PhoneWindowManager响应电源键

首先按下power键后调用frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java的interceptKeyBeforeQueueing方法：

    // TODO(b/117479243): handle it in InputPolicy/** {@inheritDoc} */@Overridepublic int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {......// Handle special keys.switch (keyCode) {......case KeyEvent.KEYCODE_POWER: {EventLogTags.writeInterceptPower(KeyEvent.actionToString(event.getAction()),mPowerKeyHandled ? 1 : 0, mPowerKeyPressCounter);// Any activity on the power button stops the accessibility shortcutcancelPendingAccessibilityShortcutAction();result &= ~ACTION_PASS_TO_USER;isWakeKey = false; // wake-up will be handled separatelyif (down) {interceptPowerKeyDown(event, interactive);} else {interceptPowerKeyUp(event, interactive, canceled);}break;}......}......}

调用了PhoneWindowManager的interceptPowerKeyUp方法：

    private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {final boolean handled = canceled || mPowerKeyHandled;mScreenshotChordPowerKeyTriggered = false;cancelPendingScreenshotChordAction();cancelPendingPowerKeyAction();if (!handled) {......// No other actions.  Handle it immediately.powerPress(eventTime, interactive, mPowerKeyPressCounter);}// Done.  Reset our state.finishPowerKeyPress();}

调用了PhoneWindowManager的powerPress方法：

    private void powerPress(long eventTime, boolean interactive, int count) {......if (count == 2) {powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);} else if (count == 3) {powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);} else if (interactive && !mBeganFromNonInteractive) {switch (mShortPressOnPowerBehavior) {......case SHORT_PRESS_POWER_GO_TO_SLEEP:goToSleepFromPowerButton(eventTime, 0);break;......}}}

调用了PhoneWindowManager的goToSleepFromPowerButton方法：

    /*** Sends the device to sleep as a result of a power button press.** @return True if the was device was sent to sleep, false if sleep was suppressed.*/private boolean goToSleepFromPowerButton(long eventTime, int flags) {// Before we actually go to sleep, we check the last wakeup reason.// If the device very recently woke up from a gesture (like user lifting their device)// then ignore the sleep instruction. This is because users have developed// a tendency to hit the power button immediately when they pick up their device, and we// don't want to put the device back to sleep in those cases.final PowerManager.WakeData lastWakeUp = mPowerManagerInternal.getLastWakeup();if (lastWakeUp != null && lastWakeUp.wakeReason == PowerManager.WAKE_REASON_GESTURE) {final int gestureDelayMillis = Settings.Global.getInt(mContext.getContentResolver(),Settings.Global.POWER_BUTTON_SUPPRESSION_DELAY_AFTER_GESTURE_WAKE,POWER_BUTTON_SUPPRESSION_DELAY_DEFAULT_MILLIS);final long now = SystemClock.uptimeMillis();if (mPowerButtonSuppressionDelayMillis > 0&& (now < lastWakeUp.wakeTime + mPowerButtonSuppressionDelayMillis)) {Slog.i(TAG, "Sleep from power button suppressed. Time since gesture: "+ (now - lastWakeUp.wakeTime) + "ms");return false;}}goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, flags);return true;}

调用了PhoneWindowManager的goToSleep方法：

    private void goToSleep(long eventTime, int reason, int flags) {mRequestedOrGoingToSleep = true;mPowerManager.goToSleep(eventTime, reason, flags);}

PowerMangerService处理灭屏

调用了frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java的静态内部类BinderService的goToSleep方法：

        @Override // Binder callpublic void goToSleep(long eventTime, int reason, int flags) {if (eventTime > mClock.uptimeMillis()) {throw new IllegalArgumentException("event time must not be in the future");}mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);final int uid = Binder.getCallingUid();final long ident = Binder.clearCallingIdentity();try {goToSleepInternal(eventTime, reason, flags, uid);} finally {Binder.restoreCallingIdentity(ident);}}

调用了PowerManagerService的goToSleepInternal方法：

    private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {synchronized (mLock) {if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {updatePowerStateLocked();}}}

