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本篇文章主要介绍 Android 开发中的部分知识点,通过阅读本篇文章,您将收获以下内容:

1.前言

2.Power键灭屏

3.超时灭屏

4.PSensor灭屏

PowerManagerService 之前系列文章请参考如下

1.PowerManagerService分析(一)之PMS启动

2.PowerManagerService分析(二)之updatePowerStateLocked()核心

3.PowerManagerService分析(三)之WakeLock机制

4.Android手机亮屏流程分析前言

在之前的PMS文章分析中知道,PMS中定义了四种屏幕状态:

  • Awake状态:表示唤醒状态
  • Dream状态:表示处于屏保状态
  • Doze状态:表示处于Doze状态
  • Asleep状态:表示处于休眠状态

Power键灭屏

当power键灭屏时,会在PhoneWindowManager中处理按键事件后,调用到PMS的gotoSleep()进行灭屏处理,下面直接看看PhoneWindowManger中对Power键灭屏的处理以及和PMS的交互。

在按power后,PWS中如下:

case KeyEvent.KEYCODE_POWER: { ....... if (down) {//按下时 //处理按下事件 interceptPowerKeyDown(event, interactive); } else //抬起时 //处理抬起事件 interceptPowerKeyUp(event, interactive, canceled); } break;}

在处理Power键interceptPowerKeyUp抬起事件时,开始了灭屏流程:

 private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {  ....... if (!handled) {  // No other actions. Handle it immediately.开始灭屏流程 powerPress(eventTime, interactive, mPowerKeyPressCounter); } // Done. Reset our state. finishPowerKeyPress(); }

powerPress灭屏流程

private void powerPress(long eventTime, boolean interactive, int count) { if (mScreenOnEarly && !mScreenOnFully) { Slog.i(TAG, "Suppressed redundant power key press while " + "already in the process of turning the screen on."); return; } if (count == 2) { ...... } else if (interactive && !mBeganFromNonInteractive) { switch (mShortPressOnPowerBehavior) { //灭屏 case SHORT_PRESS_POWER_GO_TO_SLEEP: goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0); break; //灭屏,直接跳过Doze状态 case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP: goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE); break; } else { shortPressPowerGoHome(); } break; } } }}

在这里调用了goToSleep()方法,该方法如下:

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

最终,PhoneWindowManager中调用了PowerManager的goToSleep()方法来灭屏。

现在我们进入到PowerManager.goToSleep()方法:

public void goToSleep(long time, int reason, int flags) { try { mService.goToSleep(time, reason, flags); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); }}

可以看到,在PowerManger中开始向下调用到了PoweManagerService(以下简称PMS)中的goToSleep()中。

我们进入PMS中,就需要详细分析其中的方法了,先来看看goToSleep()方法:

/** * @param eventTime 时间 * @param reason 原因,Power键灭屏则是PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON * @param flags 目前只有两个值:0和1(GO_TO_SLEEP_FLAG_NO_DOZE) */@Override // Binder callpublic void goToSleep(long eventTime, int reason, int flags) { if (eventTime > SystemClock.uptimeMillis()) { throw new IllegalArgumentException("event time must not be in the future"); } //检查权限 mContext.enforceCallingOrSelfPermission( android.Manifest.permission.DEVICE_POWER, null); final int uid = Binder.getCallingUid(); final long ident = Binder.clearCallingIdentity(); try { //调用gotToSleepInternal goToSleepInternal(eventTime, reason, flags, uid); } finally { Binder.restoreCallingIdentity(ident); }}

这个方法的参数和PowerManager,PhoneWindowManager中的同名方法对应,需要注意的是第二个参数和第三个参数;

第二个参数:表示灭屏原因,在PowerManager中定义了一些常量值来表示;

第三个参数:是一个标识,用来表示是否直接进入灭屏,一般的灭屏流程,都会先进入Doze状态,然后才会进入Sleep状态,如果将flag设置为1,则将会直接进入Sleep状态,这部分会在下文中逐渐分析到。

在goToSleep()方法中,检查权限之后,开始调用了goToSleepInternal()方法,该方法如下:

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

这个方法逻辑很简单,首先是调用了goToSleepNoUpdateLocked()方法,并根据该方法返回值来决定是否调用updatePowerStateLocked()方法。

