詳解Android廣播Broadcast的啟動(dòng)流程

更新時(shí)間：2023年03月30日 15:05:38 作者：新小夢(mèng)

這篇文章主要為大家介紹了Android廣播Broadcast啟動(dòng)流程詳解，有需要的朋友可以借鑒參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪

正文

本文整體閱讀下來(lái)相對(duì)Activity和Service的啟動(dòng)流程較容易，比較貼近我們?nèi)粘４a開(kāi)發(fā)習(xí)慣。我們?cè)?jīng)有個(gè)整機(jī)項(xiàng)目，多個(gè)APP跨進(jìn)程交互，本來(lái)想采用AIDL進(jìn)行的，但最終考慮到項(xiàng)目工期和其他同事的能力，最終在采用廣播方式進(jìn)行IPC。

那時(shí)，自己也在想，這么多個(gè)APP相互發(fā)信息，數(shù)據(jù)量也大，對(duì)整機(jī)性能有影響么？會(huì)不會(huì)存在丟失和內(nèi)存問(wèn)題。一臉茫然，網(wǎng)上也不會(huì)有類(lèi)似信息告訴總結(jié)這種情況，本文也不會(huì)總結(jié)這個(gè)答案，因?yàn)榭赐曛笮闹凶匀挥袛?shù)了。

在AMS中持有集合用于存儲(chǔ)所有的廣播，應(yīng)用程序可以從向其注冊(cè)和解注冊(cè)廣播。當(dāng)應(yīng)用發(fā)送廣播時(shí)，AMS檢查相關(guān)權(quán)限和特殊的Intent。然后再根據(jù)對(duì)應(yīng)IntentFilter匹配到一個(gè)或多個(gè)Receiver，在應(yīng)用進(jìn)程回調(diào)其onReceive函數(shù)。

閱讀源碼本身就是一份苦活，不可能一次就讀懂，或者了解透的。只有反復(fù)的閱讀，輸入與輸出，才會(huì)越來(lái)越輕松。所以個(gè)人建議，先粗讀，了解個(gè)大概的思路就行。收藏或點(diǎn)贊，等自己ready，再好好結(jié)合源碼閱讀。一定要Fuck Code!

廣播的注冊(cè)

我們常在Activity或Service、甚至Application中調(diào)用registerReceiver函數(shù)來(lái)注冊(cè)動(dòng)態(tài)廣播，該函數(shù)其實(shí)來(lái)自它們共同的父類(lèi)ContextWrapper中。ContextWrapper是Context的子類(lèi)，我們會(huì)在介紹Context的文章介紹它們的關(guān)系。

public Intent registerReceiver(
    BroadcastReceiver receiver, IntentFilter filter) {
    return mBase.registerReceiver(receiver, filter);
}

這里Context類(lèi)型的mBase，在Activity的創(chuàng)建過(guò)程實(shí)際被賦值為ContextImpl實(shí)例。

public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
    return registerReceiver(receiver, filter, null, null);
}
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
    String broadcastPermission, Handler scheduler) {
	return registerReceiverInternal(receiver, getUserId(),
        	filter, broadcastPermission, scheduler, getOuterContext(), 0);
}

經(jīng)過(guò)registerReceiver重載函數(shù)，調(diào)用了registerReceiverInternal函數(shù)。

    private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
            IntentFilter filter, String broadcastPermission,
            Handler scheduler, Context context, int flags) {
        IIntentReceiver rd = null;
        //分析一
        if (receiver != null) {
            if (mPackageInfo != null &amp;&amp; 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 {
        	分析二：
            final Intent intent = ActivityManager.getService().registerReceiverWithFeature(
                    mMainThread.getApplicationThread(), mBasePackageName, getAttributionTag(), rd,
                    filter, broadcastPermission, userId, flags);
            if (intent != null) {
                intent.setExtrasClassLoader(getClassLoader());
                intent.prepareToEnterProcess();
            }
            return intent;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

分析一:

