大概
Android的ANR主要有两种方式：
1. 通过handler的延迟机制触发ANR
2. Input事件触发ANR
Service、BroadcastReceiver、ContentProvider都是通过Hander机制触发ANR。
ANR的发生的场景有：
- service timeout:前台服务在20s未执行完，后台服务200s未执行完。
- BroadcastQueue timeout:前台广播在10s未执行完，后台广播在60s未执行完。
- ContentProvider timeout: ContentProvider在发布时超过10s未执行完。
- InputDispatching Timeout：输入分发事件超过5s未执行完。
ANR的过程总体就是：装炸弹、拆炸弹、引爆炸弹
1. Service Timeout
在文章startService启动流程可以知道Service的生命周期和启动流程。
Service的生命周期
启动流程
装弹
在ActiveServices.realStartServiceLocked()方法中开始真正执行Service的生命周期方法，并开始装炸弹的开始。
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
// handle发送延迟消息，如果在规定时间还没有被取消，则证明方法执行时间长，则抛ANR异常。
bumpServiceExecutingLocked(r, execInFg, "create");
//...
try {
//调用Service对应onCreate()方法
app.thread.scheduleCreateService(r, r.serviceInfo,
mAm.compatibilityInfoForPackage(r.serviceInfo.applicationInfo),
app.getReportedProcState());
} catch (DeadObjectException e) {
mAm.appDiedLocked(app, "Died when creating service");
throw e;
} finally {
//...
}
}
// 通过Handler发送延迟时间，到时间内没被取消则抛ANR异常
private final void bumpServiceExecutingLocked(ServiceRecord r, boolean fg, String why) {
....
// 发送Handler
scheduleServiceTimeoutLocked(r.app);
}
// 发送延迟消息
void scheduleServiceTimeoutLocked(ProcessRecord proc) {
if (proc.executingServices.size() == 0 || proc.thread == null) {
return;
}
Message msg = mAm.mHandler.obtainMessage(
ActivityManagerService.SERVICE_TIMEOUT_MSG);
msg.obj = proc;
//当超时后仍没有remove该SERVICE_TIMEOUT_MSG消息，则执行service Timeout流程
mAm.mHandler.sendMessageDelayed(msg,
proc.execServicesFg ? SERVICE_TIMEOUT : SERVICE_BACKGROUND_TIMEOUT);
}
static final int SERVICE_TIMEOUT = 20 * 1000;
static final int SERVICE_BACKGROUND_TIMEOUT = SERVICE_TIMEOUT * 10;
在执行生命周期的方法前会通过bumpServiceExecutingLocked()方法进行装炸弹，通过Handler机制发送一个标志为SERVICE_TIMEOUT_MSG的延迟消息，如果是前台则20s,是后台则200s执行。
拆弹
在执行完Service的生命周期方法后就会执行拆弹，比如onCreate()方法在Application.handleCreateService()执行完毕：
private class ApplicationThread extends IApplicationThread.Stub {
// 创建对应的Service并执行onCreate()方法
private void handleCreateService(CreateServiceData data) {
try {
....
// 调用service.attach绑定资源文件
service.attach(context, this, data.info.name, data.token, app,
ActivityManager.getService());
// 调用 service.onCreate()方法
service.onCreate();
try {
// onCreate()执行完成，拆弹过程，最终调用到ActiveServices.serviceDoneExecutingLocked方法
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
} catch (Exception e) {
//...
}
}
// AMS
public void serviceDoneExecuting(IBinder token, int type, int startId, int res) {
synchronized (this) {
if (!(token instanceof ServiceRecord)) {
Slog.e(TAG, "serviceDoneExecuting: Invalid service token=" + token);
throw new IllegalArgumentException("Invalid service token");
}
mServices.serviceDoneExecutingLocked((ServiceRecord) token, type, startId, res);
}
}
// ActiveServices
private void serviceDoneExecutingLocked(ServiceRecord r, boolean inDestroying,
boolean finishing) {
//...
