PowerManagerService流程分析(电源管理)

原文地址：http://www.cnblogs.com/joker8/p/7087321.html

一、PowerManagerService简介

　　PowerManagerService主要服务Android系统电源管理工作，这样讲比较笼统，就具体细节上大致可以认为PowerManagerService集中处理用户活动（如点击屏幕，按电源键等）、电量变化、用户设置（如在Setting中设置省电模式，飞行模式）、插拔充电器（无线冲，有线冲）等。当发生以上事件时，PowerManagerService都要进行各种状态的更新，以下把PMS作为PowerManagerService的简称

二、PowerManagerService启动流程

2.1、PMS启动

        // Power manager needs to be started early because other services need it.        // Native daemons may be watching for it to be registered so it must be ready        // to handle incoming binder calls immediately (including being able to verify        // the permissions for those calls).        mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);    .    .    .        try {            // TODO: use boot phase            mPowerManagerService.systemReady(mActivityManagerService.getAppOpsService());        } catch (Throwable e) {            reportWtf("making Power Manager Service ready", e);        }

 

2.2、SystemServiceManager.startService()

 

 1     public <T extends SystemService> T startService(Class<T> serviceClass) { 2         final String name = serviceClass.getName(); 3         Slog.i(TAG, "Starting " + name); 4  5         // Create the service. 6         if (!SystemService.class.isAssignableFrom(serviceClass)) { 7             throw new RuntimeException("Failed to create " + name 8                     + ": service must extend " + SystemService.class.getName()); 9         }10         final T service;11         try {12             Constructor<T> constructor = serviceClass.getConstructor(Context.class);13             service = constructor.newInstance(mContext);14         } catch (InstantiationException ex) {15             throw new RuntimeException("Failed to create service " + name16                     + ": service could not be instantiated", ex);17         } catch (IllegalAccessException ex) {18             throw new RuntimeException("Failed to create service " + name19                     + ": service must have a public constructor with a Context argument", ex);20         } catch (NoSuchMethodException ex) {21             throw new RuntimeException("Failed to create service " + name22                     + ": service must have a public constructor with a Context argument", ex);23         } catch (InvocationTargetException ex) {24             throw new RuntimeException("Failed to create service " + name25                     + ": service constructor threw an exception", ex);26         }27 28         // Register it.29         mServices.add(service);30 31         // Start it.32         try {33             service.onStart();34         } catch (RuntimeException ex) {35             throw new RuntimeException("Failed to start service " + name36                     + ": onStart threw an exception", ex);37         }38         return service;39     }

 在Android5.0以后SystemServer启动服务的方式发生了改变，在Android4.4以前SystemServer通过new方法创建服务的对象，并把服务注册到SystemManager中；Android5.0以后SystemServer通过SystemServiceManager.startService来启动服务，主要通过反射的方式获取服务的构造方法，并创建服务对象；最后调用服务重写的onStart（）方法。

说明：Android5.0以后所有服务都实现SystemService接口，这样方法服务的统一管理。

2.3 、PMS构造方法

 

 public PowerManagerService(Context context) {        super(context);        mContext = context;        //启动一个线程，创建一个handler，handler发送的消息由该线程来处理        mHandlerThread = new ServiceThread(TAG,                Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);        mHandlerThread.start();        mHandler = new PowerManagerHandler(mHandlerThread.getLooper());        synchronized (mLock) {            //创建两个suspendBlocker对象，获取suspendblocker防止cpu进去休眠            mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");            mDisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.Display");            mDisplaySuspendBlocker.acquire();            mHoldingDisplaySuspendBlocker = true;            mHalAutoSuspendModeEnabled = false;            mHalInteractiveModeEnabled = true;            mWakefulness = WAKEFULNESS_AWAKE;            //初始化电源相关设置，这些方法通过jni调动native方法            nativeInit();            nativeSetAutoSuspend(false);            nativeSetInteractive(true);            nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);        }    }

 

2.4、OnStart()方法

 