调用了PowerManagerService的goToSleepNoUpdateLocked方法：

    /*** Puts the system in doze.** This method is called goToSleep for historical reasons but actually attempts to DOZE,* and only tucks itself in to SLEEP if requested with the flag* {@link PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE}.*/@SuppressWarnings("deprecation")private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) {if (DEBUG_SPEW) {Slog.d(TAG, "goToSleepNoUpdateLocked: eventTime=" + eventTime+ ", reason=" + reason + ", flags=" + flags + ", uid=" + uid);}if (eventTime < mLastWakeTime|| getWakefulnessLocked() == WAKEFULNESS_ASLEEP|| getWakefulnessLocked() == WAKEFULNESS_DOZING|| !mSystemReady|| !mBootCompleted) {return false;}Trace.traceBegin(Trace.TRACE_TAG_POWER, "goToSleep");try {reason = Math.min(PowerManager.GO_TO_SLEEP_REASON_MAX,Math.max(reason, PowerManager.GO_TO_SLEEP_REASON_MIN));Slog.i(TAG, "Going to sleep due to " + PowerManager.sleepReasonToString(reason)+ " (uid " + uid + ")...");mLastSleepTime = eventTime;mLastSleepReason = reason;mSandmanSummoned = true;mDozeStartInProgress = true;setWakefulnessLocked(WAKEFULNESS_DOZING, reason, eventTime);// Report the number of wake locks that will be cleared by going to sleep.int numWakeLocksCleared = 0;final int numWakeLocks = mWakeLocks.size();for (int i = 0; i < numWakeLocks; i++) {final WakeLock wakeLock = mWakeLocks.get(i);switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {case PowerManager.FULL_WAKE_LOCK:case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:case PowerManager.SCREEN_DIM_WAKE_LOCK:numWakeLocksCleared += 1;break;}}EventLogTags.writePowerSleepRequested(numWakeLocksCleared);// Skip dozing if requested.if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) {reallyGoToSleepNoUpdateLocked(eventTime, uid);}} finally {Trace.traceEnd(Trace.TRACE_TAG_POWER);}return true;}

调用了PowerManagerService的setWakefulnessLocked方法，传入了WAKEFULNESS_DOZING：

    @VisibleForTestingvoid setWakefulnessLocked(int wakefulness, int reason, long eventTime) {if (getWakefulnessLocked() != wakefulness) {// Under lock, invalidate before set ensures caches won't return stale values.mInjector.invalidateIsInteractiveCaches();mWakefulnessRaw = wakefulness;mWakefulnessChanging = true;mDirty |= DIRTY_WAKEFULNESS;// This is only valid while we are in wakefulness dozing. Set to false otherwise.mDozeStartInProgress &= (getWakefulnessLocked() == WAKEFULNESS_DOZING);if (mNotifier != null) {mNotifier.onWakefulnessChangeStarted(wakefulness, reason, eventTime);}mAttentionDetector.onWakefulnessChangeStarted(wakefulness);}}

调用了frameworks/base/services/core/java/com/android/server/power/Notifier.java的onWakefulnessChangeStarted方法：

    /*** Notifies that the device is changing wakefulness.* This function may be called even if the previous change hasn't finished in* which case it will assume that the state did not fully converge before the* next transition began and will recover accordingly.*/public void onWakefulnessChangeStarted(final int wakefulness, int reason, long eventTime) {final boolean interactive = PowerManagerInternal.isInteractive(wakefulness);if (DEBUG) {Slog.d(TAG, "onWakefulnessChangeStarted: wakefulness=" + wakefulness+ ", reason=" + reason + ", interactive=" + interactive);}// Tell the activity manager about changes in wakefulness, not just interactivity.// It needs more granularity than other components.mHandler.post(new Runnable() {@Overridepublic void run() {mActivityManagerInternal.onWakefulnessChanged(wakefulness);}});// Handle any early interactive state changes.// Finish pending incomplete ones from a previous cycle.if (mInteractive != interactive) {// Finish up late behaviors if needed.if (mInteractiveChanging) {handleLateInteractiveChange();}// Start input as soon as we start waking up or going to sleep.mInputManagerInternal.setInteractive(interactive);mInputMethodManagerInternal.setInteractive(interactive);// Notify battery stats.try {mBatteryStats.noteInteractive(interactive);} catch (RemoteException ex) { }FrameworkStatsLog.write(FrameworkStatsLog.INTERACTIVE_STATE_CHANGED,interactive ? FrameworkStatsLog.INTERACTIVE_STATE_CHANGED__STATE__ON :FrameworkStatsLog.INTERACTIVE_STATE_CHANGED__STATE__OFF);// Handle early behaviors.mInteractive = interactive;mInteractiveChangeReason = reason;mInteractiveChangeStartTime = eventTime;mInteractiveChanging = true;handleEarlyInteractiveChange();}}

