android屏幕亮度自动调节解析

屏幕亮度自动调节：

主要是从Sensor分析之中分离出来分析LIGHT 光线感应器，因此就分析一下自动调节屏幕亮度（手机随着光线的强度自我调节，也就是在亮的光线下屏幕自动调亮一些，暗的时候就自动调暗一些，省得光线对眼睛有刺激）.....

    (本人从历经挫折才大概了解流程)，现在就开始讲一下流程，如果有不对地方希望牛人指出来。。。

    先从Sttings入手吧，在diaplay中有屏幕亮度调节，有一个进度调，上面有一个checkbox（自动调节屏幕亮度的），



那么我们当然去找settings下的文件开始看了，先找到

DiaplaySettings.java文件以及display_setting.xml文件，display_setting.xml里面能找到相应的组件，但是 在DiaplaySettings.java文件中却不能找到调用相应组件的代码，

那么我们再到settings中去找，能找到BrightnessPreference.java文件，没错这个文件就是自动调节亮度的文件，我们先看看代码：

构造函数中有mAutomaticAvailable = context.getResources().getBoolean(com.android.internal.R.bool.config_automatic_brightness_available);

开始以为mAutomaticAvailabl的值（为true，在config.xml中）是判断是否自动调节亮度，因为在我跟进到PowerManagerService.java中，在initInThread() 中

  mUseSoftwareAutoBrightness = resources.getBoolean(

                com.android.internal.R.bool.config_automatic_brightness_available);

       

        if (mUseSoftwareAutoBrightness) {

            mAutoBrightnessLevels = resources.getIntArray(

                    com.android.internal.R.array.config_autoBrightnessLevels);//得到自动化调节的值调用 getAutoBrightnessValue(int sensorValue, int[] values) 方法

            mLcdBacklightValues = resources.getIntArray(

                    com.android.internal.R.array.config_autoBrightnessLcdBacklightValues);

            mButtonBacklightValues = resources.getIntArray(

                    com.android.internal.R.array.config_autoBrightnessButtonBacklightValues);

            mKeyboardBacklightValues = resources.getIntArray(。。。。。

。。。。。。这里看起来好像是当mUseSoftwareAutoBrightness为true时就取得config.xml文件config_autoBrightnessLevels的值，再去根据光线自动调节，但是mAutomaticAvailabl的值只是说明有没有自动调节屏幕的功能（比如说你将config.xml文件的config_automatic_brightness_available的值改为false，编译替换framework-res.apk那么在屏幕亮度调节中将没有自动调节的checkbox），这也能解释构造函数一开始就初始化mAutomaticAvailabl的值。

接下来在BrightnessPreference.java文件中有onProgressChanged，onStartTrackingTouch(SeekBar seekBar)，onStopTrackingTouch(SeekBar seekBar)方法，这些一看也能懂就不介绍了，在onBindDialogView(View view)方法中有

mCheckBox = (CheckBox)view.findViewById(R.id.automatic_mode);

        if (mAutomaticAvailable) {//当有自动调节功能

            mCheckBox.setOnCheckedChangeListener(this);//为checkbox添加监听事件

            try {

                mOldAutomatic = Settings.System.getInt(getContext().getContentResolver(),

                        Settings.System.SCREEN_BRIGHTNESS_MODE);

。。。。。。

主要看public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

        setMode(isChecked ? Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC

                : Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);

        if (!isChecked) {

            setBrightness(mSeekBar.getProgress() + MINIMUM_BACKLIGHT);

        }

    }

这里才是你选择自动调节亮度的checkbox，如果选择则setMode（Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC）；并将数据存放到数据库中。

这里是重点：这里有个数据库，当监测到数据库中的值发生改变时也就是变为Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC时，就会跳到

powerManagerService.java的initInThread()中ContentResolver resolver = mContext.getContentResolver();

        Cursor settingsCursor = resolver.query(Settings.System.CONTENT_URI, null,

                "(" + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?) or ("

                        + Settings.System.NAME + "=?)",

                new String[]{STAY_ON_WHILE_PLUGGED_IN, SCREEN_OFF_TIMEOUT, DIM_SCREEN, XEC_DLS_CONTROL,

                        SCREEN_BRIGHTNESS_MODE, WINDOW_ANIMATION_SCALE, TRANSITION_ANIMATION_SCALE},

                null);

        mSettings = new ContentQueryMap(settingsCursor, Settings.System.NAME, true, mHandler);

        SettingsObserver settingsObserver = new SettingsObserver();

        mSettings.addObserver(settingsObserver);

数据库中数据发生改变时触发事件的发生。

在 powerManagerService.java的systemReady()（只在开机调用一次就不再调用）中

 if (mUseSoftwareAutoBrightness) {

            Log.i("frist","frist="+"aaaa");

            mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);

            enableLightSensor(true);

        }

而mUseSoftwareAutoBrightness是在initInThread()线程中取得了true值，那么就到enableLightSensor(true);方法去看

 if (enable) {

                    mSensorManager.registerListener(mLightListener, mLightSensor,

                            SensorManager.SENSOR_DELAY_NORMAL);

                }

如果传递来的值为true也就是enable=true就监听而且用匹配屏幕方向变化的感应SENSOR_DELAY_NORMAL。

再看mLightListener事件：SensorEventListener mLightListener = new SensorEventListener() {

        public void onSensorChanged(SensorEvent event) {

            synchronized (mLocks) {

                int value = (int)event.values[0];//从event里面获取当前数据

                Log.i("value","value="+value);       

                long milliseconds = SystemClock.elapsedRealtime();

                if (mDebugLightSensor) {

                    Slog.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);

                    } 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);//到mAutoBrightnessTask线程去完成自动调节

                    }

                } else {

                    mLightSensorPendingValue = -1;

                }

            }

        }

当前屏幕亮度肯定不等与-1，所以做else中的mHandler.postDelayed(mAutoBrightnessTask, LIGHT_SENSOR_DELAY)，那么我们再到mAutoBrightnessTask

线程看：private Runnable mAutoBrightnessTask = new Runnable() {

        public void run() {

            synchronized (mLocks) {

                int value = (int)mLightSensorPendingValue;

                Log.i("mLightSensorPendingValue","mLightSensorPendingValue"+mLightSensorPendingValue);

                if (value >= 0) {

                    mLightSensorPendingValue = -1;

                    lightSensorChangedLocked(value);

                }

            }

        }

    };就是不断的去调用lightSensorChangedLocked(value)

private void lightSensorChangedLocked(int value) {

。。。。。。。

if (mLightSensorValue != value) {

            mLightSensorValue = value;

            if ((mPowerState & BATTERY_LOW_BIT) == 0) {

                // Use light sensor value no matter it is in a dock or not.

                int lcdValue = getAutoBrightnessValue(

                        value,

                        mLcdBacklightValues);// 取得mLcdBacklightValues里面的值

                int buttonValue = getAutoBrightnessValue(value, mButtonBacklightValues);

                int keyboardValue;

                if (mKeyboardVisible) {

                    keyboardValue = getAutoBrightnessValue(value, mKeyboardBacklightValues);

                } else {

                    keyboardValue = 0;

                }

。。。

if (mAutoBrightessEnabled && mScreenBrightnessOverride < 0) {//设置屏幕亮度

                    mScreenBrightness.setTargetLocked(lcdValue, AUTOBRIGHTNESS_ANIM_STEPS,

                            INITIAL_SCREEN_BRIGHTNESS, (int)mScreenBrightness.curValue);

                }

。。。。。

   }