在开发调试android 系统的Setting时，总是会见到以下的代码。

Settings.System.getInt(contentResolver, Settings.System.SOUND_EFFECTS_ENABLED, 1)
Settings.System.putInt(getActivity().getContentResolver(),
                Settings.System.SOUND_EFFECTS_ENABLED, enabled ? 1 : 0);
Settings.Global.putInt

其实这些值都是setting 里面设置的默认值。例如 wifi ，蓝牙，声音开关等。有时候我们想要去在系统出厂时将一些默认值修改。则可以更改以下的配置文件。其实以上的getInt等都是load的下面配置文件中的值。
frameworks\base\packages\SettingsProvider\res\values

<?xml version="1.0" encoding="utf-8"?>
<!--
/**
 * Copyright (c) 2009, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
-->
<resources>
    <bool name="def_dim_screen">true</bool>
    <integer name="def_screen_off_timeout">60000</integer>
    <integer name="def_sleep_timeout">-1</integer>
    <bool name="def_airplane_mode_on">false</bool>
    <bool name="def_theater_mode_on">false</bool>
    <!-- Comma-separated list of bluetooth, wifi, and cell. -->
    <string name="def_airplane_mode_radios" translatable="false">cell,bluetooth,wifi,nfc,wimax</string>
    <string name="airplane_mode_toggleable_radios" translatable="false">bluetooth,wifi,nfc</string>
    <string name="def_bluetooth_disabled_profiles" translatable="false">0</string>
    <bool name="def_auto_time">true</bool>
    <bool name="def_auto_time_zone">true</bool>
    <bool name="def_accelerometer_rotation">false</bool>
    <!-- Default screen brightness, from 0 to 255.  102 is 40%. -->
    <integer name="def_screen_brightness">102</integer>
    <bool name="def_screen_brightness_automatic_mode">false</bool>
    <fraction name="def_window_animation_scale">100%</fraction>
    <fraction name="def_window_transition_scale">100%</fraction>
    <bool name="def_haptic_feedback">true</bool>

    <bool name="def_bluetooth_on">true</bool>
    <bool name="def_wifi_display_on">false</bool>
    <bool name="def_install_non_market_apps">false</bool>
    <bool name="def_package_verifier_enable">true</bool>
    <!-- Comma-separated list of location providers.
         Network location is off by default because it requires
         user opt-in via Setup Wizard or Settings.
    -->
    <string name="def_location_providers_allowed" translatable="false">gps</string>
    <bool name="assisted_gps_enabled">true</bool>
    <bool name="def_netstats_enabled">true</bool>
    <bool name="def_usb_mass_storage_enabled">true</bool>
    <bool name="def_wifi_on">false</bool>
    <!-- 0 == never, 1 == only when plugged in, 2 == always -->
    <integer name="def_wifi_sleep_policy">2</integer>
    <bool name="def_wifi_wakeup_enabled">true</bool>
    <bool name="def_networks_available_notification_on">true</bool>

    <bool name="def_backup_enabled">false</bool>
    <string name="def_backup_transport" translatable="false">android/com.android.internal.backup.LocalTransport</string>

    <!-- Default value for whether or not to pulse the notification LED when there is a
         pending notification -->
    <bool name="def_notification_pulse">true</bool>

    <bool name="def_mount_play_notification_snd">true</bool>
    <bool name="def_mount_ums_autostart">false</bool>
    <bool name="def_mount_ums_prompt">true</bool>
    <bool name="def_mount_ums_notify_enabled">true</bool>

    <!-- user interface sound effects -->
    <integer name="def_power_sounds_enabled">1</integer>
    <string name="def_low_battery_sound" translatable="false">/system/media/audio/ui/LowBattery.ogg</string>
    <integer name="def_dock_sounds_enabled">0</integer>
    <integer name="def_dock_sounds_enabled_when_accessibility">0</integer>
    <string name="def_desk_dock_sound" translatable="false">/system/media/audio/ui/Dock.ogg</string>
    <string name="def_desk_undock_sound" translatable="false">/system/media/audio/ui/Undock.ogg</string>
    <string name="def_car_dock_sound" translatable="false">/system/media/audio/ui/Dock.ogg</string>
    <string name="def_car_undock_sound" translatable="false">/system/media/audio/ui/Undock.ogg</string>
    <integer name="def_lockscreen_sounds_enabled">1</integer>
    <string name="def_lock_sound" translatable="false">/system/media/audio/ui/Lock.ogg</string>
    <string name="def_unlock_sound" translatable="false">/system/media/audio/ui/Unlock.ogg</string>
    <string name="def_trusted_sound" translatable="false">/system/media/audio/ui/Trusted.ogg</string>
    <string name="def_wireless_charging_started_sound" translatable="false">/system/media/audio/ui/WirelessChargingStarted.ogg</string>
    <string name="def_charging_started_sound" translatable="false">/system/media/audio/ui/ChargingStarted.ogg</string>

