接上篇文章辈赋，這篇文章主要是總結前面知識鲫忍，并且了解一些細節(jié)問題，加深對廣播機制的理解钥屈，比如有播有序是怎么保證有序的悟民？廣播攔截機制是怎么實現的？廣播發(fā)送超時了是怎么處理的篷就？registerReceiver方法發(fā)返回值有什么用射亏？粘性廣播等等。
Android源碼解析四大組件系列（五）---廣播的注冊過程
Android源碼解析四大組件系列（六）---廣播的處理過程
Android源碼解析四大組件系列（七）---廣播的發(fā)送過程
1、廣播相關數據結構的再次理解
ReceiverDispatcher: 客戶端廣播分發(fā)者對象智润，第一篇講的很清楚了及舍，ReceiverDispatcher的內部類InnerReceiver為binder對象，用于與AMS的傳遞與通信窟绷。
ReceiverList: 繼承自ArrayList锯玛，存放了Receiver的binder對象以及其注冊的BroadcastFilter列表。AMS中定義了
final HashMap<IBinder, ReceiverList> mRegisteredReceivers = new HashMap<>();key為InnerReceiver的binder對象钾麸，值為ReceiverList更振，ReceiverList內部記錄的是動態(tài)注冊的廣播接收者，mRegisteredReceivers只有動態(tài)注冊的時候才會有內容饭尝。BroadcastFilter: 封裝了IntentFilter肯腕，描述動態(tài)廣播，是動態(tài)廣播節(jié)點钥平。
ResolveInfo:Parcelable子類实撒，描述靜態(tài)廣播，是靜態(tài)廣播節(jié)點涉瘾。
IntentResolver: 解析Intent践美，在addFilter時即進行解析璃岳。其內部有mSchemeToFilter，mActionToFilter，mTypedActionToFilter三個map對象庶艾。key為對應的action（scheme或者type）骂束，value為Filter传于。
BroadcastRecord:描述一個廣播碉克， 將intent等一堆信息，封裝成BroadcastRecord赁还，交給BroadcastQueue進行處理妖泄。
BroadcastQueue: BroadcastQueue為Broadcast處理隊列，分為前臺隊列mFgBroadcastQueue和后臺隊列mBgBroadcastQueue艘策，mFgBroadcastQueue會有更高的權限蹈胡，被優(yōu)先處理。mFgBroadcastQueue和mBgBroadcastQueue兩個隊列中都含有mOrderedBroadcasts和mParallelBroadcasts兩個列表用來表示有序廣播列表和無序廣播列表朋蔫。
２罚渐、有序廣播是怎么保證有序的
上一篇文章中說了processNextBroadcast()只會處理一個BroadcastRecord的一個receiver，那怎么將廣播傳遞給下一個receiver呢驯妄？廣播接受者有“動態(tài)”和“靜態(tài)”之分搅轿，廣播消息也有“串行”和“并行”之分，或者叫“有序”和“無序”之分富玷。廣播的處理方式跟廣播的接收者和廣播消息類型有關系。有序廣播是怎么保證有序的這個問題，得分情況討論赎懦，對于動態(tài)注冊的receiver雀鹃，先回到最終onReceive回調的地方，分析如下：
static final class ReceiverDispatcher {
.....
final class Args extends BroadcastReceiver.PendingResult implements Runnable {
.....
public Args(Intent intent, int resultCode, String resultData, Bundle resultExtras,
boolean ordered, boolean sticky, int sendingUser) {
//mRegistered傳進來的是true
super(resultCode, resultData, resultExtras,
mRegistered ? TYPE_REGISTERED : TYPE_UNREGISTERED, ordered,
sticky, mIIntentReceiver.asBinder(), sendingUser, intent.getFlags());
mCurIntent = intent;
mOrdered = ordered;
}
public void run() {
.....
