Android LCD和键盘 背光亮度设置

本网站用的阿里云ECS,推荐大家用。自己搞个学习研究也不错
亮度设置
 应用设计
1.1 设置进度条范围
背光设置是在:设置->声音和显示->亮度,通过进度条来设置的。

文件:packages/apps/Settings/src/com/Android/settings/BrightnessPreference.java

private static final int MINIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_DIM + 10;

private static final int MAXIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_ON;

mSeekBar.setMax(MAXIMUM_BACKLIGHT – MINIMUM_BACKLIGHT);

设置进度条的范围,BRIGHTNESS_DIM = 20  BRIGHTNESS_ON=255,它们的定义在:

frameworks/base/core/java/android/os/Power.java

1.2 设置亮度
文件:packages/apps/Settings/src/com/android/settings/BrightnessPreference.java

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);

        }

    }

private void setBrightness(int brightness) {

        try {

            IPowerManager power = IPowerManager.Stub.asInterface(

                    ServiceManager.getService(“power”));

            if (power != null) {

                power.setBacklightBrightness(brightness);

            }

        } catch (RemoteException doe) {

           

        }       

}

由以上代码可知,brightness的范围是:20~255;代码通过服务管理器(ServiceManager)获得power服务,然后通过power服务设置亮度。

power.setBacklightBrightness的定义在:

rameworks/base/core/java/android/os/IPowerManager.aidl.java

frameworks/base/core/java/android/os/PowerManager.java

2, Power服务
文件:frameworks/base/core/java/android/os/Power.java

/**

     * Brightness value for dim backlight

     */

    public static final int BRIGHTNESS_DIM = 20;

    /**

     * Brightness value for fully on

     */

public static final int BRIGHTNESS_ON = 255;

文件:frameworks/base/core/java/android/os/PowerManager.java

/**

     * sets the brightness of the backlights (screen, keyboard, button).

     *

     * @param brightness value from 0 to 255

     *

     * {@hide}

     */

    public void setBacklightBrightness(int brightness)

    {

        try {

            mService.setBacklightBrightness(brightness);

        } catch (RemoteException e) {

        }

}

电源管理器(powermager)将brightness转给电源服务,该服务位置如下:

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

public void setBacklightBrightness(int brightness) {

        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);

        // Don’t let applications turn the screen all the way off

        brightness = Math.max(brightness, Power.BRIGHTNESS_DIM);

        mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_BACKLIGHT, brightness,

                HardwareService.BRIGHTNESS_MODE_USER);

        mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_KEYBOARD,

            (mKeyboardVisible ? brightness : 0), HardwareService.BRIGHTNESS_MODE_USER);

        mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_BUTTONS, brightness,

            HardwareService.BRIGHTNESS_MODE_USER);

        long identity = Binder.clearCallingIdentity();

        try {

            mBatteryStats.noteScreenBrightness(brightness);

        } catch (RemoteException e) {

            Log.w(TAG, “RemoteException calling noteScreenBrightness on BatteryStatsService”, e);

        } finally {

            Binder.restoreCallingIdentity(identity);

        }

        // update our animation state

        if (ANIMATE_SCREEN_LIGHTS) {

            mScreenBrightness.curValue = brightness;

            mScreenBrightness.animating = false;

            mScreenBrightness.targetValue = -1;

        }

        if (ANIMATE_KEYBOARD_LIGHTS) {

            mKeyboardBrightness.curValue = brightness;

            mKeyboardBrightness.animating = false;

            mKeyboardBrightness.targetValue = -1;

        }

        if (ANIMATE_BUTTON_LIGHTS) {

            mButtonBrightness.curValue = brightness;

            mButtonBrightness.animating = false;

            mButtonBrightness.targetValue = -1;

        }

    }

由以上代码可知,同时设置了背光、键盘、按钮的亮度。mHardware 是硬件服务,通过该服务调用底层与设备打交道的C\C++代码,setLightBrightness_UNCHECKED原型如下:

文件:frameworks/base/services\java\com\android\server\HardwareService.java

void setLightBrightness_UNCHECKED(int light, int brightness, int brightnessMode) {

        int b = brightness & 0x000000ff;

        b = 0x

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