这个方法首先通知AMS状态变为WAKEFULNESS_DOZING，然后通知InputManager为不可交互状态，最后调用了Notifier的handleEarlyInteractiveChange方法：

    /*** Handle early interactive state changes such as getting applications or the lock* screen running and ready for the user to see (such as when turning on the screen).*/private void handleEarlyInteractiveChange() {synchronized (mLock) {if (mInteractive) {// Waking up...mHandler.post(new Runnable() {@Overridepublic void run() {final int why = translateOnReason(mInteractiveChangeReason);mPolicy.startedWakingUp(why);}});// Send interactive broadcast.mPendingInteractiveState = INTERACTIVE_STATE_AWAKE;mPendingWakeUpBroadcast = true;updatePendingBroadcastLocked();} else {// Going to sleep...// Tell the policy that we started going to sleep.final int why = translateOffReason(mInteractiveChangeReason);mHandler.post(new Runnable() {@Overridepublic void run() {mPolicy.startedGoingToSleep(why);}});}}}

PhoneWindowManager执行startedGoingToSleep

调用了frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java的startedGoingToSleep方法：

    // Called on the PowerManager's Notifier thread.@Overridepublic void startedGoingToSleep(int why) {if (DEBUG_WAKEUP) {Slog.i(TAG, "Started going to sleep... (why="+ WindowManagerPolicyConstants.offReasonToString(why) + ")");}mGoingToSleep = true;mRequestedOrGoingToSleep = true;if (mKeyguardDelegate != null) {mKeyguardDelegate.onStartedGoingToSleep(why);}}

通知keyguard的onStartedGoingToSleep

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceDelegate.java的onStartedGoingToSleep方法：

    public void onStartedGoingToSleep(int why) {if (mKeyguardService != null) {mKeyguardService.onStartedGoingToSleep(why);}mKeyguardState.offReason = why;mKeyguardState.interactiveState = INTERACTIVE_STATE_GOING_TO_SLEEP;}

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceWrapper.java的onStartedGoingToSleep方法：

    @Overridepublic void onStartedGoingToSleep(int reason) {try {mService.onStartedGoingToSleep(reason);} catch (RemoteException e) {Slog.w(TAG , "Remote Exception", e);}}

通过binder调用了systemui进程中frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardService.java的成员变量mBinder的onStartedGoingToSleep方法：

        @Override // Binder interfacepublic void onStartedGoingToSleep(int reason) {checkPermission();mKeyguardViewMediator.onStartedGoingToSleep(reason);mKeyguardLifecyclesDispatcher.dispatch(KeyguardLifecyclesDispatcher.STARTED_GOING_TO_SLEEP);}

PowerManagerService更新电源状态

回到PowerManagerService的goToSleepInternal方法中，接下来调用了PowerManagerService的updatePowerStateLocked方法：

    /*** Updates the global power state based on dirty bits recorded in mDirty.** This is the main function that performs power state transitions.* We centralize them here so that we can recompute the power state completely* each time something important changes, and ensure that we do it the same* way each time.  The point is to gather all of the transition logic here.*/private void updatePowerStateLocked() {if (!mSystemReady || mDirty == 0) {return;}if (!Thread.holdsLock(mLock)) {Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");}Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");try {// Phase 0: Basic state updates.updateIsPoweredLocked(mDirty);updateStayOnLocked(mDirty);updateScreenBrightnessBoostLocked(mDirty);// Phase 1: Update wakefulness.// Loop because the wake lock and user activity computations are influenced// by changes in wakefulness.final long now = mClock.uptimeMillis();int dirtyPhase2 = 0;for (;;) {int dirtyPhase1 = mDirty;dirtyPhase2 |= dirtyPhase1;mDirty = 0;updateWakeLockSummaryLocked(dirtyPhase1);updateUserActivitySummaryLocked(now, dirtyPhase1);updateAttentiveStateLocked(now, dirtyPhase1);if (!updateWakefulnessLocked(dirtyPhase1)) {break;}}// Phase 2: Lock profiles that became inactive/not kept awake.updateProfilesLocked(now);// Phase 3: Update display power state.final boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);// Phase 4: Update dream state (depends on display ready signal).updateDreamLocked(dirtyPhase2, displayBecameReady);// Phase 5: Send notifications, if needed.finishWakefulnessChangeIfNeededLocked();// Phase 6: Update suspend blocker.// Because we might release the last suspend blocker here, we need to make sure// we finished everything else first!updateSuspendBlockerLocked();} finally {Trace.traceEnd(Trace.TRACE_TAG_POWER);}}