傳遞進(jìn)來(lái)的BroadcastReceiver不為null，LoadedApk類(lèi)型的mPackageInfo只要應(yīng)用進(jìn)程啟動(dòng)，該屬性就會(huì)被賦值，context這里指向Activity。scheduler為null，賦值為主線程的H類(lèi)型mH對(duì)象。分析一，主要通過(guò)上面的變量來(lái)獲得IIntentReceiver類(lèi)型rd對(duì)象。

getReceiverDispatcher函數(shù)先從緩存檢測(cè)是否有相同類(lèi)型的BroadcastReceiver對(duì)應(yīng)的ReceiverDispatcher。沒(méi)有的話(huà)，則新建并緩存起來(lái)。一個(gè)context對(duì)應(yīng)多個(gè)BroadcastReceiver，而一個(gè)BroadcastReceiver對(duì)應(yīng)用一個(gè)ReceiverDispatcher。

ReceiverDispatcher是LoadedDispatcher的靜態(tài)內(nèi)部類(lèi)，其內(nèi)部還有一個(gè)AIDL類(lèi)型本地實(shí)現(xiàn)靜態(tài)類(lèi)InnerReceiver。在ReceiverDispatcher的構(gòu)造函數(shù)中會(huì)創(chuàng)建InnerReceiver的實(shí)例。

public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
        Context context, Handler handler,
        Instrumentation instrumentation, boolean registered) {
    synchronized (mReceivers) {
        LoadedApk.ReceiverDispatcher rd = null;
        ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> 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<BroadcastReceiver, LoadedApk.ReceiverDispatcher>();
                    mReceivers.put(context, map);
                }
                map.put(r, rd);
            }
        } else {
            rd.validate(context, handler);
        }
        rd.mForgotten = false;
        return rd.getIIntentReceiver();
    }
}

回到registerReceiverInternal函數(shù)的分析二，調(diào)用了AMS的registerReceiverWithFeature函數(shù)。

該函數(shù)是Broadcast整個(gè)注冊(cè)過(guò)程結(jié)束的地方，根據(jù)新注冊(cè)的BroadcastReceiver，處理粘性廣播的發(fā)送和當(dāng)前注冊(cè)Receiver的添加。

分析一：

粘性廣播存儲(chǔ)在AMS的SparseArray<ArrayMap<String, ArrayList<Intent>>>類(lèi)型的 mStickyBroadcasts中。SparseArray的key為userId,而ArrayMap的key為action,value為Intent。即我們可以通過(guò)用戶(hù)id在mStickyBroadcasts找到當(dāng)前進(jìn)程對(duì)應(yīng)所有粘性廣播（和針對(duì)所有進(jìn)程的粘性廣播），然后根據(jù)對(duì)應(yīng)的action找到對(duì)應(yīng)的Intent。這里將他們收集到stickyIntents集合中。

分析二：

所有廣播的接收者BroacastReceiver存儲(chǔ)在AMS類(lèi) HashMap<IBinder, ReceiverList>類(lèi)型的mRegisteredReceivers中。這里的IBinder類(lèi)型就是應(yīng)用進(jìn)程前面創(chuàng)建的InnerReceiver類(lèi)實(shí)例在AMS的引用。因?yàn)閺V播接收者BroadcastReceiver對(duì)應(yīng)一個(gè)或多個(gè)Broadcast,所以這里通過(guò)繼承自ArrayList<BroadcastFilter>的ReceiverList來(lái)表達(dá)這種關(guān)系。通過(guò)BroadcastFilter來(lái)表示當(dāng)前接收者感興趣的廣播。

