接收者BroadcastReceiver和Intent过滤条件IntentFilter；
- 创建对象LoadedApk.ReceiverDispatcher.InnerReceiver，该对象继承于IIntentReceiver.Stub；
- 通过AMS把当前进程的ApplicationThread和InnerReceiver对象的代理类，注册登记到system_server进程；
- 当广播receiver没有注册过，则创建广播接收者队列ReceiverList，该对象继承于ArrayList
， 并添加到AMS.mRegisteredReceivers(已注册广播队列)； - 创建BroadcastFilter，并添加到AMS.mReceiverResolver；
- 将BroadcastFilter添加到该广播接收者的ReceiverList
另外，当注册的是Sticky广播：
- 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。
- 根据注册广播的Intent是否包含FLAG_RECEIVER_FOREGROUND，则mFgBroadcastQueue
广播注册完, 另一个操作便是在广播发送过程.
三、 发送广播
发送广播是在Activity或Service中调用sendBroadcast()方法，而Activity或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]
public 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) {
...
}
}
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_TRANSACTION
mRemote.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：
| 类型 | serialized | sticky |
|---|---|---|
| sendBroadcast | false | false |
| sendOrderedBroadcast | true | false |
| sendStickyBroadcast | false | true |
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) {
//step1: 设置flag
//step2: 广播权限验证
//step3: 处理系统相关广播
//step4: 增加sticky广播
//step5: 查询receivers和registeredReceivers
//step6: 处理并行广播
//step7: 合并registeredReceivers到receivers
//step8: 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。
3.4.1 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package
intent.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
3.4.2 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())) {
...
}
} 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；
- 否则当调用者进程为空 或者非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。
- 当发送的是受保护广播
3.4.3 处理系统相关广播
final String action = intent.getAction();
if (action != null) {
switch (action) {
case Intent.ACTION_UID_REMOVED: //uid移除
case Intent.ACTION_PACKAGE_REMOVED: //package移除
case Intent.ACTION_PACKAGE_ADDED: //增加package
case Intent.ACTION_PACKAGE_CHANGED: //package改变
case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE: //外部设备不可用
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE: //外部设备可用
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
}
}
这个过主要处于系统相关的10类广播,这里不就展开讲解了.
3.4.4 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 intent
list.set(i, new Intent(intent));
break;
}
}
//新的intent追加到list
if (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。
3.4.5 查询receivers和registeredReceivers
List receivers = null;
List<BroadcastFilter> registeredReceivers = null;
//当允许静态接收者处理该广播，则通过PKMS根据Intent查询相应的静态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 == Process.SHELL_UID) {
...
} else {
// 查询相应的动态注册的广播
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。
其他说明：
- 根据userId来决定广播是发送给全部的接收者，还是指定的userId;
- 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;
}
3.4.6 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) {
//根据intent的flag来判断前台队列或者后台队列[见小节2.5.3]
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[见下文]
queue.enqueueParallelBroadcastLocked(r);
//处理广播【见小节4.1】
queue.scheduleBroadcastsLocked();
}
//动态注册的广播接收者处理完成，则会置空该变量；
registeredReceivers = null;
NR = 0;
}
广播队列中有一个成员变量mParallelBroadcasts，类型为ArrayList
// 并行广播,加入mParallelBroadcasts队列
public void enqueueParallelBroadcastLocked(BroadcastRecord r) {
mParallelBroadcasts.add(r);
r.enqueueClockTime = System.currentTimeMillis();
}
3.4.7 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)) {
...