    <!-- sound trigger detection service default values -->
    <integer name="def_max_sound_trigger_detection_service_ops_per_day" translatable="false">1000</integer>
    <integer name="def_sound_trigger_detection_service_op_timeout" translatable="false">15000</integer>

    <bool name="def_lockscreen_disabled">false</bool>
    <bool name="def_device_provisioned">false</bool>
    <integer name="def_dock_audio_media_enabled">1</integer>

    <!-- Notifications use ringer volume -->
    <bool name="def_notifications_use_ring_volume">true</bool>

    <!-- Default for Settings.System.VIBRATE_IN_SILENT -->
    <bool name="def_vibrate_in_silent">true</bool>

    <!-- Default for Settings.Secure.SYNC_PARENT_SOUNDS -->
    <bool name="def_sync_parent_sounds">true</bool>

    <!-- Default for Settings.Secure.ACCESSIBILITY_SPEAK_PASSWORD -->
    <bool name="def_accessibility_speak_password">true</bool>

    <!-- Default for Settings.Secure.TOUCH_EXPLORATION_ENABLED -->
    <bool name="def_touch_exploration_enabled">false</bool>

    <!-- Default value for Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_SCALE -->
    <fraction name="def_accessibility_display_magnification_scale">200%</fraction>

    <!-- Default value for Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_ENABLED -->
    <bool name="def_accessibility_display_magnification_enabled">false</bool>

    <!-- Default value for Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_AUTO_UPDATE -->
    <bool name="def_accessibility_display_magnification_auto_update">true</bool>

    <!-- Default for Settings.System.USER_ROTATION -->
    <integer name="def_user_rotation">0</integer>

    <!-- Default for Settings.Secure.DOWNLOAD_MAX_BYTES_OVER_MOBILE. <=0 if no limit -->
    <integer name="def_download_manager_max_bytes_over_mobile">-1</integer>
    <!-- Default for Settings.Secure.DOWNLOAD_RECOMMENDED_MAX_BYTES_OVER_MOBILE. <=0 if no limit -->
    <integer name="def_download_manager_recommended_max_bytes_over_mobile">-1</integer>

    <!-- Default for Settings.Secure.LONG_PRESS_TIMEOUT_MILLIS -->
    <integer name="def_long_press_timeout_millis">400</integer>

    <!-- Default for Settings.Secure.MULTI_PRESS_TIMEOUT -->
    <integer name="def_multi_press_timeout_millis">300</integer>

    <!-- Default for Settings.Secure.SHOW_IME_WITH_HARD_KEYBOARD -->
    <bool name="def_show_ime_with_hard_keyboard">false</bool>

    <!-- Default for Settings.System.POINTER_SPEED -->
    <integer name="def_pointer_speed">0</integer>

    <!-- Default for DTMF tones enabled -->
    <bool name="def_dtmf_tones_enabled">true</bool>
    <!-- Default for UI touch sounds enabled -->
    <bool name="def_sound_effects_enabled">true</bool>

    <!-- Development settings -->
    <bool name="def_stay_on_while_plugged_in">false</bool>

    <!-- Number of retries for connecting to DHCP.
         Value here is the same as WifiStateMachine.DEFAULT_MAX_DHCP_RETRIES -->
    <integer name="def_max_dhcp_retries">9</integer>

    <!-- Default for Settings.Secure.USER_SETUP_COMPLETE -->
    <bool name="def_user_setup_complete">false</bool>

    <!-- Default for Settings.Global.LOW_BATTERY_SOUND_TIMEOUT.
         0 means no timeout; battery sounds will always play
         >0 is milliseconds of screen-off time after which battery sounds will not play -->
    <integer name="def_low_battery_sound_timeout">0</integer>

    <!-- Initial value for the Settings.Secure.IMMERSIVE_MODE_CONFIRMATIONS setting,
         which is a comma separated list of packages that no longer need confirmation
         for immersive mode.
         Override to disable immersive mode confirmation for certain packages. -->
    <string name="def_immersive_mode_confirmations" translatable="false"></string>

    <!-- Default for Settings.Global.WIFI_SCAN_ALWAYS_AVAILABLE -->
    <integer name="def_wifi_scan_always_available">0</integer>

    <!-- Default for Settings.Secure.LOCK_SCREEN_SHOW_NOTIFICATIONS, 1==on -->
    <integer name="def_lock_screen_show_notifications">1</integer>