// 取消SERVICE_TIMEOUT_MSG消息，拆出炸弹
mAm.mHandler.removeMessages(ActivityManagerService.SERVICE_TIMEOUT_MSG, r.app);
//...
}
如果在生命周期方法内执行完，会回调AMS的方法，解除SERVICE_TIMEOUT_MSG延迟发送的消息。
引爆弹
如果Service方法在规定时间内没有执行完成，则会执行AMS.MainHandler的SERVICE_TIMEOUT_MSG类型的消息：
// AMS
final class MainHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SERVICE_TIMEOUT_MSG: {
mServices.serviceTimeout((ProcessRecord) msg.obj);
}
break;
}
}
}
// ActiveServices
void serviceTimeout(ProcessRecord proc) {
// 如果超时，调用appNotResponding()方法
if (anrMessage != null) {
mAm.mAnrHelper.appNotResponding(proc, anrMessage);
}
}
如果超时则会触发ANR,调用mAm.mAnrHelper.appNotResponding()方法。
2. BroadcastReceiver Timeout
装弹
在文章广播的注册、发送原理流程可以了解，发送广播后调用之行对应的广播接收器的方法，对应的方法在BroadcastQueue.processNextBroadcast()：
public final class BroadcastQueue {
final void processNextBroadcastLocked(boolean fromMsg, boolean skipOomAdj) {
BroadcastRecord r;
// 处理当前有序广播
do {
// 获取BroadcastRecord
final long now = SystemClock.uptimeMillis();
r = mDispatcher.getNextBroadcastLocked(now);
//当广播处理时间超时，则强制结束这条广播
if (mService.mProcessesReady && !r.timeoutExempt && r.dispatchTime > 0) {
if ((numReceivers > 0) &&
(now > r.dispatchTime + (2 * mConstants.TIMEOUT * numReceivers))) {
broadcastTimeoutLocked(false); // forcibly finish this broadcast
forceReceive = true;
r.state = BroadcastRecord.IDLE;
}
}
//...
if (r.receivers == null || r.nextReceiver >= numReceivers
|| r.resultAbort || forceReceive) {
if (r.resultTo != null) {
//...
//处理广播消息消息，调用到onReceive()
performReceiveLocked(r.callerApp, r.resultTo,
new Intent(r.intent), r.resultCode,
r.resultData, r.resultExtras, false, false, r.userId);
//...
}
//拆炸弹
cancelBroadcastTimeoutLocked();
r = null;
looped = true;
continue;
}
//..
} while (r == null);
//获取下一个receiver的index
int recIdx = r.nextReceiver++;
if (!mPendingBroadcastTimeoutMessage) {
long timeoutTime = r.receiverTime + mTimeoutPeriod;
//装炸弹，设置广播超时时间，发送BROADCAST_TIMEOUT_MSG
setBroadcastTimeoutLocked(timeoutTime);
}
//...
}
// 装弹
final void setBroadcastTimeoutLocked(long timeoutTime) {
if (!mPendingBroadcastTimeoutMessage) {
Message msg = mHandler.obtainMessage(BROADCAST_TIMEOUT_MSG, this);
mHandler.sendMessageAtTime(msg, timeoutTime);
mPendingBroadcastTimeoutMessage = true;
}
}
}
通过setBroadcastTimeoutLocked()方法进行装弹。
拆弹
通过上面的processNextBroadcastLocked()方法可知，调用cancelBroadcastTimeoutLocked()进行拆弹。
// 拆弹
final void cancelBroadcastTimeoutLocked() {
if (mPendingBroadcastTimeoutMessage) {
mHandler.removeMessages(BROADCAST_TIMEOUT_MSG, this);
mPendingBroadcastTimeoutMessage = false;
}
}
引爆弹
通过BroadcastHandler的BROADCAST_TIMEOUT_MSG类型的消息的执行，进行引爆炸弹。
public void handleMessage(Message msg) {
switch (msg.what) {
case BROADCAST_TIMEOUT_MSG: {
synchronized (mService) {
// 调用broadcastTimeoutLocked()方法
broadcastTimeoutLocked(true);
}
}
break;
}
}
final void broadcastTimeoutLocked(boolean fromMsg) {
...
