1. 修改android系統顯示亮度的最大最小限制
        修改 frameworks\base\core\res\res\values\config.xml  （很多預設配置都是在這個檔案裡修改的）以下程式碼
    <!-- Minimum screen brightness setting allowed by the power manager.
         The user is forbidden from setting the brightness below this level. -->
    <integer name="config_screenBrightnessSettingMinimum">110</integer>


    <!-- Maximum screen brightness allowed by the power manager.
         The user is forbidden from setting the brightness above this level. -->
    <integer name="config_screenBrightnessSettingMaximum">255</integer>


    <!-- Default screen brightness setting.
         Must be in the range specified by minimum and maximum. -->
    <integer name="config_screenBrightnessSettingDefault">220</integer>


    <!-- Screen brightness used to dim the screen when the user activity
         timeout expires.  May be less than the minimum allowed brightness setting
         that can be set by the user. -->

    <integer name="config_screenBrightnessDim">110</integer>

2. 修改預設顯示亮度

   全志的是在這個檔案： device\softwinner\wing-clover\overlay\frameworks\base\packages\SettingsProvider\res\values\defaults.xml 

  大部分開發板的在這個檔案：frameworks\base\packages\SettingsProvider\res\values\defaults.xml
<integer name="def_screen_brightness">250</integer><!--102-->

改完重新編譯就ok了