 1     @Override 2     public void onStart() { 3         //BinderService继承IPowerManager.Stub，其实就是PowerManager的服务端 4         //这里其实就是把BinderService对象注册到ServiceManager中 5         publishBinderService(Context.POWER_SERVICE, new BinderService()); 6         publishLocalService(PowerManagerInternal.class, new LocalService()); 7  8         //加入Watchdog监听 9         Watchdog.getInstance().addMonitor(this);10         Watchdog.getInstance().addThread(mHandler);11     }

 

2.5、systemReady()方法

    public void systemReady(IAppOpsService appOps) {        synchronized (mLock) {            mSystemReady = true;            mAppOps = appOps;            mDreamManager = getLocalService(DreamManagerInternal.class);            mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);            mPolicy = getLocalService(WindowManagerPolicy.class);            mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);            PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);            //最大、最小、默认的屏幕亮超时时间            mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();            mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();            mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();            //传感器相关，传感器检查到外部事件可以通过发送消息到mHandler的消息队列中处理            SensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());            // The notifier runs on the system server's main looper so as not to interfere            // with the animations and other critical functions of the power manager.            mBatteryStats = BatteryStatsService.getService();                        //注意上面的注释，notifier运行在system server的主线程中，并且参数中传入了一个SuspendBlocker对象，应该发送通知的时候需要点亮屏幕            mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,                    mAppOps, createSuspendBlockerLocked("PowerManagerService.Broadcasts"),                    mPolicy);            //无线充电器相关，参数中传入了sensorManager，并且参数中传入了一个SuspendBlocker对象，也是为了有外部事件发生时点亮屏幕            mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,                    createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),                    mHandler);            //ContentObserver对象，用来监听电源相关设置的改变            mSettingsObserver = new SettingsObserver(mHandler);            mLightsManager = getLocalService(LightsManager.class);            mAttentionLight = mLightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);            // Initialize display power management.            mDisplayManagerInternal.initPowerManagement(                    mDisplayPowerCallbacks, mHandler, sensorManager);            // Register for broadcasts from other components of the system.            //注册一些广播监听器，如电量变化、用户切换(多用户模式，一般手机就是单用户)            IntentFilter filter = new IntentFilter();            filter.addAction(Intent.ACTION_BATTERY_CHANGED);            filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);            mContext.registerReceiver(new BatteryReceiver(), filter, null, mHandler);            filter = new IntentFilter();            filter.addAction(Intent.ACTION_DREAMING_STARTED);            filter.addAction(Intent.ACTION_DREAMING_STOPPED);            mContext.registerReceiver(new DreamReceiver(), filter, null, mHandler);            filter = new IntentFilter();            filter.addAction(Intent.ACTION_USER_SWITCHED);            mContext.registerReceiver(new UserSwitchedReceiver(), filter, null, mHandler);            filter = new IntentFilter();            filter.addAction(Intent.ACTION_DOCK_EVENT);            mContext.registerReceiver(new DockReceiver(), filter, null, mHandler);            // Register for settings changes.            //监听系统中对电源的设置，如开启省电模式、默认休眠超时时间、屏幕亮度、充电是否亮屏等等            final ContentResolver resolver = mContext.getContentResolver();            resolver.registerContentObserver(Settings.Secure.getUriFor(                    Settings.Secure.SCREENSAVER_ENABLED),                    false, mSettingsObserver, UserHandle.USER_ALL);            .......            .......            .......            // Go.            //读取资源文件中电源相关设置            readConfigurationLocked();            //更新设置中对电源的相关设置            updateSettingsLocked();            mDirty |= DIRTY_BATTERY_STATE;            //更新电源状态，这里统一处理了所有的状态更新，该方法会被频繁调用            updatePowerStateLocked();        }    }

 

2.6、updatePowerStateLocked()方法

 