// 如果超时，调用AMS.mAnrHelper.appNotResponding
if (!debugging && anrMessage != null) {
mService.mAnrHelper.appNotResponding(app, anrMessage);
}
}
最后也是调用AMS.mAnrHelper.appNotResponding()方法
3. ContentProvider Timeout
装弹
ContentProvider的注册在启动进程的时候就开始执行，在注册的过程中会向AMS绑定Application，如果有ContentProvider就装弹，方法在AMS.attachApplicationLocked()方法中：
// AMS
private boolean attachApplicationLocked(@NonNull IApplicationThread thread,
int pid, int callingUid, long startSeq) {
//...
boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
List providers = normalMode ? generateApplicationProvidersLocked(app) : null;
if (providers != null && checkAppInLaunchingProvidersLocked(app)) {
// 装弹
Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg,
ContentResolver.CONTENT_PROVIDER_PUBLISH_TIMEOUT_MILLIS);
}
}
public static final int CONTENT_PROVIDER_PUBLISH_TIMEOUT_MILLIS = 10 * 1000;
在绑定Application时，会判断是否有ContentProvider时会装炸弹进行一个CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG消息的延迟发送。
拆弹
在AT.installContentProviders()安装完后会调用AMS.publishContentProviders()方法进行拆弹。
public final void publishContentProviders(IApplicationThread caller,
List providers) {
...
// 拆弹，移除CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG消息
mHandler.removeMessages(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG, r)
}
引爆弹
如果消息没被移除则引爆炸弹,CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG的handler在AMS.MainHandler中，
public void handleMessage(Message msg) {
switch (msg.what) {
case CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG: {
ProcessRecord app = (ProcessRecord) msg.obj;
synchronized (ActivityManagerService.this) {
processContentProviderPublishTimedOutLocked(app);
}
}
break;
}
}
private final void processContentProviderPublishTimedOutLocked(ProcessRecord app) {
//移除死亡的provider
cleanupAppInLaunchingProvidersLocked(app, true);
//移除mProcessNames中的相应对象
mProcessList.removeProcessLocked(app, false, true,
ApplicationExitInfo.REASON_INITIALIZATION_FAILURE,
ApplicationExitInfo.SUBREASON_UNKNOWN,
"timeout publishing content providers");
}
4. InputDispatching Timeout
InputReader 不断的从EventHub中监听是否有Input事件，InputReader把事件分发给InputDispatcher。
InputDispatcher调用dispatchOnce()方法开始把事件分发给对应的View,就从InputDispatcher的分发开始监控ANR，InputDispatcher的ANR区间是查找窗口findFocusedWindowTargetsLocked()方法到resetANRTimeoutsLocked()重置方法。
void InputDispatcher::dispatchOnce() {
...
// 调用dispatchOnceInnerLocked进行分析
dispatchOnceInnerLocked(&nextWakeupTime);
}
void InputDispatcher::dispatchOnceInnerLocked(nsecs_t*nextWakeupTime) {
nsecs_t currentTime = now();
// ...
// 重置标记
resetANRTimeoutsLocked();
switch (mPendingEvent -> type) {
case EventEntry::TYPE_KEY: {
...
// key类型
done = dispatchKeyLocked(currentTime, typedEntry, & dropReason, nextWakeupTime);
break;
}
case EventEntry::TYPE_MOTION: {
...