一般来说,goToSleepNoUpdateLocked()都会返回true,现在看看该方法:

@SuppressWarnings("deprecation")private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) { if (eventTime < mLastWakeTime || mWakefulness == WAKEFULNESS_ASLEEP || mWakefulness == WAKEFULNESS_DOZING || !mBootCompleted || !mSystemReady) { return false; } try { switch (reason) { case PowerManager.GO_TO_SLEEP_REASON_DEVICE_ADMIN: Slog.i(TAG, "Going to sleep due to device administration policy " + "(uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_TIMEOUT: Slog.i(TAG, "Going to sleep due to screen timeout (uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_LID_SWITCH: Slog.i(TAG, "Going to sleep due to lid switch (uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON: Slog.i(TAG, "Going to sleep due to power button (uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_SLEEP_BUTTON: Slog.i(TAG, "Going to sleep due to sleep button (uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_HDMI: Slog.i(TAG, "Going to sleep due to HDMI standby (uid " + uid +")..."); break; case PowerManager.GO_TO_SLEEP_REASON_ACCESSIBILITY: Slog.i(TAG, "Going to sleep by an accessibility service request (uid " + uid +")..."); break; default: Slog.i(TAG, "Going to sleep by application request (uid " + uid +")..."); reason = PowerManager.GO_TO_SLEEP_REASON_APPLICATION; break; } //标记最后一次灭屏时间 mLastSleepTime = eventTime; //用于判定是否进入屏保 mSandmanSummoned = true; //设置wakefulness值为WAKEFULNESS_DOZING,因此先进Doze状态 setWakefulnessLocked(WAKEFULNESS_DOZING, reason); // Report the number of wake locks that will be cleared by going to sleep. //灭屏时,将清除以下三种使得屏幕保持亮屏的wakelock锁,numWakeLocksCleared统计下个数 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; } } // Skip dozing if requested. //如果带有PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE的flag,则直接进入Sleep状态,不再进入Doze状态 if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) { //该方法才会真正地进入睡眠 reallyGoToSleepNoUpdateLocked(eventTime, uid); } } finally { Trace.traceEnd(Trace.TRACE_TAG_POWER); } return true;}

在这个方法中:

首先,是判断调用该方法的原因并打印log,该log在日常分析问题时非常有用;

然后,通过setWakefulnessLocked()将当前wakefulness设置为Doze状态;

最后,通过flag判断,如果flag为1,则调用reallyGoToSleepNoUpdateLocked()方法直接进入Sleep状态。

因此,系统其他模块在调用PM.goToSleep()灭屏时,在除指定flag为PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE的情况外,都会首先进入Doze,再由Doze进入Sleep。

setWakefulnessLocked()方法用来设置wakefulness值,同时将会调用Notifier中wakefulness相关的逻辑,这部分在之前的流程分析中也分析过,这里再来看下:

@VisibleForTestingvoid setWakefulnessLocked(int wakefulness, int reason) { if (mWakefulness != wakefulness) { //设置mWakefulness mWakefulness = wakefulness; mWakefulnessChanging = true; mDirty |= DIRTY_WAKEFULNESS; if (mNotifier != null) { //调用Notifier中的方法,做wakefulness改变开始时的工作 mNotifier.onWakefulnessChangeStarted(wakefulness, reason); } }}

我们跟着执行流程来进行分析,Notifier是PMS模块中用于进行“通知”的一个组件类,比如发送亮灭屏广播就是它来负责,具体详细的分析请点击这里 查看。这里针对于灭屏场景,再来看下其中的逻辑:

public void onWakefulnessChangeStarted(final int wakefulness, int reason) { //由于wakefulness为Doze,故interactive为false final boolean interactive = PowerManagerInternal.isInteractive(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(); } // Handle early behaviors. mInteractive = interactive; mInteractiveChangeReason = reason; mInteractiveChanging = true; //处理早期工作 handleEarlyInteractiveChange(); }}

在这个方法中,首先根据wakefulness值判断了系统当前的交互状态,如果是处于Awake状态和Dream状态,则表示可交互;如果处于Doze和Asleep状态,则表示不可交互;

