源码角度分析BroadcastReceiver

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BroadcastReceiver

一般广播的使用，都是先注册，后发送。注册可以分为静态注册和动态注册

动态注册

ContextImpl.registerReceiver
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@Override
    public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
            String broadcastPermission, Handler scheduler) {
        return registerReceiverInternal(receiver, getUserId(),
                filter, broadcastPermission, scheduler, getOuterContext(), 0);
}
ContextImpl.registerReceiverInternal
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private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
            IntentFilter filter, String broadcastPermission,
            Handler scheduler, Context context, int flags) {
    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 = ActivityManager.getService().registerReceiver(
                mMainThread.getApplicationThread(), mBasePackageName, rd, filter,
                broadcastPermission, userId, flags);
        if (intent != null) {
            intent.setExtrasClassLoader(getClassLoader());
            intent.prepareToEnterProcess();
        }
        return intent;
    } catch (RemoteException e) {
        throw e.rethrowFromSystemServer();
    }
}

通过ContextImpl注册。创建IIntentReceiver，然后通过ActivityManagerService注册广播

AMS.registerReceiver
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public Intent registerReceiver(IApplicationThread caller, String callerPackage,
            IIntentReceiver receiver, IntentFilter filter, String permission, int userId,
            int flags) {
                ...
            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);
                } else {
                    try {
                        receiver.asBinder().linkToDeath(rl, 0);
                    } catch (RemoteException e) {
                        return sticky;
                    }
                    rl.linkedToDeath = true;
                }
                mRegisteredReceivers.put(receiver.asBinder(), rl);
            }

            ...
            final int stickyCount = allSticky.size();
            for (int i = 0; i < stickyCount; i++) {
                Intent intent = allSticky.get(i);
                BroadcastQueue queue = broadcastQueueForIntent(intent);
                BroadcastRecord r = new BroadcastRecord(queue, intent, null,
                        null, -1, -1, false, null, null, AppOpsManager.OP_NONE, null, receivers,
                        null, 0, null, null, false, true, true, -1);
                queue.enqueueParallelBroadcastLocked(r);
                queue.scheduleBroadcastsLocked();
            }
}

检查是否是sticky broadcast。搜索已注册的广播，如果不存在，创建并缓存。通过每个广播意图，获取对应的前台广播队列或者后台广播队列。然后将新的广播信息入列

BroadcastQueue.scheduleBroadcastsLocked
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public void scheduleBroadcastsLocked() {
    if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Schedule broadcasts ["
            + mQueueName + "]: current="
            + mBroadcastsScheduled);

    if (mBroadcastsScheduled) {
        return;
    }
    mHandler.sendMessage(mHandler.obtainMessage(BROADCAST_INTENT_MSG, this));
    mBroadcastsScheduled = true;
}

通过Handler来处理广播消息

BroadcastQueue.processNextBroadcast
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final void processNextBroadcast(boolean fromMsg) {
    ...
    while (mParallelBroadcasts.size() > 0) {
        r = mParallelBroadcasts.remove(0);
        ...
        final int N = r.receivers.size();
        for (int i=0; i<N; i++) {
            Object target = r.receivers.get(i);
            if (DEBUG_BROADCAST)  Slog.v(TAG_BROADCAST,
                    "Delivering non-ordered on [" + mQueueName + "] to registered "
                    + target + ": " + r);
            deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false, i);
        }
        addBroadcastToHistoryLocked(r);
    }

    ...
    performReceiveLocked(r.callerApp, r.resultTo,
                                new Intent(r.intent), r.resultCode,
                                r.resultData, r.resultExtras, false, false, r.userId);
}

