一、Android应用程序注册广播接收器（registerReceiver）的过程分析
参考Android应用程序注册广播接收器（registerReceiver）的过程分析http://blog.csdn.net/luoshengyang/article/details/6737352和《Android系统源代码情景分析》，作者罗升阳。
0、总图：
1、MainActivity和CounterService所在应用程序主线程向ActivityManagerService进程发送REGISTER_RECEIVER_TRANSACTION
如图：第一步
~/Android/frameworks/base/core/java/android/app
----ActivityManagerNative.java
class ActivityManagerProxy implements IActivityManager
{
......
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;
}
......
}
其中receiver为InnerReceiver对象，如下图。还要filter，主要关注这两个参数。
如图：第二步，省略binder_transaction传输过程，因为上面已经分析过了。
如图：第三步
~/Android/frameworks/base/core/java/android/app
----ActivityManagerNative.java
public abstract class ActivityManagerNative extends Binder implements IActivityManager
{
......
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
switch (code) {
case REGISTER_RECEIVER_TRANSACTION:
{
data.enforceInterface(IActivityManager.descriptor);
IBinder b = data.readStrongBinder();
IApplicationThread app =
b != null ? ApplicationThreadNative.asInterface(b) : null;
b = data.readStrongBinder();
IIntentReceiver rec
= b != null ? IIntentReceiver.Stub.asInterface(b) : null;
IntentFilter filter = IntentFilter.CREATOR.createFromParcel(data);
String perm = data.readString();
Intent intent = registerReceiver(app, rec, filter, perm);
reply.writeNoException();
if (intent != null) {
reply.writeInt(1);
intent.writeToParcel(reply, 0);
} else {
reply.writeInt(0);
}
return true;
}
.......
} rec为IIntentReceiver.Stub.Proxy对象，如上图所示。还要filter，主要关注这两个参数。如图：第四步
~/Android/frameworks/base/services/java/com/android/server/am
----ActivityManagerService.java
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) {
......
}
}
.......
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 {
......
}
mRegisteredReceivers.put(receiver.asBinder(), rl);
}
BroadcastFilter bf = new BroadcastFilter(filter, rl, permission);
rl.add(bf);
......
mReceiverResolver.addFilter(bf);
// Enqueue broadcasts for all existing stickies that match
// this filter.
if (allSticky != null) {
......
}
return sticky;
}
}
......
} 主要做了以下几件事：
（1）根据receiver创建ReceiverList。
（2）根据filter和rl创建BroadcastFilter。
（3）mReceiver.addFilter(bf)。
二、Android应用程序发送广播（sendBroadcast）的过程分析
0、总图
1、MainActivity和CounterService所在应用程序主线程向ActivityManagerService进程发送BROADCAST_INTENT_TRANSACTION
如图：第一步
~/Android/frameworks/base/core/java/android/app
----ActivityManagerNative.java
class ActivityManagerProxy implements IActivityManager
{
......
public int broadcastIntent(IApplicationThread caller,
Intent intent, String resolvedType, IIntentReceiver resultTo,
int resultCode, String resultData, Bundle map,
String requiredPermission, boolean serialized,
boolean sticky) 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.writeString(requiredPermission);
data.writeInt(serialized ? 1 : 0);
data.writeInt(sticky ? 1 : 0);
mRemote.transact(BROADCAST_INTENT_TRANSACTION, data, reply, 0);
reply.readException();
int res = reply.readInt();
reply.recycle();
data.recycle();
return res;
}
......
} 其中主要关注intent参数。如图：第二步，省略binder_transaction传输过程，因为上面已经分析过了。
如图：第三步
~/Android/frameworks/base/core/java/android/app
----ActivityManagerNative.java
public abstract class ActivityManagerNative extends Binder implements IActivityManager
{
......
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
switch (code) {
case BROADCAST_INTENT_TRANSACTION:
{
data.enforceInterface(IActivityManager.descriptor);
IBinder b = data.readStrongBinder();
IApplicationThread app =
b != null ? ApplicationThreadNative.asInterface(b) : null;
Intent intent = Intent.CREATOR.createFromParcel(data);
String resolvedType = data.readString();
b = data.readStrongBinder();
IIntentReceiver resultTo =
b != null ? IIntentReceiver.Stub.asInterface(b) : null;
int resultCode = data.readInt();
String resultData = data.readString();
Bundle resultExtras = data.readBundle();
String perm = data.readString();
boolean serialized = data.readInt() != 0;
boolean sticky = data.readInt() != 0;
int res = broadcastIntent(app, intent, resolvedType, resultTo,
resultCode, resultData, resultExtras, perm,
serialized, sticky);
reply.writeNoException();
reply.writeInt(res);
return true;
}
.......