由于在setWakefulnessLocked()中已经设置了wakefulness为DOZE状态,因此此时处于不可交互状态,接下来开始执行handleEarlyInteractiveChange()方法:

private void handleEarlyInteractiveChange() { synchronized (mLock) { //此时为false if (mInteractive) { // Waking up... mHandler.post(new Runnable() { @Override public void run() { // Note a SCREEN tron event is logged in PowerManagerService. mPolicy.startedWakingUp(); } }); // Send interactive broadcast. mPendingInteractiveState = INTERACTIVE_STATE_AWAKE; mPendingWakeUpBroadcast = true; updatePendingBroadcastLocked(); } else { final int why = translateOffReason(mInteractiveChangeReason); mHandler.post(new Runnable() { @Override public void run() { //通过PhoneWindowManager设置锁屏 mPolicy.startedGoingToSleep(why); } }); } }}

在这个方法中,将调用mPolicy.startedGoingToSleep(why)进行锁屏流程(Keyguard的绘制)。

回到PMS中,在处理完setWakefulnessLocked()方法后,由于没有PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE,所以不会立即执行reallyGoToSleepNoUpdateLocked()方法,此时goToSleepNoUpdateLocked()方法完毕并返回true。

之后开始执行updatePowerStateLocked()方法了,这个方法对于熟悉PMS模块的人来说再熟悉不过了,它是整个PMS的核心,详细的分析请点击这里 , 在这里我们只看其灭屏时的一些处理。

在updatePowerStateLocked()方法中,和灭屏直接相关的有如下部分:

// 更新屏幕状态

boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);

//更新屏保信息

updateDreamLocked(dirtyPhase2, displayBecameReady);

// 收尾工作

finishWakefulnessChangeIfNeededLocked();

//释放锁

updateSuspendBlockerLocked();

  • updateDisplayPowerStateLocked()将会向DisplayPowerController请求新的屏幕状态,完成屏幕的更新;
  • updateDreamLocked()方法用来更新屏保信息,除此之外还有一个任务
  • 调用reallyGoToSleep()方法进入休眠,即由DOZE状态进入Sleep状态。
  • finishWakefulnessChangeIfNeededLocked()方法用来做最后的收尾工作,当然,在这里会调用到Notifier中进行收尾。
  • updateSuspendBlockerLocked()方法将用来更新SuspendBlocker锁,会根据当前的WakeLock类型以及屏幕状态来决定是否需要申请SuspendBlocker锁。

在updateDreamLocked()中更新屏保状态时,如果此时处于Doze状态且没有进行屏保,则将调用reallyGoToSleepNoUpdateLocked()方法,将wakefulness值设置为了Sleep,部分代码如下:

else if (wakefulness == WAKEFULNESS_DOZING) { if (isDreaming) { return; // continue dozing } // Doze has ended or will be stopped. Update the power state. reallyGoToSleepNoUpdateLocked(SystemClock.uptimeMillis(), Process.SYSTEM_UID); updatePowerStateLocked(); }

再来看看该方法:

private boolean reallyGoToSleepNoUpdateLocked(long eventTime, int uid) { if (eventTime < mLastWakeTime || mWakefulness == WAKEFULNESS_ASLEEP || !mBootCompleted || !mSystemReady) { return false; } try { //设置为ASLEEP状态 setWakefulnessLocked(WAKEFULNESS_ASLEEP,  PowerManager.GO_TO_SLEEP_REASON_TIMEOUT); } finally { Trace.traceEnd(Trace.TRACE_TAG_POWER); } return true;}

以上就是整个Power键灭屏PMS部分的流程,其时序图如下:

0bb32a515506f43da2575a9205ceb69a.png

超时灭屏

经过上面的分析,我们知道了Power键灭屏由PhoneWindowManager发起了goToSleep,现在来看看超时灭屏是如何实现的。

超时灭屏主要有两个影响因素:休眠时间和用户活动。休眠时间在Settings中进行设置,用户活动是指当手机处于亮屏状态,都会调用userActivityNoUpdateLocked()方法去更新用户活动时间。接下来我们就从userActivityNoUpdateLocked()方法开始分析其超时灭屏的流程。

