极力推荐AndroID 开发大总结文章：欢迎收藏
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PowerManagerService 提供AndroID系统的电源管理服务，主要功能是控制系统待机状态，屏幕显示，亮度调节，光线/距离传感器的控制等。
相关代码在以下文件中：
frameworks/base/services/java/com/androID/server/SystemServer.javaframeworks/base/core/java/androID/os/PowerManager.javaframeworks/base/services/core/java/com/androID/server/power/PowerManagerService.javaframeworks/base/services/core/jni/com_androID_server_power_PowerManagerService.cppframeworks/base/core/java/androID/os/PowerManagerInternal.javaframeworks/base/services/core/java/com/androID/server/power/NotifIEr.javadevice/qcom/common/power/power.csystem/core/libsuspend/autosuspend.charDWare/libharDWare_legacy/power/power.c
初始化流程
跟其他系统服务一样，PowerManagerService也是继承于SystemService并通过SystemServer启动。
SystemServerframeworks/base/services/java/com/androID/server/SystemServer.java
private voID startbootstrapServices() { ...... mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class); ......} PowerManagerServiceframeworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
public final class PowerManagerService extends SystemService implements Watchdog.Monitor { ......} 在SystemServer的startbootstrapServices中，通过SystemServiceManager.startService启动了PowerManagerService，下面首先来看PowerManagerService构造方法。frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
public PowerManagerService(Context context) { super(context); // mContext赋值为SystemContext mContext = context; // 创建消息处理线程并启动，创建关联消息处理线程的handler对象 mHandlerThread = new ServiceThread(TAG,Process.THREAD_PRIORITY_disPLAY,false /*allowIo*/); mHandlerThread.start(); mHandler = new PowerManagerHandler(mHandlerThread.getLooper()); qcNsrmPowExt = new QCNsrmPowerExtension(this); synchronized (mlock) { // 创建"PowerManagerService.WakeLocks"的SuspendBlocker mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks"); // 创建"PowerManagerService.display"的SuspendBlocker mdisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.display"); // 请求displaySuspendBlocker，禁止系统进入休眠 mdisplaySuspendBlocker.acquire(); mHoldingdisplaySuspendBlocker = true; mHalautoSuspendModeEnabled = false; mHalinteractiveModeEnabled = true; // 设置mWakefulness为唤醒状态 mWakefulness = WAKEFulnesS_AWAKE; // 进入到native层初始化 nativeInit(); nativeSetautoSuspend(false); nativeSetInteractive(true); nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE,0); }} PowerManagerService构造函数中首先创建了处理消息的进程及对应的handler对象以进行消息处理，然后创建SuspendBlocker对象，用于WakeLocks与display，并设置mWakefulness的初始状态为WAKEFulnesS_AWAKE，最后进入到native层初始化。下面先看一下关于mWakefulness的定义。
>>> frameworks/base/core/java/androID/os/PowerManagerInternal.java/** * 设备处于休眠状态，只能被wakeUp()唤醒． */public static final int WAKEFulnesS_ASLEEP = 0;/** * 设备处于正常工作(fully awake)状态． */public static final int WAKEFulnesS_AWAKE = 1;/** * 设备处于播放屏保状态． */public static final int WAKEFulnesS_DREAMING = 2;/** * 设备处于doze状态，只有低耗电的屏保可以运行，其他应用被挂起． */public static final int WAKEFulnesS_DOZING = 3;
继续回到PowerManagerService构造函数的native初始化中，首先来看nativeInit的实现。frameworks/base/services/core/jni/com_androID_server_power_PowerManagerService.cpp
static const JNINativeMethod gPowerManagerServiceMethods[] = { /* name,signature,funcPtr */ { "nativeInit","()V",(voID*) nativeInit },{ "nativeAcquireSuspendBlocker","(Ljava/lang/String;)V",(voID*) nativeAcquireSuspendBlocker },{ "nativeReleaseSuspendBlocker",(voID*) nativeReleaseSuspendBlocker },{ "nativeSetInteractive","(Z)V",(voID*) nativeSetInteractive },{ "nativeSetautoSuspend",(voID*) nativeSetautoSuspend },{ "nativeSendPowerHint","(II)V",(voID*) nativeSendPowerHint },{ "nativeSetFeature",(voID*) nativeSetFeature },}; PowerManagerService中的native方法定义如上，nativeInit即调用nativeInit()。frameworks/base/services/core/jni/com_androID_server_power_PowerManagerService.cpp