 1     private void updatePowerStateLocked() { 2         if (!mSystemReady || mDirty == 0) { 3             return; 4         } 5         if (!Thread.holdsLock(mLock)) { 6             Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked"); 7         } 8  9         Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");10         try {11             // Phase 0: Basic state updates.12             updateIsPoweredLocked(mDirty);13             //设置DIRTY_STAY_ON标志位14             updateStayOnLocked(mDirty);15             updateScreenBrightnessBoostLocked(mDirty);16 17             // Phase 1: Update wakefulness.18             // Loop because the wake lock and user activity computations are influenced19             // by changes in wakefulness.20             final long now = SystemClock.uptimeMillis();21             int dirtyPhase2 = 0;22             for (;;) {23                 int dirtyPhase1 = mDirty;24                 dirtyPhase2 |= dirtyPhase1;25                 mDirty = 0;26 27                 updateWakeLockSummaryLocked(dirtyPhase1);28                 updateUserActivitySummaryLocked(now, dirtyPhase1);29                 if (!updateWakefulnessLocked(dirtyPhase1)) {30                     break;31                 }32             }33 34             // Phase 2: Update display power state.35             boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);36 37             // Phase 3: Update dream state (depends on display ready signal).38             updateDreamLocked(dirtyPhase2, displayBecameReady);39 40             // Phase 4: Send notifications, if needed.41             finishWakefulnessChangeIfNeededLocked();42 43             // Phase 5: Update suspend blocker.44             // Because we might release the last suspend blocker here, we need to make sure45             // we finished everything else first!46             updateSuspendBlockerLocked();47         } finally {48             Trace.traceEnd(Trace.TRACE_TAG_POWER);49         }50     }

 

 

 

这里还是需要把代码贴出来比较好，可以直观看到updatePowerStateLocked()有6个阶段

第0阶段：基本状态更新：

2.6.1、updateIsPoweredLocked()

 1     private void updateIsPoweredLocked(int dirty) { 2         if ((dirty & DIRTY_BATTERY_STATE) != 0) { 3             final boolean wasPowered = mIsPowered; 4             final int oldPlugType = mPlugType; 5             final boolean oldLevelLow = mBatteryLevelLow; 6             //获取充电标志位、充电器类型、电量百分比、低电量标志位 7             mIsPowered = mBatteryManagerInternal.isPowered(BatteryManager.BATTERY_PLUGGED_ANY); 8             mPlugType = mBatteryManagerInternal.getPlugType(); 9             mBatteryLevel = mBatteryManagerInternal.getBatteryLevel();10             mBatteryLevelLow = mBatteryManagerInternal.getBatteryLevelLow();11 12             if (DEBUG_SPEW) {13                 Slog.d(TAG, "updateIsPoweredLocked: wasPowered=" + wasPowered14                         + ", mIsPowered=" + mIsPowered15                         + ", oldPlugType=" + oldPlugType16                         + ", mPlugType=" + mPlugType17                         + ", mBatteryLevel=" + mBatteryLevel);18             }19             //充电器插拔时间发生、或者充电器类型更变则设置DIRTY_IS_POWERED标志位20             if (wasPowered != mIsPowered || oldPlugType != mPlugType) {21                 mDirty |= DIRTY_IS_POWERED;22 23                 // Update wireless dock detection state.24                 //判断是否进行无线充电25                 final boolean dockedOnWirelessCharger = mWirelessChargerDetector.update(26                         mIsPowered, mPlugType, mBatteryLevel);27 28                 // Treat plugging and unplugging the devices as a user activity.29                 // Users find it disconcerting when they plug or unplug the device30                 // and it shuts off right away.31                 // Some devices also wake the device when plugged or unplugged because32                 // they don't have a charging LED.33                 //上面的注释意思是说插拔充电器可以看做是用户行为，当插拔充电器时如果设备没有给出提示则用户会比较疑惑34                 //特别是在设备没有充电指示灯的时，所以一般插拔充电器时会唤醒设备35                 final long now = SystemClock.uptimeMillis();36                 if (shouldWakeUpWhenPluggedOrUnpluggedLocked(wasPowered, oldPlugType,37                         dockedOnWirelessCharger)) {38                     //如果设置了插拔充电器时候需要唤醒设备，则在这里唤醒设备39                     wakeUpNoUpdateLocked(now, "android.server.power:POWER", Process.SYSTEM_UID,40                             mContext.getOpPackageName(), Process.SYSTEM_UID);41                 }42                 userActivityNoUpdateLocked(43                         now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);44 45                 // Tell the notifier whether wireless charging has started so that46                 // it can provide feedback to the user.47                 //当无线充电器开始充电时给出提示音，在mNotifier中进行处理，播放一个ogg音频文件，我的三星设备是在/system/media/audio/ui/WirelessChargingStarted.ogg48                 //该路径下有不少ogg文件，有兴趣的可以看看都是在什么情况下播的49                 if (dockedOnWirelessCharger) {50                     mNotifier.onWirelessChargingStarted();51                 }52             }53             //如果电源插拔时间发生、或者是低电量标志位发生变化54             if (wasPowered != mIsPowered || oldLevelLow != mBatteryLevelLow) {55                 if (oldLevelLow != mBatteryLevelLow && !mBatteryLevelLow) {56                     //当设备从低电量切换为非低电量，则设置自动打盹标志为false（因为已经不是低电量了）57                     if (DEBUG_SPEW) {58                         Slog.d(TAG, "updateIsPoweredLocked: resetting low power snooze");59                     }60                     mAutoLowPowerModeSnoozing = false;61                 }62                 //发送广播ACTION_POWER_SAVE_MODE_CHANGED，该广播在系统多处进行处理，在SystemUI中进行处理，如果低电量则给出提示63                 updateLowPowerModeLocked();64             }65         }66     }

