sendBroadcast、sendStickyBroadcast、sendOrderedBroadcast基本一样，只差一个参数broadcastIntent方法倒数第二个参数代表sticky，倒数第三个参数代表serialized
@Override
@Deprecated
public void sendStickyBroadcast(Intent intent) {
warnIfCallingFromSystemProcess();
String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
try {
intent.prepareToLeaveProcess(this);
// 这个true就代表是sticky
ActivityManagerNative.getDefault().broadcastIntent(
mMainThread.getApplicationThread(), intent, resolvedType, null,
Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false, true,
getUserId());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
ActivityManagerService.java
broadcastIntent→broadcastIntentLocked
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) {
// step1：设置flag
// step2：广播权限校验
// step3：处理系统广播
// step4：增加sticky广播
// step5：查询receivers（静态注册的接收者）和registeredReceivers（动态注册的接收者）
// step6：处理无序广播
// step7：合并registeredReceivers到receivers
// step8：处理有序广播
return ActivityManager.BROADCAST_SUCCESS;
}
sendBroadcast→→→→→1 2 3 x 5 6 7 8
sendStickyBroadcast→→1 2 3 4 5 6 7 8
sendOrderedBroadcast→1 2 3 x 5 x 7 8
注意这3个方法执行的step，下面会详细说明
step1：设置广播flag
intent = new Intent(intent);
//广播不会发送给已停止的package
intent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);
//当没有启动完成时，不允许启动新进程
if (!mProcessesReady && (intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0) {
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
}
userId = handleIncomingUser(callingPid, callingUid, userId,
true, ALLOW_NON_FULL, "broadcast", callerPackage);
//当非USER_ALL广播且当前用户并没有处于Running的情况下，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 && !isUserRunningLocked(userId, false)) {
if ((callingUid != Process.SYSTEM_UID
|| (intent.getFlags() & Intent.FLAG_RECEIVER_BOOT_UPGRADE) == 0)
&& !Intent.ACTION_SHUTDOWN.equals(intent.getAction())) {
return ActivityManager.BROADCAST_FAILED_USER_STOPPED;
}
}
BroadcastReceiver还有其他flag，位于Intent.java常量
FLAG_RECEIVER_REGISTERED_ONLY //只允许已注册receiver接收广播
FLAG_RECEIVER_REPLACE_PENDING //新广播会替代相同广播
FLAG_RECEIVER_FOREGROUND //只允许前台receiver接收广播
FLAG_RECEIVER_NO_ABORT //对于有序广播，先接收到的receiver无权抛弃广播
FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT //Boot完成之前，只允许已注册receiver接收广播
FLAG_RECEIVER_BOOT_UPGRADE //升级模式下，允许系统准备就绪前可以发送广播
step2：广播权限验证
//对于callingAppId为SYSTEM_UID，PHONE_UID，SHELL_UID，BLUETOOTH_UID，NFC_UID或者callingUid == 0时直接通过
int callingAppId = UserHandle.getAppId(callingUid);
if (callingAppId == Process.SYSTEM_UID || callingAppId == Process.PHONE_UID
|| callingAppId == Process.SHELL_UID || callingAppId == Process.BLUETOOTH_UID
|| callingAppId == Process.NFC_UID || callingUid == 0) {
//直接通过
} else if (callerApp == null || !callerApp.persistent) {
try {
if (AppGlobals.getPackageManager().isProtectedBroadcast(
intent.getAction())) {
//不允许发送给受保护的广播
throw new SecurityException(msg);
} else if (AppWidgetManager.ACTION_APPWIDGET_CONFIGURE.equals(intent.getAction())) {
...