分析三：

對(duì)匹配到的粘性Intent進(jìn)入廣播隊(duì)列廣播。

    public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,
            String callerFeatureId, IIntentReceiver receiver, IntentFilter filter,
            String permission, int userId, int flags) {
        enforceNotIsolatedCaller("registerReceiver");
		//粘性Intent
		ArrayList<Intent> stickyIntents = null;
        ProcessRecord callerApp = null;
        final boolean visibleToInstantApps
                = (flags & Context.RECEIVER_VISIBLE_TO_INSTANT_APPS) != 0;
        int callingUid;
        int callingPid;
        boolean instantApp;
        synchronized(this) {
            if (caller != null) {
            	//獲得當(dāng)前引用進(jìn)程的ProcessRecord
                callerApp = getRecordForAppLocked(caller);
               	...
                callingUid = callerApp.info.uid;
                callingPid = callerApp.pid;
            } else {
                callerPackage = null;
                callingUid = Binder.getCallingUid();
                callingPid = Binder.getCallingPid();
            }
			//是否快應(yīng)用（類(lèi)似小程序）
            instantApp = isInstantApp(callerApp, callerPackage, callingUid);
            userId = mUserController.handleIncomingUser(callingPid, callingUid, userId, true,
                    ALLOW_FULL_ONLY, "registerReceiver", callerPackage);
			//分析一：當(dāng)前注冊(cè)廣播中感興趣的action列表
            Iterator<String> actions = filter.actionsIterator();
            if (actions == null) {
                ArrayList<String> noAction = new ArrayList<String>(1);
                noAction.add(null);
                actions = noAction.iterator();
            }
			//從歷史粘性廣播中查找與當(dāng)前注冊(cè)的action一致的intent
			//添加到stickyIntents
            // Collect stickies of users
            int[] userIds = { UserHandle.USER_ALL, UserHandle.getUserId(callingUid) };
            while (actions.hasNext()) {
                String action = actions.next();
                for (int id : userIds) {
                    ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(id);
                    if (stickies != null) {
                        ArrayList<Intent> intents = stickies.get(action);
                        if (intents != null) {
                            if (stickyIntents == null) {
                                stickyIntents = new ArrayList<Intent>();
                            }
                            stickyIntents.addAll(intents);
                        }
                    }
                }
            }
        }
		//處理content類(lèi)型的Intent
        ArrayList<Intent> allSticky = null;
        if (stickyIntents != null) {
            final ContentResolver resolver = mContext.getContentResolver();
            // Look for any matching sticky broadcasts...
            for (int i = 0, N = stickyIntents.size(); i < N; i++) {
                Intent intent = stickyIntents.get(i);
                // Don't provided intents that aren't available to instant apps.
                if (instantApp &&
                        (intent.getFlags() & Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS) == 0) {
                    continue;
                }
                //當(dāng)前注冊(cè)廣播IntentFilter是否與action一致的intent的匹配
                //處理content類(lèi)型
                if (filter.match(resolver, intent, true, TAG) >= 0) {
                    if (allSticky == null) {
                        allSticky = new ArrayList<Intent>();
                    }
                    allSticky.add(intent);
                }
            }
        }
        //receiver為null，直接返回null或者第一個(gè)粘性intent
        Intent sticky = allSticky != null ? allSticky.get(0) : null;
        if (receiver == null) {
            return sticky;
        }
        synchronized (this) {
            ...
            //分析二：
			//從緩存或新建ReceiverList對(duì)象，與Receiver綁定
            ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
            if (rl == null) {
                rl = new ReceiverList(this, callerApp, callingPid, callingUid,
                        userId, receiver);
                if (rl.app != null) {
                    final int totalReceiversForApp = rl.app.receivers.size();
                    if (totalReceiversForApp >= MAX_RECEIVERS_ALLOWED_PER_APP) {
                        throw new IllegalStateException("Too many receivers, total of "
                                + totalReceiversForApp + ", registered for pid: "
                                + rl.pid + ", callerPackage: " + callerPackage);
                    }
					//添加到ProcessRecord記錄中
                    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);
            }
            ...
			//新建BroadcastFilter，并添加到BroadcastList
            BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage, callerFeatureId,
                    permission, callingUid, userId, instantApp, visibleToInstantApps);
            if (rl.containsFilter(filter)) {
                ...
            } else {
                rl.add(bf);
                //添加到接收者解析器
                mReceiverResolver.addFilter(bf);
            }
            // Enqueue broadcasts for all existing stickies that match
            // this filter.
            //分析三：對(duì)匹配到action的粘性廣播進(jìn)行廣播
            if (allSticky != null) {
                ArrayList receivers = new ArrayList();
                receivers.add(bf);
                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, null, -1, -1, false, null, null, OP_NONE, null, receivers,
                            null, 0, null, null, false, true, true, -1, false,
                            false /* only PRE_BOOT_COMPLETED should be exempt, no stickies */);
                    queue.enqueueParallelBroadcastLocked(r);
                    queue.scheduleBroadcastsLocked();
                }
            }
            return sticky;
        }
    }

廣播的解注冊(cè)

回到ContextWrapper的unregisterReceiver函數(shù)。

#ContextWrapper
public void unregisterReceiver(BroadcastReceiver receiver) {
    mBase.unregisterReceiver(receiver);
}
#ContextImpl
public void unregisterReceiver(BroadcastReceiver receiver) {
    if (mPackageInfo != null) {
        IIntentReceiver rd = mPackageInfo.forgetReceiverDispatcher(
                getOuterContext(), receiver);
        try {
            ActivityManager.getService().unregisterReceiver(rd);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    } else {
        throw new RuntimeException("Not supported in system context");
    }
}

