BroadCast 注册广播得源码分析
基于Android4.4 源码分析 Android Broadcast 得registerReceiver （注册过程）
注册广播往往是在Activity/Service中调用registerReceiver（方法），Activity 和Service 都是间接继承Context抽象类得，真正执行得是ComtextImpl类。
看先ContextImpl.java中得registerReceiver函数得源码。
@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());
}
broadcastPermission是拥有广播得权限控制，scheduler是执行onRecive得执行线程，默认是在主线程执行。 接着看下registerReceiverInternal是如何执行得。
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) {
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 {
return ActivityManagerNative.getDefault().registerReceiver(
mMainThread.getApplicationThread(), mBasePackageName,
rd, filter, broadcastPermission, userId);
} catch (RemoteException e) {
return null;
}
}主要是将主线程得Handler赋值给 scheduler，然后获取IIntentReceiver对象，最后调用ActivityManagerProxy得registerReceiver函数，该函数得参数中有getApplicationThread返回得是ApplicationThread，这是Binder用于 system_server进程通信得。
接着看下getReceiverDispatcher得源码。
public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
Context context, Handler handler,
Instrumentation instrumentation, boolean registered) {
synchronized (mReceivers) {
LoadedApk.ReceiverDispatcher rd = null;
ArrayMap map = null;
if (registered) {
map = mReceivers.get(context);
if (map != null) {
rd = map.get(r);
}
}
if (rd == null) {
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 {
rd.validate(context, handler);
}
rd.mForgotten = false;
return rd.getIIntentReceiver();
}
} 主要是创建ReceiverDispatcher，然后把ReceiverDispatcher保存到一个ArrayMap数组中。看下ReceiverDispatcher得构造函数。
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();
}创建InnerReceiver ， mActivityThread 是前面传递过来得主线程得Handler,看下InnerReceiver 是什么。
final static class InnerReceiver extends IIntentReceiver.Stub {
.........
}InnerReceiver 是ReceiverDispatcher得一个内部类，继承与IIntentReceiver.Stub，这是一个Binder服务端，广播通过 ReceiverDispatcher 可以获取到Binder服务端得对象，用于 IPC通信。
接着看下ActivityManagerNative.java中得registerReceiver得流程。
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);
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;
}caller和receiver都是Binder得服务端对象，ActivityManagerProxy通过Binder驱动将这些信息发给 system_server进程中得ActivityManagerServer对象。看下ActivityManagerServer中得registerReceiver得执行流程。
public Intent registerReceiver(IApplicationThread caller, String callerPackage,
IIntentReceiver receiver, IntentFilter filter, String permission, int userId) {
enforceNotIsolatedCaller("registerReceiver");
int callingUid;
int callingPid;
synchronized(this) {
ProcessRecord callerApp = null;
if (caller != null) {
//获取调用者得进程信息
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 != Process.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();
}
userId = this.handleIncomingUser(callingPid, callingUid, userId,
true, ALLOW_FULL_ONLY, "registerReceiver", callerPackage);
List allSticky = null;
// Look for any matching sticky broadcasts...
//获取IntentFilter中得action。
Iterator actions = filter.actionsIterator();
if (actions != null) {
while (actions.hasNext()) {
//查询黏性广播
String action = (String)actions.next();
allSticky = getStickiesLocked(action, filter, allSticky,
UserHandle.USER_ALL);
allSticky = getStickiesLocked(action, filter, allSticky,
UserHandle.getUserId(callingUid));
}
} else {
allSticky = getStickiesLocked(null, filter, allSticky,
UserHandle.USER_ALL);
allSticky = getStickiesLocked(null, filter, allSticky,
UserHandle.getUserId(callingUid));
}
// The first sticky in the list is returned directly back to
// the client.
