android安全问题（七） 抢先接收广播

现在给出第二步分的分析

下面就来看看发送广播的流程

Context中的sendBroadCast函数的 实现是在ContextImpl中，和发送广播相关的有如下六个函数

void android.app.ContextImpl.sendBroadcast(Intent intent)

void android.app.ContextImpl.sendBroadcast(Intent intent, String receiverPermission)

void android.app.ContextImpl.sendOrderedBroadcast(Intent intent, String receiverPermission)

void android.app.ContextImpl.sendOrderedBroadcast(Intent intent, String receiverPermission, BroadcastReceiver resultReceiver, Handler scheduler, int initialCode, String initialData, Bundle initialExtras)

void android.app.ContextImpl.sendStickyBroadcast(Intent intent)

void android.app.ContextImpl.sendStickyOrderedBroadcast(Intent intent, BroadcastReceiver resultReceiver, Handler scheduler, int initialCode, String initialData, Bundle initialExtras)

可以分为3组：1普通广播；2Ordered广播；3Sticky广播

不论哪种，最后都会 由ActivityManagerService处理

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)

以第一种情况为 例，流程图大概是这个样子的

ordered和sticky用来区分上面3组广播

下面我们仔细看看这个方 法都干了些什么

删减了一些代码

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) {
    ...//处理特殊intent
    // Add to the sticky list if requested.
    ...//处理sticky广播
    // Figure out who all will receive this broadcast.
    List receivers = null;
    List<BroadcastFilter> registeredReceivers = null;
    try {
        if (intent.getComponent() != null) {
            // Broadcast is going to one specific receiver class...
            ActivityInfo ai = AppGlobals.getPackageManager().
                getReceiverInfo(intent.getComponent(), STOCK_PM_FLAGS);
            if (ai != null) {
                receivers = new ArrayList();
                ResolveInfo ri = new ResolveInfo();
                ri.activityInfo = ai;
                receivers.add(ri);
            }
        } else {
            // Need to resolve the intent to interested receivers...
            if ((intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY)
                     == 0) {
                receivers =
                    AppGlobals.getPackageManager().queryIntentReceivers(
                            intent, resolvedType, STOCK_PM_FLAGS);
            }
            registeredReceivers = mReceiverResolver.queryIntent(intent, resolvedType, false);
        }
    } catch (RemoteException ex) {
        // pm is in same process, this will never happen.
    }  

    final boolean replacePending =
            (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;
    ...
    int NR = registeredReceivers != null ? registeredReceivers.size() : 0;
    ...//如果广播是非ordered，先处理动态注册的接收器
    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);
        ...
    //mParallelBroadcasts只含有动态注册的receiver
        boolean replaced = false;
        if (replacePending) {
            for (int i=mParallelBroadcasts.size()-1; i>=0; i--) {
                if (intent.filterEquals(mParallelBroadcasts.get(i).intent)) {
                    if (DEBUG_BROADCAST) Slog.v(TAG,
                            "***** DROPPING PARALLEL: " + intent);
                    mParallelBroadcasts.set(i, r);
                    replaced = true;
                    break;
                }
            }
        }
        if (!replaced) {
            mParallelBroadcasts.add(r);
            scheduleBroadcastsLocked();
        }
        registeredReceivers = null;
        NR = 0;
    }  

    // Merge into one list.
    //如果广播是ordered，合并静态、动态接收器
    //否则之前处理过动态接收器，这里registeredReceivers为null
    int ir = 0;
    if (receivers != null) {
        ...
        //合并的过程，注意顺序
        int NT = receivers != null ? receivers.size() : 0;
        int it = 0;
        ResolveInfo curt = null;
        BroadcastFilter curr = null;
        while (it < NT && ir < NR) {
            if (curt == null) {
                curt = (ResolveInfo)receivers.get(it);
            }
            if (curr == null) {
                curr = registeredReceivers.get(ir);
            }
            //如果动态接收器优先级高，那么就插到前面
            //否则进入else，然后进行下一轮比较，拿下一个静态接收器与之前的动态接收器比较，直到找到自己的位置才插入进列表中
            //在这里，调整好接收器的顺序，同等优先级的，显然动态的要在静态的前面
            if (curr.getPriority() >= 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 < NR) {
        if (receivers == null) {
            receivers = new ArrayList();
        }
        receivers.add(registeredReceivers.get(ir));
        ir++;
    }  

    if ((receivers != null && receivers.size() > 0)
            || resultTo != null) {
        BroadcastRecord r = new BroadcastRecord(intent, callerApp,
                callerPackage, callingPid, callingUid, requiredPermission,
                receivers, resultTo, resultCode, resultData, map, ordered,
                sticky, false);
        ...
        if (!replaced) {
            mOrderedBroadcasts.add(r);
            scheduleBroadcastsLocked();
        }
    }  

    return BROADCAST_SUCCESS;
}

以上是小编为您精心准备的的内容，在的博客、问答、公众号、人物、课程等栏目也有的相关内容，欢迎继续使用右上角搜索按钮进行搜索string
， int
， 广播
， null
， android 广播
， intent
， 广播处理
， sticky
， Broadcast的接收
， received
， broadcast静态注册
， broadcast动态注册
， receive
receiver
android 接收广播、android 广播接收器、android 广播接收者、android广播接收不到、android 接收系统广播，以便于您获取更多的相关知识。