首先来看该方法:

 private boolean userActivityNoUpdateLocked(long eventTime, int event, int flags, int uid) { if (eventTime < mLastSleepTime || eventTime < mLastWakeTime || !mBootCompleted || !mSystemReady) { return false; } mNotifier.onUserActivity(event, uid);  if (mUserInactiveOverrideFromWindowManager) { mUserInactiveOverrideFromWindowManager = false; mOverriddenTimeout = -1; } //如果wakefulness为Asleep或Doze,不再计算超时时间,直接返回 if (mWakefulness == WAKEFULNESS_ASLEEP || mWakefulness == WAKEFULNESS_DOZING || (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) { return false; } //如果带有该flag,则会小亮一会儿再灭屏 if ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS) != 0) { if (eventTime > mLastUserActivityTimeNoChangeLights && eventTime > mLastUserActivityTime) { //将当前时间赋值给mLastUserActivityTimeNoChangeLights mLastUserActivityTimeNoChangeLights = eventTime; mDirty |= DIRTY_USER_ACTIVITY; if (event == PowerManager.USER_ACTIVITY_EVENT_BUTTON) { mDirty |= DIRTY_QUIESCENT; } return true; } } else { if (eventTime > mLastUserActivityTime) { //将当前时间赋值给mLastUserActivityTime mLastUserActivityTime = eventTime; mDirty |= DIRTY_USER_ACTIVITY; if (event == PowerManager.USER_ACTIVITY_EVENT_BUTTON) { mDirty |= DIRTY_QUIESCENT; } return true; } } } finally { Trace.traceEnd(Trace.TRACE_TAG_POWER); } return false; }

在这个方法中,如果传入的参数flag为PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS,则将事件时间赋值给mLastUserActivityTimeNoChangeLights,否则将事件时间赋值给mLastUserActivityTime。这个flag标志用于延长亮屏或Dim的时长一小会儿。

当这个方法执行之后,就得到了mLastUserActivityTime或者mLastUserActivityTimeNoChangeLights的值,然后经过一些调用后,又会进入updatePowerStateLocked()方法中。在这个方法中,和超市灭屏直接相关的就是for循环部分:

 for (;;) { int dirtyPhase1 = mDirty; dirtyPhase2 |= dirtyPhase1; mDirty = 0; updateWakeLockSummaryLocked(dirtyPhase1); updateUserActivitySummaryLocked(now, dirtyPhase1); if (!updateWakefulnessLocked(dirtyPhase1)) { break; } }

其中updateWakeLockSummaryLocked()用来统计WakeLock,这里就不分析该方法了,详细的分析请点击这里,现在从updateUserActivitySummaryLocked()方法开始分析,该方法如下:

