注册广播接收器（registerReceiver）分析

动态注册registerReceiver:主要就是将广播接收器receiver封装到LoadedApk的InnerReceiver（继承IIntentReceiver接口的binder对象）及广播类型filter传给ActivityManagerService保存起来，别人在发送广播时，在AMS过滤后发送过来.
时序图：

类图可以参考 一张图看懂bindService源码流程（包括进程内和新进程）
Step1:注册广播代码

public class TestReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
    }
}
IntentFilter filter = new IntentFilter("cn.umbrella.chanage");
registerReceiver(new TestReceiver(), filter);

Step2:ContextImpl.registerReceiver():

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, getUserId(),
                filter, broadcastPermission, scheduler, getOuterContext());
    }
    @Override
    public Intent registerReceiverAsUser(BroadcastReceiver receiver, UserHandle user,
            IntentFilter filter, String broadcastPermission, Handler scheduler) {
        return registerReceiverInternal(receiver, user.getIdentifier(),
                filter, broadcastPermission, scheduler, getOuterContext());
    }
    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 {
            final Intent intent = ActivityManagerNative.getDefault().registerReceiver(
                    mMainThread.getApplicationThread(), mBasePackageName,
                    rd, filter, broadcastPermission, userId);
            if (intent != null) {
                intent.setExtrasClassLoader(getClassLoader());
                intent.prepareToEnterProcess();
            }
            return intent;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }
}

getOuterContext()就是XXXActivity.
Setp3:scheduler = mMainThread.getHandler()是handler：

public final class ActivityThread {
    private class H extends Handler {
    } 
    final Handler getHandler() {
        return mH;
    }
}

Step 4:LoadedApk.getReceiverDispatcher，返回IIntentReceiver接口对象rd的Binder对象:

public final class LoadedApk {
    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();
        }
    }
}

从LoadedApk的成员变量mReceivers获取相应的ReceiverDispatcher，如果不存在则新建一个,并保存起来。
Step5:LoadedApk .ReceiverDispatcher :

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;
                ...
            }
        }
        ReceiverDispatcher(BroadcastReceiver receiver, Context context,
                Handler activityThread, Instrumentation instrumentation,
                boolean registered) {
            ...
            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;
        }
    }
}

新建ReceiverDispatcher同时,会创建一个实现IIntentReceiver接口的binder对象:InnerReceiver,这是用来和AMS通讯时调用performReceive
Step6:ActivityManagerProxy .registerReceiver

class ActivityManagerProxy implements IActivityManager{
     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;
    }
}

这个函数通过Binder驱动程序就进入到ActivityManagerService中的registerReceiver函数中去了。
Step 7:AMS.registerReceiver:

public final class ActivityManagerService extends ActivityManagerNative
        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
     public Intent registerReceiver(IApplicationThread caller, String callerPackage,
            IIntentReceiver receiver, IntentFilter filter, String permission, int userId) {
        enforceNotIsolatedCaller("registerReceiver");
        ...
        synchronized (this) {
            ...
            ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
            if (rl == null) {
                rl = new ReceiverList(this, callerApp, callingPid, callingUid,
                        userId, receiver);
                if (rl.app != null) {
                    rl.app.receivers.add(rl);
                } 
                ...
                mRegisteredReceivers.put(receiver.asBinder(), rl);
            } 
            ...
            BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,
                    permission, callingUid, userId);
            rl.add(bf);
            mReceiverResolver.addFilter(bf);
            ...
            return sticky;
        }
    }
}

把广播接收器receiver和filter关联起来，并保存到mReceiverResolver.这样，广播接收器注册到这边就可以了。