[移动开发] Android系统App之SettingsProvider

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[移动开发]Android系统App之SettingsProvider

（1）概述

（A）

SettingsProvider顾名思义是一个提供设置数据共享的Provider，SettingsProvider和Android系统其它Provider有很多不一样的地方，如：

SettingsProvider只接受int、float、string等基本类型的数据；
SettingsProvider由Android系统framework进行了封装，使用更加快捷方便；
SettingsProvider的数据由键值对组成；

（B）

SettingsProvider有点类似Android的SystemProperties。SystemProperties除具有SettingsProvider以上的三个特性，SettingsProvider和SystemProperties的不同点在于：

数据保存方式不同：SystemProperties的数据保存属性文件中（/system/build.prop等），开机后会被加载到system properties store，SettingsProvider的数据保存在文件/data/system/users/0/settings_***.xml和数据库settings.db中；
作用范围不同：SystemProperties可以实现跨进程、跨层次调用，即底层的c/c++可以调用，java层也可以调用，SettingProvider只能在java层（APP）使用；

在Android 6.0版本时，SettingsProvider被重构，Android从性能、安全等方面考虑，把SettingsProvider中原本保存在settings.db中的数据，目前全部保存在XML文件中。

（C）

SettingsProvider对数据进行了分类，分别是Global、System、Secure三种类型，它们的区别如下：

Global：所有的偏好设置对系统的所有用户公开，第三方APP有读没有写的权限；
System：包含各种各样的用户偏好系统设置；
Secure：安全性的用户偏好系统设置，第三方APP有读没有写的权限；

上面对Global、System、Secure分别生成一个File对象实例，它们的File对象分别对应的文件是：

/data/system/users/0/settings_global.xml
/data/system/users/0/settings_system.xml
/data/system/users/0/settings_secure.xml

也就是说，Global类型的数据保存在文件settings_global.xml中，System类型的数据保存在文件settings_system.xml中，Secure类型的数据保存在文件settings_secure.xml中。

（2）AndroidManifest.xml

//frameworks/base/packages/SettingsProvider/AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.android.providers.settings"
        coreApp="true"
        android:sharedUserId="android.uid.system">

    <application android:allowClearUserData="false"
                 android:label="@string/app_label"
                 android:process="system"
                 android:backupAgent="SettingsBackupAgent"
                 android:killAfterRestore="false"
                 android:restoreAnyVersion="true"
                 android:icon="@mipmap/ic_launcher_settings"
                 android:defaultToDeviceProtectedStorage="true"
                 android:forceQueryable="true"
                 android:directBootAware="true">

        <provider android:name="SettingsProvider"
                  android:authorities="settings"
                  android:multiprocess="false"
                  android:exported="true"
                  android:singleUser="true"
                  android:initOrder="100"
                  android:visibleToInstantApps="true" />

    </application>
</manifest>

由上面Manifest配置的sharedUserId可知，SettingsProvider运行在系统进程中，定义的ContentProvider实现类是SettingsProvider。

（3）Code位置

在frameworks中跟Setting默认值相关的几个文件：

/frameworks/base/packages/SettingsProvider/res/values/defaults.xml
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
/frameworks/base/core/java/android/provider/Settings.java

（4）defaults.xml
在defaults.xml文件中定义了相关的值，DatabaseHelper.java会把相应的值读取出来保存到ContentProvider。