在Phase 3中调用了PowerManagerService的updateDisplayPowerStateLocked方法：

    /*** Updates the display power state asynchronously.* When the update is finished, mDisplayReady will be set to true.  The display* controller posts a message to tell us when the actual display power state* has been updated so we come back here to double-check and finish up.** This function recalculates the display power state each time.** @return True if the display became ready.*/private boolean updateDisplayPowerStateLocked(int dirty) {final boolean oldDisplayReady = mDisplayReady;if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS| DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED | DIRTY_BOOT_COMPLETED| DIRTY_SETTINGS | DIRTY_SCREEN_BRIGHTNESS_BOOST | DIRTY_VR_MODE_CHANGED |DIRTY_QUIESCENT)) != 0) {if ((dirty & DIRTY_QUIESCENT) != 0) {sQuiescent = false;}mDisplayPowerRequest.policy = getDesiredScreenPolicyLocked();// Determine appropriate screen brightness and auto-brightness adjustments.final boolean autoBrightness;final float screenBrightnessOverride;if (!mBootCompleted) {// Keep the brightness steady during boot. This requires the// bootloader brightness and the default brightness to be identical.autoBrightness = false;screenBrightnessOverride = mScreenBrightnessSettingDefault;} else if (isValidBrightness(mScreenBrightnessOverrideFromWindowManager)) {autoBrightness = false;screenBrightnessOverride = mScreenBrightnessOverrideFromWindowManager;} else {autoBrightness = (mScreenBrightnessModeSetting ==Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC);screenBrightnessOverride = PowerManager.BRIGHTNESS_INVALID_FLOAT;}// Update display power request.mDisplayPowerRequest.screenBrightnessOverride = screenBrightnessOverride;mDisplayPowerRequest.useAutoBrightness = autoBrightness;mDisplayPowerRequest.useProximitySensor = shouldUseProximitySensorLocked();mDisplayPowerRequest.boostScreenBrightness = shouldBoostScreenBrightness();updatePowerRequestFromBatterySaverPolicy(mDisplayPowerRequest);if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DOZE) {mDisplayPowerRequest.dozeScreenState = mDozeScreenStateOverrideFromDreamManager;if ((mWakeLockSummary & WAKE_LOCK_DRAW) != 0&& !mDrawWakeLockOverrideFromSidekick) {if (mDisplayPowerRequest.dozeScreenState == Display.STATE_DOZE_SUSPEND) {mDisplayPowerRequest.dozeScreenState = Display.STATE_DOZE;}if (mDisplayPowerRequest.dozeScreenState == Display.STATE_ON_SUSPEND) {mDisplayPowerRequest.dozeScreenState = Display.STATE_ON;}}mDisplayPowerRequest.dozeScreenBrightness =mDozeScreenBrightnessOverrideFromDreamManagerFloat;} else {mDisplayPowerRequest.dozeScreenState = Display.STATE_UNKNOWN;mDisplayPowerRequest.dozeScreenBrightness =PowerManager.BRIGHTNESS_INVALID_FLOAT;}mDisplayReady = mDisplayManagerInternal.requestPowerState(mDisplayPowerRequest,mRequestWaitForNegativeProximity);mRequestWaitForNegativeProximity = false;if (DEBUG_SPEW) {Slog.d(TAG, "updateDisplayPowerStateLocked: mDisplayReady=" + mDisplayReady+ ", policy=" + mDisplayPowerRequest.policy+ ", mWakefulness=" + getWakefulnessLocked()+ ", mWakeLockSummary=0x" + Integer.toHexString(mWakeLockSummary)+ ", mUserActivitySummary=0x" + Integer.toHexString(mUserActivitySummary)+ ", mBootCompleted=" + mBootCompleted+ ", screenBrightnessOverride=" + screenBrightnessOverride+ ", useAutoBrightness=" + autoBrightness+ ", mScreenBrightnessBoostInProgress=" + mScreenBrightnessBoostInProgress+ ", mIsVrModeEnabled= " + mIsVrModeEnabled+ ", sQuiescent=" + sQuiescent);}}return mDisplayReady && !oldDisplayReady;}