Intent sticky = allSticky != null ? (Intent)allSticky.get(0) : null;
if (DEBUG_BROADCAST) Slog.v(TAG, "Register receiver " + filter
+ ": " + sticky);
if (receiver == null) {
return sticky;
}
ReceiverList rl
= (ReceiverList)mRegisteredReceivers.get(receiver.asBinder());
if (rl == null) {
//对于没有注册得广播，创建广播接受者队列
rl = new ReceiverList(this, callerApp, callingPid, callingUid,
userId, receiver);
if (rl.app != null) {
rl.app.receivers.add(rl);
} else {
try {
//注册死亡通知
receiver.asBinder().linkToDeath(rl, 0);
} catch (RemoteException e) {
return sticky;
}
rl.linkedToDeath = true;
}
//新创建的接收者队列，添加到已注册广播队列
mRegisteredReceivers.put(receiver.asBinder(), rl);
} else if (rl.uid != callingUid) {
throw new IllegalArgumentException(
"Receiver requested to register for uid " + callingUid
+ " was previously registered for uid " + rl.uid);
} else if (rl.pid != callingPid) {
throw new IllegalArgumentException(
"Receiver requested to register for pid " + callingPid
+ " was previously registered for pid " + rl.pid);
} else if (rl.userId != userId) {
throw new IllegalArgumentException(
"Receiver requested to register for user " + userId
+ " was previously registered for user " + rl.userId);
}
BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,
permission, callingUid, userId);
rl.add(bf);
if (!bf.debugCheck()) {
Slog.w(TAG, "==> For Dynamic broadast");
}
//将新创建得广播BroadcastFilter 添加到mReceiverResolver 队列中
mReceiverResolver.addFilter(bf);
// Enqueue broadcasts for all existing stickies that match
// this filter.
if (allSticky != null) {
ArrayList receivers = new ArrayList();
receivers.add(bf);
int N = allSticky.size();
for (int i=0; i主要是mRegisteredReceivers记录着所有得已注册得广播。在BroadcastQueue 中有两个广播队列 mParallelBroadcasts：并行队列广播，立即执行，不用等待另外一个广播得运行。mOrderedBroadcasts：有序广播，同一时间只允许执行一个广播。
看下getRecordForAppLocked得源码。
final ProcessRecord getRecordForAppLocked(
IApplicationThread thread) {
if (thread == null) {
return null;
}
int appIndex = getLRURecordIndexForAppLocked(thread);
return appIndex >= 0 ? mLruProcesses.get(appIndex) : null;
}
mLruProcesses数据类型为ArrayList，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。
看下是如何匹配广播得match得源码。
/**
* Test whether this filter matches the given intent.
*
* @param intent The Intent to compare against.
* @param resolve If true, the intent's type will be resolved by calling
* Intent.resolveType(); otherwise a simple match against
* Intent.type will be performed.
* @param logTag Tag to use in debugging messages.
*
* @return Returns either a valid match constant (a combination of
* {@link #MATCH_CATEGORY_MASK} and {@link #MATCH_ADJUSTMENT_MASK}),
* or one of the error codes {@link #NO_MATCH_TYPE} if the type didn't match,
* {@link #NO_MATCH_DATA} if the scheme/path didn't match,
* {@link #NO_MATCH_ACTION} if the action didn't match, or
* {@link #NO_MATCH_CATEGORY} if one or more categories didn't match.
*
* @see #match(String, String, String, android.net.Uri , Set, String)
*/
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) {
if (action != null && !matchAction(action)) {
if (false) Log.v(
logTag, "No matching action " + action + " for " + this);
return NO_MATCH_ACTION;
}
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;
}
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;
}
主要是匹配action,type,data,category中得任何一个不成功，都会匹配失败。
小结：
1 。传递得参数为广播接收者BroadcastReceiver和Intent过滤条件IntentFiletr。
2 。创建对象LoadedApk.ReceiverDispatcher.InnerReceiver，该对象继承于IIntentReceiver.Stub；
3.。通过ActicityManagerServer把当前进程得ApplicationThread和InnerReceiver对象代理类，注册到system_server中。
4 。创建BroadcastFiletr，并添加到mReceiverResolver中，将BroadcastFilter添加到该广播接收者的ReceiverList。