最近分析一个问题，在锁屏窗口中启动应用会出现卡顿5秒，比如拨打电话，启动Google日历等。
拿拨打电话来举例，启动的action为 android.intent.action.CALL，对应处理的Activity在Telecom中：
//packages/services/Telecomm/AndroidManifest.xml:
<activity android:name=".components.UserCallActivity"
android:label="@string/userCallActivityLabel"
android:theme="@style/Theme.Telecomm.Transparent"
android:permission="android.permission.CALL_PHONE"
android:excludeFromRecents="true"
android:process=":ui">
<!-- CALL action intent filters for the various ways of initiating an outgoing call. -->
<intent-filter>
<action android:name="android.intent.action.CALL" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="tel" />
</intent-filter>
</activity>
出现卡屏的UserCallActivity比较特别，没有界面，启动之后就会在onCreate里面直接finish，其他的没有出现这个问题快捷方式都是在启动的Activity直接显示。
启动Activity com.android.server.telecom/.components.UserCallActivity的时候调用AMS的方法：
com/android/server/am/ActivityStackSupervisor.java：
final boolean realStartActivityLocked(ActivityRecord r, ProcessRecord app,
boolean andResume, boolean checkConfig) throws RemoteException {
//…
if (mKeyguardController.isKeyguardLocked()) {//锁屏状态下调用
r.notifyUnknownVisibilityLaunched();
}
//…
}
接着调用ActivityRecord# notifyUnknownVisibilityLaunched方法：
com/android/server/am/ActivityRecord.java：
void notifyUnknownVisibilityLaunched() {
// No display activities never add a window, so there is no point in waiting them for
// relayout.
if (!noDisplay) {
mWindowContainerController.notifyUnknownVisibilityLaunched();
}
}
最终调用到UnknownAppVisibilityController#notifyLaunched方法，UnknownAppVisibilityController里面的成员变量mUnknownApps记录了锁屏状态下调用AppWindowToken的状态列表，它有几个状态：
UNKNOWN_STATE_WAITING_RESUME 等待执行完onResume
UNKNOWN_STATE_WAITING_RELAYOUT 等待执行完layout
UNKNOWN_STATE_WAITING_VISIBILITY_UPDATE 等待可见性的更新
目前看来这个类的目的就是控制锁屏界面下启动的Activity显示，要等待锁屏下开启的Activity完全显示以后才能显示其他的Activity，如果一直不显示也会其他被启动的Acitivity也有一个5s的超时被强制显示。
com/android/server/wm/UnknownAppVisibilityController.java
/**
* Manages the set of {@link AppWindowToken}s for which we don't know yet whether it's visible or
* not. This happens when starting an activity while the lockscreen is showing. In that case, the
* keyguard flags an app might set influence it's visibility, so we wait until this is resolved to
* start the transition to avoid flickers.（防止闪烁先显示Launcer，然后又快速地切换到显示目标Activity）
*/
class UnknownAppVisibilityController {
/**
* Notifies that {@param appWindow} has been launched behind Keyguard, and we need to wait * until it is resumed and relaid out to resolve the visibility.
* Keyguard状态下启动Activity的时候调用
*/
void notifyLaunched(@NonNull AppWindowToken appWindow) {
if (DEBUG_UNKNOWN_APP_VISIBILITY) {
Slog.d(TAG, "App launched appWindow=" + appWindow);
}
mUnknownApps.put(appWindow, UNKNOWN_STATE_WAITING_RESUME);
}
/**
* Notifies that {@param appWindow} has finished resuming. Acitivty#onResume完成调用
*/
void notifyAppResumedFinished(@NonNull AppWindowToken appWindow) {
if (mUnknownApps.containsKey(appWindow)
&& mUnknownApps.get(appWindow) == UNKNOWN_STATE_WAITING_RESUME) {
if (DEBUG_UNKNOWN_APP_VISIBILITY) {
Slog.d(TAG, "App resume finished appWindow=" + appWindow);
}
mUnknownApps.put(appWindow, UNKNOWN_STATE_WAITING_RELAYOUT);
}
}
/**
* Notifies that {@param appWindow} has relaid out.