}
} catch (RemoteException e) {
return ActivityManager.BROADCAST_SUCCESS;
}
}
step3：处理系统相关广播
final String action = intent.getAction();
if (action != null) {
switch (action) {
case Intent.ACTION_UID_REMOVED:
case Intent.ACTION_PACKAGE_REMOVED:
case Intent.ACTION_PACKAGE_CHANGED:
case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE:
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE:
// Handle special intents: if this broadcast is from the package
// manager about a package being removed, we need to remove all of
// its activities from the history stack.
if (checkComponentPermission(
android.Manifest.permission.BROADCAST_PACKAGE_REMOVED,
callingPid, callingUid, -1, true)
!= PackageManager.PERMISSION_GRANTED) {
String msg = "Permission Denial: " + intent.getAction()
+ " broadcast from " + callerPackage + " (pid=" + callingPid
+ ", uid=" + callingUid + ")"
+ " requires "
+ android.Manifest.permission.BROADCAST_PACKAGE_REMOVED;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
switch (action) {
case Intent.ACTION_UID_REMOVED:
final Bundle intentExtras = intent.getExtras();
final int uid = intentExtras != null
? intentExtras.getInt(Intent.EXTRA_UID) : -1;
if (uid >= 0) {
mBatteryStatsService.removeUid(uid);
mAppOpsService.uidRemoved(uid);
}
break;
case Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE:
// If resources are unavailable just force stop all those packages
// and flush the attribute cache as well.
String list[] =
intent.getStringArrayExtra(Intent.EXTRA_CHANGED_PACKAGE_LIST);
if (list != null && list.length > 0) {
for (int i = 0; i < list.length; i++) {
forceStopPackageLocked(list[i], -1, false, true, true,
false, false, userId, "storage unmount");
}
mRecentTasks.cleanupLocked(UserHandle.USER_ALL);
sendPackageBroadcastLocked(
IApplicationThread.EXTERNAL_STORAGE_UNAVAILABLE, list,
userId);
}
break;
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE:
mRecentTasks.cleanupLocked(UserHandle.USER_ALL);
break;
case Intent.ACTION_PACKAGE_REMOVED:
case Intent.ACTION_PACKAGE_CHANGED:
Uri data = intent.getData();
String ssp;
if (data != null && (ssp=data.getSchemeSpecificPart()) != null) {
boolean removed = Intent.ACTION_PACKAGE_REMOVED.equals(action);
boolean fullUninstall = removed &&
!intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);
if (!intent.getBooleanExtra(Intent.EXTRA_DONT_KILL_APP, false)) {
forceStopPackageLocked(ssp, UserHandle.getAppId(
intent.getIntExtra(Intent.EXTRA_UID, -1)),
false, true, true, false, fullUninstall, userId,
removed ? "pkg removed" : "pkg changed");
}
if (removed) {
sendPackageBroadcastLocked(IApplicationThread.PACKAGE_REMOVED,
new String[] {ssp}, userId);
if (fullUninstall) {
mAppOpsService.packageRemoved(
intent.getIntExtra(Intent.EXTRA_UID, -1), ssp);
// Remove all permissions granted from/to this package
removeUriPermissionsForPackageLocked(ssp, userId, true);
removeTasksByPackageNameLocked(ssp, userId);
mBatteryStatsService.notePackageUninstalled(ssp);
}
} else {
cleanupDisabledPackageComponentsLocked(ssp, userId,
intent.getStringArrayExtra(
Intent.EXTRA_CHANGED_COMPONENT_NAME_LIST));
}
}
break;
}
break;
case Intent.ACTION_PACKAGE_ADDED:
// Special case for adding a package: by default turn on compatibility mode.
Uri data = intent.getData();
String ssp;
if (data != null && (ssp = data.getSchemeSpecificPart()) != null) {
final boolean replacing =
intent.getBooleanExtra(Intent.EXTRA_REPLACING, false);
mCompatModePackages.handlePackageAddedLocked(ssp, replacing);
try {
ApplicationInfo ai = AppGlobals.getPackageManager().
getApplicationInfo(ssp, 0, 0);
mBatteryStatsService.notePackageInstalled(ssp,
ai != null ? ai.versionCode : 0);
} catch (RemoteException e) {
}
}
break;
case Intent.ACTION_TIMEZONE_CHANGED:
// If this is the time zone changed action, queue up a message that will reset
// the timezone of all currently running processes. This message will get
// queued up before the broadcast happens.
