android--广播接收者BroadcastReceiver的注册过程
前面文章《android--监听SMS》中简单实现了接受短信信息的功能，下面棘突分析一下源码是怎么实现的。
广播接收者的注册分为静态注册和动态注册，在AndroidManifest.xml中配置的属于静态注册，而动态注册需要调用context中的registerReceiver方法进行注册。
这次我们对动态注册进行分析
1、代码如下：
IntentFilter counterActionFilter = new IntentFilter(CounterService.BROADCAST_COUNTER_ACTION); registerReceiver(counterActionReceiver, counterActionFilter);
注释：
（1）、IntentFilter 顾名思义，IntentFilter对象负责过滤掉组件无法响应和处理的Intent，只将自己关心的Intent接收进来进行处理。 IntentFilter实行“白名单”管理，即只列出组件乐意接受的Intent，但IntentFilter只会过滤隐式Intent，显式的Intent会直接传送到目标组件。 Android组件可以有一个或多个IntentFilter，每个IntentFilter之间相互独立，只需要其中一个验证通过则可。
创建IntentFilter对象的源码：
public class IntentFilter implements Parcelable {
private int mPriority;
private final ArrayList<String> mActions;
public IntentFilter(String action) {
mPriority = 0;
mActions = new ArrayList<String>();
addAction(action);
}
。。。
}
把CounterService.BROADCAST_COUNTER_ACTION字符串放到了mActions中。
2、registerReceiver的源码：
public class ContextWrapper extends Context {
Context mBase;
public ContextWrapper(Context base) {
mBase = base;
}
@Override
public Intent registerReceiver(
BroadcastReceiver receiver, IntentFilter filter) {
return mBase.registerReceiver(receiver, filter);
}
。。。
}
mBase是ContextImpl对象。
3、mBase.registerReceiver(receiver, filter)的源码：
class ContextImpl extends Context {
。。。。
@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, filter, broadcastPermission,
scheduler, getOuterContext());
}
private Intent registerReceiverInternal(BroadcastReceiver receiver,
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(),
rd, filter, broadcastPermission);
} catch (RemoteException e) {
return null;
}
}
。。。
}
注释：
（1）通过getReceiverDispatcher()将广播接收者封装成实现IintentReceiver接口的binder本地对象rd。
3.1 mPackageInfo.getReceiverDispatcher()的源码：
public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
Context context, Handler handler,
Instrumentation instrumentation, boolean registered) {
synchronized (mReceivers) {
LoadedApk.ReceiverDispatcher rd = null;
HashMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> 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 HashMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher>();
mReceivers.put(context, map);
}
map.put(r, rd);
}
} else {
rd.validate(context, handler);
}
return rd.getIIntentReceiver();
}
}
3.2 new ReceiverDispatcher 的源码：
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;
}
}
final IIntentReceiver.Stub mIIntentReceiver;
final BroadcastReceiver mReceiver;
final Context mContext;
final Handler mActivityThread;
final Instrumentation mInstrumentation;
final boolean mRegistered;
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();
}
IIntentReceiver getIIntentReceiver() {
return mIIntentReceiver;
}
mReceiver表示广播接受者
mContext表示activity组件，也就是这个广播接受者在哪一个activity中注册的。
mActivityThread表示与activity相关的handle
mIIntentReceiver指向了创建的ReceiverDispatcher对象。
（2）ActivityManagerNative. getDefault()获得是ActivityManagerProxy对象
总结：activity组件在注册一个广播接收者时，并不是真的将广播接收者注册到ActivityManagerService中，而是将与它相关联的IntentReceiver对象注册到ActivityManagerService中，当ActivityManagerService接受到一个广播的时候，他就会根据广播的类型在内部找到对应的IntentReceiver对象，然后再通过他找到广播接收者。
4、ActivityManagerProxy中怎么实现的registerReceiver方法 ，源码：
public Intent registerReceiver(IApplicationThread caller,
IIntentReceiver receiver,
IntentFilter filter, String perm) throws RemoteException
{
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IActivityManager.descriptor);
data.writeStrongBinder(caller != null ? caller.asBinder() : null);
data.writeStrongBinder(receiver != null ? receiver.asBinder() : null);
filter.writeToParcel(data, 0);
data.writeString(perm);
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;
}
注释：binder代理对象mRemote向ActivityManagerService发送一个类型为REGISTER_RECEIVER_TRANSACTION的进程间通信请求。
5、ActivityManagerService中的源码：
public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
public Intent registerReceiver(IApplicationThread caller,
IIntentReceiver receiver, IntentFilter filter, String permission) {
synchronized(this) {
ProcessRecord callerApp = null;
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);
}
}
List allSticky = null;
// Look for any matching sticky broadcasts...
Iterator actions = filter.actionsIterator();
if (actions != null) {
while (actions.hasNext()) {
String action = (String)actions.next();
allSticky = getStickiesLocked(action, filter, allSticky);
}
} else {
allSticky = getStickiesLocked(null, filter, allSticky);
}
// 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) {
rl = new ReceiverList(this, callerApp,
Binder.getCallingPid(),
Binder.getCallingUid(), receiver);
if (rl.app != null) {
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);
}
BroadcastFilter bf = new BroadcastFilter(filter, rl, permission);
rl.add(bf);
if (!bf.debugCheck()) {
Slog.w(TAG, "==> For Dynamic broadast");
}
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<N; i++) {
Intent intent = (Intent)allSticky.get(i);
BroadcastRecord r = new BroadcastRecord(intent, null,
null, -1, -1, null, receivers, null, 0, null, null,
false, true, true);
if (mParallelBroadcasts.size() == 0) {
scheduleBroadcastsLocked();
}
mParallelBroadcasts.add(r);
}
}
return sticky;
}
}
。。。
}
注释：
创建一个BroadcastFilter，用来描述正在注册的广播接收者。广播注册到这就分析完了。