初识Android PowerManagerService省电模式

PowerManagerService(Context context, Injector injector) {
    super(context);
    // ...

    // Class to decide whether to turn on battery saver mode for specific services.
    mBatterySaverPolicy =
            mInjector.createBatterySaverPolicy(mLock, mContext, mBatterySavingStats);

    // Responsible for battery saver mode transition logic.
    mBatterySaverController = mInjector.createBatterySaverController(mLock, mContext,
            mBatterySaverPolicy, mBatterySavingStats);

    //  Decides when to enable / disable battery saver.
    mBatterySaverStateMachine = mInjector.createBatterySaverStateMachine(mLock, mContext,
            mBatterySaverController);
   
    // ...
}

public BatterySaverPolicy(Object lock, Context context, BatterySavingStats batterySavingStats) {
    super(BackgroundThread.getHandler());
    mLock = lock;
    mHandler = BackgroundThread.getHandler();
    mContext = context;
    mContentResolver = context.getContentResolver();
    mBatterySavingStats = batterySavingStats;
}
public BatterySaverController(Object lock, Context context, Looper looper,
        BatterySaverPolicy policy, BatterySavingStats batterySavingStats) {
    mLock = lock;
    mContext = context;
    mHandler = new MyHandler(looper);
    mBatterySaverPolicy = policy;
    // 注意，监听了 policy change
    mBatterySaverPolicy.addListener(this);
    
    // FileUpdater 负责向底层文件节点写值，例如向CPU频率的节点写值，控制CPU频率
    mFileUpdater = new FileUpdater(context);
    
    mBatterySavingStats = batterySavingStats;

    // 刷新获取省电模式的缓存
    PowerManager.invalidatePowerSaveModeCaches();
}
public BatterySaverStateMachine(Object lock,
        Context context, BatterySaverController batterySaverController) {
    mLock = lock;
    mContext = context;
    mBatterySaverController = batterySaverController;
    mState = STATE_OFF;
    // Whether or not battery saver should be "sticky" when manually enabled.
    // false
    // 注意了，值为 false，表明这个 battery saver sticky 功能是打开的
    mBatterySaverStickyBehaviourDisabled = mContext.getResources().getBoolean(
            com.android.internal.R.bool.config_batterySaverStickyBehaviourDisabled);
            
    //  Config flag to track default disable threshold for Dynamic power savings enabled battery saver.
    // 80
    mDynamicPowerSavingsDefaultDisableThreshold = mContext.getResources().getInteger(
            com.android.internal.R.integer.config_dynamicPowerSavingsDefaultDisableThreshold);
}

public void systemReady(IAppOpsService appOps) {
    synchronized (mLock) {
        // ...
        mBatterySaverController.systemReady();
        mBatterySaverPolicy.systemReady();
        
        // ...
    }   
}

public void systemReady() {
    // 监听这些东西，来控制 battery saver
    final IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
    filter.addAction(Intent.ACTION_SCREEN_OFF);
    filter.addAction(Intent.ACTION_BATTERY_CHANGED);
    filter.addAction(PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED);
    filter.addAction(PowerManager.ACTION_LIGHT_DEVICE_IDLE_MODE_CHANGED);
    mContext.registerReceiver(mReceiver, filter);

    // 如果 Runtime 重启，那么读取 /data/system/battery-saver/default-values.xml 保存的数据，否则删除这个文件。
    mFileUpdater.systemReady(LocalServices.getService(ActivityManagerInternal.class)
            .isRuntimeRestarted());
    // 这里的处理逻辑为空
    mHandler.postSystemReady();
}

public void systemReady() {
    ConcurrentUtils.wtfIfLockHeld(TAG, mLock);

    // 下面两个字段，目前没有值，但是会控制省电模式策略，进而影响省电模式
    mContentResolver.registerContentObserver(Settings.Global.getUriFor(
            Settings.Global.BATTERY_SAVER_CONSTANTS), false, this);
    mContentResolver.registerContentObserver(Settings.Global.getUriFor(
            Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS), false, this);