 

2.6.2、updateScreenBrightnessBoostLocked()

 1     private void updateScreenBrightnessBoostLocked(int dirty) { 2         if ((dirty & DIRTY_SCREEN_BRIGHTNESS_BOOST) != 0) { 3             if (mScreenBrightnessBoostInProgress) { 4                 final long now = SystemClock.uptimeMillis(); 5                 //删除屏幕亮度提升超时广播 6                 mHandler.removeMessages(MSG_SCREEN_BRIGHTNESS_BOOST_TIMEOUT); 7                 if (mLastScreenBrightnessBoostTime > mLastSleepTime) { 8                     final long boostTimeout = mLastScreenBrightnessBoostTime + 9                             SCREEN_BRIGHTNESS_BOOST_TIMEOUT;10                     //如果超时还没有发生，则重新发送广播（定时广播)11                     if (boostTimeout > now) {12                         Message msg = mHandler.obtainMessage(MSG_SCREEN_BRIGHTNESS_BOOST_TIMEOUT);13                         msg.setAsynchronous(true);14                         mHandler.sendMessageAtTime(msg, boostTimeout);15                         return;16                     }17                 }18                 //运行到这里有2个条件19                 //mLastScreenBrightnessBoostTime <= mLastSleepTime 说明还在睡眠中20                 //boostTimeout <= now 说明屏幕提升超时发生21                 mScreenBrightnessBoostInProgress = false;22                 mNotifier.onScreenBrightnessBoostChanged();23                 userActivityNoUpdateLocked(now,24                         PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);25             }26         }27     }

第1阶段：基本状态更新： 

2.6.3、updateWakeLockSummaryLocked()