DisplayManagerService更新电源状态

通过mDisplayManagerInternal.requestPowerState调用了frameworks/base/services/core/java/com/android/server/display/DisplayManagerService.java的内部类LocalService的requestPowerState方法：

        @Overridepublic boolean requestPowerState(DisplayPowerRequest request,boolean waitForNegativeProximity) {synchronized (mSyncRoot) {return mDisplayPowerController.requestPowerState(request, waitForNegativeProximity);}}

DisplayPowerController更新电源状态

调用了frameworks/base/services/core/java/com/android/server/display/DisplayPowerController.java的requestPowerState方法：

        @Overridepublic boolean requestPowerState(DisplayPowerRequest request,boolean waitForNegativeProximity) {synchronized (mSyncRoot) {return mDisplayPowerController.requestPowerState(request, waitForNegativeProximity);}}

调用了DisplayPowerController的sendUpdatePowerStateLocked方法：

    private void sendUpdatePowerStateLocked() {if (!mPendingUpdatePowerStateLocked) {mPendingUpdatePowerStateLocked = true;Message msg = mHandler.obtainMessage(MSG_UPDATE_POWER_STATE);mHandler.sendMessage(msg);}}

这个消息在DisplayPowerController的内部类DisplayControllerHandler的handleMessage方法中处理：

        @Overridepublic void handleMessage(Message msg) {switch (msg.what) {case MSG_UPDATE_POWER_STATE:updatePowerState();break;......}}

调用了DisplayPowerController的updatePowerState方法：

    private void updatePowerState() {......animateScreenStateChange(state, performScreenOffTransition);......}

调用了DisplayPowerController的animateScreenStateChange方法：

    private void animateScreenStateChange(int target, boolean performScreenOffTransition) {......if (target == Display.STATE_ON) {......} else if (target == Display.STATE_VR) {......} else if (target == Display.STATE_DOZE) {......} else if (target == Display.STATE_DOZE_SUSPEND) {......} else if (target == Display.STATE_ON_SUSPEND) {......} else {// Want screen off.mPendingScreenOff = true;if (!mColorFadeEnabled) {mPowerState.setColorFadeLevel(0.0f);}if (mPowerState.getColorFadeLevel() == 0.0f) {// Turn the screen off.// A black surface is already hiding the contents of the screen.setScreenState(Display.STATE_OFF);mPendingScreenOff = false;mPowerState.dismissColorFadeResources();} else if (performScreenOffTransition&& mPowerState.prepareColorFade(mContext,mColorFadeFadesConfig ?ColorFade.MODE_FADE : ColorFade.MODE_COOL_DOWN)&& mPowerState.getScreenState() != Display.STATE_OFF) {// Perform the screen off animation.mColorFadeOffAnimator.start();} else {// Skip the screen off animation and add a black surface to hide the// contents of the screen.mColorFadeOffAnimator.end();}}}

这里第一次进来会调用mColorFadeOffAnimator.start开始ColorFade动画，再次进来时ColorFade动画跑完了，条件mPowerState.getColorFadeLevel() == 0.0f满足，会调用DisplayPowerController的setScreenState方法：