    <!-- Default for Settings.Secure.LOCK_SCREEN_ALLOW_PRIVATE_NOTIFICATIONS -->
    <bool name="def_lock_screen_allow_private_notifications">true</bool>

    <!-- Default for Settings.Global.HEADS_UP_NOTIFICATIONS_ENABLED, 1==on -->
    <integer name="def_heads_up_enabled">1</integer>

    <!-- Default for Settings.Global.DEVICE_NAME $1=MANUFACTURER $2=MODEL-->
    <string name="def_device_name">%1$s %2$s</string>

    <!-- Default for Settings.Global.DEVICE_NAME $1=MODEL-->
    <string name="def_device_name_simple">%1$s</string>

    <!-- Default for Settings.Secure.WAKE_GESTURE_ENABLED -->
    <bool name="def_wake_gesture_enabled">true</bool>

    <!-- Default state of tap to wake -->
    <bool name="def_double_tap_to_wake">true</bool>

    <!-- Default for Settings.Secure.NFC_PAYMENT_COMPONENT -->
    <string name="def_nfc_payment_component"></string>

    <!-- Default setting for ability to add users from the lock screen -->
    <bool name="def_add_users_from_lockscreen">false</bool>

    <!--  default setting for Settings.System.END_BUTTON_BEHAVIOR : END_BUTTON_BEHAVIOR_SLEEP -->
    <integer name="def_end_button_behavior">0x2</integer>

    <!-- default setting for Settings.Global.DEFAULT_RESTRICT_BACKGROUND_DATA -->
    <bool name="def_restrict_background_data">false</bool>

    <!-- Default for Settings.Secure.BACKUP_MANAGER_CONSTANTS -->
    <string name="def_backup_manager_constants"></string>

    <!-- Default setting for Settings.Global.MOBILE_DATA_ALWAYS_ON -->
    <bool name="def_mobile_data_always_on">true</bool>

    <!-- Default for Settings.Secure.BACKUP_LOCAL_TRANSPORT_PARAMETERS -->
    <string name="def_backup_local_transport_parameters"></string>

    <!-- Default for Settings.Global.ZEN_DURATION
        If 0, turning on dnd manually will last indefinitely.
        Else if non-negative, turning on dnd manually will last for this many minutes.
        Else (if negative), turning on dnd manually will surface a dialog that prompts
            user to specify a duration.-->
    <integer name="def_zen_duration">0</integer>

    <!-- Default for Settings.Global.BACKUP_AGENT_TIMEOUT_PARAMETERS -->
    <string name="def_backup_agent_timeout_parameters"></string>

    <!-- Default for Settings.System.VIBRATE_WHEN_RINGING -->
    <bool name="def_vibrate_when_ringing">false</bool>
</resources>

以上代码中的key 值，即Settings.System.SOUND_EFFECTS_ENABLED 都是在以下文件中定义的

frameworks\base\core\java\android\provider

public final class Settings {
    
	public static final class System extends NameValueTable {
        //内部类
        // NOTE: If you add new settings here, be sure to add them to
        // com.android.providers.settings.SettingsProtoDumpUtil#dumpProtoSystemSettingsLocked.

        private static final float DEFAULT_FONT_SCALE = 1.0f;

        /**
         * The content:// style URL for this table
         */
        public static final Uri CONTENT_URI =
            Uri.parse("content://" + AUTHORITY + "/system");     //内容提供者

        private static final ContentProviderHolder sProviderHolder =
                new ContentProviderHolder(CONTENT_URI);

        private static final NameValueCache sNameValueCache = new NameValueCache(
                CONTENT_URI,
                CALL_METHOD_GET_SYSTEM,
                CALL_METHOD_PUT_SYSTEM,
                sProviderHolder);

        public static final String SCREEN_OFF_TIMEOUT = "screen_off_timeout";   // key 值

        private static final Validator SCREEN_OFF_TIMEOUT_VALIDATOR =
                NON_NEGATIVE_INTEGER_VALIDATOR;

        /**
         * The screen backlight brightness between 0 and 255.
         */
        public static final String SCREEN_BRIGHTNESS = "screen_brightness";
}

在真机中，通过setting设置的值都是存在在以下目录下的

/data/data/com.android.providers.settings/databases/settings.db里，里面有三个表global, system, secure.

可以通常这样查看数据

adb shell sqlite3 data/data/com.android.providers.settings/databases/settings.db "select * from secure"

但是自从android 6.0以后这几个表都变为了xml文件。具体位置如下：

不同用户放不同的路径下，如果没有创建新用户，则在/data/system/users/0下

settings_global.xml, settings_system.xml, settings_secure.xml

另外，如果需要在串口或者adb 调试的话，可以直接使用命令是改变这些值

   settings get global 系统属性key

   settings put global 系统属性key 系统属性值