 1  @SuppressWarnings("deprecation") 2     private void updateWakeLockSummaryLocked(int dirty) { 3         if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_WAKEFULNESS)) != 0) { 4             mWakeLockSummary = 0; 5             //mWakeLocks保存了用户创建的所有wakelock 6             final int numWakeLocks = mWakeLocks.size(); 7             for (int i = 0; i < numWakeLocks; i++) { 8                 final WakeLock wakeLock = mWakeLocks.get(i); 9                 switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {10                     case PowerManager.PARTIAL_WAKE_LOCK:11                         if (!wakeLock.mDisabled) {12                             // We only respect this if the wake lock is not disabled.13                             if(!wakeLock.mPackageName.equals("com.google.android.gms")){14                                 mWakeLockSummary |= WAKE_LOCK_CPU;15                             }16                         }17                         break;18                     case PowerManager.FULL_WAKE_LOCK:19                         mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_BUTTON_BRIGHT;20                         break;21                     case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:22                         mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT;23                         break;24                     case PowerManager.SCREEN_DIM_WAKE_LOCK:25                         mWakeLockSummary |= WAKE_LOCK_SCREEN_DIM;26                         break;27                     case PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK:28                         mWakeLockSummary |= WAKE_LOCK_PROXIMITY_SCREEN_OFF;29                         break;30                     case PowerManager.DOZE_WAKE_LOCK:31                         mWakeLockSummary |= WAKE_LOCK_DOZE;32                         break;33                     case PowerManager.DRAW_WAKE_LOCK:34                         mWakeLockSummary |= WAKE_LOCK_DRAW;35                         break;36                 }37             }38             /**39                 根据mWakefullness的状态取消某些锁的作用，意思就是说在系统处于特定状态时，有些锁是没有意义的，需要取消mWakeLockSummary中相应的标志位40             */41             // Cancel wake locks that make no sense based on the current state.42             if (mWakefulness != WAKEFULNESS_DOZING) {43                 mWakeLockSummary &= ~(WAKE_LOCK_DOZE | WAKE_LOCK_DRAW);44             }45             /**46                 注意这里，当mWakefulless状态为asleep时，WAKE_LOCK_SCREEN_BRIGHT、WAKE_LOCK_SCREEN_DIM、WAKE_LOCK_BUTTON_BRIGHT、WAKE_LOCK_PROXIMITY_SCREEN_OFF47                 这几种WakeLock的标志位都会被清空，标志位被清空作用就是类似系统释放了这些锁；仔细看唯独WAKE_LOCK_CPU标志位不变，说明PARTIAL_WAKE_LOCK在系统休眠的48                 时候是不是会自动清空的，如果系统中存在PARTIAL_WAKE_LOCK，那么除非手动释放，不然系统将没办法进入休眠49                 如果第三方的应用获取了PARTIAL_WAKE_LOCK，但是在系统休眠时又不是释放该怎么办呢?在后面调试经验中会给出答案。50             */51             if (mWakefulness == WAKEFULNESS_ASLEEP52                     || (mWakeLockSummary & WAKE_LOCK_DOZE) != 0) {53                 mWakeLockSummary &= ~(WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM54                         | WAKE_LOCK_BUTTON_BRIGHT);55                 if (mWakefulness == WAKEFULNESS_ASLEEP) {56                     mWakeLockSummary &= ~WAKE_LOCK_PROXIMITY_SCREEN_OFF;57                 }58             }59             /**60                 根据mWakefullness的状态增加某些锁的作用，就是说当系统处于特定状态时，需要某些锁来保持系统的状态，比如WAKEFULNESS_AWAKE状态肯定是要保持CPU运行的，所以61                 需要添加WAKE_LOCK_CPU标志位以确保cpu处于运行状态62             */63             // Infer implied wake locks where necessary based on the current state.64             if ((mWakeLockSummary & (WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM)) != 0) {65                 if (mWakefulness == WAKEFULNESS_AWAKE) {66                     mWakeLockSummary |= WAKE_LOCK_CPU | WAKE_LOCK_STAY_AWAKE;67                 } else if (mWakefulness == WAKEFULNESS_DREAMING) {68                     mWakeLockSummary |= WAKE_LOCK_CPU;69                 }70             }71             if ((mWakeLockSummary & WAKE_LOCK_DRAW) != 0) {72                 mWakeLockSummary |= WAKE_LOCK_CPU;73             }74 75             if (DEBUG_SPEW) {76                 Slog.d(TAG, "updateWakeLockSummaryLocked: mWakefulness="77                         + PowerManagerInternal.wakefulnessToString(mWakefulness)78                         + ", mWakeLockSummary=0x" + Integer.toHexString(mWakeLockSummary));79             }80         }81     }

 

 2.6.4、updateUserActivitySummaryLocked()

　　这个方法只是更新mUserActivitySummary的值，内容比较简单，这里不再贴代码分析了，读者自行分析吧

2.6.5、updateWakefulnessLocked()

