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Android源码解析四大组件系列(六)---广播的处理过程

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这篇文章紧接着上篇分析广播的发送过程,发送广播都是调用ContextImpl的接口去实现的,总共有二十多个,最终都是调用到AMS的broadcastIntent。主要分成下面九小节来说明。
1、设置Flag
2、检查BroadcastOptions
3、当前是否有权力发出广播
4、处理系统相关广播
5、处理粘性广播
6、registeredReceivers和receivers查询
7、处理并行广播
8、整理两个receiver列表
9、处理串行广播

1、上层调用sendBroadcast发送广播

    @Override
    public void sendBroadcast(Intent intent) {
        warnIfCallingFromSystemProcess();
        String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
        try {
            // 准备离开应用程序进程,进入SysfangfatemServer进程  
            intent.prepareToLeaveProcess(this);
            ActivityManagerNative.getDefault().broadcastIntent(
                    mMainThread.getApplicationThread(), intent, resolvedType, null,
                    Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false, false,
                    getUserId());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

省去跨进程的过程,进入AMS的broadcastIntent方法


  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) {
        enforceNotIsolatedCaller("broadcastIntent");
        synchronized(this) {
            intent = verifyBroadcastLocked(intent);
            //从mLruProcesses列表中查询到进程
            final ProcessRecord callerApp = getRecordForAppLocked(caller);
            final int callingPid = Binder.getCallingPid();
            final int callingUid = Binder.getCallingUid();
            final long origId = Binder.clearCallingIdentity();
            int res = broadcastIntentLocked(callerApp,
                    callerApp != null ? callerApp.info.packageName : null,
                    intent, resolvedType, resultTo, resultCode, resultData, resultExtras,
                    requiredPermissions, appOp, bOptions, serialized, sticky,
                    callingPid, callingUid, userId);
            Binder.restoreCallingIdentity(origId);
            return res;
        }
    }

2、broadcastIntentLocked中处理广播

broadcastIntentLocked的方法接近600行代码,需要分段阅读,才比较清楚。

    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) {

        //设置Flag
        //检查BroadcastOptions
        //当前是否有权力发出广播
        //处理系统相关广播
        //处理粘性广播
        //registeredReceivers和receivers查询
        // 处理并行广播
        //整理两个receiver列表
        // 处理串行广播

}
2.1、设置Flag
         intent = new Intent(intent);

        // 设置这个flag后,广播不会发送给已经停止的应用,看来系统默认是不让我们的广播发送给已经停止的应用的
        intent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);

        //如果AMS还没有启动好,不允许启动一个新的进程
        if (!mProcessesReady && (intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0) {
            //这个flag表示只有动态注册的广播接收者能收到广播,如果你错误的设置了这个标记,广播又是静态注册的,那么就收不到广播
            intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
        }

      // 当不是USER_ALL广播且当前用户不是运行状态,除非是系统升级广播或者关机广播,否则直接返回
    if (userId != UserHandle.USER_ALL && !mUserController.isUserRunningLocked(userId, 0)) {
            if ((callingUid != Process.SYSTEM_UID
                    || (intent.getFlags() & Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0)
                    && !Intent.ACTION_SHUTDOWN.equals(intent.getAction())) {
                Slog.w(TAG, "Skipping broadcast of " + intent
                        + ": user " + userId + " is stopped");
                return ActivityManager.BROADCAST_FAILED_USER_STOPPED;
            }
        }

Intent中有两个FLAG,FLAG_INCLUDE_STOPPED_PACKAGES和FLAG_EXCLUDE_STOPPED_PACKAGES,表示intent是否要激活“处于停止状态的”应用,如果确定要激活“处于停止状态的”应用,那么Intent add FLAG_INCLUDE_STOPPED_PACKAGES就行了。
“`
/**
* If set, this intent will not match any components in packages that
* are currently stopped. If this is not set, then the default behavior
* is to include such applications in the result.
*/
public static final int FLAG_EXCLUDE_STOPPED_PACKAGES = 0x00000010;
/**
* If set, this intent will always match any components in packages that
* are currently stopped. This is the default behavior when
* {@link #FLAG_EXCLUDE_STOPPED_PACKAGES} is not set. If both of these
* flags are set, this one wins (it allows overriding of exclude for
* places where the framework may automatically set the exclude flag).
*/
public static final int FLAG_INCLUDE_STOPPED_PACKAGES = 0x00000020;