try {
ClassLoader cl = mReceiver.getClass().getClassLoader();
intent.setExtrasClassLoader(cl);
intent.prepareToEnterProcess();
setExtrasClassLoader(cl);
receiver.setPendingResult(this);
//廣播的onReceive方法回調
receiver.onReceive(mContext, intent);
} catch (Exception e) {
if (mRegistered && ordered) {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing failed broadcast to " + mReceiver);
sendFinished(mgr);
}
if (mInstrumentation == null ||
!mInstrumentation.onException(mReceiver, e)) {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
throw new RuntimeException(
"Error receiving broadcast " + intent
+ " in " + mReceiver, e);
}
}
if (receiver.getPendingResult() != null) {
finish();
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
}
}
因為在調用onReceive之前励两，執(zhí)行了 receiver.setPendingResult(this)黎茎，所以在下面receiver.getPendingResult()就不是null,則就進入BroadcastReceiver的內部類PendingResult的finish方法。
public final void finish() {
if (mType == TYPE_COMPONENT) {
final IActivityManager mgr = ActivityManagerNative.getDefault();
if (QueuedWork.hasPendingWork()) {
......
QueuedWork.singleThreadExecutor().execute( new Runnable() {
@Override public void run() {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast after work to component " + mToken);
sendFinished(mgr);
}
});
} else {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to component " + mToken);
sendFinished(mgr);
}
} else if (mOrderedHint && mType != TYPE_UNREGISTERED) {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to " + mToken);
final IActivityManager mgr = ActivityManagerNative.getDefault();
sendFinished(mgr);
}
}
finish方法中根據mType的值有兩個分支当悔。mType是PendingResult的成員變量傅瞻，在PendingResult的構造函數中進行賦值的。
public PendingResult(int resultCode, String resultData, Bundle resultExtras, int type,
boolean ordered, boolean sticky, IBinder token, int userId, int flags) {
mResultCode = resultCode;
mResultData = resultData;
mResultExtras = resultExtras;
mType = type;
mOrderedHint = ordered;
mInitialStickyHint = sticky;
mToken = token;
mSendingUser = userId;
mFlags = flags;
}
這個構造方法是在BroadcastReceiver.PendingResult的子類Args中調用的
final class Args extends BroadcastReceiver.PendingResult implements Runnable {
private Intent mCurIntent;
private final boolean mOrdered;
private boolean mDispatched;
public Args(Intent intent, int resultCode, String resultData, Bundle resultExtras,
boolean ordered, boolean sticky, int sendingUser) {
super(resultCode, resultData, resultExtras,
mRegistered ? TYPE_REGISTERED : TYPE_UNREGISTERED, ordered,
sticky, mIIntentReceiver.asBinder(), sendingUser, intent.getFlags());
mCurIntent = intent;
mOrdered = ordered;
}
}
由于mRegistered是動態(tài)注冊廣播接收者傳進來的盲憎，值是true,所以上面mType的值是TYPE_REGISTERED嗅骄，由于是有序廣播ordered值是true，那么mOrderedHint為true,所以要走第二個分支：
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to " + mToken);
final IActivityManager mgr = ActivityManagerNative.getDefault();
sendFinished(mgr);
BroadcastReceiver的sendFinished方法如下：
public void sendFinished(IActivityManager am) {
synchronized (this) {
if (mFinished) {
throw new IllegalStateException("Broadcast already finished");
}
mFinished = true;
try {
if (mResultExtras != null) {
mResultExtras.setAllowFds(false);
}
if (mOrderedHint) {
am.finishReceiver(mToken, mResultCode, mResultData, mResultExtras,
mAbortBroadcast, mFlags);
} else {
// This broadcast was sent to a component; it is not ordered,
// but we still need to tell the activity manager we are done.
