sendBroadcast通过Binder进程间通信机制发给ActivityManagerService进程，ActivityManagerService会找出相应的广播接收器，放到自己的消息队列中去，对广播的异步分发，通过binder进程间通信机制分发给注册广播进程接收器LoadedApk.ReceiverDispatcher,
ReceiverDispatcher的内部类Args在接收广播进程的UI线程里面处理注册的BroadcastReceiver实例的onReceive函数
Step1:ContextImpl.broadcastIntent
Intent intent = new Intent("cn.umbrella.chanage");
intent.putExtra("key","vaule");
sendBroadcast(intent);
class ContextImpl extends Context {
@Override
public void sendBroadcast(Intent intent) {
warnIfCallingFromSystemProcess();
String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
try {
intent.prepareToLeaveProcess(this);
ActivityManagerNative.getDefault().broadcastIntent(
mMainThread.getApplicationThread(), intent, resolvedType, null,
Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false, false,
getUserId());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
Step2:ActivityManagerProxy.broadcastIntent:
class ActivityManagerProxy implements IActivityManager{
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);
mRemote.transact(BROADCAST_INTENT_TRANSACTION, data, reply, 0);
reply.readException();
int res = reply.readInt();
reply.recycle();
data.recycle();
return res;
}
}
要传递的参数封装好，然后通过Binder驱动程序进入到ActivityManagerService进程的broadcastIntent函数中
Step3:ActivityManagerService.broadcastIntent及broadcastIntent:
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 resultExtras,
String[] requiredPermissions, int appOp, Bundle bOptions,
boolean serialized, boolean sticky, int userId) {
enforceNotIsolatedCaller("broadcastIntent");
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, resultExtras,
requiredPermissions, appOp, bOptions, serialized, sticky,
callingPid, callingUid, userId);
Binder.restoreCallingIdentity(origId);
return res;
}
}
}
public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
final int broadcastIntentLocked(ProcessRecord callerApp,
String callerPackage, Intent intent, String resolvedType,
IIntentReceiver resultTo, int resultCode, String resultData,
Bundle resultExtras, String[] requiredPermissions, int appOp, Bundle bOptions,
boolean ordered, boolean sticky, int callingPid, int callingUid, int userId) {
....
// Figure out who all will receive this broadcast.
List receivers = null;
List registeredReceivers = null;
// Need to resolve the intent to interested receivers...
...
registeredReceivers = mReceiverResolver.queryIntent(intent,
resolvedType, false, userId);
....
if ((receivers != null && receivers.size() > 0)
|| resultTo != null) {
BroadcastQueue queue = broadcastQueueForIntent(intent);
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) {
queue.enqueueOrderedBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
}
....
return ActivityManager.BROADCAST_SUCCESS;
}
}
根据intent找出相应的广播接收器,BroadcastQueue queue.enqueueOrderedBroadcastLocked(r)把所有相应的广播接收器放到数组里面，queue.scheduleBroadcastsLocked再做广播消息处理.
Step4:BroadcastQueue.scheduleBroadcastsLocked、
Step5:mHandler.sendMessage
public final class BroadcastQueue {
final BroadcastHandler mHandler;
private final class BroadcastHandler extends Handler {
public BroadcastHandler(Looper looper) {
super(looper, null, true);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case BROADCAST_INTENT_MSG: {
...
processNextBroadcast(true);
} break;
...
}
}
}
public void scheduleBroadcastsLocked() {
...
if (mBroadcastsScheduled) {
return;
}
mHandler.sendMessage(mHandler.obtainMessage(BROADCAST_INTENT_MSG, this));
mBroadcastsScheduled = true;
}
}
Step6:BroadcastQueue.processNextBroadcast:
public final class BroadcastQueue {
final void processNextBroadcast(boolean fromMsg) {
synchronized(mService) {
BroadcastRecord r;
...
// First, deliver any non-serialized broadcasts right away.
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);
deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false, i);
}
addBroadcastToHistoryLocked(r);
}
...
}
}
}
while循环中的for循环把这个广播发送给每一个订阅了该广播的接收器
Step 7:BroadcastQueue .deliverToRegisteredReceiverLocked
public final class BroadcastQueue {
private void deliverToRegisteredReceiverLocked(BroadcastRecord r,
BroadcastFilter filter, boolean ordered, int index) {
boolean skip = false;
...
try {
...
performReceiveLocked(filter.receiverList.app, filter.receiverList.receiver,
new Intent(r.intent), r.resultCode, r.resultData,
r.resultExtras, r.ordered, r.initialSticky, r.userId);
...
