Android 70 ActivityManagerService5 广播Broadcast相关流程分析2.docx

1、Android 70 ActivityManagerService5 广播Broadcast相关流程分析2Android 7.0 ActivityManagerService(5) 广播(Broadcast)相关流程分析（2）4 broadcastIntentLocked函数Part IV./ Merge into one list.int ir = 0;if (receivers != null) / A special case for PACKAGE_ADDED: do not allow the package / being added to see this broadcast.

2、This prevents them from / using this as a back door to get run as soon as they are / installed. Maybe in the future we want to have a special install / broadcast or such for apps, but wed like to deliberately make / this decision. /处理特殊的Action，例如PACKAGE_ADDED，系统不希望有些应用一安装就能启动 /APP安装后，PKMS将发送PACKAGE_

3、ADDED广播 /若没有这个限制，在刚安装的APP内部静态注册监听该消息的BroadcastReceiver，新安装的APP就能直接启动 String skipPackages = null; if (Intent.ACTION_PACKAGE_ADDED.equals(intent.getAction() | Intent.ACTION_PACKAGE_RESTARTED.equals(intent.getAction() | Intent.ACTION_PACKAGE_DATA_CLEARED.equals(intent.getAction() Uri data = intent.getD

4、ata(); if (data != null) String pkgName = data.getSchemeSpecificPart(); if (pkgName != null) skipPackages = new String pkgName ; else if (Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE.equals(intent.getAction() skipPackages = intent.getStringArrayExtra(Intent.EXTRA_CHANGED_PACKAGE_LIST); if (skipPack

5、ages != null & (skipPackages.length 0) for (String skipPackage : skipPackages) if (skipPackage != null) int NT = receivers.size(); for (int it=0; itNT; it+) ResolveInfo curt = (ResolveInfo)receivers.get(it); if (curt.activityInfo.packageName.equals(skipPackage) /将skipPackages对应的BroadcastReceiver移出re

6、ceivers receivers.remove(it); it-; NT-; int NT = receivers != null ? receivers.size() : 0; int it = 0; ResolveInfo curt = null; BroadcastFilter curr = null; /NT对应的是静态BroadcastReceiver的数量 /NR对应的是动态BroadcastReceiver的数量 /若发送的是无序广播，此时NR为0 /若是有序广播，才会进入下面两个while循环 /下面两个while循环就是将静态注册的BroadcastReceiver和动态注

7、册的BroadcastReceiver /按照优先级合并到一起（有序广播才会合并） while (it NT & ir = curt.priority) / Insert this broadcast record into the final list. receivers.add(it, curr); ir+; curr = null; it+; NT+; else / Skip to the next ResolveInfo in the final list. it+; curt = null; while (ir 0) | resultTo != null) BroadcastQue

8、ue queue = broadcastQueueForIntent(intent); /构造对应的BroadcastRecord BroadcastRecord r = new BroadcastRecord(.); . /同样判断是否需要替换，这里是Ordered Queue boolean replaced = replacePending & queue.replaceOrderedBroadcastLocked(r); if (!replaced) /没替换时，就加入Ordered Queue queue.enqueueOrderedBroadcastLocked(r); /触发发送

9、流程 queue.scheduleBroadcastsLocked(); else / There was nobody interested in the broadcast, but we still want to record / that it happened. if (intent.getComponent() = null & intent.getPackage() = null & (intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY) = 0) / This was an implicit broadcast. le

10、ts record it for posterity. /没有处理的静态或有序广播，保存起来 /感觉保存起来也没什么用啊 addBroadcastStatLocked(intent.getAction(), callerPackage, 0, 0, 0); .简单来说，broadcastIntentLocked的第四部分工作就是为有序广播和静态广播，构造对应的BroadcastRecord（按优先级顺序）， 然后将BroadcastRecord加入到Ordered Queue中，并触发广播发送流程。至此，整个broadcastIntentLocked函数分析完毕，除去一些条件判断的细节外，整个

11、工作流程如下图所示：1、处理粘性广播。 由于粘性广播的特性（BroadcastReceiver注册即可接收），系统必须首先保存粘性广播。2、处理普通动态广播。 普通广播是并发的，系统优先为动态注册的BroadcastReceiver发送广播。 动态广播对应的BroadcastRecord加入到Parallel Queue中。3、处理静态广播和有序广播。 这一步主要是为静态注册的BroadcastReceiver发送广播，对应的BroadcastRecord加入到Ordered Queue中。此外，需要注意的是： 如果广播是有序的，那么第2步不会为动态注册的BroadcastReceiver发送

12、广播，而是在第3步统一发送。 发送有序广播时，AMS将按照BroadcastReceiver的优先级，依次构造BroadcastRecord加入到Ordered Queue中。四、BroadcastQueue的scheduleBroadcastsLocked函数流程分析 从上面的代码，我们知道广播发送方调用sendBroadcast后，AMS会构造对应的BroadcastRecord加入到BroadcastQueue中， 然后调用BroadcastQueue的scheduleBroadcastsLocked函数。现在，我们就来看一下scheduleBroadcastsLocked相关的流程。p