首先处理所有无序广播，然后处理有序广播。之后调用performReceiveLocked

BroadcastQueue.performReceiveLocked
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void performReceiveLocked(ProcessRecord app, IIntentReceiver receiver,
            Intent intent, int resultCode, String data, Bundle extras,
            boolean ordered, boolean sticky, int sendingUser) throws RemoteException {
    // 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 {
                app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
                        data, extras, ordered, sticky, sendingUser, app.repProcState);
            // TODO: Uncomment this when (b/28322359) is fixed and we aren't getting
            // DeadObjectException when the process isn't actually dead.
            //} catch (DeadObjectException ex) {
            // Failed to call into the process.  It's dying so just let it die and move on.
            //    throw ex;
            } catch (RemoteException ex) {
                // Failed to call into the process. It's either dying or wedged. Kill it gently.
                synchronized (mService) {
                    Slog.w(TAG, "Can't deliver broadcast to " + app.processName
                            + " (pid " + app.pid + "). Crashing it.");
                    app.scheduleCrash("can't deliver broadcast");
                }
                throw ex;
            }
        } else {
            // Application has died. Receiver doesn't exist.
            throw new RemoteException("app.thread must not be null");
        }
    } else {
        receiver.performReceive(intent, resultCode, data, extras, ordered,
                sticky, sendingUser);
    }
}

如果app进程还存在，那么直接通知ApplicationThread处理消息，以保证广播的顺序。最终都是调用IIntentReceiver

LoadApk.ReceiverDispatcher.InnerReceiver
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@Override
public void performReceive(Intent intent, int resultCode, String data,
        Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
    final LoadedApk.ReceiverDispatcher rd;
    if (intent == null) {
        Log.wtf(TAG, "Null intent received");
        rd = null;
    } else {
        rd = mDispatcher.get();
    }
    if (ActivityThread.DEBUG_BROADCAST) {
        int seq = intent.getIntExtra("seq", -1);
        Slog.i(ActivityThread.TAG, "Receiving broadcast " + intent.getAction()
                + " seq=" + seq + " to " + (rd != null ? rd.mReceiver : null));
    }
    if (rd != null) {
        rd.performReceive(intent, resultCode, data, extras,
                ordered, sticky, sendingUser);
    } else {
        // The activity manager dispatched a broadcast to a registered
        // receiver in this process, but before it could be delivered the
        // receiver was unregistered.  Acknowledge the broadcast on its
        // behalf so that the system's broadcast sequence can continue.
        if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
                "Finishing broadcast to unregistered receiver");
        IActivityManager mgr = ActivityManager.getService();
        try {
            if (extras != null) {
                extras.setAllowFds(false);
            }
            mgr.finishReceiver(this, resultCode, data, extras, false, intent.getFlags());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }
}

通过IPC从AMS通讯回到LoadedApk

静态注册

在AndroidManifest.xml中注册广播。广播发出后，会经由PackageManagerService获取当前进程的所有配置信息，然后会做比对

广播发送

AMS.broadcastIntent
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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) {
        synchronized(this) {
            intent = verifyBroadcastLocked(intent);
            ...
            int res = broadcastIntentLocked(callerApp,
                    callerApp != null ? callerApp.info.packageName : null,
                    intent, resolvedType, resultTo, resultCode, resultData, resultExtras,
                    requiredPermissions, appOp, bOptions, serialized, sticky,
                    callingPid, callingUid, userId);
        }
}

校验广播意图

AMS.broadcastIntentLocked
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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) {
                ...

                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.
            if (isCallerSystem) {
                checkBroadcastFromSystem(intent, callerApp, callerPackage, callingUid,
                        isProtectedBroadcast, registeredReceivers);
            }
            final BroadcastQueue queue = broadcastQueueForIntent(intent);
            BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
                    callerPackage, callingPid, callingUid, callerInstantApp, resolvedType,
                    requiredPermissions, appOp, brOptions, registeredReceivers, resultTo,
                    resultCode, resultData, resultExtras, ordered, sticky, false, userId);
            if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueueing parallel broadcast " + r);
            final boolean replaced = replacePending
                    && (queue.replaceParallelBroadcastLocked(r) != null);
            // Note: We assume resultTo is null for non-ordered broadcasts.
            if (!replaced) {
                queue.enqueueParallelBroadcastLocked(r);
                queue.scheduleBroadcastsLocked();
            }
            registeredReceivers = null;
            NR = 0;
        }
}