} catch (RemoteException e) {
...
}
}
}
检查广播发送和接收的权限，然后performReceiveLocked处理。
Step 8:BroadcastQueue .performReceiveLocked:
public final class BroadcastQueue {
void performReceiveLocked(ProcessRecord app, IIntentReceiver receiver,
Intent intent, int resultCode, String data, Bundle extras,
boolean ordered, boolean sticky, int sendingUser) throws RemoteException {
if (app != null) {
if (app.thread != null) {
..
app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
data, extras, ordered, sticky, sendingUser, app.repProcState);
...
} else {
...
}
}
}
ProcessRecord app,进程记录块，是接收广播的进程，app.thread是一个Binder远程对象，它的类型是ApplicationThreadProxy。
Step 9:ApplicationThreadProxy.performReceiveLocked:
class ApplicationThreadProxy implements IApplicationThread {
void performReceiveLocked(ProcessRecord app, IIntentReceiver receiver,
Intent intent, int resultCode, String data, Bundle extras,
boolean ordered, boolean sticky, int sendingUser) throws RemoteException {
if (app != null) {
if (app.thread != null) {
..
app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
data, extras, ordered, sticky, sendingUser, app.repProcState);
...
} else {
...
}
}
}
通过Binder驱动程序就进入到接收广播的进程的ApplicationThread.scheduleRegisteredReceiver函数:
Step10:ApplicationThread.scheduleRegisteredReceiver
public final class ActivityThread {
private class ApplicationThread extends ApplicationThreadNative {
public void scheduleRegisteredReceiver(IIntentReceiver receiver, Intent intent,
int resultCode, String dataStr, Bundle extras, boolean ordered,
boolean sticky, int sendingUser, int processState) throws RemoteException {
updateProcessState(processState, false);
receiver.performReceive(intent, resultCode, dataStr, extras, ordered,
sticky, sendingUser);
}
}
}
其中receiver就是LoadedApk.ReceiverDispatcher.InnerReceiver
Step 11:ReceiverDispatcher.InnerReceiver.performReceive:
public final class LoadedApk {
...
static final class ReceiverDispatcher {
final static class InnerReceiver extends IIntentReceiver.Stub {
final WeakReference mDispatcher;
final LoadedApk.ReceiverDispatcher mStrongRef;
InnerReceiver(LoadedApk.ReceiverDispatcher rd, boolean strong) {
mDispatcher = new WeakReference(rd);
mStrongRef = strong ? rd : null;
}
@Override
public void performReceive(Intent intent, int resultCode, String data,
Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
final LoadedApk.ReceiverDispatcher rd;
...
if (rd != null) {
rd.performReceive(intent, resultCode, data, extras,
ordered, sticky, sendingUser);
}
...
}
}
}
调用LoadedApk类里面的一个内部类ReceiverDispatcher的performReceive函数来处理
Step 12:ReceiverDispatcher.performReceive:
public final class LoadedApk {
static final class ReceiverDispatcher {
public void performReceive(Intent intent, int resultCode, String data,
Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
final Args args = new Args(intent, resultCode, data, extras, ordered,
sticky, sendingUser);
...
if (intent == null || !mActivityThread.post(args)) {
if (mRegistered && ordered) {
...
}
}
}
}
}
mActivityThread是handler,post放到消息队列中,到接收广播的UI线程里实行Runnable 的run：
Step 12:mActivityThread.post(args):
public final class LoadedApk {
...
static final class ReceiverDispatcher {
final class Args extends BroadcastReceiver.PendingResult implements Runnable {
private Intent mCurIntent;
private final boolean mOrdered;
private boolean mDispatched;
...
public void run() {
final BroadcastReceiver receiver = mReceiver;
final boolean ordered = mOrdered;
...
try {
ClassLoader cl = mReceiver.getClass().getClassLoader();
intent.setExtrasClassLoader(cl);
intent.prepareToEnterProcess();
setExtrasClassLoader(cl);
receiver.setPendingResult(this);
receiver.onReceive(mContext, intent);
} catch (Exception e) {
...
}
...
}
}
}
}
这样就实行到onReceive:
Step 13:TestReceiver.onReceive:
public class TestReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
}
}