done = dispatchMotionLocked(currentTime, typedEntry,
& dropReason, nextWakeupTime);
break;
}
default:
ALOG_ASSERT(false);
break;
}
}
void InputDispatcher::resetANRTimeoutsLocked() {
// 将mInputTargetWaitCause设置为INPUT_TARGET_WAIT_CAUSE_NONE
mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_NONE;
mInputTargetWaitApplicationToken.clear();
}
在分发之前会调用resetANRTimeoutsLocked()方法，重置mInputTargetWaitCause标记为：INPUT_TARGET_WAIT_CAUSE_NONE。接着根据下发的类型，寻找对应的窗口，比如KEY类型，则调用dispatchKeyLocked()方法。
bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, KeyEntry*entry,
DropReason*dropReason, nsecs_t*nextWakeupTime) {
// 寻找目标窗口
int32_t injectionResult = findFocusedWindowTargetsLocked(currentTime,
entry, inputTargets, nextWakeupTime);
// 给目标窗口分发事件
dispatchEventLocked(currentTime, entry, inputTargets);
return true;
}
int32_t InputDispatcher::findFocusedWindowTargetsLocked(nsecs_t currentTime,
const EventEntry*entry, std::vector&inputTargets, nsecs_t*nextWakeupTime) {
...
// 检查窗口不能input的原因
reason = checkWindowReadyForMoreInputLocked(currentTime,
focusedWindowHandle, entry, "focused");
if (!reason.empty()) {
// 调用handleTargetsNotReadyLocked()方法
injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
focusedApplicationHandle, focusedWindowHandle, nextWakeupTime, reason.c_str());
goto Unresponsive;
}
...
return injectionResult;
}
int32_t InputDispatcher::handleTargetsNotReadyLocked(nsecs_t currentTime,const EventEntry*entry,const sp&applicationHandle,const sp&windowHandle,
nsecs_t*nextWakeupTime, const char*reason) {
// 在resetANRTimeoutsLocked方法中，mInputTargetWaitCause为INPUT_TARGET_WAIT_CAUSE_NONE
if (mInputTargetWaitCause != INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY) {
// DEFAULT_INPUT_DISPATCHING_TIMEOUT为5s
nsecs_t timeout;
if (windowHandle != nullptr) {
timeout = windowHandle -> getDispatchingTimeout(DEFAULT_INPUT_DISPATCHING_TIMEOUT);
} else if (applicationHandle != nullptr) {
timeout = applicationHandle -> getDispatchingTimeout(
DEFAULT_INPUT_DISPATCHING_TIMEOUT);
} else {
timeout = DEFAULT_INPUT_DISPATCHING_TIMEOUT;
}
// 要等到下次调用resetANRTimeoutsLocked时才能进
mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY;
// 当前时间加上5s
mInputTargetWaitTimeoutTime = currentTime + timeout;
mInputTargetWaitTimeoutExpired = false;
mInputTargetWaitApplicationToken.clear();
}
if (mInputTargetWaitTimeoutExpired) {
return INPUT_EVENT_INJECTION_TIMED_OUT;
}
if (currentTime >= mInputTargetWaitTimeoutTime) {
// 当前时间超过设定的5s，后执行onANRLocked()的ANR方法
onANRLocked(currentTime, applicationHandle, windowHandle,
entry -> eventTime, mInputTargetWaitStartTime, reason);
return INPUT_EVENT_INJECTION_PENDING;
} else {
// Force poll loop to wake up when timeout is due.
if (mInputTargetWaitTimeoutTime < *nextWakeupTime){
*nextWakeupTime = mInputTargetWaitTimeoutTime;
}
return INPUT_EVENT_INJECTION_PENDING;
}
}
在分发一次事件时，会调用resetANRTimeoutsLocked将标记为INPUT_TARGET_WAIT_CAUSE_NONE,所以第一次事件会设置一个5s后的超时时间，并把标记设置为INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY，如果下次事件来临时当前的时间超过上次设置的5s时间就会调用onANRLocked()方法产生ANR。
void InputDispatcher::onANRLocked(
nsecs_t currentTime, const sp&applicationHandle,
const sp&windowHandle,
nsecs_t eventTime, nsecs_t waitStartTime, const char*reason) {
float dispatchLatency = (currentTime - eventTime) * 0.000001f;
float waitDuration = (currentTime - waitStartTime) * 0.000001f;
// 收集ANR现场信息
time_t t = time(nullptr);
struct tm tm;
localtime_r( & t, &tm);
char timestr[ 64];
strftime(timestr, sizeof(timestr), "%F %T", & tm);
mLastANRState.clear();
mLastANRState += INDENT "ANR:\n";
mLastANRState += StringPrintf(INDENT2"Time: %s\n", timestr);
mLastANRState += StringPrintf(INDENT2"Window: %s\n",
getApplicationWindowLabel(applicationHandle, windowHandle).c_str());
mLastANRState += StringPrintf(INDENT2"DispatchLatency: %0.1fms\n", dispatchLatency);
mLastANRState += StringPrintf(INDENT2"WaitDuration: %0.1fms\n", waitDuration);
mLastANRState += StringPrintf(INDENT2"Reason: %s\n", reason);
//dump信息
dumpDispatchStateLocked(mLastANRState);
//将ANR命令加入commandQueue
CommandEntry * commandEntry = postCommandLocked(
& InputDispatcher::doNotifyANRLockedInterruptible);
commandEntry -> inputApplicationHandle = applicationHandle;
commandEntry -> inputChannel = windowHandle != nullptr ?