am.finishReceiver(mToken, 0, null, null, false, mFlags);
}
} catch (RemoteException ex) {
}
}
}
有序廣播mOrderedHint值為true,所以進入到AMS的finishReceiver方法饼疙。
public void finishReceiver(IBinder who, int resultCode, String resultData,
Bundle resultExtras, boolean resultAbort, int flags) {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Finish receiver: " + who);
// Refuse possible leaked file descriptors
if (resultExtras != null && resultExtras.hasFileDescriptors()) {
throw new IllegalArgumentException("File descriptors passed in Bundle");
}
final long origId = Binder.clearCallingIdentity();
try {
boolean doNext = false;
BroadcastRecord r;
synchronized(this) {
BroadcastQueue queue = (flags & Intent.FLAG_RECEIVER_FOREGROUND) != 0
? mFgBroadcastQueue : mBgBroadcastQueue;
r = queue.getMatchingOrderedReceiver(who);
if (r != null) {
doNext = r.queue.finishReceiverLocked(r, resultCode,
resultData, resultExtras, resultAbort, true);
}
}
if (doNext) {
//再次執(zhí)行processNextBroadcast處理廣播
r.queue.processNextBroadcast(false);
}
trimApplications();
} finally {
Binder.restoreCallingIdentity(origId);
}
}
上面是分析了動態(tài)的廣播接收者是怎么按照一個接著一個處理的溺森。在看看靜態(tài)注冊的receiver，回到靜態(tài)廣播回調onReceive方法的地方窑眯。
private void handleReceiver(ReceiverData data) {
....
IActivityManager mgr = ActivityManagerNative.getDefault();
BroadcastReceiver receiver;
try {
java.lang.ClassLoader cl = packageInfo.getClassLoader();
data.intent.setExtrasClassLoader(cl);
data.intent.prepareToEnterProcess();
data.setExtrasClassLoader(cl);
//反射出BroadcastReceiver
receiver = (BroadcastReceiver)cl.loadClass(component).newInstance();
} catch (Exception e) {
....
}
try {
Application app = packageInfo.makeApplication(false, mInstrumentation);
....
ContextImpl context = (ContextImpl)app.getBaseContext();
sCurrentBroadcastIntent.set(data.intent);
receiver.setPendingResult(data);
//回調廣播的onReceive方法
receiver.onReceive(context.getReceiverRestrictedContext(),data.intent);
} catch (Exception e) {
....
}
} finally {
sCurrentBroadcastIntent.set(null);
}
if (receiver.getPendingResult() != null) {
data.finish();
}
}
在回調onReceiver方法之前屏积， 執(zhí)行了 receiver.setPendingResult(data)，所以下面receiver.getPendingResult() != null成立磅甩，走 data.finish()炊林，data是ReceiverData對象，handleReceiver方法傳進來的卷要，在scheduleReceiver方法中初始化渣聚。
public final void scheduleReceiver(Intent intent, ActivityInfo info,
CompatibilityInfo compatInfo, int resultCode, String data, Bundle extras,
boolean sync, int sendingUser, int processState) {
updateProcessState(processState, false);
ReceiverData r = new ReceiverData(intent, resultCode, data, extras,
sync, false, mAppThread.asBinder(), sendingUser);
r.info = info;
r.compatInfo = compatInfo;
sendMessage(H.RECEIVER, r);
}
我們看 data.finish()方法
public final void finish() {
if (mType == TYPE_COMPONENT) {
final IActivityManager mgr = ActivityManagerNative.getDefault();
if (QueuedWork.hasPendingWork()) {
QueuedWork.singleThreadExecutor().execute( new Runnable() {
@Override public void run() {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast after work to component " + mToken);
sendFinished(mgr);
}
});
} else {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to component " + mToken);
sendFinished(mgr);
}
} else if (mOrderedHint && mType != TYPE_UNREGISTERED) {
if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
"Finishing broadcast to " + mToken);
final IActivityManager mgr = ActivityManagerNative.getDefault();
sendFinished(mgr);
}
}
此時mType分析后值是TYPE_COMPONENT，同樣會走sendFinished却妨，后面AMS的處理邏輯是一樣的饵逐，不贅述。
３彪标、廣播超時是怎么處理的?