//frameworks/base/packages/SettingsProvider/res/values/defaults.xml
<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>
    <!-- 0 == off, 3 == on -->
    <integer name="def_location_mode">3</integer>
    <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">com.android.localtransport/.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">/product/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">/product/media/audio/ui/Dock.ogg</string>
    <string name="def_desk_undock_sound" translatable="false">/product/media/audio/ui/Undock.ogg</string>
    <string name="def_car_dock_sound" translatable="false">/product/media/audio/ui/Dock.ogg</string>
    <string name="def_car_undock_sound" translatable="false">/product/media/audio/ui/Undock.ogg</string>
    <integer name="def_lockscreen_sounds_enabled">1</integer>
    <string name="def_lock_sound" translatable="false">/product/media/audio/ui/Lock.ogg</string>
    <string name="def_unlock_sound" translatable="false">/product/media/audio/ui/Unlock.ogg</string>
    <string name="def_trusted_sound" translatable="false">/product/media/audio/ui/Trusted.ogg</string>
    <string name="def_wireless_charging_started_sound" translatable="false">/product/media/audio/ui/WirelessChargingStarted.ogg</string>
    <string name="def_charging_started_sound" translatable="false">/product/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>

    <!-- Default for Settings.Global.APPLY_RAMPING_RINGER -->
    <bool name="def_apply_ramping_ringer">false</bool>

    <!-- Default for Settings.Secure.CHARGING_VIBRATION_ENABLED -->
    <bool name="def_charging_vibration_enabled">true</bool>

    <!-- Default for Settings.Secure.CHARGING_SOUNDS_ENABLED -->
    <bool name="def_charging_sounds_enabled">true</bool>

    <!-- Default for Settings.Secure.NOTIFICATION_BUBBLES -->
    <bool name="def_notification_bubbles">true</bool>

    <!-- Default for Settings.Secure.AWARE_ENABLED -->
    <bool name="def_aware_enabled">false</bool>

    <!-- Default for Settings.Secure.SKIP_GESTURE -->
    <bool name="def_skip_gesture">false</bool>

    <!-- Default for Settings.Secure.SILENCE_GESTURE -->
    <bool name="def_silence_gesture">false</bool>

    <!-- Default for Settings.Secure.AWARE_LOCK_ENABLED -->
    <bool name="def_aware_lock_enabled">false</bool>

    <!-- Default for setting for Settings.Global.HDMI_CONTROL_AUTO_DEVICE_OFF_ENABLED -->
    <bool name="def_hdmiControlAutoDeviceOff">false</bool>
</resources>

（5）DatabaseHelper.java

//frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java

class DatabaseHelper extends SQLiteOpenHelper {
    private static final String TAG = "SettingsProvider";
    private static final String DATABASE_NAME = "settings.db";

	private static final int DATABASE_VERSION = 118;
	private static final String DATABASE_BACKUP_SUFFIX = "-backup";

    private static final String TABLE_SYSTEM = "system";
    private static final String TABLE_SECURE = "secure";
    private static final String TABLE_GLOBAL = "global";


	private void createSecureTable(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE secure (" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                "name TEXT UNIQUE ON CONFLICT REPLACE," +
                "value TEXT" +
                ");");
        db.execSQL("CREATE INDEX secureIndex1 ON secure (name);");
    }

    private void createGlobalTable(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE global (" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                "name TEXT UNIQUE ON CONFLICT REPLACE," +
                "value TEXT" +
                ");");
        db.execSQL("CREATE INDEX globalIndex1 ON global (name);");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE system (" +
                    "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                    "name TEXT UNIQUE ON CONFLICT REPLACE," +
                    "value TEXT" +
                    ");");
        db.execSQL("CREATE INDEX systemIndex1 ON system (name);");

        createSecureTable(db);

        // Only create the global table for the singleton 'owner/system' user
        if (mUserHandle == UserHandle.USER_SYSTEM) {
            createGlobalTable(db);
        }

        db.execSQL("CREATE TABLE bluetooth_devices (" +
                    "_id INTEGER PRIMARY KEY," +
                    "name TEXT," +
                    "addr TEXT," +
                    "channel INTEGER," +
                    "type INTEGER" +
                    ");");

        db.execSQL("CREATE TABLE bookmarks (" +
                    "_id INTEGER PRIMARY KEY," +
                    "title TEXT," +
                    "folder TEXT," +
                    "intent TEXT," +
                    "shortcut INTEGER," +
                    "ordering INTEGER" +
                    ");");

        db.execSQL("CREATE INDEX bookmarksIndex1 ON bookmarks (folder);");
        db.execSQL("CREATE INDEX bookmarksIndex2 ON bookmarks (shortcut);");