#####2.2、检查BroadcastOptions

BroadcastOptions brOptions = null;
if (bOptions != null) {
brOptions = new BroadcastOptions(bOptions);
if (brOptions.getTemporaryAppWhitelistDuration() > 0) {
// See if the caller is allowed to do this. Note we are checking against
// the actual real caller (not whoever provided the operation as say a
// PendingIntent), because that who is actually supplied the arguments.
if (checkComponentPermission(
android.Manifest.permission.CHANGE_DEVICE_IDLE_TEMP_WHITELIST,
Binder.getCallingPid(), Binder.getCallingUid(), -1, true)
!= PackageManager.PERMISSION_GRANTED) {
String msg = “Permission Denial: ” + intent.getAction()
+ ” broadcast from ” + callerPackage + ” (pid=” + callingPid
+ “, uid=” + callingUid + “)”
+ ” requires ”
+ android.Manifest.permission.CHANGE_DEVICE_IDLE_TEMP_WHITELIST;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
}
}


#####2.3、当前是否有权力发出广播
   final String action = intent.getAction();
    final boolean isProtectedBroadcast;
    try {
      //isProtectedBroadcast为true则代表该广播在Framework/base/core/res/AndroidManifest.xml中有声明为保护广播,这样的广播只能由系统发出
        isProtectedBroadcast = AppGlobals.getPackageManager().isProtectedBroadcast(action);
    } catch (RemoteException e) {
        Slog.w(TAG, "Remote exception", e);
        return ActivityManager.BROADCAST_SUCCESS;
    }

    final boolean isCallerSystem;
    switch (UserHandle.getAppId(callingUid)) {
        case Process.ROOT_UID:
        case Process.SYSTEM_UID:
        case Process.PHONE_UID:
        case Process.BLUETOOTH_UID:
        case Process.NFC_UID:
             //以上进程都有权限发送广播
            isCallerSystem = true;
            break;
        default:
            isCallerSystem = (callerApp != null) && callerApp.persistent;
            break;
    }

    // First line security check before anything else: stop non-system apps from
    // sending protected broadcasts.
    if (!isCallerSystem) {
        if (isProtectedBroadcast) {
            String msg = "Permission Denial: not allowed to send broadcast "
                    + action + " from pid="
                    + callingPid + ", uid=" + callingUid;
            Slog.w(TAG, msg);
            throw new SecurityException(msg);

        } else if (AppWidgetManager.ACTION_APPWIDGET_CONFIGURE.equals(action)
                || AppWidgetManager.ACTION_APPWIDGET_UPDATE.equals(action)) {
            // Special case for compatibility: we don't want apps to send this,
            // but historically it has not been protected and apps may be using it
            // to poke their own app widget.  So, instead of making it protected,
            // just limit it to the caller.
            if (callerPackage == null) {
                String msg = "Permission Denial: not allowed to send broadcast "
                        + action + " from unknown caller.";
                Slog.w(TAG, msg);
                throw new SecurityException(msg);
            } else if (intent.getComponent() != null) {
                // They are good enough to send to an explicit component...  verify
                // it is being sent to the calling app.
                if (!intent.getComponent().getPackageName().equals(
                        callerPackage)) {
                    String msg = "Permission Denial: not allowed to send broadcast "
                            + action + " to "
                            + intent.getComponent().getPackageName() + " from "
                            + callerPackage;
                    Slog.w(TAG, msg);
                    throw new SecurityException(msg);
                }
            } else {
                // Limit broadcast to their own package.
                intent.setPackage(callerPackage);
            }
        }
    }
保护性广播是什么呢,frameworks/base/core/res/AndroidManifest.xml文件中可以看到定义,这些定义的广播都是保护广播,只能由系统发送,如果有不具有系统权限的应用试图发送系统中的“保护性广播”,那么到AMS的broadcastIntentLocked()处就会被拦住,AMS会抛出异常,提示"Permission Denial: not allowed to send broadcast"