AMS維護了兩個廣播隊列BroadcastQueue倍权，mFgBroadcastQueue，前臺隊列的超時時間是10秒捞烟，mBgBroadcastQueue薄声，后臺隊列的超時時間是60秒，如果廣播沒有在規(guī)定的時間內處理完就會發(fā)生ANR,如果你想你的廣播進入前臺廣播隊列题画，那么在發(fā)送的時候默辨，在intent中加入Intent.FLAG_RECEIVER_FOREGROUND標記，如果不加苍息，系統(tǒng)默認是后臺廣播缩幸。mFgBroadcastQueue會有更高的權限壹置，被優(yōu)先處理。
在processNextBroadcast方法中有下面一段代碼表谊，與廣播超時有關系钞护，一旦超時就會出現ANR。
do {
int numReceivers = (r.receivers != null) ? r.receivers.size() : 0;
if (mService.mProcessesReady && r.dispatchTime > 0) {
long now = SystemClock.uptimeMillis();
//廣播消息的第一個ANR監(jiān)測機制
if ((numReceivers > 0) &&
(now > r.dispatchTime + (2*mTimeoutPeriod*numReceivers))) {
Slog.w(TAG, "Hung broadcast ["
+ mQueueName + "] discarded after timeout failure:"
+ " now=" + now
+ " dispatchTime=" + r.dispatchTime
+ " startTime=" + r.receiverTime
+ " intent=" + r.intent
+ " numReceivers=" + numReceivers
+ " nextReceiver=" + r.nextReceiver
+ " state=" + r.state);
broadcastTimeoutLocked(false); // 超時處理
forceReceive = true;
r.state = BroadcastRecord.IDLE;
}
}
//判斷廣播有沒有處理完畢
if (r.receivers == null || r.nextReceiver >= numReceivers
|| r.resultAbort || forceReceive) {
// No more receivers for this broadcast! Send the final
// result if requested...
if (r.resultTo != null) {
try {
performReceiveLocked(r.callerApp, r.resultTo, new Intent(r.intent), r.resultCode r.resultData, r.resultExtras, false, false, r.userId);
r.resultTo = null;
} catch (RemoteException e) {
......
}
}
} while (r == null);
廣播的超時機制是針對有序廣播來說的爆办，無序廣播一次性全部處理了难咕，肯定不會超時，超時的這段邏輯都在broadcastTimeoutLocked中距辆，首先判斷是否超時余佃，公式：r.dispatchTime + 2×mTimeoutPeriod×numReceivers，現在解釋一下這幾個時間：
dispatchTime的意義是標記實際處理BroadcastRecord的起始時間跨算，有序廣播是一個接著一個進行處理的爆土，第一次dispatchTime=0,并不會進入該條件判斷
mTimeoutPeriod由當前BroadcastQueue的類型決定(mFgBroadcastQueue為10秒，mBgBroadcastQueue為60秒)
// How long we allow a receiver to run before giving up on it.
static final int BROADCAST_FG_TIMEOUT = 10*1000;
static final int BROADCAST_BG_TIMEOUT = 60*1000;
mFgBroadcastQueue = new BroadcastQueue(this, mHandler, "foreground", BROADCAST_FG_TIMEOUT, false);
mBgBroadcastQueue = new BroadcastQueue(this, mHandler, "background", BROADCAST_BG_TIMEOUT, true);
所以上面公式翻譯過來就是：實際處理BroadcastRecord的起始時間＋廣播默認的超時時間*廣播接收者的數量漂彤。話說回來雾消，這個公式為什么要這么設計呢？如果一個前臺的廣播消息有兩個接收者挫望，那么在２0秒（２ x 10）之內搞定就可以了立润，也可能第一個消息執(zhí)行了15秒，第二個消息執(zhí)行４.99秒媳板，即使第一消息超過了10秒的規(guī)定桑腮，也不會出現ＡＮＲ。但是系統(tǒng)任務繁忙蛉幸，可能有其他活要干破讨，我們要盡可能的減少ANR的發(fā)生，所以前面乘以２倍奕纫。
假設現在廣播超時還沒處理提陶，滿足if條件，就會進入匹层，打印Hung broadcast ["+ mQueueName + "] discarded after timeout failure....的log隙笆，然后執(zhí)行 broadcastTimeoutLocked(false)強制停止廣播，broadcastTimeoutLocked相關代碼代碼如下：
final void broadcastTimeoutLocked(boolean fromMsg) {
.....