    // 无障碍相关
    final AccessibilityManager acm = mContext.getSystemService(AccessibilityManager.class);
    acm.addAccessibilityStateChangeListener(enabled -> mAccessibilityEnabled.update(enabled));
    mAccessibilityEnabled.initialize(acm.isEnabled());

    // 汽车相关
    UiModeManager uiModeManager = mContext.getSystemService(UiModeManager.class);
    uiModeManager.addOnProjectionStateChangedListener(UiModeManager.PROJECTION_TYPE_AUTOMOTIVE,
            mContext.getMainExecutor(), mOnProjectionStateChangedListener);
    mAutomotiveProjectionActive.initialize(
            uiModeManager.getActiveProjectionTypes() != UiModeManager.PROJECTION_TYPE_NONE);

    // 监听 SettingProvider 的 config 表中，关于 battery_saver 命名空间下的所有字段值。
    // 目前，这些字段都为空，但是这些字段会影响省电模式策略，进而控制省电模式
    DeviceConfig.addOnPropertiesChangedListener(DeviceConfig.NAMESPACE_BATTERY_SAVER,
            mContext.getMainExecutor(), this);
    mLastDeviceConfigProperties =
            DeviceConfig.getProperties(DeviceConfig.NAMESPACE_BATTERY_SAVER);
    onChange(true, null);
}

public void onBootPhase(int phase) {
    synchronized (mLock) {
        if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {
            incrementBootCount();

        } else if (phase == PHASE_BOOT_COMPLETED) {
            // ...

            mBatterySaverStateMachine.onBootCompleted();
            
            // ...
        }
    }
}

public void onBootCompleted() {
    putGlobalSetting(Settings.Global.LOW_POWER_MODE, 0);
    runOnBgThread(() -> {

        // 监听数据库字段
        final ContentResolver cr = mContext.getContentResolver();
        // Settings.Global.LOW_POWER_MODE 代表省电模式是否打开
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.LOW_POWER_MODE),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.LOW_POWER_MODE_STICKY 代表 battery saver sticky 功能是否打开
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.LOW_POWER_MODE_STICKY),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.LOW_POWER_MODE_TRIGGER_LEVEL 代表触发省电模式的电量百分比
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.LOW_POWER_MODE_TRIGGER_LEVEL),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.AUTOMATIC_POWER_SAVE_MODE 代表自动省电模式的类型
        // 类型有三个，根据电量百分比触发，动态省电模式模式，或者none
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.AUTOMATIC_POWER_SAVE_MODE),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.DYNAMIC_POWER_SAVINGS_ENABLED 代表是否打开动态省电模式
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.DYNAMIC_POWER_SAVINGS_ENABLED),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.DYNAMIC_POWER_SAVINGS_DISABLE_THRESHOLD 代表动态省电模式关闭的阈值
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.DYNAMIC_POWER_SAVINGS_DISABLE_THRESHOLD),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.LOW_POWER_MODE_STICKY_AUTO_DISABLE_ENABLED 表示是否打开了 battery saver sticky auto disable
        // 对应于 Settings->Battery->Battery Saver->Turn off when charging
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.LOW_POWER_MODE_STICKY_AUTO_DISABLE_ENABLED),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);
        // Settings.Global.LOW_POWER_MODE_STICKY_AUTO_DISABLE_LEVEL 表示  battery saver sticky auto disable 的阈值
        cr.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.LOW_POWER_MODE_STICKY_AUTO_DISABLE_LEVEL),
                false, mSettingsObserver, UserHandle.USER_SYSTEM);


        synchronized (mLock) {
            /**
             * If 1, battery saver ({@link #LOW_POWER_MODE}) will be re-activated after the device
             * is unplugged from a charger or rebooted.
             */
            // battery saver sticky 功能是否被打开
            final boolean lowPowerModeEnabledSticky = getGlobalSetting(
                    Settings.Global.LOW_POWER_MODE_STICKY, 0) != 0;
            if (lowPowerModeEnabledSticky) {
                mState = STATE_PENDING_STICKY_ON;
            }

            mBootCompleted = true;

            // 读取数据库字段，并根据情况，打开/关闭省电模式
            refreshSettingsLocked();

            // 自动打开/关闭省电模式
            doAutoBatterySaverLocked();
        }
    });
}