 private void updateUserActivitySummaryLocked(long now, int dirty) { // Update the status of the user activity timeout timer. if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS | DIRTY_SETTINGS)) != 0) { mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT); long nextTimeout = 0; if (mWakefulness == WAKEFULNESS_AWAKE || mWakefulness == WAKEFULNESS_DREAMING || mWakefulness == WAKEFULNESS_DOZING) { //获取睡眠时长,为Settings.Secure.SLEEP_TIMEOUT的值和最小休眠时间的最大值,Settings.Secure.SLEEP_TIMEOUT一般为-1, //表示禁用,因此该值默认为-1 final int sleepTimeout = getSleepTimeoutLocked(); //获取休眠时长,在Settings中设置的值 final int screenOffTimeout = getScreenOffTimeoutLocked(sleepTimeout); //获取Dim时长,由休眠时长剩Dim百分比得到 final int screenDimDuration = getScreenDimDurationLocked(screenOffTimeout); //用户活动是否由Window覆盖 final boolean userInactiveOverride = mUserInactiveOverrideFromWindowManager; //该值用来统计用户活动状态,每次进入该方法,置为0 mUserActivitySummary = 0; //上次用户活动时间>=上次唤醒时间 if (mLastUserActivityTime >= mLastWakeTime) { //下次超时时间为上次用户活动时间+休眠时间-Dim时间,到达这个时间后,将进入Dim状态 nextTimeout = mLastUserActivityTime + screenOffTimeout - screenDimDuration; //如果当前时间nextTimeout,此时有两种情况,要么进入Dim要么进入Sleep //将上次用户活动时间+灭屏时间赋值给nextTimeout,如果该值大于当前时间,则说明此时应该处于Dim状态 //因此将标记mUserActivitySummary为USER_ACTIVITY_SCREEN_DIM nextTimeout = mLastUserActivityTime + screenOffTimeout; if (now < nextTimeout) { mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM; } } } //判断和USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS标记相关,如果带有此标记,才会进入该if if (mUserActivitySummary == 0 && mLastUserActivityTimeNoChangeLights >= mLastWakeTime) { //下次超时时间=上次用户活动时间+灭屏时间 nextTimeout = mLastUserActivityTimeNoChangeLights + screenOffTimeout; //根据当前时间和nextTimeout设置mUserActivitySummary if (now < nextTimeout) { if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_BRIGHT || mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_VR) { mUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT; } else if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DIM) { mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM; } } } //不满足以上条件时,此时mUserActivitySummary为0,这种情况应该为当mUserActivitySummary经历了USER_ACTIVITY_SCREEN_BRIGHT //和USER_ACTIVITY_SCREEN_DIM之后才会执行到这里 if (mUserActivitySummary == 0) { if (sleepTimeout >= 0) { //获取上次用户活动时间的最后一次时间 final long anyUserActivity = Math.max(mLastUserActivityTime, mLastUserActivityTimeNoChangeLights); if (anyUserActivity >= mLastWakeTime) { nextTimeout = anyUserActivity + sleepTimeout; //将mUserActivitySummary值置为USER_ACTIVITY_SCREEN_DREAM,表示屏保 if (now < nextTimeout) { mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM; } } } else { //将mUserActivitySummary值置为USER_ACTIVITY_SCREEN_DREAM,表示屏保 mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM; nextTimeout = -1; } } if (mUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM && userInactiveOverride) { if ((mUserActivitySummary & (USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0) { // Device is being kept awake by recent user activity if (nextTimeout >= now && mOverriddenTimeout == -1) { // Save when the next timeout would have occurred mOverriddenTimeout = nextTimeout; } } mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM; nextTimeout = -1; } if (mUserActivitySummary != 0 && nextTimeout >= 0) { //发送一个异步Handler定时消息 Message msg = mHandler.obtainMessage(MSG_USER_ACTIVITY_TIMEOUT); msg.setAsynchronous(true); mHandler.sendMessageAtTime(msg, nextTimeout); } } else {//当wakefulness=Sleep的时候,直接将mUserActivitySummary置为0 mUserActivitySummary = 0; } } }

该方法用来更新用户活动状态,其中细节在代码中都进行了注释,该方法中来看,通过Handler多次再此进入updatePowerStateLocked()从而调用updateUserActivitySummaryLocked()方法,直到nextTime=-1和mUserActivitySummary=0时将不再发送Handler,从而完成了mUserActivitySummary的更新。根据流程来看,当设备从亮屏到休眠时间到达灭屏,mUserActivitySummary的值的变化应为:

USER_ACTIVITY_SCREEN_BRIGHT—>USER_ACTIVITY_SCREEN_DIM—>USER_ACTIVITY_SCREEN_DREAM—>0.

Handler的调用处理逻辑如下:

 @Override public void handleMessage(Message msg) { switch (msg.what) { case MSG_USER_ACTIVITY_TIMEOUT: handleUserActivityTimeout(); break; } } private void handleUserActivityTimeout() { // runs on handler thread synchronized (mLock) { mDirty |= DIRTY_USER_ACTIVITY; updatePowerStateLocked(); } }

