先来一张时序图。注：这里查看的是 9.0 源码
registerReceiver-时序图.png
sendBroadcast-时序图.png
第一个是 registerReceiver 方法的时序图，第二个是 sendBroadcast 方法的时序图。先来分析 registerReceiver 方法
@Override
public Intent registerReceiver(
BroadcastReceiver receiver, IntentFilter filter) {
return mBase.registerReceiver(receiver, filter);
}
还是调用 mBase 的 registerReceiver 方法，去到ContextImpl中
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), 0);
}
private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
IntentFilter filter, String broadcastPermission,
Handler scheduler, Context context, int flags) {
IIntentReceiver rd = null;
//.....
rd = new LoadedApk.ReceiverDispatcher(
receiver, context, scheduler, null, true).getIIntentReceiver();
//.....
final Intent intent = ActivityManager.getService().registerReceiver(
mMainThread.getApplicationThread(), mBasePackageName, rd, filter,
broadcastPermission, userId, flags);
}
一路调用自身的方法，有去到AMS中的 registerReceiver 方法，需要注意的是 IIntentReceiver 对象实例是 LoadedApk.ReceiverDispatcher.InnerReceiver ，这个类实现了 IIntentReceiver.Stub 接口，专门用于跨进程通信，作为数据进行传输。进到AMS中
public Intent registerReceiver(IApplicationThread caller, String callerPackage,
IIntentReceiver receiver, IntentFilter filter, String permission, int userId,
int flags) {
//....
//获取 actions
Iterator<String> actions = filter.actionsIterator();
if (actions == null) {
ArrayList<String> noAction = new ArrayList<String>(1);
noAction.add(null);
actions = noAction.iterator();
}
// 将 actions 添加到 mStickyBroadcasts 中
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);
}
}
}
}
}
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.
//判断是否为粘性广播，如果不是就继续循环下一个数据
//如果是则在 allSticky 中添加数据
if (instantApp &&
(intent.getFlags() & Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS) == 0) {
continue;
}
if (filter.match(resolver, intent, true, TAG) >= 0) {
if (allSticky == null) {
allSticky = new ArrayList<Intent>();
}
allSticky.add(intent);
}
}
}
synchronized (this) {
if (callerApp != null && (callerApp.thread == null
|| callerApp.thread.asBinder() != caller.asBinder())) {
// Original caller already died
return null;
}
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();
//将当前注册的广播添加到 receivers 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);
}
BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage,
permission, callingUid, userId, instantApp, visibleToInstantApps);
//判断 rl 中是否包含了当前的 filter ，没有就将当前的 filter 添加到 rl 中
if (rl.containsFilter(filter)) {
Slog.w(TAG, "Receiver with filter " + filter
+ " already registered for pid " + rl.pid
+ ", callerPackage is " + callerPackage);
} else {
rl.add(bf);
if (!bf.debugCheck()) {
Slog.w(TAG, "==> For Dynamic broadcast");
}
mReceiverResolver.addFilter(bf);
}
//判断粘性广播是否不为空
//如果不为空，则直接执行 scheduleBroadcastsLocked 方法
//这个方法后面在分析
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, -1, -1, false, null, null, OP_NONE, null, receivers,
null, 0, null, null, false, true, true, -1);
queue.enqueueParallelBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
}
return sticky;
}
}
AMS中的操作很简单，就是往对应集合中增加数据，并且判断当前注册的广播是否为粘性广播，如果为粘性广播则直接执行 scheduleBroadcastsLocked 方法，这个方法后面再分析。
到这里 registerReceiver 方法就完成了，接下来分析 sendBroadcast 方法
@Override
public void sendBroadcast(Intent intent) {
mBase.sendBroadcast(intent);
}
又是 mBase ，去到ContextImpl中
@Override
public void sendBroadcast(Intent intent) {
warnIfCallingFromSystemProcess();
String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
try {
intent.prepareToLeaveProcess(this);
ActivityManager.getService().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();
}
}
又去到AMS 中
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);
//获取对应进程的ID
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;
}
}
上面的方法就是获取对应进程的ID，继续走
@GuardedBy("this")
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) {
//.....