mHandler.sendEmptyMessage(UPDATE_TIME_ZONE);
break;
case Intent.ACTION_TIME_CHANGED:
// If the user set the time, let all running processes know.
final int is24Hour =
intent.getBooleanExtra(Intent.EXTRA_TIME_PREF_24_HOUR_FORMAT, false) ? 1
: 0;
mHandler.sendMessage(mHandler.obtainMessage(UPDATE_TIME, is24Hour, 0));
BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();
synchronized (stats) {
stats.noteCurrentTimeChangedLocked();
}
break;
case Intent.ACTION_CLEAR_DNS_CACHE:
mHandler.sendEmptyMessage(CLEAR_DNS_CACHE_MSG);
break;
case Proxy.PROXY_CHANGE_ACTION:
ProxyInfo proxy = intent.getParcelableExtra(Proxy.EXTRA_PROXY_INFO);
mHandler.sendMessage(mHandler.obtainMessage(UPDATE_HTTP_PROXY_MSG, proxy));
break;
}
}
主要处理系统相关的广播，10个case
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: //外部设备不可用时，强制停止所有波及的应用并清空cache数据
case Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE: //外部设备可用
case Intent.ACTION_PACKAGE_ADDED: //增加package，处于兼容考虑
case Intent.ACTION_TIMEZONE_CHANGED: //时区改变，通知所有运行中的进程
case Intent.ACTION_TIME_CHANGED: //时间改变，通知所有运行中的进程
case Intent.ACTION_CLEAR_DNS_CACHE: //dns缓存清空
case Proxy.PROXY_CHANGE_ACTION: //网络代理改变
step4：增加sticky广播
// Add to the sticky list if requested.
if (sticky) {
if (checkPermission(android.Manifest.permission.BROADCAST_STICKY,
callingPid, callingUid)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException(msg);
}
if (requiredPermissions != null && requiredPermissions.length > 0) {
return ActivityManager.BROADCAST_STICKY_CANT_HAVE_PERMISSION;
}
if (intent.getComponent() != null) {
throw new SecurityException(
"Sticky broadcasts can't target a specific component");
}
// We use userId directly here, since the "all" target is maintained
// as a separate set of sticky broadcasts.
if (userId != UserHandle.USER_ALL) {
// But first, if this is not a broadcast to all users, then
// make sure it doesn't conflict with an existing broadcast to
// all users.
...
}
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))) {
// This sticky already exists, replace it.
list.set(i, new Intent(intent));
break;
}
}
// 新的intent追加到list
if (i >= stickiesCount) {
list.add(new Intent(intent));
}
}
简单说，就是如果sticky==true，则mStickyBroadcasts增加一条广播
step5：查询receivers和registeredReceivers
int[] users;
if (userId == UserHandle.USER_ALL) {
// 广播给所有已启动用户
// Caller wants broadcast to go to all started users.
users = mStartedUserArray;
} 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) {
// 根据intent查找静态注册的广播，已经按priority（默认值是0）从高到低排好顺序
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
UserManagerService ums = getUserManagerLocked();
for (int i = 0; i < users.length; i++) {
if (ums.hasUserRestriction(
UserManager.DISALLOW_DEBUGGING_FEATURES, users[i])) {
continue;
}
// 查询动态注册的广播，已经按priority从高到低排好顺序
List<BroadcastFilter> registeredReceiversForUser =
mReceiverResolver.queryIntent(intent,
resolvedType, false, users[i]);
if (registeredReceivers == null) {
registeredReceivers = registeredReceiversForUser;
} else if (registeredReceiversForUser != null) {
registeredReceivers.addAll(registeredReceiversForUser);
}
}
} else {
// 查询动态注册的广播，已经按priority从高到低排好顺序
registeredReceivers = mReceiverResolver.queryIntent(intent,
resolvedType, false, userId);
}
}
查询静态注册的广播
private List<ResolveInfo> collectReceiverComponents(Intent intent, String resolvedType,
int callingUid, int[] users) {
List<ResolveInfo> receivers = null;
try {
HashSet<ComponentName> singleUserReceivers = null;
boolean scannedFirstReceivers = false;
for (int user : users) {
// Skip users that have Shell restrictions
if (callingUid == Process.SHELL_UID
&& getUserManagerLocked().hasUserRestriction(
UserManager.DISALLOW_DEBUGGING_FEATURES, user)) {
continue;
}
// 调用PackageManagerService.queryIntentReceivers，获取AndroidManifest.xml声明的接收者信息
List<ResolveInfo> newReceivers = AppGlobals.getPackageManager()
.queryIntentReceivers(intent, resolvedType, STOCK_PM_FLAGS, user);
if (user != UserHandle.USER_OWNER && newReceivers != null) {
// If this is not the primary user, we need to check for
// any receivers that should be filtered out.