}
//[3.4.6]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receivers
int 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++;
}
动态注册的registeredReceivers，全部合并都receivers，再统一按串行方式处理。
3.4.8 处理串行广播
if ((receivers != null && receivers.size() > 0)
|| resultTo != null) {
//根据intent的flag来判断前台队列或者后台队列[见小节2.5.3]
BroadcastQueue queue = broadcastQueueForIntent(intent);
//创建BroadcastRecord
BroadcastRecord 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
// 串行广播 加入mOrderedBroadcasts队列
public void enqueueOrderedBroadcastLocked(BroadcastRecord r) {
mOrderedBroadcasts.add(r);
r.enqueueClockTime = System.currentTimeMillis();
}
3.5 小结
发送广播过程:
- 默认不发送给已停止（Intent.FLAG_EXCLUDE_STOPPED_PACKAGES）的应用包；
- 处理各种PACKAGE,TIMEZONE等相关的系统广播；
- 当为粘性广播，则将sticky广播增加到list，并放入mStickyBroadcasts里面；
- 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()方法来完成的不同广播处理:
处理方式：
- Sticky广播: 广播注册过程处理AMS.registerReceiver，开始处理粘性广播，见小节[2.5];
- 创建BroadcastRecord对象；
- 并添加到mParallelBroadcasts队列；
- 然后执行queue.scheduleBroadcastsLocked；
- 并行广播： 广播发送过程处理，见小节[3.4.6]
- 只有动态注册的mRegisteredReceivers才会并行处理；
- 会创建BroadcastRecord对象;
- 并添加到mParallelBroadcasts队列；
- 然后执行queue.scheduleBroadcastsLocked;
- 串行广播： 广播发送广播处理，见小节[3.4.8]
- 所有静态注册的receivers以及动态注册mRegisteredReceivers合并到一张表处理；
- 创建BroadcastRecord对象；
- 并添加到mOrderedBroadcasts队列；
- 然后执行queue.scheduleBroadcastsLocked；
可见不管哪种广播方式，都是通过broadcastQueueForIntent()来根据intent的flag来判断前台队列或者后台队列，然后再调用对应广播队列的scheduleBroadcastsLocked方法来处理广播；
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：
4.1.1 BroadcastHandler
public ActivityManagerService(Context systemContext) {
//名为"ActivityManager"的线程
mHandlerThread = new ServiceThread(TAG,
android.os.Process.THREAD_PRIORITY_FOREGROUND, false);
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);
...
}
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;
}
由此可见BroadcastHandler采用的是”ActivityManager”线程的Looper
private final class BroadcastHandler extends Handler {
public 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) {
//part1: 处理并行广播
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
}
//part2: 处理当前有序广播
do {
if (mOrderedBroadcasts.size() == 0) {
mService.scheduleAppGcsLocked(); //没有更多的广播等待处理
if (looped) {
mService.updateOomAdjLocked();
}
return;
}
r = mOrderedBroadcasts.get(0); //获取串行广播的第一个广播
boolean forceReceive = false;
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))) {
broadcastTimeoutLocked(false); //当广播处理时间超时，则强制结束这条广播
}
}
...
if (r.receivers == null || r.nextReceiver >= numReceivers
|| r.resultAbort || forceReceive) {
if (r.resultTo != null) {
//处理广播消息消息，调用到onReceive()
performReceiveLocked(r.callerApp, r.resultTo,
new Intent(r.intent), r.resultCode,
r.resultData, r.resultExtras, false, false, r.userId);
}
cancelBroadcastTimeoutLocked(); //取消BROADCAST_TIMEOUT_MSG消息
addBroadcastToHistoryLocked(r);
mOrderedBroadcasts.remove(0);
continue;
}
} while (r == null);
//part3: 获取下一个receiver
r.receiverTime = SystemClock.uptimeMillis();
if (recIdx == 0) {
r.dispatchTime = r.receiverTime;
r.dispatchClockTime = System.currentTimeMillis();
}
if (!mPendingBroadcastTimeoutMessage) {
long timeoutTime = r.receiverTime + mTimeoutPeriod;
setBroadcastTimeoutLocked(timeoutTime); //设置广播超时延时消息
}
//part4: 处理下条有序广播
ProcessRecord app = mService.getProcessRecordLocked(targetProcess,
info.activityInfo.applicationInfo.uid, false);
if (app != null && app.thread != null) {
app.addPackage(info.activityInfo.packageName,
info.activityInfo.applicationInfo.versionCode, mService.mProcessStats);
processCurBroadcastLocked(r, app); //[处理串行广播]
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) {
...
return;
}
}
}
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。
- 设置广播超时延时消息: setBroadcastTimeoutLocked:
- 当广播接收者等待时间过长，则调用broadcastTimeoutLocked(false);
- 当执行完广播,则调用cancelBroadcastTimeoutLocked;
4.2.1 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
}
通过while循环, 一次性分发完所有的并发广播后,则分发完成后则添加到历史广播队列. fromMsg是指processNextBroadcast()是否由BroadcastHandler所调用的.