這里通過(guò)receiver和context獲得IIntentReceiver實(shí)例rd，然后調(diào)用AMS的unregisterReceiver函數(shù)。其中LoadedApk的forgetReceiverDispatcher函數(shù)，主要是從mReceivers獲取IIntentReceiver的實(shí)例，并將receiver對(duì)應(yīng)的內(nèi)容從緩存移除。

AMS的unregisterReceiver函數(shù)。主要是將注冊(cè)過(guò)程添加到mRegisteredReceivers、ProcessProcess.Receivers、mReceiverResolver中對(duì)應(yīng)的內(nèi)容移除。并終止正在發(fā)送的廣播。

   public void unregisterReceiver(IIntentReceiver receiver) {
		...
        final long origId = Binder.clearCallingIdentity();
        try {
            boolean doTrim = false;
            synchronized(this) {
            	//獲得當(dāng)前對(duì)應(yīng)的ReceiverList
                ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());
                if (rl != null) {
					//默認(rèn)情況為null，看看廣播發(fā)送是否會(huì)賦值
					//從處理邏輯來(lái)看，就是廣播內(nèi)容
                    final BroadcastRecord r = rl.curBroadcast;
                    if (r != null &amp;&amp; r == r.queue.getMatchingOrderedReceiver(r)) {
                        final boolean doNext = r.queue.finishReceiverLocked(
                                r, r.resultCode, r.resultData, r.resultExtras,
                                r.resultAbort, false);
                        if (doNext) {
                            doTrim = true;
                            r.queue.processNextBroadcast(false);
                        }
                    }
					//從processRecord中移除
                    if (rl.app != null) {
                        rl.app.receivers.remove(rl);
                    }
                    //從mRegisteredReceivers和mReceiverResolver移除
                    removeReceiverLocked(rl);
                    if (rl.linkedToDeath) {
                        rl.linkedToDeath = false;
                        rl.receiver.asBinder().unlinkToDeath(rl, 0);
                    }
                }
            }
            // If we actually concluded any broadcasts, we might now be able
            // to trim the recipients' apps from our working set
            if (doTrim) {
                trimApplications(OomAdjuster.OOM_ADJ_REASON_FINISH_RECEIVER);
                return;
            }
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
    }
void removeReceiverLocked(ReceiverList rl) {
    mRegisteredReceivers.remove(rl.receiver.asBinder());
    for (int i = rl.size() - 1; i &gt;= 0; i--) {
        mReceiverResolver.removeFilter(rl.get(i));
    }
}

廣播的發(fā)送

定位到ContextWrapper的sendBroadcast函數(shù)。

public void sendBroadcast(Intent intent) {
    mBase.sendBroadcast(intent);
}
public void sendBroadcast(Intent intent) {
    warnIfCallingFromSystemProcess();
    String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
    try {
        intent.prepareToLeaveProcess(this);
        ActivityManager.getService().broadcastIntentWithFeature(mMainThread.getApplicationThread(), getAttributionTag(), intent, resolvedType,null, Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false,false, getUserId());
    } catch (RemoteException e) {
        throw e.rethrowFromSystemServer();
    }
}

調(diào)用AMS的broadcastIntentWithFeature函數(shù)。內(nèi)部又調(diào)用了broadcastIntentLocked函數(shù)。是所有Intent處理的地方，很長(zhǎng)很長(zhǎng)。有對(duì)特殊類(lèi)型的Intent處理，例如Intent.ACTION_PACKAGE_REMOVED和Intent.ACTION_TIME_CHANGED。該函數(shù)主要將有序和無(wú)序廣播接收者（匹配Intent）添加到receivers列表，并創(chuàng)建BroadcastRecord對(duì)象r，持有receivers列表。并根據(jù)intent獲得對(duì)應(yīng)的廣播隊(duì)列queue，將r添加到queue中，執(zhí)行queue.scheduleBroadcastsLocked函數(shù)。

