背光之關閉（turnOff）

相關檔案：

frameworks/base/services/java/com/android/server/PowerManagerService.java

frameworks/base/services/java/com/android/server/NotificationManagerService.java 

    private void updateLightsLocked()

對于mBatteryLow是mBatteryLow和mBatteryCharging的時候電池的訓示是要顯示的，否則關閉。android做成平闆機，netbook的時候，一般是有電池訓示燈的。 另外：         // we only flash if screen is off and persistent pulsing is enabled         // and we are not currently in a call         if (mLedNotification == null || mScreenOn || mInCall) {             mNotificationLight.turnOff();         }

在電源管理的manager代碼中，在函數中可見，燈在LCD關閉的時候是要關的。

private int setScreenStateLocked(boolean on) {

int err = Power.setScreenState(on);

if (err == 0) {

mLastScreenOnTime = (on ? SystemClock.elapsedRealtime() : 0);

if (mUseSoftwareAutoBrightness) {

enableLightSensor(on);

if (!on) {

// make sure button and key backlights are off too

mButtonLight.turnOff();

mKeyboardLight.turnOff();

// clear current value so we will update based on the new conditions

// when the sensor is reenabled.

mLightSensorValue = -1;

// reset our highest light sensor value when the screen turns off

mHighestLightSensorValue = -1;

}

}

}

return err;

  注意 mUseSoftwareAutoBrightness 很多光現象都與之相關，代碼查查就好了。SCREEN_BRIGHTNESS也相關的。