static voID nativeInit(jnienv* env,jobject obj) { // 创建一个全局对象，引用PMS gPowerManagerServiceObj = env->NewGlobalRef(obj); // 利用hw_get_module加载power模块 status_t err = hw_get_module(POWER_HARDWARE_MODulE_ID,(hw_module_t const**)&gPowerModule); if (!err) { gPowerModule->init(gPowerModule); } else { ALOGE("Couldn't load %s module (%s)",POWER_HARDWARE_MODulE_ID,strerror(-err)); }} nativeInit的主要任务时装载power模块，该模块由厂商实现，以高通为例，如下。device/qcom/common/power/power.c
tatic struct hw_module_methods_t power_module_methods = { .open = NulL,};struct power_module HAL_MODulE_INFO_SYM = { .common = { .tag = HARDWARE_MODulE_TAG,.module_API_version = POWER_MODulE_API_VERSION_0_2,.hal_API_version = HARDWARE_HAL_API_VERSION,.ID = POWER_HARDWARE_MODulE_ID,.name = "QCOM Power HAL",.author = "Qualcomm",.methods = &power_module_methods,},.init = power_init,.powerHint = power_hint,.setInteractive = set_interactive,}; power_module中实现了init，powerHint，setInteractive，nativeInit最终调用到HAL power模块的power_init具体实现中。接着看native初始化nativeSetautoSuspend的实现。
frameworks/base/services/core/jni/com_androID_server_power_PowerManagerService.cpp
static voID nativeSetautoSuspend(jnienv* /* env */,jclass /* clazz */,jboolean enable) { if (enable) { ALOGD_IF_SLOW(100,"Excessive delay in autosuspend_enable() while turning screen off"); autosuspend_enable(); } else { ALOGD_IF_SLOW(100,"Excessive delay in autosuspend_disable() while turning screen on"); autosuspend_disable(); }} system/core/libsuspend/autosuspend.c
int autosuspend_disable(voID){ int ret; ret = autosuspend_init(); if (ret) { return ret; } ALOGV("autosuspend_disable\n"); if (!autosuspend_enabled) { return 0; } ret = autosuspend_ops->disable(); if (ret) { return ret; } autosuspend_enabled = false; return 0;} nativeSetautoSuspend最终调用到libsuspend(参考AndroID电源管理系列之libsuspend)的autosuspend_disable禁止系统休眠。继续看native初始化nativeSetInteractive，nativeSetFeature的实现frameworks/base/services/core/jni/com_androID_server_power_PowerManagerService.cpp
static voID nativeSetInteractive(jnienv* /* env */,jboolean enable) { if (gPowerModule) { if (enable) { ALOGD_IF_SLOW(20,"Excessive delay in setInteractive(true) while turning screen on"); gPowerModule->setInteractive(gPowerModule,true); } else { ALOGD_IF_SLOW(20,"Excessive delay in setInteractive(false) while turning screen off"); gPowerModule->setInteractive(gPowerModule,false); } }}static voID nativeSetFeature(jnienv *env,jclass clazz,jint featureID,jint data) { int data_param = data; if (gPowerModule && gPowerModule->setFeature) { gPowerModule->setFeature(gPowerModule,(feature_t)featureID,data_param); }} 同nativeInit一样，最终都是调用到HAL power模块的具体实现中。以上是构造函数的分析流程，下面继续看PowerManagerService在系统启动过程中回调onStart()，onBootPhase()，systemReady()的实现。frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
public voID onStart() { publishBinderService(Context.POWER_SERVICE,new BinderService()); publishLocalService(PowerManagerInternal.class,new LocalService()); Watchdog.getInstance().addMonitor(this); Watchdog.getInstance().addThread(mHandler);}private final class BinderService extends IPowerManager.Stub ｛ ......｝private final class LocalService extends PowerManagerInternal { ......} onStart()中发布了BinderService，LocalService分别供其他进程，进程内其他服务调用，并将PowerManagerService加入到Watchdog监控中。
frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
public voID onBootPhase(int phase) { synchronized (mlock) { if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) { ...... } else if (phase == PHASE_BOOT_COMPLETED) { final long Now = SystemClock.uptimeMillis(); // 设置mBootCompleted状态 mBootCompleted = true; mDirty |= DIRTY_BOOT_COMPLETED; // 更新userActivity及PowerState，后面分析 userActivityNoUpdateLocked( Now,PowerManager.USER_ACTIVITY_EVENT_OTHER,Process.SYstem_UID); updatePowerStateLocked(); // 执行mBootCompletedRunnables中的runnable方法 if (!ArrayUtils.isEmpty(mBootCompletedRunnables)) { Slog.d(TAG,"Posting " + mBootCompletedRunnables.length + " delayed runnables"); for (Runnable r : mBootCompletedRunnables) { BackgroundThread.getHandler().post(r); } } mBootCompletedRunnables = null; } }} onBootPhase中主要设置mBootCompleted状态，更新PowerState状态，并执行mBootCompletedRunnables中的runnables方法(低电量模式会设置)。frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