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);
if (!replaced) {
queue.enqueueParallelBroadcastLocked(r);
queue.scheduleBroadcastsLocked();
}
//.....
return ActivityManager.BROADCAST_SUCCESS;
}
省略了一大堆，因为我们这里只关注流程，这个方法内容想了解的可以自行了解。enqueueParallelBroadcastLocked 方法是往 mParallelBroadcasts 中增加数据，最后到 scheduleBroadcastsLocked 方法中
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;
}
又是通过 Handler ，mHandler 为 BroadcastHandler ，所以进入到 BroadcastHandler 的 handleMessage 方法
private final class BroadcastHandler extends Handler {
public BroadcastHandler(Looper looper) {
super(looper, null, true);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case BROADCAST_INTENT_MSG: {
if (DEBUG_BROADCAST) Slog.v(
TAG_BROADCAST, "Received BROADCAST_INTENT_MSG");
processNextBroadcast(true);
} break;
case BROADCAST_TIMEOUT_MSG: {
synchronized (mService) {
broadcastTimeoutLocked(true);
}
} break;
}
}
}
根据发送时传过来的 what ，知道走到 processNextBroadcast 方法中
final void processNextBroadcast(boolean fromMsg) {
synchronized (mService) {
processNextBroadcastLocked(fromMsg, false);
}
}
final void processNextBroadcastLocked(boolean fromMsg, boolean skipOomAdj) {
BroadcastRecord r;
//.....
//还记得前面的 enqueueParallelBroadcastLocked 方法吗，就是往 mParallelBroadcasts 中添加数据
while (mParallelBroadcasts.size() > 0) {
r = mParallelBroadcasts.remove(0);
r.dispatchTime = SystemClock.uptimeMillis();
r.dispatchClockTime = System.currentTimeMillis();
//.....
//还记得 registerReceiver 时候，就是往 receivers 中添加数据
final int N = r.receivers.size();
if (DEBUG_BROADCAST_LIGHT) Slog.v(TAG_BROADCAST, "Processing parallel broadcast ["
+ mQueueName + "] " + r);
for (int i=0; i<N; i++) {
Object target = r.receivers.get(i);
//执行
deliverToRegisteredReceiverLocked(r, (BroadcastFilter)target, false, i);
}
//.....
}
通过前面的分析，我们知道 mParallelBroadcasts 和 receivers 中都有数据，所以会执行到 deliverToRegisteredReceiverLocked 方法中。
private void deliverToRegisteredReceiverLocked(BroadcastRecord r,
BroadcastFilter filter, boolean ordered, int index) {
//.....
try {
//....
performReceiveLocked(filter.receiverList.app, filter.receiverList.receiver,
new Intent(r.intent), r.resultCode, r.resultData,
r.resultExtras, r.ordered, r.initialSticky, r.userId);
}
}
最后到 performReceiveLocked 方法中
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.
app.thread.scheduleRegisteredReceiver(receiver, intent, resultCode,
data, extras, ordered, sticky, sendingUser, app.repProcState);
}
又通过跨进程，回到Activity的进程中，去到 ApplicationThread 中
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);
}
还记得 registerReceiver 提到过的 IIntentReceiver 的实例对象是 LoadedApk.ReceiverDispatcher.InnerReceiver，所以到这里面去
@Override
public void performReceive(Intent intent, int resultCode, String data,
Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
final LoadedApk.ReceiverDispatcher rd;
rd.performReceive(intent, resultCode, data, extras,
ordered, sticky, sendingUser);
}
}
调用 LoadedApk.ReceiverDispatcher 中的 performReceive 方法
public void performReceive(Intent intent, int resultCode, String data,
Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
final Args args = new Args(intent, resultCode, data, extras, ordered,
sticky, sendingUser);
//.....
if (intent == null || !mActivityThread.post(args.getRunnable())) {
if (mRegistered && ordered) {
IActivityManager mgr = ActivityManager.getService();
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing sync broadcast to " + mReceiver);
args.sendFinished(mgr);
}
}
}
mActivityThread 是 Handler 对象，通过 Handler 的机制可以知道会调用 args.getRunnable()
public final Runnable getRunnable() {
return () -> {
final BroadcastReceiver receiver = mReceiver;
final boolean ordered = mOrdered;
//.....
//调用 onReceive 方法
receiver.onReceive(mContext, intent);
}
最后调用 onReceive 方法。mReceiver 就是我们在 registerReceiver 传进来的 BroadcastReceiver 对象，所以最后会回到到 onReceive 方法中。