#####2.4、处理系统相关广播
if (action != null) {
        switch (action) {
            case Intent.ACTION_UID_REMOVED://uid移除
            case Intent.ACTION_PACKAGE_REMOVED://package移除
            case Intent.ACTION_PACKAGE_CHANGED://package改变
            case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE:  app正在移动到SD卡中,发出的广播
            case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE: app完成移动到SD的操作,发出的广播  

    case Intent.ACTION_PACKAGES_SUSPENDED:

    case Intent.ACTION_PACKAGES_UNSUSPENDED:

            case Intent.ACTION_PACKAGE_REPLACED://替换一个现有的安装包时发出的广播(不管现在安装的APP比之前的新还是旧,都会发出此广播)

            case Intent.ACTION_PACKAGE_ADDED: //增加package

            case Intent.ACTION_PACKAGE_DATA_CLEARED:

            case Intent.ACTION_TIMEZONE_CHANGED://时区改变

            case Intent.ACTION_TIME_CHANGED://时间改变

            case Intent.ACTION_CLEAR_DNS_CACHE://DNS缓存清空

            case Proxy.PROXY_CHANGE_ACTION://网络代理改变

            case android.hardware.Camera.ACTION_NEW_PICTURE:

            case android.hardware.Camera.ACTION_NEW_VIDEO:

        }
    }
还有更多[系统广播](http://uiuno.com/2017/05/07/android%E5%B8%B8%E7%94%A8%E7%B3%BB%E7%BB%9F%E5%B9%BF%E6%92%AD/)

#####2.5、处理粘性广播

if (sticky) {
//需要android.Manifest.permission.BROADCAST_STICKY才能发送粘性广播
if (checkPermission(android.Manifest.permission.BROADCAST_STICKY,
callingPid, callingUid)
!= PackageManager.PERMISSION_GRANTED) {
String msg = “Permission Denial: broadcastIntent() requesting a sticky broadcast from pid=”
+ callingPid + “, uid=” + callingUid
+ ” requires ” + android.Manifest.permission.BROADCAST_STICKY;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
//发送粘性广播不能强制添加别的权限
if (requiredPermissions != null && requiredPermissions.length > 0) {
Slog.w(TAG, “Can’t broadcast sticky intent ” + intent
+ ” and enforce permissions ” + Arrays.toString(requiredPermissions));
return ActivityManager.BROADCAST_STICKY_CANT_HAVE_PERMISSION;
}
//粘性广播也不能指定特定的组件名称
if (intent.getComponent() != null) {
throw new SecurityException(
“Sticky broadcasts can’t target a specific component”);
}

        if (userId != UserHandle.USER_ALL) {
         //根据广播类型,取出stickies
            ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(
                    UserHandle.USER_ALL);
            if (stickies != null) {
              //广播是使用Intent描述的,用action取出广播列表
                ArrayList<Intent> list = stickies.get(intent.getAction());
                if (list != null) {
                    int N = list.size();
                    int i;
                    for (i=0; i<N; i++) {
                      //粘性广播发送后是会保存下来的,故如果已经存在则不需要重新发送  ,
                      // filterEquals函数会比较两个intent的action、data、type、class以及categories等信息,
                        if (intent.filterEquals(list.get(i))) {
                            throw new IllegalArgumentException(
                                    "Sticky broadcast " + intent + " for user "
                                    + userId + " conflicts with existing global broadcast");
                        }
                    }
                }
            }
        }
        ArrayMap<String, ArrayList<Intent>> stickies = mStickyBroadcasts.get(userId);
        if (stickies == null) {
            stickies = new ArrayMap<>();
            mStickyBroadcasts.put(userId, stickies);
        }
        ArrayList<Intent> list = stickies.get(intent.getAction());
        if (list == null) {
            list = new ArrayList<>();
            stickies.put(intent.getAction(), list);
        }
        final int stickiesCount = list.size();
        int i;
        for (i = 0; i < stickiesCount; i++) {
            if (intent.filterEquals(list.get(i))) {
                // 新发送的intent在ArrayList中已经有个“相等的”旧intent时,则会用新的替掉旧的
                list.set(i, new Intent(intent));
                break;
            }
        }
        if (i >= stickiesCount) {
            list.add(new Intent(intent));
        }
    }
sticky为true,表示是粘性广播,发送粘性广播,一定要有android.Manifest.permission.BROADCAST_STICKY权限,没有的话就抛出SecurityException,Permission Denial: broadcastIntent() requesting a sticky broadcast...。在AMS中,所有相同的粘性广播都被保存在一个List中,这些List最终被保存在AMS成员变量mStickyBroadcasts中, mStickyBroadcasts的定义是这样的: final HashMap<String, ArrayList<Intent>> mStickyBroadcasts =  new HashMap<String, ArrayList<Intent>>();注意粘性广播是在注册的时候加入到广播队列并且处理的,请移步[Android源码解析---广播的注册过程](http://www.jianshu.com/p/ca02cecc0d1d)


