动态注册Broadcast Receiver
Base on: Android 13
Branch: android-13.0.0_r30
流程图
下图中为注册Receiver的过程。
APP端注册Receiver
//定义过滤器，想要监听什么广播，就添加相应的Action
intentFilter = new IntentFilter();
intentFilter.addAction("com.example.broadcast.MY_BROADCAST");
//定义广播处理类
myReceiver = new MyReceiver();
//注册本地广播监听器
registerReceiver(myReceiver, intentFilter);
将IntentFilter与MyReceiver进行绑定，然后注册到系统中。另外在注册接收器前可以对intentFilter设置优先级，优先级数值越大，优先级就越高，那么该接收器就越早接收到广播。设置优先级对只对有序广播有效。
intentFilter.setPriority(10);
ContextWrapper.registerReceiver()
public Intent registerReceiver(@Nullable BroadcastReceiver receiver, IntentFilter filter) {
return mBase.registerReceiver(receiver, filter);
}
mBase是一个Context类，实际调用的是ContextImpl类。
ContextImpl.registerReceiver()
registerReceiver()有4个重载方法，但最后调用的都是registerReceiverInternal()。
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
int flags) {
return registerReceiver(receiver, filter, null, null, flags);
}
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), 0);
}
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler, int flags) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), flags);
}
ContextImpl.registerReceiverInternal()
在这里将BroadcastReceiver对象构造为一个可跨进程传输的IIntentReceiver对象，然后调用系统服务AMS.registerReceiverWithFeature()。
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) {
scheduler = mMainThread.getHandler();
}
rd = mPackageInfo.getReceiverDispatcher(
receiver, context, scheduler,
mMainThread.getInstrumentation(), true);
} else {
if (scheduler == null) {
scheduler = mMainThread.getHandler();
}
rd = new LoadedApk.ReceiverDispatcher(
receiver, context, scheduler, null, true).getIIntentReceiver();
}
}
try {
final Intent intent = ActivityManager.getService().registerReceiverWithFeature(
mMainThread.getApplicationThread(), mBasePackageName, getAttributionTag(), rd,
filter, broadcastPermission, userId, flags);
if (intent != null) {
intent.setExtrasClassLoader(getClassLoader());
intent.prepareToEnterProcess();
}
return intent;
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
AMS.registerReceiverWithFeature()
该函数中大约200行代码，主要是对Receiver端进程的检查、对Receiver在系统端进行注册，以及构造粘性广播的BroadcastRecord。
检查caller进程
对caller进程（Receiver所在进程）进行检查，判断其当前状态是否正常。
public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,
String callerFeatureId, IIntentReceiver receiver, IntentFilter filter,
String permission, int userId, int flags) {
enforceNotIsolatedCaller("registerReceiver");
ArrayList<Intent> stickyIntents = null;
ProcessRecord callerApp = null;
final boolean visibleToInstantApps
= (flags & Context.RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
int callingUid;
int callingPid;
boolean instantApp;
synchronized(this) {
//查询调用者的相关信息
if (caller != null) {
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();
}
//...
}
//...
}
处理粘性广播
调用sendStickyBroadcast()来发送某个action类型的广播时，系统会把这个广播的Intent保存在AMS.mStickyBroadcasts中。当之后每次其它进程调用registerReceiver()来注册某个action类型的广播接收器，AMS.mStickyBroadcasts就会查询是否有该action类型Intent。
如果当前注册的Receiver符合粘性广播，则通过queue、intent、BroadcastFilter构造粘性广播的BroadcastRecord对象，然后添加到并行广播队列，之后进行分发。
public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,
String callerFeatureId, IIntentReceiver receiver, IntentFilter filter,
String permission, int userId, int flags) {
enforceNotIsolatedCaller("registerReceiver");
ArrayList<Intent> stickyIntents = null;
ProcessRecord callerApp = null;
final boolean visibleToInstantApps
= (flags & Context.RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
int callingUid;
int callingPid;
boolean instantApp;
synchronized(this) {
//查询调用者的相关信息...