13、ublic void scheduleBroadcastsLocked() . /避免短时间内重复发送BROADCAST_INTENT_MSG if (mBroadcastsScheduled) return; mHandler.sendMessage(mHandler.obtainMessage(BROADCAST_INTENT_MSG, this); mBroadcastsScheduled = true;上面的代码将发送BROADCAST_INTENT_MSG，触发BroadcastQueue调用processNextBroadcast进行处理。 processNextBroadcast

14、函数同样非常的长，大概有500多行。我们还是分段进行分析。1 processNextBroadcast函数Part Ifinal void processNextBroadcast(boolean fromMsg) synchronized(mService) BroadcastRecord r; . /更新CPU的使用情况 /处理静态广播时，可能需要拉起对应进程，因此在这里先记录一下CPU情况 mService.updateCpuStats(); if (fromMsg) /处理BROADCAST_INTENT_MSG后，将mBroadcastsScheduled置为false /sched

15、uleBroadcastsLocked就可以再次被调用了 mBroadcastsScheduled = false; / First, deliver any non-serialized broadcasts right away. /先处理“并发”发送的普通广播 while (mParallelBroadcasts.size() 0) /依次取出BroadcastRecord r = mParallelBroadcasts.remove(0); /记录发送的时间 r.dispatchTime = SystemClock.uptimeMillis(); r.dispatchClockTime

16、 = System.currentTimeMillis(); final int N = r.receivers.size(); . for (int i=0; i 0) for (int i = 0; i r.requiredPermissions.length; i+) String requiredPermission = r.requiredPermissionsi; int perm = mService.checkComponentPermission(requiredPermission, filter.receiverList.pid, filter.receiverList.

17、uid, -1, true); if (perm != PackageManager.PERMISSION_GRANTED) . /只要一条权限不满足，就结束 skip = true; break; /进一步检查权限的合理性 int appOp = AppOpsManager.permissionToOpCode(requiredPermission); if (appOp != AppOpsManager.OP_NONE & appOp != r.appOp & mService.mAppOpsService.noteOperation(appOp, filter.receiverList.

18、uid, filter.packageName) != AppOpsManager.MODE_ALLOWED) . skip = true; break; /这段代码我看的有些懵逼，发送方没要求权限，还检查啥？ if (!skip & (r.requiredPermissions = null | r.requiredPermissions.length = 0) int perm = mService.checkComponentPermission(null, filter.receiverList.pid, filter.receiverList.uid, -1, true); if (

19、perm != PackageManager.PERMISSION_GRANTED) . skip = true; /还有一些其它的检查，不再分析代码了。 /包括是否允许以background的方式发送、IntentFirewall是否允许广播中的Intent发送 . if (skip) /不满足发送条件的话，标记一下，结束发送 r.deliveryindex = BroadcastRecord.DELIVERY_SKIPPED; return; / If permissions need a review before any of the app components can run, w

20、e drop / the broadcast and if the calling app is in the foreground and the broadcast is / explicit we launch the review UI passing it a pending intent to send the skipped / broadcast. /特殊情况，还需要再次检查权限，中断广播发送 /再次满足发送条件后，会重新进入到后续的发送流程 if (Build.PERMISSIONS_REVIEW_REQUIRED) if (!requestStartTargetPermis

21、sionsReviewIfNeededLocked(r, filter.packageName, filter.owningUserId) r.deliveryindex = BroadcastRecord.DELIVERY_SKIPPED; return; /可以发送了，标记一下 r.deliveryindex = BroadcastRecord.DELIVERY_DELIVERED; / If this is not being sent as an ordered broadcast, then we / dont want to touch the fields that keep t

22、rack of the current / state of ordered broadcasts. if (ordered) /如果发送的是有序广播，则记录一些状态信息等，不涉及广播发送的过程 . try . /若BroadcastReceiver对应的进程处于fullBackup状态（备份和恢复），则不发送广播 if (filter.receiverList.app != null & filter.receiverList.app.inFullBackup) if (ordered) /有序广播必须处理完一个，才能处理下一个，因此这里主动触发一下 skipReceiverLocked(r

23、); else /执行发送工作 performReceiveLocked(.); if (ordered) r.state = BroadcastRecord.CALL_DONE_RECEIVE; catch (RemoteException e) . deliverToRegisteredReceiverLocked看起来很长，但大部分内容都是进行权限检查等操作，实际的发送工作交给了performReceiveLocked函数。 广播是一种可以携带数据的跨进程、跨APP通信机制，为了避免安全泄露的问题，Android才在此处使用了大量的篇幅进行权限检查的工作。在这一部分的最后，我们跟进一下p

24、erformReceiveLocked函数：void performReceiveLocked(.) / Send the intent to the receiver asynchronously using one-way binder calls. if (app != null) if (app.thread != null) / If we have an app thread, do the call through that so it is / correctly ordered with other one-way calls. try /通过Binder通信，将广播信息发往BroadcastReceiver处在的进程 app.thread.scheduleRegisteredReceiver(.); catch (RemoteException ex) / Failed to call into the