#####2.6、registeredReceivers和receivers查询

为了合理处理“串行广播”和“并行广播”,broadcastIntentLocked()方法中搞出了两个list,一个是receivers,另一个是registeredReceivers,registeredReceivers是动态广播接收器列表 ,receivers是静态广播接收器列表 。
    List receivers = null;
    List<BroadcastFilter> registeredReceivers = null;
    // Need to resolve the intent to interested receivers...
    if ((intent.getFlags()&Intent.FLAG_RECEIVER_REGISTERED_ONLY)
             == 0) {
    //collectReceiverComponents内部调用包管理器的queryIntentReceivers()接口,查询出和intent匹配的所有静态receivers,此时所返回的查询结果本身已经排好序了,因此,该返回值被直接赋值给了receivers变量
        receivers = collectReceiverComponents(intent, resolvedType, callingUid, users);
    }
    if (intent.getComponent() == null) {
        if (userId == UserHandle.USER_ALL && callingUid == Process.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;
                }
              //此时返回的registeredReceivers中的子项是没有经过排序的,在后面queue.scheduleBroadcastsLocked()会被处理掉
                List<BroadcastFilter> registeredReceiversForUser =
                        mReceiverResolver.queryIntent(intent,
                                resolvedType, false, users[i]);
                if (registeredReceivers == null) {
                    registeredReceivers = registeredReceiversForUser;
                } else if (registeredReceiversForUser != null) {
                    registeredReceivers.addAll(registeredReceiversForUser);
                }
            }
        } else {
            registeredReceivers = mReceiverResolver.queryIntent(intent,
                    resolvedType, false, userId);
        }
    }
#####2.7 处理并行广播
上面已经获取了并行广播和串行广播,现在现将并行广播给处理掉
    final boolean replacePending =
            (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;

    if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueing broadcast: " + intent.getAction()
            + " replacePending=" + replacePending);
    //并行广播列表大小
    int NR = registeredReceivers != null ? registeredReceivers.size() : 0;
    //参数ordered标记当前发送的广播是否是有序广播,可以看到如果发送的是无序广播,进入的是并行广播队列
    if (!ordered && NR > 0) {
        // 如果不是有序广播, 不用等待目标组件是否启动,就可以发送
        if (isCallerSystem) {
            checkBroadcastFromSystem(intent, callerApp, callerPackage, callingUid,
                    isProtectedBroadcast, registeredReceivers);
        }
        //构建广播队列
        final BroadcastQueue queue = broadcastQueueForIntent(intent);
       //广播实体类
        BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
                callerPackage, callingPid, callingUid, 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);
        if (!replaced) {
            //加入到并行广播队列
            queue.enqueueParallelBroadcastLocked(r);
           //处理上面加入并行广播消息队列里面的广播
            queue.scheduleBroadcastsLocked();
        }
        //处理完之后,registeredReceivers要赋值为null
        registeredReceivers = null;
        NR = 0;
    }
关于上面的广播队列BroadcastQueue,AMS内部维持了后台广播队列和前台广播队列