 1     private boolean updateWakefulnessLocked(int dirty) { 2         boolean changed = false; 3         if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_BOOT_COMPLETED 4                 | DIRTY_WAKEFULNESS | DIRTY_STAY_ON | DIRTY_PROXIMITY_POSITIVE 5                 | DIRTY_DOCK_STATE)) != 0) { 6                 //注意这里会改变mWakefullness的值，但是mWakefullness的值会影响锁的有效性，因此阶段2的处理在一个for循环中 7             if (mWakefulness == WAKEFULNESS_AWAKE && isItBedTimeYetLocked()) { 8                 if (DEBUG_SPEW) { 9                     Slog.d(TAG, "updateWakefulnessLocked: Bed time...");10                 }11                 final long time = SystemClock.uptimeMillis();12                 if (shouldNapAtBedTimeLocked()) {13                     changed = napNoUpdateLocked(time, Process.SYSTEM_UID);14                 } else {15                     changed = goToSleepNoUpdateLocked(time,16                             PowerManager.GO_TO_SLEEP_REASON_TIMEOUT, 0, Process.SYSTEM_UID);17                 }18             }19         }20         return changed;21     }

第2、3、4、5代码比较简单，这里就不分析了，读者自行分析，下面我们来关注第6阶段

阶段6：

 

2.6.6、updateSuspendBlockerLocked()

 

 

 1     private void updateSuspendBlockerLocked() { 2         final boolean needWakeLockSuspendBlocker = ((mWakeLockSummary & WAKE_LOCK_CPU) != 0); 3         final boolean needDisplaySuspendBlocker = needDisplaySuspendBlockerLocked(); 4         final boolean autoSuspend = !needDisplaySuspendBlocker; 5         final boolean interactive = mDisplayPowerRequest.isBrightOrDim(); 6  7         // Disable auto-suspend if needed. 8         // FIXME We should consider just leaving auto-suspend enabled forever since 9         // we already hold the necessary wakelocks.10         if (!autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {11             setHalAutoSuspendModeLocked(false);12         }13         /**14             从上面我们知道有WAKE_LOCK_CPU标志的话就获取一个suspendblocker，这才是正真会阻止cpu待机的东西15         */16         // First acquire suspend blockers if needed.17         if (needWakeLockSuspendBlocker && !mHoldingWakeLockSuspendBlocker) {18             mWakeLockSuspendBlocker.acquire();19             mHoldingWakeLockSuspendBlocker = true;20         }21         /*22             只有屏幕亮的时候才需要display suspendblocker，当屏幕灭或者doz的时候这里不会获取suspendblocker23         */24         if (needDisplaySuspendBlocker && !mHoldingDisplaySuspendBlocker) {25             mDisplaySuspendBlocker.acquire();26             mHoldingDisplaySuspendBlocker = true;27         }28 29         /*30             设置设备为可交互模式31         */32         // Inform the power HAL about interactive mode.33         // Although we could set interactive strictly based on the wakefulness34         // as reported by isInteractive(), it is actually more desirable to track35         // the display policy state instead so that the interactive state observed36         // by the HAL more accurately tracks transitions between AWAKE and DOZING.37         // Refer to getDesiredScreenPolicyLocked() for details.38         if (mDecoupleHalInteractiveModeFromDisplayConfig) {39             // When becoming non-interactive, we want to defer sending this signal40             // until the display is actually ready so that all transitions have41             // completed.  This is probably a good sign that things have gotten42             // too tangled over here...43             if (interactive || mDisplayReady) {44                 setHalInteractiveModeLocked(interactive);45             }46         }47         /*48             注意这里needWakeLockSuspendBlocker为ture的话是不会释放mWakeLockSuspendBlocker的，所以系统会无法待机49             这样就能解释的通为什么PARTIAL_WAKE_LOCK级别的锁会导致不能待机了:50             app-->newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,flag) --->PMS设置mWakeLockSummary的WAKE_LOCK_CPU标志位51             --->PMS 因为WAKE_LOCK_CPU标志位存在mWakeLockSuspendBlocker.acquire()-->待机失败52         */53         // Then release suspend blockers if needed.54         if (!needWakeLockSuspendBlocker && mHoldingWakeLockSuspendBlocker) {55             mWakeLockSuspendBlocker.release();56             mHoldingWakeLockSuspendBlocker = false;57         }58         if (!needDisplaySuspendBlocker && mHoldingDisplaySuspendBlocker) {59             mDisplaySuspendBlocker.release();60             mHoldingDisplaySuspendBlocker = false;61         }62 63         //如果条件成立的话设置自动待机模式64         // Enable auto-suspend if needed.65         if (autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {66             setHalAutoSuspendModeLocked(true);67         }68     }