private final void addBroadcastToHistoryLocked(BroadcastRecord r) {
if (r.callingUid < 0) {
return;
}
r.finishTime = SystemClock.uptimeMillis(); //记录分发完成时间
mBroadcastHistory[mHistoryNext] = r;
mHistoryNext = ringAdvance(mHistoryNext, 1, MAX_BROADCAST_HISTORY);
mBroadcastSummaryHistory[mSummaryHistoryNext] = r.intent;
mSummaryHistoryEnqueueTime[mSummaryHistoryNext] = r.enqueueClockTime;
mSummaryHistoryDispatchTime[mSummaryHistoryNext] = r.dispatchClockTime;
mSummaryHistoryFinishTime[mSummaryHistoryNext] = System.currentTimeMillis();
mSummaryHistoryNext = ringAdvance(mSummaryHistoryNext, 1, MAX_BROADCAST_SUMMARY_HISTORY);
}
4.2.2 处理串行广播
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) {
return; //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
} 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gc
mService.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，调用到onReceive()
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。广播超时为2*mTimeoutPeriod*numReceivers，接收者个数numReceivers越多则广播超时总时长越大。
4.2.3 获取下条有序广播
//获取下一个receiver的index
int 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_MSG
setBroadcastTimeoutLocked(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=true
if (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false
AppGlobals.getPackageManager().setPackageStoppedState(
r.curComponent.getPackageName(), false, UserHandle.getUserId(r.callingUid));
4.2.4 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receiver
finishReceiverLocked(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，且对应进程尚未创建，则调用startProcessLocked创建进程。
接下来,介绍deliverToRegisteredReceiverLocked的处理流程:
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 performReceiveLocked
[-> 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intent
if (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
[-> ApplicationThreadNative.java ::ApplicationThreadProxy]
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_TRANSACTION
mRemote.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(oneway调用方式), 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 ::ApplicationThread]
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) {
//【见小节4.8】
rd.performReceive(intent, resultCode, data, extras, ordered, sticky, sendingUser);
} else {
...
}
}
此处方法LoadedApk()属于LoadedApk.ReceiverDispatcher.InnerReceiver, 也就是LoadedApk内部类的内部类InnerReceiver.
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)) {
//消息成功post到主线程，则不会走此处。
if (mRegistered && ordered) {
IActivityManager mgr = ActivityManagerNative.getDefault();
args.sendFinished(mgr);
}
}
}
其中Args继承于BroadcastReceiver.PendingResult，实现了接口Runnable; 其中mActivityThread是当前进程的主线程, 是由[小节2.3.1]完成赋值过程.
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 ReceiverDispatcher.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(); //【见小节4.10】
}
}
}
}
接下来,便进入主线程,最终调用BroadcastReceiver具体实现类的onReceive()方法。
4.10 PendingResult.finish
[-> BroadcastReceiver.java ::PendingResult]
public final void finish() {
if (mType == TYPE_COMPONENT) { //代表是静态注册的广播
final IActivityManager mgr = ActivityManagerNative.getDefault();
if (QueuedWork.hasPendingWork()) {
QueuedWork.singleThreadExecutor().execute( new Runnable() {
void run() {
sendFinished(mgr); //[见小节4.10.1]
}
});
} else {
sendFinished(mgr); //[见小节4.10.1]
}
} else if (mOrderedHint && mType != TYPE_UNREGISTERED) { //动态注册的串行广播
final IActivityManager mgr = ActivityManagerNative.getDefault();
sendFinished(mgr); //[见小节4.10.1]
}
}
主要功能:
- 静态注册的广播接收者:
- 当QueuedWork工作未完成, 即SharedPreferences写入磁盘的操作没有完成, 则等待完成再执行sendFinished方法;
- 当QueuedWork工作已完成, 则直接调用sendFinished方法;
- 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方法.
另外常量参数说明:
- TYPE_COMPONENT: 静态注册
- TYPE_REGISTERED: 动态注册
- TYPE_UNREGISTERED: 取消注册
4.10.1 sendFinished
[-> BroadcastReceiver.java ::PendingResult]
public void sendFinished(IActivityManager am) {
synchronized (this) {
mFinished = true;
...
// mOrderedHint代表发送是否为串行广播 [见小节4.10.2]
if (mOrderedHint) {
am.finishReceiver(mToken, mResultCode, mResultData, mResultExtras,
mAbortBroadcast, mFlags);
} else {
//并行广播, 但属于静态注册的广播, 仍然需要告知AMS. [见小节4.10.2]
am.finishReceiver(mToken, 0, null, null, false, mFlags);
}
...
