android 自动亮度控制

  一)Setting相关处理                                    
Settings->display->auto rotate(自动旋转屏幕)                                    
/packages/apps/Settings/res/values/strings.xml                                    
                                    
<string name="accelerometer_title">Auto-rotate screen</string>                                    
                                    
                                    
packages/apps/Settings/res/xml/display_settings.xml                                    
                                    
        <CheckBoxPreference                                    
            android:key="accelerometer"                                    
            android:title="@string/accelerometer_title"/>                                    
                                    
                        
packages/apps/Settings/src/com/android/settings/DisplaySettings.java                                    
                                    
                                    
        mAccelerometer.setChecked(Settings.System.getInt(                                            if (preference == mAccelerometer) {
                getContentResolver(),                                                Settings.System.putInt(getContentResolver(),
                Settings.System.ACCELEROMETER_ROTATION, 0) != 0);                                                       Settings.System.ACCELEROMETER_ROTATION,
                                                        mAccelerometer.isChecked() ? 1 : 0);
Settings.System.ACCELEROMETER_ROTATION表示重力感应,横竖屏切换                                            }
                                    
                                    
                                    
                                    
                                    
二)自动转屏的实现                                    
                                    
frameworks/policies/base/phone/com/android/internal/policy/impl/PhoneWindowManager.java                                    
                                    
        void observe() {                                    
            ContentResolver resolver = mContext.getContentResolver();                                    
            resolver.registerContentObserver(Settings.System.getUriFor(                                    
                    Settings.System.END_BUTTON_BEHAVIOR), false, this);                                    
            resolver.registerContentObserver(Settings.Secure.getUriFor(                                    
                    Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR), false, this);                                    
            resolver.registerContentObserver(Settings.System.getUriFor(                                    
                    Settings.System.ACCELEROMETER_ROTATION), false, this);                                    
                                    
            int accelerometerDefault = Settings.System.getInt(resolver,                                    
                    Settings.System.ACCELEROMETER_ROTATION, DEFAULT_ACCELEROMETER_ROTATION);                                    
            if (mAccelerometerDefault != accelerometerDefault) {                                    
                mAccelerometerDefault = accelerometerDefault;                                    
                updateOrientationListenerLp();                                    
            }                                    
                                    
MyOrientationListener mOrientationListener;                                    
                                    
                                    
packages/apps/Phone/src/com/android/phone/AccelerometerListener.java                                    
 private void onSensorEvent(double x, double y, double z) {                                    
。。。                                    
        setOrientation(orientation);                                    
    }                                    
                                   
                              
2)加速度(accelerometer)是否就是重力感应                                 
自动调整亮度说明
自动调整亮度,即:当阳光很强时,由于外界亮度大,需要加亮屏幕,才能看清,否则觉得屏幕昏暗;当外界光线很弱时,屏幕只需要低一点的亮度就够看清了,否则觉得刺眼。                                                   
要启动自动调整亮度,
1)首先,必须配置config.xml                                                   
在frameworks/base/core/res/res/values/config.xml里面的配置项config_automatic_brightness_available设置为true,缺省是false                                                   
                                                   
2)在第一步设置之后,Settings->display->亮度设置,界面上会多出一个“自动调整亮度”选择框,如果选择框打勾,则表示真正启动了自动亮度调整                                                   
                                                   
                                             
                                             
以下是自动亮度调整的代码跟踪                                                   
                                                   
PowerManagerService.java                                                   
systemReady方法里面代码片段是                                                   
if (mUseSoftwareAutoBrightness) {                                                   
            if (mDebugLightSensor)                                                    
                Log.d(TAG, "mUseSoftwareAutoBrightness=true");                                                   
            mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);                                                   
            enableLightSensor(true);                                                   
        }                                                   
(mUseSoftwareAutoBrightness从frameworks/base/core/res/res/values/config.xml里面的配置项config_automatic_brightness_available获取,                                                   
如果为true,则调用enableLightSensor(true);                                                          
                                                   
enableLightSensor函数会调用                                                   
                    mSensorManager.registerListener(mLightListener, mLightSensor,                                                   
                            SensorManager.SENSOR_DELAY_NORMAL);                                                   
其中mSensorManager是PowerManagerService中的SensorManager对象成员变量,                                                   
mLightListener是注册的监听器类SensorEventListener对象,如果亮度变化,会触发其方法的调用,                                                   
mLightSensor是PowerManagerService中的LightSensor对象成员变量,代表光传感器。                                                  
SensorEventListener类定义如下                                                   
   SensorEventListener mLightListener = new SensorEventListener() {                                                   
        public void onSensorChanged(SensorEvent event) {                                                   
            synchronized (mLocks) {                                                   
                // ignore light sensor while screen is turning off                                                   
                if (isScreenTurningOffLocked()) {                                                   
                    Log.d(TAG, "ScreenTurningOffLocked, just return.");                                                   
                    return;                                                   
                }                                                   
                                                   