* layout完成
*/
void notifyRelayouted(@NonNull AppWindowToken appWindow) {
if (!mUnknownApps.containsKey(appWindow)) {
return;
}
if (DEBUG_UNKNOWN_APP_VISIBILITY) {
Slog.d(TAG, "App relayouted appWindow=" + appWindow);
}
int state = mUnknownApps.get(appWindow);
if (state == UNKNOWN_STATE_WAITING_RELAYOUT) { //当layout完成并且可见，也会从集合里移除
mUnknownApps.put(appWindow, UNKNOWN_STATE_WAITING_VISIBILITY_UPDATE);
mService.notifyKeyguardFlagsChanged(this::notifyVisibilitiesUpdated);
}
}
//在Activity#onDestroy方法执行完成通知AMS的时候才会调用，mUnknownApps移除对应的appWindow
void appRemovedOrHidden(@NonNull AppWindowToken appWindow) {
if (DEBUG_UNKNOWN_APP_VISIBILITY) {
Slog.d(TAG, "App removed or hidden appWindow=" + appWindow);
}
mUnknownApps.remove(appWindow);
}
//这个方法在AppTrasition的时候后判断是否有mUnknownApps存在
boolean allResolved() {
return mUnknownApps.isEmpty();
}
｝
下面是UnknownAppVisibility的日志，可以看到UserCallActivity的AppWindowToken被放到了mUnknownApps里面，过了5s之后才执行UserCallActivity#onDestory方法，从mUnknownApps里面移除。
LOG:
06-02 09:54:44.352 D/UnknownAppVisibility( 777): App launched appWindow=AppWindowToken{99d9676 token=Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288}}}
06-02 09:54:45.263 D/UnknownAppVisibility( 777): App resume finished appWindow=AppWindowToken{99d9676 token=Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288}}}
06-02 09:54:51.455 V/ActivityManagerService_Switch( 777): ACTIVITY DESTROYED: Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288 f}} [这个地方的onDestroy不是正常finish后调用的，而是AMS的超时机制触发]
06-02 09:54:51.460 D/UnknownAppVisibility( 777): App removed or hidden appWindow=AppWindowToken{99d9676 token=Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288}}}
在启动Activity的时候，会调用continueSurfaceLayout：
com/android/server/am/ActivityStarter.java:
private int startActivity(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask, ActivityRecord[] outActivity) {
//…
try {
mService.mWindowManager.deferSurfaceLayout();
result = startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor,
startFlags, doResume, options, inTask, outActivity);
} finally {
mService.mWindowManager.continueSurfaceLayout();
}
return result;
}
最终会调用到WindowSurfacePlacer # transitionGoodToGo这个方法，判断是否准备好可以执行transition：
com/android/server/wm/WindowSurfacePlacer.java：
int handleAppTransitionReadyLocked() {
int appsCount = mService.mOpeningApps.size();
if (!transitionGoodToGo(appsCount, mTempTransitionReasons)) {
return 0;
｝
//…
if (DEBUG_APP_TRANSITIONS) Slog.v(TAG, "**** GOOD TO GO");
mService.mH.removeMessages(H.APP_TRANSITION_TIMEOUT);//如果成功，从handler移除AppTransition超时处理
//…
}
//下面是个关键的地方， UnknownAppVisibilityController里面保存了在锁屏情况下启动Activity的AppWindowToken，导致不能正常的transition
private boolean transitionGoodToGo(int appsCount, SparseIntArray outReasons) {
//...
if (!mService.mAppTransition.isTimeout()) {
//...
if (!mService.mUnknownAppVisibilityController.allResolved()) {
if (DEBUG_APP_TRANSITIONS) {
Slog.v(TAG, "unknownApps is not empty: "
+ mService.mUnknownAppVisibilityController.getDebugMessage());
}
return false;
}
//....
return false;
}
return true;
}
LOG
06-02 09:54:45.229 V/WindowSurfacePlacer( 777): unknownApps is not empty: app=AppWindowToken{99d9676 token=Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288}}} state=1
//….