getInputChannelLocked(windowHandle -> getToken()) : nullptr;
commandEntry -> reason = reason;
}
在下次执行InputDispatcher.dispatchOnce时会先执行commandQueue的队列命令，这里把InputDispatcher::doNotifyANRLockedInterruptible放入到了队列。
void InputDispatcher::doNotifyANRLockedInterruptible(CommandEntry*commandEntry) {
mLock.unlock();
//mPolicy是指NativeInputManager
nsecs_t newTimeout = mPolicy -> notifyANR(
commandEntry -> inputApplicationHandle,
commandEntry -> inputChannel ? commandEntry -> inputChannel -> getToken() : nullptr,
commandEntry -> reason);
mLock.lock();
resumeAfterTargetsNotReadyTimeoutLocked(newTimeout,
commandEntry -> inputChannel);
}
mPolicy -> notifyANR通过JNI最终调用到InputManagerService.notifyANR()方法：
// InputManagerService
private long notifyANR(InputApplicationHandle inputApplicationHandle, IBinder token,
String reason) {
return mWindowManagerCallbacks.notifyANR(inputApplicationHandle,
token, reason);
}
这里的mWindowManagerCallbacks是InputManagerCallback对象
//InputManagerCallback
public long notifyANR(InputApplicationHandle inputApplicationHandle, IBinder token,
String reason) {
final long startTime = SystemClock.uptimeMillis();
try {
return notifyANRInner(inputApplicationHandle, token, reason);
} finally {
}
}
private long notifyANRInner(InputApplicationHandle inputApplicationHandle, IBinder token,
String reason) {
...
// 调用AMS的inputDispatchingTimedOut()方法
long timeout = mService.mAmInternal.inputDispatchingTimedOut(windowPid, aboveSystem,
reason);
return 0; // abort dispatching
}
最终调用到AMS.inputDispatchingTimedOut()方法
// AMS
long inputDispatchingTimedOut(int pid, final boolean aboveSystem, String reason) {
if (checkCallingPermission(FILTER_EVENTS) != PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Requires permission " + FILTER_EVENTS);
}
ProcessRecord proc;
long timeout;
synchronized (this) {
synchronized (mPidsSelfLocked) {
proc = mPidsSelfLocked.get(pid);
}
timeout = proc != null ? proc.getInputDispatchingTimeout() : KEY_DISPATCHING_TIMEOUT_MS;
}
// 调用inputDispatchingTimedOut
if (inputDispatchingTimedOut(proc, null, null, null, null, aboveSystem, reason)) {
return -1;
}
return timeout;
}
boolean inputDispatchingTimedOut(ProcessRecord proc, String activityShortComponentName,
ApplicationInfo aInfo, String parentShortComponentName,
WindowProcessController parentProcess, boolean aboveSystem, String reason) {
// 调用appNotResponding方法
mAnrHelper.appNotResponding(proc, activityShortComponentName, aInfo,
parentShortComponentName, parentProcess, aboveSystem, annotation);
return true;
}
还是执行appNotResponding()方法。