                int value = (int)event.values[0]; //从event里面获取当前数据,亮度大概在0到二十几                                                  
                long milliseconds = SystemClock.elapsedRealtime();                                                   
                if (mDebugLightSensor) {                                                   
                    Log.d(TAG, "onSensorChanged: light value: " + value);                                                   
                }                                                   
                mHandler.removeCallbacks(mAutoBrightnessTask);                                                   
                if (mLightSensorValue != value) { //mLightSensorValue是当前的屏幕亮度                                                   
                    if (mLightSensorValue == -1 ||                                                   
                            milliseconds < mLastScreenOnTime + mLightSensorWarmupTime) {                                                  
                        // process the value immediately if screen has just turned on                                                   
                        lightSensorChangedLocked(value); //屏幕刚刚打开                                                   
                    } else {                                                   
                        // delay processing to debounce the sensor                                                   
                        mLightSensorPendingValue = value;  //mLightSensorPendingValue是准备要设置的亮度                                                  
                        mHandler.postDelayed(mAutoBrightnessTask, LIGHT_SENSOR_DELAY); //在mAutoBrightnessTask任务里面延后处理                                                   
                    }                                                   
                } else {                                                   
                    mLightSensorPendingValue = -1;                                                   
                }                                                   
            }                                                   
        }                                                   
。。。                                                   
    };                                                   
mAutoBrightnessTask这个AutoBrightnessTask线程的run方法里面调用                                                   
private void lightSensorChangedLocked(int value) //此value的就是即将要设置的亮度值                                                  
                                                   
mScreenBrightness.setTargetLocked(lcdValue,                                                   
                                AUTOBRIGHTNESS_ANIM_STEPS, INITIAL_SCREEN_BRIGHTNESS,                                                  
                                (int)mScreenBrightness.curValue)                                                   
然后启动mLightAnimator                                                   
                                                   
说明,除了设置config_automatic_brightness_available为true之外,还必须设置其他一些数据项,否则运行时报异常                                                  
2124行getAutoBrightnessValue的return values[i];报错                                                   
参考$ANDROID_ROOT/device/htc/passion-common/overlay/frameworks/base/core/res/res/values/config.xml的内容,修改$ANDROID_ROOT/frameworks/base/core/res/res/values/config.xml                                                   
一共有以下几个配置项数据需要配置                                                   
config_autoBrightnessLevels -保存在PowerManagerService的mAutoBrightnessLevels变量中                                                  
config_autoBrightnessLcdBacklightValues  --mLcdBacklightValues                                                   
config_autoBrightnessButtonBacklightValues                                            <integer-array name="config_autoBrightnessLevels">           
config_autoBrightnessKeyboardBacklightValues                                                <item>200</item>           
以上每个项里面有多个子项,用于提供给数组的数据。                                                <item>400</item>           
设置完之后,运行时不报异常,打印日志如下:                                                <item>1000</item>           
                                                <item>3000</item>           
01-08 02:14:48.319: DEBUG/PowerManagerService(131): onSensorChanged: light value: 7                                           </integer-array>           
01-08 02:14:50.322: DEBUG/PowerManagerService(131): lightSensorChangedLocked 7                                                  
01-08 02:14:50.322: DEBUG/PowerManagerService(131): lcdValue 25                                            <!-- Array of output values for LCD backlight corresponding to the LUX values           
01-08 02:14:50.322: DEBUG/PowerManagerService(131): buttonValue 255                                                 in the config_autoBrightnessLevels array.  This array should have size one greater           
01-08 02:14:50.322: DEBUG/PowerManagerService(131): keyboardValue 0                                                 than the size of the config_autoBrightnessLevels array.           
但看上去并没有根据外界亮度改变屏幕和键盘等亮度,所以代码还待分析。                                                 This must be overridden in platform specific overlays -->           
                                            <integer-array name="config_autoBrightnessLcdBacklightValues">           
重新分析LightSensorChangedLocked方法里面的代码片段                                                <item>25</item>           
                int lcdValue = getAutoBrightnessValue(                                                <item>55</item>           
                        (mIsDocked ? value : mHighestLightSensorValue),                         //第一个参数取二者的最大值                       <item>70</item>           
                        mLcdBacklightValues);                                                <item>70</item>           
                                                <item>250</item>           
                                            </integer-array>           
                                                   
                                                   
   private int getAutoBrightnessValue(int sensorValue, int[] values) {                                                   
        try {                                                   
            int i;                                                   
            for (i = 0; i < mAutoBrightnessLevels.length; i++) {                                                   
                if (sensorValue < mAutoBrightnessLevels[i]) {                                                   
                    break;                                                   
                }                                                   
            }                                                   
            return values[i];                                                   
        } catch (Exception e) {                                                   
            // guard against null pointer or index out of bounds errors                                                   
            Slog.e(TAG, "getAutoBrightnessValue", e);                                                   
            return 255;                                                   
        }                                                   
    }                                                   
此段代码的意思是,如果传入的sensorValue比config_autoBrightnessLevels的第i个值要小,则获得值是config_autoBrightnessLcdBacklightValues的第i个值                                                   
目前传入的sensorValue总是比config_autoBrightnessLevels的第一个值要小,所以每次lcdValue得到的值都是config_autoBrightnessLcdBacklightValues的第一个值                                                   
所以亮度一直都没实际变动。                                                   
前面根据日志,onSensorChanged方法里面每次获取当前亮度在0到20几之间,似乎和config_autoBrightnessLevels 的配置不协调,显得太小了。

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