long timeoutTime = r.receiverTime + mTimeoutPeriod;
if (timeoutTime > now) {
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Premature timeout ["
+ mQueueName + "] @ " + now + ": resetting BROADCAST_TIMEOUT_MSG for "
+ timeoutTime);
setBroadcastTimeoutLocked(timeoutTime);
return;
}
}
.....
}
內部調用setBroadcastTimeoutLocked()設置一個延遲消息
final void setBroadcastTimeoutLocked(long timeoutTime) {
if (! mPendingBroadcastTimeoutMessage) {
Message msg = mHandler.obtainMessage(BROADCAST_TIMEOUT_MSG, this);
mHandler.sendMessageAtTime(msg, timeoutTime);
mPendingBroadcastTimeoutMessage = true;
}
}
如果廣播消息能夠處理完畢升筏，就會執(zhí)行cancelBroadcastTimeoutLocked撑柔，將超時的Message移除掉。
final void cancelBroadcastTimeoutLocked() {
if (mPendingBroadcastTimeoutMessage) {
mHandler.removeMessages(BROADCAST_TIMEOUT_MSG, this);
mPendingBroadcastTimeoutMessage = false;
}
如果廣播消息沒有在timeout時間內處理掉您访，下面BroadcastHandler發(fā)送的消息就會執(zhí)行铅忿。
private final class BroadcastHandler extends Handler {
.....
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
.....
case BROADCAST_TIMEOUT_MSG: {
synchronized (mService) {
broadcastTimeoutLocked(true);
}
} break;
.....
}
}
}
再次進入broadcastTimeoutLocked方法里面
final void broadcastTimeoutLocked(boolean fromMsg) {
//傳進來是ture
if (fromMsg) {
mPendingBroadcastTimeoutMessage = false;
}
//隊列沒有廣播處理了，返回
if (mOrderedBroadcasts.size() == 0) {
return;
}
long now = SystemClock.uptimeMillis();
BroadcastRecord r = mOrderedBroadcasts.get(0);
if (fromMsg) {
//正在執(zhí)行dexopt,返回
if (mService.mDidDexOpt) {
// Delay timeouts until dexopt finishes.
mService.mDidDexOpt = false;
long timeoutTime = SystemClock.uptimeMillis() + mTimeoutPeriod;
setBroadcastTimeoutLocked(timeoutTime);
return;
}
//系統(tǒng)還沒有進入ready狀態(tài)
if (!mService.mProcessesReady) {
// Only process broadcast timeouts if the system is ready. That way
// PRE_BOOT_COMPLETED broadcasts can't timeout as they are intended
// to do heavy lifting for system up.
return;
}
//如果當前正在執(zhí)行的receiver沒有超時灵汪，則重新設置廣播超時
long timeoutTime = r.receiverTime + mTimeoutPeriod;
if (timeoutTime > now) {
// We can observe premature timeouts because we do not cancel and reset the
// broadcast timeout message after each receiver finishes. Instead, we set up
// an initial timeout then kick it down the road a little further as needed
// when it expires.
if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST,
"Premature timeout ["
+ mQueueName + "] @ " + now + ": resetting BROADCAST_TIMEOUT_MSG for "
+ timeoutTime);
setBroadcastTimeoutLocked(timeoutTime);
return;
}
}
//當前正在執(zhí)行的receiver沒有超時檀训，則重新設置廣播超時柑潦，處理下一條廣播
BroadcastRecord br = mOrderedBroadcasts.get(0);
if (br.state == BroadcastRecord.WAITING_SERVICES) {
// In this case the broadcast had already finished, but we had decided to wait
// for started services to finish as well before going on. So if we have actually
// waited long enough time timeout the broadcast, let's give up on the whole thing
// and just move on to the next.