 

 

 

 

三、PowerManager用法

 

PowerManager的用法很简单，我们主要看下PowerManager创建锁这部分：

newWakeLock(int levelAndFlags, String tag)

levelAndFlags： 就是上边表格中的几个flag，可以看到不同的flag对系统的影响并不一样

 

PARTIAL_WAKE_LOCK： 保持cpu运转状态，屏幕键盘灭，按power键该锁不会被系统自动释放，所以系统无法进去待机休眠

SCREEN_DIM_WAKE_LOCK： 保持cpu处于运行状态，屏幕微亮、键盘灭，但是按power键进入待机休眠时会自动释放

SCREEN_BRIGHT_WAKE_LOCK： 保持cpu处于运行状态，屏幕亮、键盘灭，但是按power键进入待机休眠时会自动释放

FULL_WAKE_LOCK： 保持cpu处于运行状态，屏幕、键盘亮，但是按power键进入待机休眠时会自动释放

 

注意：官方的文档介绍尽量不要使用WAKE_LOCK，用FLAG_KEEP_SCREEN_ON标志位代替WAKE_LOCK，用如下方式：

1 getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

当然该方法只是针对当前Activity，如果要整个应用都保持屏幕亮，则可以写了BaseActivity并设置该标志位，其他Activity继承BaseActivity即可。

四、PowerManagerService调试

PMS中最容易出现的问题就是待机待不下去，原因就是上面说的PARTIAL_WAKE_LOCK级别的锁没有释放，按道理说这种锁的释放应该由应用自身来作的，但是一些第三方的应用（Google的一些应用就很多这种锁）没有释放的话该怎么办呢？

下面介绍两种办法：

1、强制不给设置WAKE_LOCK_CPU标志位

 1     private void updateWakeLockSummaryLocked(int dirty) { 2         if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_WAKEFULNESS)) != 0) { 3             mWakeLockSummary = 0; 4             //mWakeLocks保存了用户创建的所有wakelock 5             final int numWakeLocks = mWakeLocks.size(); 6             for (int i = 0; i < numWakeLocks; i++) { 7                 final WakeLock wakeLock = mWakeLocks.get(i); 8                 switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) { 9                     case PowerManager.PARTIAL_WAKE_LOCK:10                         if (!wakeLock.mDisabled) {11                             // We only respect this if the wake lock is not disabled.12                             //com.google.android.gms获取了PARTIAL_WAKE_LOCK，但是不给设置WAKE_LOCK_CPU标志位13                             if(!wakeLock.mPackageName.equals("com.google.android.gms")){14                                 mWakeLockSummary |= WAKE_LOCK_CPU;15                             }else{16                                 mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT;17                             }18                         }

 2、让系统自动清楚WAKE_LOCK_CPU标志

1             if (mWakefulness == WAKEFULNESS_ASLEEP2                     || (mWakeLockSummary & WAKE_LOCK_DOZE) != 0) {3                 mWakeLockSummary &= ~(WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM4                         | WAKE_LOCK_BUTTON_BRIGHT |WAKE_LOCK_CPU); //待机休眠时清楚 WAKE_LOCK_CPU5                 if (mWakefulness == WAKEFULNESS_ASLEEP) {6                     mWakeLockSummary &= ~WAKE_LOCK_PROXIMITY_SCREEN_OFF;7                 }8             }

 dumpsysy power可打印PMS中锁信息：

 

五、总结

总的来说PMS的流程并不复杂，不过需要静下心来分析代码仍然不是一件很容易的事情，本人水平有限，有不足之处请指出，后续我会持续更新修改。