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Android中收到短信等事件都是通过广播发送给应用程序的，手机卫士等程序都是通过注册高优先级的BroadcastReceiver来实现短信防火墙等功能。对于我们来说很想知道系统中都有哪些程序注册了BroadcastReceiver，但是通过什么方法能获取系统BroadcastReceiver的列表呢？
我在群里问了一下，他们告诉我的答案居然是分析所有apk的AndroidManifest.xml，再加上解析dex里面的动态注册！而这根本不是我想达到的目的，我要知道的是目前系统中实时的BroadcastReceiver，而不是通过静态分析得到。于是我开始看Android Framework代码，想搞清楚广播的实现机制到底是怎样的。
注册BroadcastReceiver的过程是这样的：Activity调用registerReceiver，然后经过几层内部类接口的调用之后，通过Binder机制与ActivityManagerService通信，而ActivityManagerService里有一个ReceiverList保存着系统所有的BroadcastReceiver。
发送广播的过程是：Activity向ActivityManagerService发送广播，ActivityManagerService查找ReceiverList，通过比对IntentFilter找到所有对应的BroadcastReceiver，根据BroadcastReceiver的优先级进行排序后，扔进广播发送队列里。而后由专门的线程负责投递广播消息。
大致的过程就是这样的，那么目标就是获取ActivityManagerService中的ReceiverList。一开始我想的办法是：因为ActivityManagerService是一个单独的进程（system_server），我们可以通过注入system_server进程来获得ReceiverList。但是由于ActivityManagerService是java实现的，无法直接获得ReceiverList，要解析java的数据结构难度就太大了。
于是又再次查看
frameworks/base/services/java/com/android/server/am/ActivityManagerService.java：
public final class ActivityManagerService extends ActivityManagerNative implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback { ...... private final int broadcastIntentLocked(ProcessRecord callerApp, String callerPackage, Intent intent, String resolvedType, IIntentReceiver resultTo, int resultCode, String resultData, Bundle map, String requiredPermission, boolean ordered, boolean sticky, int callingPid, int callingUid) { intent = new Intent(intent); ...... // Figure out who all will receive this broadcast. List receivers = null; List<BroadcastFilter> registeredReceivers = null; try { if (intent.getComponent() != null) { ...... } else { ...... registeredReceivers = mReceiverResolver.queryIntent(intent, resolvedType, false); } } catch (RemoteException ex) { ...... } final boolean replacePending = (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0; int NR = registeredReceivers != null ? registeredReceivers.size() : 0; if (!ordered && NR > 0) { // If we are not serializing this broadcast, then send the // registered receivers separately so they don‘t wait for the // components to be launched. BroadcastRecord r = new BroadcastRecord(intent, callerApp, callerPackage, callingPid, callingUid, requiredPermission, registeredReceivers, resultTo, resultCode, resultData, map, ordered, sticky, false); ...... boolean replaced = false; if (replacePending) { for (int i=mParallelBroadcasts.size()-1; i>=0; i--) { if (intent.filterEquals(mParallelBroadcasts.get(i).intent)) { ...... mParallelBroadcasts.set(i, r); replaced = true; break; } } } if (!replaced) { mParallelBroadcasts.add(r); scheduleBroadcastsLocked(); } registeredReceivers = null; NR = 0; } ...... } ...... }
代码:
registeredReceivers = mReceiverResolver.queryIntent(intent, resolvedType, false);
到frameworks\base\services\java\com\android\server\IntentReslover.java中，注意到一个特性：
public List<R> queryIntent(Intent intent, String resolvedType, boolean defaultOnly) { String scheme = intent.getScheme(); ArrayList<R> finalList = new ArrayList<R>(); final boolean debug = localLOGV || ((intent.getFlags() & Intent.FLAG_DEBUG_LOG_RESOLUTION) != 0); if (debug) Slog.v( TAG, "Resolving type " + resolvedType + " scheme " + scheme + " of intent " + intent); sortResults(finalList); ............ if (debug) { Slog.v(TAG, "Final result list:"); for (R r : finalList) { Slog.v(TAG, " " + r); } } return finalList; }
这个有个debug选项可以打印出最终获得的ReceiverList，还是按照优先级排过序的有木有？
于是乎获取接收器列表就太简单了，只需要三行代码即可：
Intent intent = new Intent("android.provider.Telephony.SMS_RECEIVED");
intent.addFlags(Intent.FLAG_DEBUG_LOG_RESOLUTION); sendBroadcast(intent);
重点就是第二句，设置了FLAG_DEBUG_LOG_RESOLUTION，这样就会在LogCat中打印出所有注册了android.provider.Telephony.SMS_RECEIVED的BroadcastReceiver。用IntentResolver作为TAG过滤一下看起来更方便：
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原文地址：http://www.cnblogs.com/mingfeng002/p/5121570.html