instantApp = isInstantApp(callerApp, callerPackage, callingUid);
userId = mUserController.handleIncomingUser(callingPid, callingUid, userId, true,
ALLOW_FULL_ONLY, "registerReceiver", callerPackage);
//取出filter中的所有action，返回一个迭代器
Iterator<String> actions = filter.actionsIterator();
if (actions == null) {
ArrayList<String> noAction = new ArrayList<String>(1);
noAction.add(null);
actions = noAction.iterator();
}
// Collect stickies of users
//callingUid为注册receiver的APP的Uid，此处的userIds表示所有应该接收粘性广播的用户
int[] userIds = { UserHandle.USER_ALL, UserHandle.getUserId(callingUid) };
while (actions.hasNext()) {
String action = actions.next();
for (int id : userIds) {
//查询该userId是否有待执行的粘性广播，若有则返回
ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(id);
if (stickies != null) {
//从stickies中取出粘性广播的action
ArrayList<Intent> intents = stickies.get(action);
if (intents != null) {
if (stickyIntents == null) {
stickyIntents = new ArrayList<Intent>();
}
//stickyIntents存储所有粘性广播的intent
stickyIntents.addAll(intents);
}
}
}
}
}
ArrayList<Intent> allSticky = null;
if (stickyIntents != null) {
final ContentResolver resolver = mContext.getContentResolver();
// Look for any matching sticky broadcasts...
for (int i = 0, N = stickyIntents.size(); i < N; i++) {
Intent intent = stickyIntents.get(i);
// Don't provided intents that aren't available to instant apps.
if (instantApp &&
(intent.getFlags() & Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS) == 0) {
continue;
}
// 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.
//查询filter中是否有粘性广播的intent
if (filter.match(resolver, intent, true, TAG) >= 0) {
if (allSticky == null) {
allSticky = new ArrayList<Intent>();
}
allSticky.add(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) {
//将receiver和filter进行注册
//...
// 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);
BroadcastQueue queue = broadcastQueueForIntent(intent);
BroadcastRecord r = new BroadcastRecord(queue, intent, null,
null, null, -1, -1, false, null, null, OP_NONE, null, receivers,
null, 0, null, null, false, true, true, -1, false,
false /* only PRE_BOOT_COMPLETED should be exempt, no stickies */);
queue.enqueueParallelBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
}
return sticky;
}
}
将receiver和filter进行注册
将receiver和filter进行注册，将它们关联后分别加入的维护队列中（及AMS的成员变量mRegisteredReceivers与mReceiverResolver中）。
- 通过IIntentReceiver receiver构造ReceiverList对象rl；
- 通过rl、filter等构造BroadcastFilter对象bf（bf中包含rl对象的引用）；
- 将rl与bf关联：rl.add(bf)（rl中包含bf对象）;
public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,
String callerFeatureId, IIntentReceiver receiver, IntentFilter filter,
String permission, int userId, int flags) {
enforceNotIsolatedCaller("registerReceiver");
ArrayList<Intent> stickyIntents = null;
ProcessRecord callerApp = null;
final boolean visibleToInstantApps
= (flags & Context.RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
int callingUid;
int callingPid;
boolean instantApp;
synchronized(this) {
//查询调用者的相关信息...
//处理粘性广播...
}
synchronized (this) {
if (callerApp != null && (callerApp.thread == null
|| callerApp.thread.asBinder() != caller.asBinder())) {
// Original caller already died
return null;
}
ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
if (rl == null) {
rl = new ReceiverList(this, callerApp, callingPid, callingUid,
userId, receiver);
if (rl.app != null) {
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);
}
rl.app.receivers.add(rl);
} else {
try {
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);
}
BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage, callerFeatureId,
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");
}
mReceiverResolver.addFilter(bf);
}
// 粘性广播的处理代码...