for (int i=0; i<newReceivers.size(); i++) {
ResolveInfo ri = newReceivers.get(i);
if ((ri.activityInfo.flags&ActivityInfo.FLAG_PRIMARY_USER_ONLY) != 0) {
// 移除FLAG_PRIMARY_USER_ONLY的receiver
newReceivers.remove(i);
i--;
}
}
}
if (newReceivers != null && newReceivers.size() == 0) {
newReceivers = null;
}
if (receivers == null) {
receivers = newReceivers;
} else if (newReceivers != null) {
// We need to concatenate the additional receivers
// found with what we have do far. This would be easy,
// but we also need to de-dup any receivers that are
// singleUser.
// 将所有用户的receiver整合到receivers
...
}
}
} catch (RemoteException ex) {
// pm is in same process, this will never happen.
}
return receivers;
}
step6：处理无序广播
如果ordered ==false，并且有动态注册的接收者，那么就会进入这个步骤。
在无序广播队列增加一条广播，然后遍历动态注册的接收者并通知。
final boolean replacePending =
(intent.getFlags()&Intent.FLAG_RECEIVER_REPLACE_PENDING) != 0;
int NR = registeredReceivers != null ? registeredReceivers.size() : 0;
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.
final BroadcastQueue queue = broadcastQueueForIntent(intent);
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) {
// 详情参考[Broadcast（二）registerReceiver时sticky广播]
queue.enqueueParallelBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
// 注意这2变量重置
registeredReceivers = null;
NR = 0;
}
step7：合并registeredReceivers到receivers
按priority从高到低，把动态注册的接收者和静态注册的接收者合并。相同的priority，动态注册的接收者优先
// 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.
// 防止应用监听该广播，在安装时直接运行
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);
}
// 将skipPackages相关的广播接收者从receivers中移除
if (skipPackages != null && (skipPackages.length > 0)) {
for (String skipPackage : skipPackages) {
if (skipPackage != null) {
int NT = receivers.size();
for (int it=0; it<NT; it++) {
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;
// 如果处理了无序广播，那么NR=0
while (it < NT && ir < NR) {
if (curt == null) {
curt = (ResolveInfo)receivers.get(it);
}
if (curr == null) {
curr = registeredReceivers.get(ir);
}
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++;
}
step8：处理有序广播
如果你明白上面7步做了什么，那你应该知道当ordered==true或者有静态注册的接收者的时候（显然只有这2个条件至少满足一个，receivers.size()才会大于0）就会进入这个步骤。
if ((receivers != null && receivers.size() > 0)
|| resultTo != null) {
BroadcastQueue queue = broadcastQueueForIntent(intent);
BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp,
callerPackage, callingPid, callingUid, resolvedType,
requiredPermissions, appOp, brOptions, receivers, resultTo, resultCode,
resultData, resultExtras, ordered, sticky, false, userId);
boolean replaced = replacePending && queue.replaceOrderedBroadcastLocked(r);
if (!replaced) {
// 见[Broadcast （四）有序广播和ANR]
queue.enqueueOrderedBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
}
参考引用
Gityuan Android Broadcast广播机制分析
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