Slog.i(TAG, "Waited long enough for: " + (br.curComponent != null
? br.curComponent.flattenToShortString() : "(null)"));
br.curComponent = null;
br.state = BroadcastRecord.IDLE;
processNextBroadcast(false);
return;
}
Slog.w(TAG, "Timeout of broadcast " + r + " - receiver=" + r. receiver
+ ", started " + (now - r.receiverTime) + "ms ago");
r.receiverTime = now;
r.anrCount++;
// Current receiver has passed its expiration date.
if (r.nextReceiver <= 0) {
Slog.w(TAG, "Timeout on receiver with nextReceiver <= 0");
return;
}
ProcessRecord app = null;
String anrMessage = null;
Object curReceiver = r.receivers.get(r.nextReceiver-1);
r.delivery[r.nextReceiver-1] = BroadcastRecord.DELIVERY_TIMEOUT;
Slog.w(TAG, "Receiver during timeout: " + curReceiver);
logBroadcastReceiverDiscardLocked(r);
if (curReceiver instanceof BroadcastFilter) {
BroadcastFilter bf = (BroadcastFilter)curReceiver;
if (bf.receiverList.pid != 0
&& bf.receiverList.pid != ActivityManagerService.MY_PID) {
synchronized (mService.mPidsSelfLocked) {
app = mService.mPidsSelfLocked.get(
bf.receiverList.pid);
}
}
} else {
app = r.curApp;
}
//進程存在，anrMessage賦值
if (app != null) {
anrMessage = "Broadcast of " + r.intent.toString();
}
if (mPendingBroadcast == r) {
mPendingBroadcast = null;
}
// Move on to the next receiver.
finishReceiverLocked(r, r.resultCode, r.resultData,
r.resultExtras, r.resultAbort, false);
//處理下一條廣播
scheduleBroadcastsLocked();
if (anrMessage != null) {
// Post the ANR to the handler since we do not want to process ANRs while
// potentially holding our lock.
mHandler.post(new AppNotResponding(app, anrMessage));
}
}
所以當一個receiver超時后肢扯，系統(tǒng)會放棄繼續(xù)處理它給出ANR提示妒茬，并再次調用scheduleBroadcastsLocked()，嘗試處理下一個receiver蔚晨，
private final class AppNotResponding implements Runnable {
private final ProcessRecord mApp;
private final String mAnnotation;
public AppNotResponding(ProcessRecord app, String annotation) {
mApp = app;
mAnnotation = annotation;
}
@Override
public void run() {
//內部創(chuàng)建ANR顯示的Dialog
mService.mAppErrors.appNotResponding(mApp, null, null, false, mAnnotation);
}
}
４、廣播攔截處理分析
廣播消息可以有多個接收者肛循，對于有序廣播是一個接著一個處理的铭腕，優(yōu)先級高的接收者可以優(yōu)先執(zhí)行，并且可以調用BroadcastReceiver的abortBroadcast()方法攔截廣播多糠，如果我們在receiver的onReceive()中調用這個方法累舷，那么它后面的接收者就不會收到廣播。
public abstract class BroadcastReceiver {
private PendingResult mPendingResult;
public final void abortBroadcast() {
checkSynchronousHint();
mPendingResult.mAbortBroadcast = true;
}
}
```
把BroadcastReceiver::PendingResult的成員變量mAbortBroadcast設置成true夹孔，
final class Args extends BroadcastReceiver.PendingResult implements Runnable {
private Intent mCurIntent;
private final boolean mOrdered;
private boolean mDispatched;
public Args(Intent intent, int resultCode, String resultData, Bundle resultExtras,
boolean ordered, boolean sticky, int sendingUser) {
super(resultCode, resultData, resultExtras,
mRegistered ? TYPE_REGISTERED : TYPE_UNREGISTERED, ordered,
sticky, mIIntentReceiver.asBinder(), sendingUser, intent.getFlags());
mCurIntent = intent;
mOrdered = ordered;
}
public void run() {
.....
try {
ClassLoader cl = mReceiver.getClass().getClassLoader();
intent.setExtrasClassLoader(cl);
intent.prepareToEnterProcess();
setExtrasClassLoader(cl);
//設置PendingResult被盈，這個PendingResult中mAbortBroadcast為true
receiver.setPendingResult(this);
receiver.onReceive(mContext, intent);
} catch (Exception e) {
.....