}
mRegisteredReceivers与mReceiverResolver关系
AMS有两个与广播相关的成员变量mRegisteredReceivers与mReceiverResolver。
(1) mRegisteredReceivers
mRegisteredReceivers存储的是系统中所有进程的动态注册的Receiver。
mRegisteredReceivers是一个HashMap，key为Receiver的IBinder代理对象（即receiver.asBinder()，receiver是一个IIntentReceiver对象），value为一个ReceiverList对象。
/**
* Keeps track of all IIntentReceivers that have been registered for broadcasts.
* Hash keys are the receiver IBinder, hash value is a ReceiverList.
*/
final HashMap<IBinder, ReceiverList> mRegisteredReceivers = new HashMap<>();
(2) mReceiverResolver
mReceiverResolver存储的是所有动态注册的Receiver的BroadcastFilter（由IntentFilter构造而来）。是一个IntentResolver<BF, BF>对象。
/**
* Resolver for broadcast intents to registered receivers.
* Holds BroadcastFilter (subclass of IntentFilter).
*/
final IntentResolver<BroadcastFilter, BroadcastFilter> mReceiverResolver
= new IntentResolver<BroadcastFilter, BroadcastFilter>() {...}
(3) 两者关系
public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,
String callerFeatureId, IIntentReceiver receiver, IntentFilter filter,
String permission, int userId, int flags) {
//...
//从mRegisteredReceivers中通过IIntentReceiver查询并获取ReceiverList对象
ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
// 如果rl == null，则表示该Receiver还未加入（注册）到mRegisteredReceivers中
if (rl == null) {
//构造ReceiverList并加入到mRegisteredReceivers
rl = new ReceiverList(this, callerApp, callingPid, callingUid,
userId, receiver);
//...
mRegisteredReceivers.put(receiver.asBinder(), rl);
}
//根据IntentFilter、ReceiverList等信息生成BroadcastFilter
BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage, callerFeatureId,
permission, callingUid, userId, instantApp, visibleToInstantApps);
//如果rl中已经包含给该intentFilter，则说明以及注册过了，不用再重复注册了
if (rl.containsFilter(filter)) {
Slog.w(TAG, "Receiver with filter " + filter
+ " already registered for pid " + rl.pid
+ ", callerPackage is " + callerPackage);
} else { //未注册过，执行注册流程
// 将BroadcastFilter加入到Receiver的记录中
rl.add(bf);
if (!bf.debugCheck()) {
Slog.w(TAG, "==> For Dynamic broadcast");
}
//将BroadcastFilter加入到mReceiverResolver列表中
mReceiverResolver.addFilter(bf);
}
//...
}
mRegisteredReceivers维护的是ReceiverList，每个ReceiverList包含一个或多个BroadcastFilter。
mReceiverResolver维护的是BroadcastFilter，从构造函数可以看出BroadcastFilter也会记录自己属于哪个ReceiverList。
静态注册Broadcast Receiver
APP端注册Receiver
<receiver
android:name=".MyReceiver"
android:enabled="true"
android:exported="true">
<intent-filter
android:priority="9">
<action android:name="com.example.broadcast.MY_BROADCAST1"/>
</intent-filter>
</receiver>
系统端注册
系统端注册是由PMS解析AndroidManifest.xml文件的，最后PMS将PMS.将Receiver相关信息添加到PMS.mComponentResolver中。
这里暂时略过，以后用空再补充。
查询静态注册Receiver
当发送广播，AMS在AMS.broadcastIntentLocked()中查询可以匹配的Receiver时，调用栈如下：
AMS.broadcastIntentLocked() ->
AppGlobals.getPackageManager().queryIntentReceivers() ->
PMS.queryIntentReceiversInternal() ->
PMS.mComponentResolver.queryReceivers() ->
最后返回一个List