    private boolean setScreenState(int state) {return setScreenState(state, false /*reportOnly*/);}private boolean setScreenState(int state, boolean reportOnly) {final boolean isOff = (state == Display.STATE_OFF);if (mPowerState.getScreenState() != state) {// If we are trying to turn screen off, give policy a chance to do something before we// actually turn the screen off.if (isOff && !mScreenOffBecauseOfProximity) {if (mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_ON) {setReportedScreenState(REPORTED_TO_POLICY_SCREEN_TURNING_OFF);blockScreenOff();mWindowManagerPolicy.screenTurningOff(mPendingScreenOffUnblocker);unblockScreenOff();} else if (mPendingScreenOffUnblocker != null) {// Abort doing the state change until screen off is unblocked.return false;}}if (!reportOnly) {Trace.traceCounter(Trace.TRACE_TAG_POWER, "ScreenState", state);// TODO(b/153319140) remove when we can get this from the above trace invocationSystemProperties.set("debug.tracing.screen_state", String.valueOf(state));mPowerState.setScreenState(state);// Tell battery stats about the transition.try {mBatteryStats.noteScreenState(state);} catch (RemoteException ex) {// same process}}}// Tell the window manager policy when the screen is turned off or on unless it's due// to the proximity sensor.  We temporarily block turning the screen on until the// window manager is ready by leaving a black surface covering the screen.// This surface is essentially the final state of the color fade animation and// it is only removed once the window manager tells us that the activity has// finished drawing underneath.if (isOff && mReportedScreenStateToPolicy != REPORTED_TO_POLICY_SCREEN_OFF&& !mScreenOffBecauseOfProximity) {setReportedScreenState(REPORTED_TO_POLICY_SCREEN_OFF);unblockScreenOn();mWindowManagerPolicy.screenTurnedOff();} else if (!isOff&& mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_TURNING_OFF) {// We told policy already that screen was turning off, but now we changed our minds.// Complete the full state transition on -> turningOff -> off.unblockScreenOff();mWindowManagerPolicy.screenTurnedOff();setReportedScreenState(REPORTED_TO_POLICY_SCREEN_OFF);}......// Return true if the screen isn't blocked.return mPendingScreenOnUnblocker == null;}

PhoneWindowManager执行screenTurningOff

这个方法首先调用了frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java的screenTurningOff方法：

    @Overridepublic void screenTurningOff(ScreenOffListener screenOffListener) {mWindowManagerFuncs.screenTurningOff(screenOffListener);synchronized (mLock) {if (mKeyguardDelegate != null) {mKeyguardDelegate.onScreenTurningOff();}}}

在灭屏前截屏

这个方法首先调用了frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java的screenTurningOff方法：

    @Overridepublic void screenTurningOff(ScreenOffListener listener) {mTaskSnapshotController.screenTurningOff(listener);}

调用了frameworks/base/services/core/java/com/android/server/wm/TaskSnapshotController.java的screenTurningOff方法：

    /*** Called when screen is being turned off.*/void screenTurningOff(ScreenOffListener listener) {if (shouldDisableSnapshots()) {listener.onScreenOff();return;}// We can't take a snapshot when screen is off, so take a snapshot now!mHandler.post(() -> {try {synchronized (mService.mGlobalLock) {mTmpTasks.clear();mService.mRoot.forAllTasks(task -> {if (task.isVisible()) {mTmpTasks.add(task);}});// Allow taking snapshot of home when turning screen off to reduce the delay of// waking from secure lock to home.final boolean allowSnapshotHome =mService.mPolicy.isKeyguardSecure(mService.mCurrentUserId);snapshotTasks(mTmpTasks, allowSnapshotHome);}} finally {listener.onScreenOff();}});}

在这里截了屏，并调用listener.onScreenOff停止阻塞灭屏。

通知keyguard的onScreenTurningOff

回到PhoneWindowManager的screenTurningOff方法，后面还调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceDelegate.java的onScreenTurningOff方法：

    public void onScreenTurningOff() {if (mKeyguardService != null) {if (DEBUG) Log.v(TAG, "onScreenTurningOff()");mKeyguardService.onScreenTurningOff();}mKeyguardState.screenState = SCREEN_STATE_TURNING_OFF;}

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceWrapper.java的onScreenTurningOff方法：

    @Overridepublic void onScreenTurningOff() {try {mService.onScreenTurningOff();} catch (RemoteException e) {Slog.w(TAG , "Remote Exception", e);}}

通过binder调用了systemui进程中frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardService.java的成员变量mBinder的onScreenTurningOff方法：