}
如图：第四步
~/Android/frameworks/base/services/java/com/android/server/am
----ActivityManagerService.java
public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
......
public final int broadcastIntent(IApplicationThread caller,
Intent intent, String resolvedType, IIntentReceiver resultTo,
int resultCode, String resultData, Bundle map,
String requiredPermission, boolean serialized, boolean sticky) {
synchronized(this) {
intent = verifyBroadcastLocked(intent);
final ProcessRecord callerApp = getRecordForAppLocked(caller);
final int callingPid = Binder.getCallingPid();
final int callingUid = Binder.getCallingUid();
final long origId = Binder.clearCallingIdentity();
int res = broadcastIntentLocked(callerApp,
callerApp != null ? callerApp.info.packageName : null,
intent, resolvedType, resultTo,
resultCode, resultData, map, requiredPermission, serialized,
sticky, callingPid, callingUid);
Binder.restoreCallingIdentity(origId);
return res;
}
}
......
} 主要做了以下几件事：
（1）根据intent找出相应的广播接收器：
List<BroadcastFilter> registeredReceivers = null; registeredReceivers = mReceiverResolver.queryIntent(intent, resolvedType, false);（2）根据intent(里面还包含数据)，registeredReceivers创建BroadcastRecord对象，并加入mParallelBroadcasts中：
BroadcastRecord r = new BroadcastRecord(intent, callerApp, callerPackage, callingPid, callingUid, requiredPermission, registeredReceivers, resultTo, resultCode, resultData, map, ordered, sticky, false); mParallelBroadcasts.add(r);（3）根据r和从r中得到的BroadcastFilter(即上面注册时的BroadcastFilter)，调用deliverToRegisteredReceiverLocked：
deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false);（4）调用filter.receiverList.receiver和new Intent(r.intent)调用performReceiveLocked：
performReceiveLocked(filter.receiverList.app, filter.receiverList.receiver, new Intent(r.intent), r.resultCode, r.resultData, r.resultExtras, r.ordered, r.initialSticky);
（5）ActivityManagerService进程向MainActivity和CounterService所在应用程序子线程发送SCHEDULE_REGISTERED_RECEIVER_TRANSACTION
app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode, data, extras, ordered, sticky);
其中receiver为IIntentReceiver.Stub.Proxy对象。intent为要传递的数据。
2、ActivityManagerService进程向MainActivity和CounterService所在应用程序子线程发送SCHEDULE_REGISTERED_RECEIVER_TRANSACTION
如图：第一步
~/Android/frameworks/base/core/java/android/app
----ApplicationThreadNative.java，ApplicationThreadProxy类
class ApplicationThreadProxy implements IApplicationThread {
......
public void scheduleRegisteredReceiver(IIntentReceiver receiver, Intent intent,
int resultCode, String dataStr, Bundle extras, boolean ordered, boolean sticky)
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);
mRemote.transact(SCHEDULE_REGISTERED_RECEIVER_TRANSACTION, data, null,
IBinder.FLAG_ONEWAY);
data.recycle();
}
......
} 其中receiver为IIntentReceiver.Stub.Proxy对象，intent为要传递的数据。如图：第二步，省略binder_transaction传输过程，因为上面已经分析过了。
如图：第三步
~/Android/frameworks/base/core/java/android/app
----ApplicationThreadNative.java
public abstract class ApplicationThreadNative extends Binder
implements IApplicationThread {
........
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
switch (code) {
case SCHEDULE_REGISTERED_RECEIVER_TRANSACTION: {
data.enforceInterface(IApplicationThread.descriptor);
IIntentReceiver receiver = IIntentReceiver.Stub.asInterface(
data.readStrongBinder());
Intent intent = Intent.CREATOR.createFromParcel(data);
int resultCode = data.readInt();
String dataStr = data.readString();
Bundle extras = data.readBundle();
boolean ordered = data.readInt() != 0;
boolean sticky = data.readInt() != 0;
scheduleRegisteredReceiver(receiver, intent,
resultCode, dataStr, extras, ordered, sticky);
return true;
}
.......
} 其中receiver为InnerReceiver。intent为要传递的数据。如图：第四步
~/Android/frameworks/base/core/java/android/app
----ActivityThread.java
public final class ActivityThread {
......
private final class ApplicationThread extends ApplicationThreadNative {
......
// 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) throws RemoteException {
receiver.performReceive(intent, resultCode, dataStr, extras, ordered, sticky);
}
......
}
......
} 经过一系列折腾，最后在MainActivity和CounterService所在应用程序主线程执行：
receiver.onReceive(mContext, intent);执行onRecevice函数：
public class MainActivity extends Activity implements OnClickListener {
......
private BroadcastReceiver counterActionReceiver = new BroadcastReceiver(){
public void onReceive(Context context, Intent intent) {
int counter = intent.getIntExtra(CounterService.COUNTER_VALUE, 0);
String text = String.valueOf(counter);
counterText.setText(text);
Log.i(LOG_TAG, "Receive counter event");
}
}
......
}