#AMS xxm
@GuardedBy("this")
final int broadcastIntentLocked(ProcessRecord callerApp, String callerPackage,
        @Nullable String callerFeatureId, 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 realCallingUid,
        int realCallingPid, int userId, boolean allowBackgroundActivityStarts,
        @Nullable int[] broadcastWhitelist) {
    intent = new Intent(intent);
    ...
    int[] users;
    if (userId == UserHandle.USER_ALL) {
        // Caller wants broadcast to go to all started users.
        users = mUserController.getStartedUserArray();
    } else {
        // Caller wants broadcast to go to one specific user.
        users = new int[] {userId};
    }
    // Figure out who all will receive this broadcast.
    List receivers = null;
    List<BroadcastFilter> registeredReceivers = null;
    // Need to resolve the intent to interested receivers...
    if ((intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY)
             == 0) {
        receivers = collectReceiverComponents(
                intent, resolvedType, callingUid, users, broadcastWhitelist);
    }
    if (intent.getComponent() == null) {
        if (userId == UserHandle.USER_ALL && callingUid == SHELL_UID) {
            // Query one target user at a time, excluding shell-restricted users
            for (int i = 0; i < users.length; i++) {
                if (mUserController.hasUserRestriction(
                        UserManager.DISALLOW_DEBUGGING_FEATURES, users[i])) {
                    continue;
                }
                //查詢(xún)已注冊(cè)的Receiver，在注冊(cè)過(guò)程會(huì)被添加
                List<BroadcastFilter> registeredReceiversForUser =
                        mReceiverResolver.queryIntent(intent,
                                resolvedType, false /*defaultOnly*/, users[i]);
                if (registeredReceivers == null) {
                    registeredReceivers = registeredReceiversForUser;
                } else if (registeredReceiversForUser != null) {
                    registeredReceivers.addAll(registeredReceiversForUser);
                }
            }
        } else {
            //查詢(xún)已注冊(cè)的Receiver，在注冊(cè)過(guò)程會(huì)被添加
            registeredReceivers = mReceiverResolver.queryIntent(intent,
                    resolvedType, false /*defaultOnly*/, userId);
        }
    }
    final boolean replacePending =
            (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;
    ...
    int NR = registeredReceivers != null ? registeredReceivers.size() : 0;
    if (!ordered && NR > 0) {
        ...
        //通過(guò)intent獲得廣播隊(duì)列
        final BroadcastQueue queue = broadcastQueueForIntent(intent);
        //將所有數(shù)據(jù)都封裝到BroadcastRecord中	
        BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp, callerPackage,
                callerFeatureId, callingPid, callingUid, callerInstantApp, resolvedType,
                requiredPermissions, appOp, brOptions, registeredReceivers, resultTo,
                resultCode, resultData, resultExtras, ordered, sticky, false, userId,
                allowBackgroundActivityStarts, timeoutExempt);
        ...
        final boolean replaced = replacePending
                && (queue.replaceParallelBroadcastLocked(r) != null);
        if (!replaced) {
            //將廣播添加到queue的mParallelBroadcasts數(shù)組列表中
            queue.enqueueParallelBroadcastLocked(r);
            queue.scheduleBroadcastsLocked();
        }
        registeredReceivers = null;
        NR = 0;
    }
    ...
    return ActivityManager.BROADCAST_SUCCESS;
}

enqueueParallelBroadcastLocked函數(shù)將BroadcastRecord對(duì)象r添加到ArrayList類(lèi)型的mParallelBroadcasts,后續(xù)執(zhí)行隊(duì)列事務(wù)會(huì)從其中取出。

scheduleBroadcastsLocked函數(shù)。調(diào)用BroadcastHandler類(lèi)型的mHandler發(fā)送一個(gè)BROADCAST_INTENT_MSG消息。

#BroadcastQueue xxm
public void scheduleBroadcastsLocked() {
    if (mBroadcastsScheduled) {
        return;
    }
    mHandler.sendMessage(mHandler.obtainMessage(BROADCAST_INTENT_MSG, this));
    mBroadcastsScheduled = true;
}

BroadcastHandler的handleMessage函數(shù)。執(zhí)行了processNextBroadcast函數(shù)。

#BroadcastHandler xxm
public void handleMessage(Message msg) {
    switch (msg.what) {
        case BROADCAST_INTENT_MSG: {
            processNextBroadcast(true);
        } break;
        case BROADCAST_TIMEOUT_MSG: {
            synchronized (mService) {
                broadcastTimeoutLocked(true);
            }
        } break;
    }
}

processNextBroadcast函數(shù)內(nèi)容太長(zhǎng)了，主要是將粘性廣播和無(wú)序廣播發(fā)送給接收者。這里只看函數(shù)前半部分對(duì)無(wú)序廣播的處理。其中無(wú)序廣播是從mParallelBroadcasts取出所有廣播，并遍歷每個(gè)廣播的過(guò)濾器filter，將廣播和廣播filter傳遞給deliverToRegisteredReceiverLocked函數(shù)