首先处理系统的广播消息。然后将广播消息入队列

BroadCastQueue.processNextBroadcast
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final void processNextBroadcast(boolean fromMsg) {
    ...
    if (app != null && app.thread != null && !app.killed) {
        try {
            app.addPackage(info.activityInfo.packageName,
                    info.activityInfo.applicationInfo.versionCode, mService.mProcessStats);
            processCurBroadcastLocked(r, app);
            return;
        }
    }
}

如果当前进程还在，那么处理当前广播

BroadCastQueue.processCurBroadcastLocked
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private final void processCurBroadcastLocked(BroadcastRecord r,
            ProcessRecord app) throws RemoteException {
                ...
                app.thread.scheduleReceiver(new Intent(r.intent), r.curReceiver,
                    mService.compatibilityInfoForPackageLocked(r.curReceiver.applicationInfo),
                    r.resultCode, r.resultData, r.resultExtras, r.ordered, r.userId,
                    app.repProcState);
}

如果当前进程正在备份，那么忽略广播。更新进程状态，调整优先级。然后通知ApplicationThread处理广播

ActivityThread.handleReceiver
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private void handleReceiver(ReceiverData data) {
    // If we are getting ready to gc after going to the background, well
    // we are back active so skip it.
    unscheduleGcIdler();

    String component = data.intent.getComponent().getClassName();

    LoadedApk packageInfo = getPackageInfoNoCheck(
            data.info.applicationInfo, data.compatInfo);

    IActivityManager mgr = ActivityManager.getService();

    Application app;
    BroadcastReceiver receiver;
    ContextImpl context;
    try {
        app = packageInfo.makeApplication(false, mInstrumentation);
        context = (ContextImpl) app.getBaseContext();
        if (data.info.splitName != null) {
            context = (ContextImpl) context.createContextForSplit(data.info.splitName);
        }
        java.lang.ClassLoader cl = context.getClassLoader();
        data.intent.setExtrasClassLoader(cl);
        data.intent.prepareToEnterProcess();
        data.setExtrasClassLoader(cl);
        receiver = (BroadcastReceiver)cl.loadClass(component).newInstance();
    } catch (Exception e) {
        if (DEBUG_BROADCAST) Slog.i(TAG,
                "Finishing failed broadcast to " + data.intent.getComponent());
        data.sendFinished(mgr);
        throw new RuntimeException(
            "Unable to instantiate receiver " + component
            + ": " + e.toString(), e);
    }

    try {
        if (localLOGV) Slog.v(
            TAG, "Performing receive of " + data.intent
            + ": app=" + app
            + ", appName=" + app.getPackageName()
            + ", pkg=" + packageInfo.getPackageName()
            + ", comp=" + data.intent.getComponent().toShortString()
            + ", dir=" + packageInfo.getAppDir());

        sCurrentBroadcastIntent.set(data.intent);
        receiver.setPendingResult(data);
        receiver.onReceive(context.getReceiverRestrictedContext(),
                data.intent);
    } catch (Exception e) {
        if (DEBUG_BROADCAST) Slog.i(TAG,
                "Finishing failed broadcast to " + data.intent.getComponent());
        data.sendFinished(mgr);
        if (!mInstrumentation.onException(receiver, e)) {
            throw new RuntimeException(
                "Unable to start receiver " + component
                + ": " + e.toString(), e);
        }
    } finally {
        sCurrentBroadcastIntent.set(null);
    }

    if (receiver.getPendingResult() != null) {
        data.finish();
    }
}

通过反射，创建广播对象，然后调用onReceive

时序图

注册

register

发送

send