当执行到这个方法后,现在就统计得到了mWakeLockSummary和mUserActivitySummary的值,现在我们看下一个方法——updateWakefulnessLocked(),在for循环中,会根据该方法返回值来决定是否进行循环,为何会如此设计呢?在分析完该方法后,就会有答案了,如下:

 private boolean updateWakefulnessLocked(int dirty) { boolean changed = false; if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_BOOT_COMPLETED | DIRTY_WAKEFULNESS | DIRTY_STAY_ON | DIRTY_PROXIMITY_POSITIVE | DIRTY_DOCK_STATE)) != 0) { //isItBedTimeYetLocked()判断是否需要"睡觉"了 if (mWakefulness == WAKEFULNESS_AWAKE && isItBedTimeYetLocked()) { final long time = SystemClock.uptimeMillis(); if (shouldNapAtBedTimeLocked()) {//进入屏保 changed = napNoUpdateLocked(time, Process.SYSTEM_UID); } else {//开始休眠 changed = goToSleepNoUpdateLocked(time, PowerManager.GO_TO_SLEEP_REASON_TIMEOUT, 0, Process.SYSTEM_UID); } } } return changed; }

这个方法中可以看到,首先根据isItBedTimeYetLocked()和mWakefulness来决定是否执行,然后根据shouldNapAtBedTimeLocked()决定进入屏保还是休眠。

该方法如果返回值为true,则说明此时屏幕状态发生改变(在goToSleepNoUpdateLocked()和napNoUpdateLocked()中会分别设置mWakefulness为DREAM和ASLEEP),因此将不会跳出for循环,再次进行一次循环。这就是为何会设置一个死循环的目的,同时也说明只有超时灭屏才会循环两次,其他情况下都会只执行一次for循环就退出。

回到该方法中,我们继续看看isItBedTimeYetLocked():

 private boolean isItBedTimeYetLocked() { return mBootCompleted && !isBeingKeptAwakeLocked(); } private boolean isBeingKeptAwakeLocked() { return mStayOn//是否需要保持常亮 || mProximityPositive//PSensor是否靠近 || (mWakeLockSummary & WAKE_LOCK_STAY_AWAKE) != 0//当前是否有Wakelock类型为屏幕相关的锁 || (mUserActivitySummary & (USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0//当前用户活动状态是否为Draem或者0 || mScreenBrightnessBoostInProgress;//是否处于亮度增强过程中 }

以上代码可以看出,如果有任意一个条件为true,那么就不能进入休眠或者屏保状态,因此只有全部为false时,才会返回false,从而说明需要“睡觉”了。

仔细看这个方法,这里正是mWakeLockSummary和mUserActivitySummary的作用体现之一。

在平时分析问题时,如果存在无法超时灭屏问题,就需要查看mWakeLockSummary和mUserActivitySummary的值了。前者查看是否存在亮屏锁,后者查看用户活动是否已经处于0了。

现在继续分析updateWakfulnessLocked()方法中的下一个逻辑,当进入if语句后,就开始判断是要进入屏保呢?还是要直接休眠呢?

如果shouldNapAtBedTimeLocked()返回true,则开始屏保,否则直接休眠,这里对于屏保相关就不再分析了,以后的时间中如果有机会,会单独进行分析。

当开始休眠时,直接调用了goToSleepNoUpdateLocked()方法中了,于是开始走休眠流程,之后的逻辑和Power键灭屏一样了。

整个超时灭屏的流程分析就到这里了,从以上流程中可以看到,mWakeLockSummary和mUserActivitySummayr的作用相当重要,我之前在android4.4手机上遇到过一个问题就是到达休眠时间后不会灭屏,分析后发现有一个应用申请了一个PowerManager.SCREEN_BRIGHT_WAKE_LOCK锁,该锁导致mWakeLockSummary & WAKE_LOCK_STAY_AWAKE) != 0,从而没有灭屏。

整个超时灭屏流程的时序图如下:

ebfc3c54e0c75a0232992741d575f6b7.png

PSensor灭屏

什么是PSensor灭屏呢?

Proximity Sensor,即距离传感器,当通话或微信时,如果脸部靠近屏幕,将会灭屏,这就是通过PSensor灭屏的。

为何会有PSensor灭屏呢?

为了防止脸部误触,有更好的用户体验。

在原生的Android系统中,PSensor灭屏不同于Power键灭屏和超时灭屏,前者仅仅是设置屏幕的状态和关闭背光,而后两者在设置屏幕的状态和关闭背光后,让CPU也进入了休眠状态(如果不持有PowerManger.PARTIAL_WAKE_LOCK)。

PSensor灭屏涉及到更多的是DisplayPowerController中的内容,因此,将会在之后的文章中进行分析。

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