BroadcastQueue mFgBroadcastQueue;//前台广播队列
BroadcastQueue mBgBroadcastQueue;//后台广播队列
final BroadcastQueue[] mBroadcastQueues = new BroadcastQueue[2];

并且在AMS的构造函数中进行初始化
    mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
            "foreground", BROADCAST_FG_TIMEOUT, false);
    mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
            "background", BROADCAST_BG_TIMEOUT, true);
    mBroadcastQueues[0] = mFgBroadcastQueue;
    mBroadcastQueues[1] = mBgBroadcastQueue;

“`
初始化之后,就可以像上面那样(通过broadcastQueueForIntent方法)获取相应的广播队列了,主要就是根据intent中有没有FLAG_RECEIVER_FOREGROUND标记。

“`
BroadcastQueue broadcastQueueForIntent(Intent intent) {
final boolean isFg = (intent.getFlags() & Intent.FLAG_RECEIVER_FOREGROUND) != 0;
if (DEBUG_BROADCAST_BACKGROUND) Slog.i(TAG_BROADCAST,
“Broadcast intent ” + intent + ” on ”
+ (isFg ? “foreground” : “background”) + ” queue”);
return (isFg) ? mFgBroadcastQueue : mBgBroadcastQueue;
}

相应的,将广播加入到队列也很esay,调用 queue.enqueueParallelBroadcastLocked(r)

public void enqueueParallelBroadcastLocked(BroadcastRecord r) {
mParallelBroadcasts.add(r);
r.enqueueClockTime = System.currentTimeMillis();
}