}
if (receiver.getPendingResult() != null) {
//告知AMS處理下一個廣播
finish();
}
}
}
```
finish()會告知AMS處理下一個廣播，在第一小節(jié)已經分析過搭伤，最終進入AMS的finishReceiver方法
public void finishReceiver(IBinder who, int resultCode, String resultData,
Bundle resultExtras, boolean resultAbort, int flags) {
.....
try {
boolean doNext = false;
BroadcastRecord r;
synchronized(this) {
BroadcastQueue queue = (flags & Intent.FLAG_RECEIVER_FOREGROUND) != 0
? mFgBroadcastQueue : mBgBroadcastQueue;
r = queue.getMatchingOrderedReceiver(who);
if (r != null) {
//resultAbort傳進來是true只怎，
doNext = r.queue.finishReceiverLocked(r, resultCode,
resultData, resultExtras, resultAbort, true);
}
}
//調用processNextBroadcast處理廣播
if (doNext) {
r.queue.processNextBroadcast(false);
}
trimApplications();
} finally {
Binder.restoreCallingIdentity(origId);
}
}
processNextBroadcast方法中有一個檢查廣播有沒有發(fā)送完畢的邏輯。
do {
.....
r = mOrderedBroadcasts.get(0);
//檢查廣播有沒有發(fā)送完怜俐，resultAbort為=ture
if (r.receivers == null || r.nextReceiver >= numReceivers
|| r.resultAbort || forceReceive) {
.....
//mOrderedBroadcasts里刪除廣播消息
mOrderedBroadcasts.remove(0);
r = null;
looped = true;
continue;
}
} while (r == null);
當resultAbort為=ture時候身堡，廣播消息從mOrderedBroadcasts刪除，后面也就收不到廣播了拍鲤。
５贴谎、理解粘性廣播
sticky廣播通過Context.sendStickyBroadcast()函數來發(fā)送，用此函數發(fā)送的廣播會一直滯留季稳，當有匹配此廣播的廣播接收器被注冊后擅这，該廣播接收器就會收到此條信息。使用此函數需要發(fā)送廣播時景鼠，需要獲得BROADCAST_STICKY權限仲翎。粘性廣播可以使用廣播接收器進行接收，但是正確的接收方式是調用registerReceiver能接受廣播莲蜘，信息將在調用registerReceiver的返回值中給出谭确。對于粘性廣播的發(fā)送，和普通廣播的發(fā)送方式是一致的票渠，例子來自與Android 粘性廣播StickyBroadcast的使用
private void sendStickyBroadcast(){
Intent i = new Intent();
i.setAction(StickyBroadcastReceiver.Action);
i.putExtra("info", "sticky broadcast has been receiver");
sendStickyBroadcast(i);
Log.i("Other","sticky broadcast send ok!");
}
可以使用BroadcastReceiver來接收
public class StickyBroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
//收到廣播
}
}
<!--使用粘性廣播發(fā)送權限-->
<uses-permission android:name="android.permission.BROADCAST_STICKY" />
IntentFilter intentFilter = new IntentFilter(StickyBroadcastReceiver.Action);
Intent data = registerReceiver(null, intentFilter);
if(data!=null&&StickyBroadcastReceiver.Action.equals(data.getAction())) {
Toast.makeText(this, data.getStringExtra("info"), Toast.LENGTH_SHORT).show();
}
好了廣播的四篇文章寫完了逐哈，準備在分析一波Service吧