06-02 09:54:45.278 V/WindowSurfacePlacer( 777): unknownApps is not empty: app=AppWindowToken{99d9676 token=Token{85511 ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCallActivity t288}}} state=2
//…
//private static final int UNKNOWN_STATE_WAITING_RESUME = 1;
//private static final int UNKNOWN_STATE_WAITING_RELAYOUT = 2;
可以看到日志UserCallActivity的state一直处于1和2的状态，阻塞了不能正常的AppTrasition
尝试在加上条件测试看是否还会出现卡屏5s的现象:
com/android/server/wm/WindowSurfacePlacer.java：
if (!mService.mUnknownAppVisibilityController.allResolved()&&
!mService.mUnknownAppVisibilityController.getDebugMessage()
.contains(“com.android.server.telecom/.components.UserCallActivity”)) {
//…
return false;
}
加上这个测试条件后就没有了卡屏5秒的情况，但是有了新问题，会出现flickers（闪烁），先显示Launcer，然后又快速地切换到显示InCallActivity。如果FUNC先解锁操作再执行拨打电话，也会出现同样的问题。这正是UnknownAppVisibilityController解决的问题。下面看UserCallActivity finish不掉的原因。
正常的情况下，在Activity#onCreate方法中直接调用finish()，在之后的onPause方法调用AMS的activityPaused，就会直接调用IApplicationThread#scheduleDestroyActivity的方法通知Activity执行onDestroy，然后执行AMS的activityDestroyed，将UnknownAppVisibilityController里面的AppWindow移除。然而锁屏的的情况有区别：
com/android/server/am/ActivityManagerService.java：
@Override
public final void activityPaused(IBinder token) {
//…
ActivityStack stack = ActivityRecord.getStackLocked(token);
if (stack != null) {
stack.activityPausedLocked(token, false);
}
}
com/android/server/am/ActivityStack.java:
final void activityPausedLocked(IBinder token, boolean timeout) {
final ActivityRecord r = isInStackLocked(token);
mHandler.removeMessages(PAUSE_TIMEOUT_MSG, r);
//…
completePauseLocked(true /* resumeNext */, null /* resumingActivity */);
//…
}
private void completePauseLocked(boolean resumeNext, ActivityRecord resuming) {
ActivityRecord prev = mPausingActivity;
if (DEBUG_PAUSE) Slog.v(TAG_PAUSE, "Complete pause: " + prev);
if (prev != null) {
final boolean wasStopping = prev.state == STOPPING;
prev.state = ActivityState.PAUSED;
if (prev.finishing) {
if (DEBUG_PAUSE) Slog.v(TAG_PAUSE, "Executing finish of activity: " + prev);
prev = finishCurrentActivityLocked(prev, FINISH_AFTER_VISIBLE, false);
} else{//...}
}
}
final ActivityRecord finishCurrentActivityLocked(ActivityRecord r, int mode, boolean oomAdj) {
// First things first: if this activity is currently visible,
// and the resumed activity is not yet visible, then hold off on
// finishing until the resumed one becomes visible.
//这里的next是Launcher, r为UserCallActivity
final ActivityRecord next = mStackSupervisor.topRunningActivityLocked();
//可以看到上面的注释就是我们的这种场景
//在锁屏的情况下会走到分支mode为FINISH_AFTER_VISIBLE，r.visible为true
//关键的是next.nowVisible为false，即Launcher现在也是不可见的
//所以就会将UserCallActivity放到 mStoppingActivities里面
if (mode == FINISH_AFTER_VISIBLE && (r.visible || r.nowVisible)
&& next != null && !next.nowVisible) {
if (!mStackSupervisor.mStoppingActivities.contains(r)) {
addToStopping(r, false /* scheduleIdle */, false /* idleDelayed */);
}
if (DEBUG_STATES) Slog.v(TAG_STATES,
"Moving to STOPPING: "+ r + " (finish requested)");
r.state = STOPPING;
return r;
}
//…
//非锁屏下走这个分支，这里就会scheduleDestroyActivity
if (mode == FINISH_IMMEDIATELY
|| (prevState == ActivityState.PAUSED
&& (mode == FINISH_AFTER_PAUSE || mStackId == PINNED_STACK_ID))
|| finishingActivityInNonFocusedStack
|| prevState == STOPPING
|| prevState == STOPPED
|| prevState == ActivityState.INITIALIZING) {
boolean activityRemoved = destroyActivityLocked(r, true, "finish-imm");
//....
return activityRemoved ? null : r;
}
}
这个时候dumpsys activity的信息如下，UserCallActivity被加到了waittingToStop列表里，没有执行scheduleDestroyActivity方法：
adb shell dumpsys activity:
Activities waiting to stop:
TaskRecord{28306a9 #433 A=com.android.server.telecom U=0 StackId=1 sz=1}
Stop #0: ActivityRecord{f676a30 u0 com.android.server.telecom/.components.UserCallActivity t433 f}
Activities waiting for another to become visible:
TaskRecord{28306a9 #433 A=com.android.server.telecom U=0 StackId=1 sz=1}
Wait #0: ActivityRecord{f676a30 u0 com.android.server.telecom/.components.UserCallActivity t433 f}
// InCallActivity已经Resume等待显示
ResumedActivity: ActivityRecord{4cd5d55 u0 com.tct.dialer/com.android.incallui.InCallActivity t432}
之后的finish操作在ActivityManagerService#activityIdle方法中处理: (每次有Activity Resume完成，就会在主线程MessageQueue的Idler中调用，也有可能会在SystemServer中闲时调用)
com/android/server/am/ActivityManagerService.java:
@Override
public final void activityIdle(IBinder token, Configuration config, boolean stopProfiling) {
synchronized (this) {
ActivityStack stack = ActivityRecord.getStackLocked(token);
if (stack != null) {
ActivityRecord r =
mStackSupervisor.activityIdleInternalLocked(token, false /* fromTimeout */,
false /* processPausingActivities */, config);
}//….