#BroadcastQueue xxm
if (fromMsg) {
    mBroadcastsScheduled = false;
}
//遍歷無(wú)序廣播數(shù)組
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);
        //開(kāi)始傳遞廣播
        deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false, i);
    }
    addBroadcastToHistoryLocked(r);
}

deliverToRegisteredReceiverLocked函數(shù)。主要進(jìn)行權(quán)限檢查。

#BroadcastQueue xxm
private void deliverToRegisteredReceiverLocked(BroadcastRecord r,
        BroadcastFilter filter, boolean ordered, int index) {
    boolean skip = false;
    ...
    //廣播filter進(jìn)行權(quán)限檢查，不通過(guò)skip=true
    ...
    if (skip) {
        r.delivery[index] = BroadcastRecord.DELIVERY_SKIPPED;
        return;
    }
    ...
    r.delivery[index] = BroadcastRecord.DELIVERY_DELIVERED;
    ...
    performReceiveLocked(filter.receiverList.app, filter.receiverList.receiver,
            new Intent(r.intent), r.resultCode, r.resultData,
            r.resultExtras, r.ordered, r.initialSticky, r.userId);
        ...
}

performReceiveLocked函數(shù)。如果接收者所在的進(jìn)程已經(jīng)啟動(dòng)，直接調(diào)用 app.thread.scheduleRegisteredReceiver,如果未啟動(dòng)，則直接回調(diào) receiver.performReceive。

#BroadcastQueue xxm
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) {
            try {
                app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
                        data, extras, ordered, sticky, sendingUser, app.getReportedProcState());
            } catch (RemoteException ex) {
                synchronized (mService) {
                    app.scheduleCrash("can't deliver broadcast");
                }
                throw ex;
            }
        } else {
            throw new RemoteException("app.thread must not be null");
        }
    } else {
        receiver.performReceive(intent, resultCode, data, extras, ordered,
                sticky, sendingUser);
    }
}

如果進(jìn)程已經(jīng)啟動(dòng)，則調(diào)用ApplicationThread的scheduleRegisteredReceiver函數(shù)。

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);
}

調(diào)用了LoadedApk.ReceiverDispatcher.InnerReceiver類(lèi)的performReceive函數(shù)。

public void performReceive(Intent intent, int resultCode, String data,
        Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
    final LoadedApk.ReceiverDispatcher rd;
    if (intent == null) {
        rd = null;
    } else {
        rd = mDispatcher.get();
    }
    if (rd != null) {
    	//分析一
        rd.performReceive(intent, resultCode, data, extras,
                ordered, sticky, sendingUser);
    } else {
        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();
        }
    }
}

調(diào)用了分析一ReceiverDispatcher的performReceive函數(shù)

public void performReceive(Intent intent, int resultCode, String data,
        Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
    //分析1
    final Args args = new Args(intent, resultCode, data, extras, ordered,
            sticky, sendingUser);
    ...
 	//分析2
 	if (intent == null || !mActivityThread.post(args.getRunnable())) {
        if (mRegistered && ordered) {
            IActivityManager mgr = ActivityManager.getService();
            args.sendFinished(mgr);
        }
    }
}

ReceiverDispatcher.performReceive函數(shù)中分析1將相關(guān)數(shù)據(jù)封裝成內(nèi)部類(lèi)Args類(lèi)型的args,然后在分析2通過(guò)Handler類(lèi)型的mActivityThread執(zhí)行getRunnable返回的Runable對(duì)象的run函數(shù)。這時(shí)切換到應(yīng)用進(jìn)程的主線程。

Args.getRunnable函數(shù)回調(diào)了我們注冊(cè)廣播是復(fù)寫(xiě)的onReceiver函數(shù)。

public final Runnable getRunnable() {
    return () -> {
			...
            ClassLoader cl = mReceiver.getClass().getClassLoader();
            intent.setExtrasClassLoader(cl);
            intent.prepareToEnterProcess();
            setExtrasClassLoader(cl);
            receiver.setPendingResult(this);
            //調(diào)用廣播接收者的onReceive
            receiver.onReceive(mContext, intent);
            ...
      }
}