}
}
此处AMP.finishReceiver，经过binder调用，进入AMS.finishReceiver方法
4.10.2 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) {
//[见小节4.10.3]
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);
}
}
4.10.3 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;
r.receiver = null;
r.intent.setComponent(null);
if (r.curApp != null && r.curApp.curReceiver == r) {
r.curApp.curReceiver = null;
}
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;
}
if (receiver == null || nextReceiver == null
|| receiver.applicationInfo.uid != nextReceiver.applicationInfo.uid
|| !receiver.processName.equals(nextReceiver.processName)) {
if (mService.mServices.hasBackgroundServices(r.userId)) {
r.state = BroadcastRecord.WAITING_SERVICES;
return false;
}
}
}
r.curComponent = null;
return state == BroadcastRecord.APP_RECEIVE
|| state == BroadcastRecord.CALL_DONE_RECEIVE;
}
五、总结
5.1 基础知识
1.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, 不需要时记得调用unregisterReceiver();
2.广播发送方式可分为三类:
| 类型 | 方法 | ordered | sticky |
|---|---|---|---|
| 普通广播 | sendBroadcast | false | false |
| 有序广播 | sendOrderedBroadcast | true | false |
| Sticky广播 | sendStickyBroadcast | false | true |
3.广播注册registerReceiver():默认将当前进程的主线程设置为scheuler. 再向AMS注册该广播相应信息, 根据类型选择加入mParallelBroadcasts或mOrderedBroadcasts队列.
4.广播发送processNextBroadcast():根据不同情况调用不同的处理过程:
- 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，且对应进程尚未创建，则调用startProcessLocked创建进程。
5.2 流程图
最后,通过一幅图来总结整个广播处理过程. 点击查看大图
5.2.1 并行广播
整个过程涉及过程进程间通信, 先来说说并行广播处理过程:
- 广播发送端所在进程: 步骤1~2;
- system_server的binder线程: 步骤3~5;
- system_server的ActivityManager线程: 步骤6~11;
- 广播接收端所在进程的binder线程: 步骤12~13;
- 广播接收端所在进程的主线程: 步骤14~15,以及23;
- system_server的binder线程: 步骤24~25.
5.2.2 串行广播
可以看出整个流程中,步骤8~15是并行广播, 而步骤16~22则是串行广播.那么再来说说串行广播的处理过程.
- 广播发送端所在进程: 步骤1~2;
- system_server的binder线程: 步骤3~5;
- system_server的ActivityManager线程:步骤6以及16~18;
- 广播接收端所在进程的binder线程: 步骤19;
- 广播接收端所在进程的主线程: 步骤20~22;
- system_server的binder线程: 步骤24~25.
再来说说几个关键的时间点:
- enqueueClockTime: 位于步骤4 scheduleBroadcastsLocked(), 这是在system_server的binder线程.
- dispatchClockTime: 位于步骤8 deliverToRegisteredReceiverLocked(),这是在system_server的ActivityManager线程.
- finishTime : 位于步骤11 addBroadcastToHistoryLocked()之后, 这是在并行广播向所有receivers发送完成后的时间点,而串行广播则是一个一个发送完成才会继续.
5.2.3 粘性广播
对于粘性广播，registerReceiver()会有一个返回值，数据类型为Intent。 只有粘性广播在注册过程过程会直接返回Intent，里面带有相关参数。 比如常见的使用场景比如Battery广播的注册。
5.3 广播处理机制
- 当发送串行广播(ordered=true)的情况下：
- 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；
- 当发送并行广播(ordered=false)的情况下：
- 静态注册的广播接收者(receivers)，依然采用串行处理；
- 动态注册的广播接收者(registeredReceivers)，采用并行处理；
简单来说，静态注册的receivers始终采用串行方式来处理（processNextBroadcast）； 动态注册的registeredReceivers处理方式是串行还是并行方式, 取决于广播的发送方式(processNextBroadcast)。
静态注册的广播往往其所在进程还没有创建，而进程创建相对比较耗费系统资源的操作，所以 让静态注册的广播串行化，能防止出现瞬间启动大量进程的喷井效应。
ANR时机：只有串行广播才需要考虑超时，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向所有的receiver分发广播事件，所以不存在彼此影响的问题，则没有广播超时；
- 串行广播超时情况1：某个广播总处理时间 > 2* receiver总个数 * mTimeoutPeriod, 其中mTimeoutPeriod，前台队列默认为10s，后台队列默认为60s;
- 串行广播超时情况2：某个receiver的执行时间超过mTimeoutPeriod；
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