        @Override // Binder interfacepublic void onScreenTurningOff() {checkPermission();mKeyguardLifecyclesDispatcher.dispatch(KeyguardLifecyclesDispatcher.SCREEN_TURNING_OFF);}

PhoneWindowManager执行screenTurnedOff

DisplayPowerController的setScreenState方法后面还会调用frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java的screenTurnedOff方法：

    // Called on the DisplayManager's DisplayPowerController thread.@Overridepublic void screenTurnedOff() {if (DEBUG_WAKEUP) Slog.i(TAG, "Screen turned off...");updateScreenOffSleepToken(true);mDefaultDisplayPolicy.screenTurnedOff();synchronized (mLock) {if (mKeyguardDelegate != null) {mKeyguardDelegate.onScreenTurnedOff();}}mDefaultDisplayRotation.updateOrientationListener();reportScreenStateToVrManager(false);}

这里通过updateScreenOffSleepToken(true)获取了灭屏的SleepToken，会对resume的Activity进行pause，详见SleepToken机制。

通知keyguard的onScreenTurnedOff

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceDelegate.java的onScreenTurnedOff方法：

    public void onScreenTurnedOff() {if (mKeyguardService != null) {if (DEBUG) Log.v(TAG, "onScreenTurnedOff()");mKeyguardService.onScreenTurnedOff();}mKeyguardState.screenState = SCREEN_STATE_OFF;}

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceWrapper.java的onScreenTurnedOff方法：

    @Overridepublic void onScreenTurnedOff() {try {mService.onScreenTurnedOff();} catch (RemoteException e) {Slog.w(TAG , "Remote Exception", e);}}

通过binder调用了systemui进程中frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardService.java的成员变量mBinder的onScreenTurnedOff方法：

        @Override // Binder interfacepublic void onScreenTurnedOff() {checkPermission();mKeyguardViewMediator.onScreenTurnedOff();mKeyguardLifecyclesDispatcher.dispatch(KeyguardLifecyclesDispatcher.SCREEN_TURNED_OFF);}

PhoneWindowManager执行finishedGoingToSleep

回到PowerManagerService的updatePowerStateLocked方法，在Phase 5调用了PowerManagerService的finishWakefulnessChangeIfNeededLocked方法：

    private void finishWakefulnessChangeIfNeededLocked() {if (mWakefulnessChanging && mDisplayReady) {if (getWakefulnessLocked() == WAKEFULNESS_DOZING&& (mWakeLockSummary & WAKE_LOCK_DOZE) == 0) {return; // wait until dream has enabled dozing} else {// Doze wakelock acquired (doze started) or device is no longer dozing.mDozeStartInProgress = false;}if (getWakefulnessLocked() == WAKEFULNESS_DOZING|| getWakefulnessLocked() == WAKEFULNESS_ASLEEP) {logSleepTimeoutRecapturedLocked();}if (getWakefulnessLocked() == WAKEFULNESS_AWAKE) {Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, TRACE_SCREEN_ON, 0);final int latencyMs = (int) (mClock.uptimeMillis() - mLastWakeTime);if (latencyMs >= SCREEN_ON_LATENCY_WARNING_MS) {Slog.w(TAG, "Screen on took " + latencyMs + " ms");}}mWakefulnessChanging = false;mNotifier.onWakefulnessChangeFinished();}}

调用了frameworks/base/services/core/java/com/android/server/power/Notifier.java的onWakefulnessChangeFinished方法：

    /*** Notifies that the device has finished changing wakefulness.*/public void onWakefulnessChangeFinished() {if (DEBUG) {Slog.d(TAG, "onWakefulnessChangeFinished");}if (mInteractiveChanging) {mInteractiveChanging = false;handleLateInteractiveChange();}}