public voID systemReady(IAppOpsService appOps) { synchronized (mlock) { mSystemReady = true; // 获取AppOpsService mAppOps = appOps; // 获取DreamManager mDreamManager = getLocalService(DreamManagerInternal.class); // 获取displayManagerService mdisplayManagerInternal = getLocalService(displayManagerInternal.class); mPolicy = getLocalService(WindowManagerPolicy.class); // 获取mBatteryService mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class); PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE); // 获取屏幕默认，最大，最小亮度 mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting(); mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting(); mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting(); // 获取SensorManager SensorManager sensorManager = new SystemSensorManager(mContext,mHandler.getLooper()); mBatteryStats = BatteryStatsService.getService(); // 创建NotifIEr对象，用于广播power state的变化 mNotifIEr = new NotifIEr(Looper.getMainLooper(),mContext,mBatteryStats,mAppOps,createSuspendBlockerLocked("PowerManagerService.broadcasts"),mPolicy); // 无线充电检测 mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),mHandler); // 监听设置的变化 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 settings changes. final ContentResolver resolver = mContext.getContentResolver(); resolver.registerContentObserver(Settings.Secure.getUriFor( Settings.Secure.SCREENSAVER_ENABLED),...... IVrManager vrManager = (IVrManager) getBinderService(VrManagerService.VR_MANAGER_BINDER_SERVICE); try { vrManager.registerListener(mVrStateCallbacks); } catch (remoteexception e) { Slog.e(TAG,"Failed to register VR mode state Listener: " + e); } // 读取配置 readConfigurationLocked(); updateSettingsLocked(); mDirty |= DIRTY_BATTERY_STATE; updatePowerStateLocked(); } // Register for broadcasts from other components of the system. 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(),mHandler); filter = new IntentFilter(); filter.addAction(Intent.ACTION_USER_SWITCHED); mContext.registerReceiver(new UserSwitchedReceiver(),mHandler); filter = new IntentFilter(); filter.addAction(Intent.ACTION_DOCK_EVENT); mContext.registerReceiver(new DockReceiver(),mHandler);} userActivity
userActivity是定义在PowerManager中的SystemAPI，用户向PowerManagerService报告用户活动，以更新PowerManagerService内部时间/状态值，推迟系统休眠的时间。下面首先来看userActivity的定义。
frameworks/base/core/java/androID/os/PowerManager.java
/** * User activity event type: UnspecifIEd event type. */public static final int USER_ACTIVITY_EVENT_OTHER = 0;/** * User activity event type: button or key pressed or released. */public static final int USER_ACTIVITY_EVENT_button = 1;/** * User activity event type: touch down,move or up. */public static final int USER_ACTIVITY_EVENT_touch = 2;/** * User activity event type: Accessibility taking action on behalf of user. */public static final int USER_ACTIVITY_EVENT_ACCESSIBIliTY = 3;@SystemAPIpublic voID userActivity(long when,int event,int flags) { try { mService.userActivity(when,event,flags); } catch (remoteexception e) { throw e.rethrowFromSystemServer(); }} frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
private final class BinderService extends IPowerManager.Stub { ...... public voID userActivity(long eventTime,int flags) { final long Now = SystemClock.uptimeMillis(); ...... if (eventTime > Now) { throw new IllegalArgumentException("event time must not be in the future"); } final int uID = Binder.getCallingUID(); final long IDent = Binder.clearCallingIDentity(); try { userActivityInternal(eventTime,flags,uID); } finally { Binder.restoreCallingIDentity(IDent); } } ......} PowerManager中userActivity请求调用服务端PowerManagerService BinderService的userActivity，即调用内部方法userActivityInternal。
frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
private voID userActivityInternal(long eventTime,int flags,int uID) { synchronized (mlock) { if (userActivityNoUpdateLocked(eventTime,uID)) { updatePowerStateLocked(); } }} userActivityInternal中首先调用userActivityNoUpdateLocked更新相关数据及状态(***NoUpdateLocked仅仅更新内部状态并不采取任何 *** 作)，然后调用updatePowerStateLocked更新所有PowerState，下面分析userActivityNoUpdateLocked的实现，updatePowerStateLocked是PowerManagerService的核心方法，在最后进行分析。
frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
private boolean userActivityNoUpdateLocked(long eventTime,int uID) { // 如果发生时间是上一次休眠或唤醒前，或当前没有开机完成到systemReady，不采取 *** 作直接返回 if (eventTime < mLastSleepTime || eventTime < mLastWakeTime || !mBootCompleted || !mSystemReady) { return false; } try { // 更新mLastInteractivePowerHintTime时间 if (eventTime > mLastInteractivePowerHintTime) { powerHintInternal(POWER_HINT_INteraCTION,0); mLastInteractivePowerHintTime = eventTime; } // 通过mNotifIEr通知BatteryStats UserActivity事件 mNotifIEr.onUserActivity(event,uID); if (mUserInactiveOverrIDeFromWindowManager) { mUserInactiveOverrIDeFromWindowManager = false; mOverrIDdenTimeout = -1; } // 如果系统处于休眠状态，不进行处理 if (mWakefulness == WAKEFulnesS_ASLEEP || mWakefulness == WAKEFulnesS_DOZING || (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) { return false; } // 根据flag是否在已变暗的情况下是否重启活动超时更新mLastUserActivityTimeNoChangelights或mLastUserActivityTime // 并且设置mDirty DIRTY_USER_ACTIVITY if ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_liGHTS) != 0) { if (eventTime > mLastUserActivityTimeNoChangelights && eventTime > mLastUserActivityTime) { mLastUserActivityTimeNoChangelights = eventTime; mDirty |= DIRTY_USER_ACTIVITY; return true; } } else { if (eventTime > mLastUserActivityTime) { mLastUserActivityTime = eventTime; mDirty |= DIRTY_USER_ACTIVITY; return true; } } } finally { Trace.traceEnd(Trace.TRACE_TAG_POWER); } return false;} gotoSleep
gotoSleep在PowerManager中的定义如下：frameworks/base/core/java/androID/os/PowerManager.java
public voID goToSleep(long time) { goToSleep(time,GO_TO_SLEEP_REASON_APPliCATION,0);}public voID goToSleep(long time,int reason,int flags) { try { mService.goToSleep(time,reason,flags); } catch (remoteexception e) { throw e.rethrowFromSystemServer(); }} 与userActivity一样，gotoSleep最终将调用到goToSleepInternal。frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
private final class BinderService extends IPowerManager.Stub { ...... public voID goToSleep(long eventTime,int flags) { if (eventTime > SystemClock.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,uID); } finally { Binder.restoreCallingIDentity(IDent); } } ......}private voID goToSleepInternal(long eventTime,int uID) { synchronized (mlock) { if (goToSleepNoUpdateLocked(eventTime,uID)) { updatePowerStateLocked(); } }} goToSleepInternal中将执行goToSleepNoUpdateLocked更新内部状态，同样在updatePowerStateLocked中更新PowerState的 *** 作。frameworks/base/services/core/java/com/androID/server/power/PowerManagerService.java
private boolean goToSleepNoUpdateLocked(long eventTime,int uID) { // 当不处于awake状态或未开机systemReady，不处理 if (eventTime < mLastWakeTime || mWakefulness == WAKEFulnesS_ASLEEP || mWakefulness == WAKEFulnesS_DOZING || !mBootCompleted || !mSystemReady) { return false; } try { ...... // 更新mLastSleepTime时间，设置DIRTY_WAKEFulnesS标志位 mLastSleepTime = eventTime; mSandmanSummoned = true; setWakefulnessLocked(WAKEFulnesS_DOZING,reason); // 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; } } // 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;} goToSleepNoUpdateLocked中更新mLastSleepTime，mWakefulness，mDirty状态。
至此，本篇已结束，如有不对的地方，欢迎您的建议与指正。同时期待您的关注，感谢您的阅读，谢谢！
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