这里又要说明一下mParallelBroadcasts了,BroadcastQueue名字叫做队列,但并不是任何集合的子类,自身不带有存储数据的功能,所以它的内部维护了两个ArrayList。mParallelBroadcasts存放并行广播(无序广播),mOrderedBroadcasts存放串行广播(有序广播)

 ```
/**
     * Lists of all active broadcasts that are to be executed immediately
     * (without waiting for another broadcast to finish).  Currently this only
     * contains broadcasts to registered receivers, to avoid spinning up
     * a bunch of processes to execute IntentReceiver components.  Background-
     * and foreground-priority broadcasts are queued separately.
     */
    final ArrayList<BroadcastRecord> mParallelBroadcasts = new ArrayList<>();

    /**
     * List of all active broadcasts that are to be executed one at a time.
     * The object at the top of the list is the currently activity broadcasts;
     * those after it are waiting for the top to finish.  As with parallel
     * broadcasts, separate background- and foreground-priority queues are
     * maintained.
     */
    final ArrayList<BroadcastRecord> mOrderedBroadcasts = new ArrayList<>();

关于最后调用scheduleBroadcastsLocked进行广播处理的,本文不分析,下篇文章分析。

2.8 整理两个receiver列表

上面判断了ordered,如果ordered==false,也就是发送的是无序广播,那么就进入并行广播队列直接处理掉,如果ordered==false,也就是发送的是有序广播,需要整合将registeredReceivers里面的合并到receivers中。

  // 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.  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 we'd like to deliberately make
            // this decision.
            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.getData();
                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 (skipPackages != null && (skipPackages.length > 0)) {
                for (String skipPackage : skipPackages) {
                    if (skipPackage != null) {
                        int NT = receivers.size();
                        for (int it=0; it<NT; it++) {
                            // 静态注册的广播是ResolveInfo类型  ,动态的是BrocastFilter
                            ResolveInfo curt = (ResolveInfo)receivers.get(it);
                            if (curt.activityInfo.packageName.equals(skipPackage)) {
                                receivers.remove(it);
                                it--;
                                NT--;
                            }
                        }
                    }
                }
            }

            int NT = receivers != null ? receivers.size() : 0;
            int it = 0;
            ResolveInfo curt = null;
            BroadcastFilter curr = null;
            while (it < NT && ir < NR) {
                if (curt == null) {
                   //  静态注册的广播是ResolveInfo类型 
                    curt = (ResolveInfo)receivers.get(it);
                }
                if (curr == null) {
                     // 动态注册的广播是BroadcastFilter类型
                    curr = registeredReceivers.get(ir);
                }
                // 如果动态注册广播接收者优先级高于等于静态广播接收者,则把动态注册的广播接收者插入到当前位置,  
            // 静态注册的广播接收者后移,所以同优先级动态注册的先于静态注册的接收到广播  
                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;
                }
            }
        }
         /// 把优先级低于所有静态注册广播接收者的动态广播接收者都追加到receivers列表中的末尾  
        while (ir < NR) {
            if (receivers == null) {
                receivers = new ArrayList();
            }
            receivers.add(registeredReceivers.get(ir));
            ir++;
        }
2.9 处理串行广播
   if ((receivers != null && receivers.size() > 0)
                || resultTo != null) {
            //获取广播队列
            BroadcastQueue queue = broadcastQueueForIntent(intent);
            //广播实体类
            BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
                    callerPackage, callingPid, callingUid, resolvedType,
                    requiredPermissions, appOp, brOptions, receivers, resultTo, resultCode,
                    resultData, resultExtras, ordered, sticky, false, userId);

            if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Enqueueing ordered broadcast " + r
                    + ": prev had " + queue.mOrderedBroadcasts.size());
            if (DEBUG_BROADCAST) Slog.i(TAG_BROADCAST,
                    "Enqueueing broadcast " + r.intent.getAction());

            boolean replaced = replacePending && queue.replaceOrderedBroadcastLocked(r);
            if (!replaced) {
                //加入串行广播队列
                queue.enqueueOrderedBroadcastLocked(r);
                //处理串行广播
                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... let's record it for posterity.
                addBroadcastStatLocked(intent.getAction(), callerPackage, 0, 0, 0);
            }
        }

在2.6小节, 有行代码是 final boolean replacePending = (intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;这是为了查看intent的flag有没有设置FLAG_RECEIVER_REPLACE_PENDING,如果设置的话, AMS就会在当前的系统中查看有没有相同的intent还未处理,如果有的话,就用当前这个新的intent 来替换旧的intent。所以当replacePending==true的时候,执行queue.replaceParallelBroadcastLocked(r)进行替换,并且返回true.


    public final boolean replaceParallelBroadcastLocked(BroadcastRecord r) {
        for (int i = mParallelBroadcasts.size() - 1; i >= 0; i--) {
            final Intent curIntent = mParallelBroadcasts.get(i).intent;
            if (r.intent.filterEquals(curIntent)) {
                if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
                        "***** DROPPING PARALLEL ["
                + mQueueName + "]: " + r.intent);
                mParallelBroadcasts.set(i, r);
                return true;
            }
        }
        return false;
    }

好了,文章比较长,在总结一下广播的发送过程,分为九个部分。
2.1、设置Flag
2.2、检查BroadcastOptions
2.3、当前是否有权力发出广播
2.4、处理系统相关广播
2.5、处理粘性广播
2.6、registeredReceivers和receivers查询
2.7 处理并行广播
2.8 整理两个receiver列表
2.9 处理串行广播

  • 对于粘性广播是在注册过程处理的,创建BroadcastRecord对象;并添加到mParallelBroadcasts队列;
    然后执行queue.scheduleBroadcastsLocked进行处理

  • 对于并行广播: 动态注册的广播会进入mRegisteredReceivers表,会创建BroadcastRecord对象,并添加到mParallelBroadcasts队列;然后执行queue.scheduleBroadcastsLocked;

  • 对于所有静态注册的广播和动态注册的有序广播会进入receivers表中(串行),会创建BroadcastRecord对象,并添加到mOrderedBroadcasts队列;然后执行queue.scheduleBroadcastsLocked;

下篇文章分析广播的处理过程,即scheduleBroadcastsLocked方法到底做了什么?暂时over!

作者:u013263323 发表于2017/7/24 11:48:33 原文链接
阅读:110 评论:0 查看评论

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