调用了Notifier的handleLateInteractiveChange方法：

    /*** Handle late interactive state changes once they are finished so that the system can* finish pending transitions (such as turning the screen off) before causing* applications to change state visibly.*/private void handleLateInteractiveChange() {synchronized (mLock) {final int interactiveChangeLatency =(int) (SystemClock.uptimeMillis() - mInteractiveChangeStartTime);if (mInteractive) {// Finished waking up.........} else {// Finished going to sleep...// This is a good time to make transitions that we don't want the user to see,// such as bringing the key guard to focus.  There's no guarantee for this// however because the user could turn the device on again at any time.// Some things may need to be protected by other mechanisms that defer screen on.// Cancel pending user activity.if (mUserActivityPending) {mUserActivityPending = false;mHandler.removeMessages(MSG_USER_ACTIVITY);}// Tell the policy we finished going to sleep.final int why = translateOffReason(mInteractiveChangeReason);mHandler.post(new Runnable() {@Overridepublic void run() {LogMaker log = new LogMaker(MetricsEvent.SCREEN);log.setType(MetricsEvent.TYPE_CLOSE);log.setSubtype(why);log.setLatency(interactiveChangeLatency);log.addTaggedData(MetricsEvent.FIELD_SCREEN_SLEEP_REASON, mInteractiveChangeReason);MetricsLogger.action(log);EventLogTags.writePowerScreenState(0, why, 0, 0, interactiveChangeLatency);mPolicy.finishedGoingToSleep(why);}});// Send non-interactive broadcast.mPendingInteractiveState = INTERACTIVE_STATE_ASLEEP;mPendingGoToSleepBroadcast = true;updatePendingBroadcastLocked();}}}

通过mHandler.post方法切换线程后调用了frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java的finishedGoingToSleep方法：

    // Called on the PowerManager's Notifier thread.@Overridepublic void finishedGoingToSleep(int why) {EventLogTags.writeScreenToggled(0);if (DEBUG_WAKEUP) {Slog.i(TAG, "Finished going to sleep... (why="+ WindowManagerPolicyConstants.offReasonToString(why) + ")");}MetricsLogger.histogram(mContext, "screen_timeout", mLockScreenTimeout / 1000);mGoingToSleep = false;mRequestedOrGoingToSleep = false;mDefaultDisplayPolicy.setAwake(false);// We must get this work done here because the power manager will drop// the wake lock and let the system suspend once this function returns.synchronized (mLock) {updateWakeGestureListenerLp();updateLockScreenTimeout();}mDefaultDisplayRotation.updateOrientationListener();if (mKeyguardDelegate != null) {mKeyguardDelegate.onFinishedGoingToSleep(why,mCameraGestureTriggeredDuringGoingToSleep);}if (mDisplayFoldController != null) {mDisplayFoldController.finishedGoingToSleep();}mCameraGestureTriggeredDuringGoingToSleep = false;}

首先打印了event log：screen_toggled: 0

通知keyguard的onFinishedGoingToSleep

然后调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceDelegate.java的onFinishedGoingToSleep方法：

    public void onFinishedGoingToSleep(int why, boolean cameraGestureTriggered) {if (mKeyguardService != null) {mKeyguardService.onFinishedGoingToSleep(why, cameraGestureTriggered);}mKeyguardState.interactiveState = INTERACTIVE_STATE_SLEEP;}

调用了frameworks/base/services/core/java/com/android/server/policy/keyguard/KeyguardServiceWrapper.java的onFinishedGoingToSleep方法：

    @Overridepublic void onFinishedGoingToSleep(int reason, boolean cameraGestureTriggered) {try {mService.onFinishedGoingToSleep(reason, cameraGestureTriggered);} catch (RemoteException e) {Slog.w(TAG , "Remote Exception", e);}}

通过binder调用了systemui进程中frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardService.java的成员变量mBinder的onFinishedGoingToSleep方法：

        @Override // Binder interfacepublic void onFinishedGoingToSleep(int reason, boolean cameraGestureTriggered) {checkPermission();mKeyguardViewMediator.onFinishedGoingToSleep(reason, cameraGestureTriggered);mKeyguardLifecyclesDispatcher.dispatch(KeyguardLifecyclesDispatcher.FINISHED_GOING_TO_SLEEP);}

总结

1 可以和亮屏流程对比来学习。

2 PhoneWindowManager会依次调用startedGoingToSleep、screenTurningOff、screenTurnedOff、finishedGoingToSleep方法

3 灭屏时SleepToken的获取和Keyguard的出现都会导致所有Activity被stop掉。

4 灭屏前会截屏，然后在灭屏动画中，这个截屏会盖在屏幕最前面，挡住所有窗口直到屏幕全黑。

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