}
}
接着调用ActivityStackSupervisor# activityIdleInternalLocked
final ActivityRecord activityIdleInternalLocked(final IBinder token, boolean fromTimeout,
boolean processPausingActivities, Configuration config) {
if (DEBUG_ALL) Slog.v(TAG, "Activity idle: " + token);
// Atomically retrieve all of the other things to do.
//查找waitingToStop的Activity，如果这里能够找出来，那么在后面finish，调用Activity#onDestory
final ArrayList<ActivityRecord> stops = processStoppingActivitiesLocked(r,
true /* remove */, processPausingActivities);
NS = stops != null ? stops.size() : 0;
//…
// Stop any activities that are scheduled to do so but have been
// waiting for the next one to start.
for (int i = 0; i < NS; i++) {
r = stops.get(i);
final ActivityStack stack = r.getStack();
if (stack != null) {
if (r.finishing) {
stack.finishCurrentActivityLocked(r, ActivityStack.FINISH_IMMEDIATELY, false);
} else {
stack.stopActivityLocked(r);
}
}
}
//...
return r;
}
//查找操作waitingStop符合条件finish的
final ArrayList<ActivityRecord> processStoppingActivitiesLocked(ActivityRecord idleActivity,
boolean remove, boolean processPausingActivities) {
ArrayList<ActivityRecord> stops = null;
//这个时候没有Activity可见，nowVisible为false
final boolean nowVisible = allResumedActivitiesVisible();
for (int activityNdx = mStoppingActivities.size() - 1; activityNdx >= 0; --activityNdx) {
ActivityRecord s = mStoppingActivities.get(activityNdx);//找到UserCallActivity
//waitingVisible为true，一直等待显示
boolean waitingVisible = mActivitiesWaitingForVisibleActivity.contains(s);
if (DEBUG_STATES) Slog.v(TAG, "Stopping " + s + ": nowVisible=" + nowVisible
+ " waitingVisible=" + waitingVisible + " finishing=" + s.finishing);
if (waitingVisible && nowVisible) {//不会进入这个分支
mActivitiesWaitingForVisibleActivity.remove(s);
waitingVisible = false;//当InCallActivity show出来，置false，
if (s.finishing) {
//...
s.setVisibility(false);
}
}
if (remove) {
final ActivityStack stack = s.getStack();
final boolean shouldSleepOrShutDown = stack != null
? stack.shouldSleepOrShutDownActivities()
: mService.isSleepingOrShuttingDownLocked();
//waitingVisible为true，进入不了这个分支
if (!waitingVisible || shouldSleepOrShutDown) {
if (!processPausingActivities && s.state == PAUSING) {
//...
continue;
}
if (DEBUG_STATES) Slog.v(TAG, "Ready to stop: " + s);
if (stops == null) {
stops = new ArrayList<>();
}
stops.add(s);
mStoppingActivities.remove(activityNdx);
}
}
}
return stops;
}
由于此时的topActivity (InCallActivity)一直没有show出来，就会导致UserCallActivity一直处于waitingToStop的状态，直到InCallActivity show出来之后，才会destroy UserCallActivity。
下面是日志，验证上面的分析：
LOG
06-02 09:54:44.464 V/ActivityStackSupervisor( 777): Stopping ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.UserCal
lActivity t288}: nowVisible=false waitingVisible=false finishing=false
06-02 09:54:45.073 V/ActivityStack_States( 777): Moving to STOPPING: ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f} (finish requested)
06-02 09:54:45.283 V/ActivityStackSupervisor( 777): Stopping ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f}: nowVisible=false waitingVisible=true finishing=true
06-02 09:54:47.607 V/ActivityStackSupervisor( 777): Stopping ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f}: nowVisible=false waitingVisible=true finishing=true
06-02 09:54:51.186 V/ActivityStackSupervisor( 777): Stopping ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f}: nowVisible=true waitingVisible=false finishing=true
06-02 09:54:51.187 V/ActivityStackSupervisor( 777): Ready to stop: ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f}
06-02 09:54:51.287 V/ActivityStack_States( 777): Moving to FINISHING: ActivityRecord{5db03d9 u0 com.android.server.telecom/.components.
UserCallActivity t288 f}
由于在锁屏界面启动Activity导致触发了WMS的 UnknownAppVisibilityController防止闪烁(显示Launcher之后又快速切换到目标Activity)的机制， UserCall Activity不能及时finish，就会导致一直处于卡屏状态，直到AppTransition超时机制才强制显示InCallActivity。
UserCallActivity是Telecomm服务里面的组件，但是它又不是真正显示UI的Acivity，针对这种情况可以使用Telecom的placeCall接口可以规避掉这种情况。但是，不能保证所有启动的Acitivty都直接显示，比如原生的Google日历也会出现卡屏5秒现象，目前看来是原生Android的bug，对于这种情况，finish之后没有将不显示的窗口及时地从UnknownAppVisibilityController移除。