        // Populate bookmarks table with initial bookmarks
        boolean onlyCore = false;
        try {
            onlyCore = IPackageManager.Stub.asInterface(ServiceManager.getService(
                    "package")).isOnlyCoreApps();
        } catch (RemoteException e) {
        }
        if (!onlyCore) {
            loadBookmarks(db);
        }

        // Load initial volume levels into DB
        loadVolumeLevels(db);

        // Load inital settings values
        loadSettings(db);
    }

	//...
	private void loadSettings(SQLiteDatabase db) {
        loadSystemSettings(db);
        loadSecureSettings(db);
        // The global table only exists for the 'owner/system' user
        if (mUserHandle == UserHandle.USER_SYSTEM) {
            loadGlobalSettings(db);
        }
    }

private void loadSystemSettings(SQLiteDatabase db) {
        SQLiteStatement stmt = null;
        try {
            stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"
                    + " VALUES(?,?);");

            loadBooleanSetting(stmt, Settings.System.DIM_SCREEN,
                    R.bool.def_dim_screen);
            loadIntegerSetting(stmt, Settings.System.SCREEN_OFF_TIMEOUT,
                    R.integer.def_screen_off_timeout);

            // Set default cdma DTMF type
            loadSetting(stmt, Settings.System.DTMF_TONE_TYPE_WHEN_DIALING, 0);

            // Set default hearing aid
            loadSetting(stmt, Settings.System.HEARING_AID, 0);

            // Set default tty mode
            loadSetting(stmt, Settings.System.TTY_MODE, 0);

            loadIntegerSetting(stmt, Settings.System.SCREEN_BRIGHTNESS,
                    R.integer.def_screen_brightness);

            loadIntegerSetting(stmt, Settings.System.SCREEN_BRIGHTNESS_FOR_VR,
                    com.android.internal.R.integer.config_screenBrightnessForVrSettingDefault);

            loadBooleanSetting(stmt, Settings.System.SCREEN_BRIGHTNESS_MODE,
                    R.bool.def_screen_brightness_automatic_mode);

            loadBooleanSetting(stmt, Settings.System.ACCELEROMETER_ROTATION,
                    R.bool.def_accelerometer_rotation);

            loadDefaultHapticSettings(stmt);

            loadBooleanSetting(stmt, Settings.System.NOTIFICATION_LIGHT_PULSE,
                    R.bool.def_notification_pulse);

            loadUISoundEffectsSettings(stmt);

            loadIntegerSetting(stmt, Settings.System.POINTER_SPEED,
                    R.integer.def_pointer_speed);

        } finally {
            if (stmt != null) stmt.close();
        }
    }
}

在DatabaseHelper.java的方法中用于加载defaults.xml定义的相关字段。

（6）封装SettingsProvider接口（Settings.java）

对ContentProvider的一些接口进行封装，以保证在整个Android的java层任何一个地方都能方便、快捷的使用SettingsProvider进行数据查询，数据更新和数据插入。所以，framework有一个类Settings.java对SettingsProvider进行了封装。如下：

//frameworks/base/core/java/android/provider/Settings.java

/**
 * The Settings provider contains global system-level device preferences.
 */
public final class Settings {

	@SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
    public static final String ACTION_SETTINGS = "android.settings.SETTINGS";

	@SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
    public static final String ACTION_USER_SETTINGS =
            "android.settings.USER_SETTINGS";

	//...
	public static final class Global extends NameValueTable {
		
		public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/global");

		public static final String AIRPLANE_MODE_ON = "airplane_mode_on";
        public static final String THEATER_MODE_ON = "theater_mode_on";
		//...
	}

	public static final class System extends NameValueTable {
		public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/system");
	}

	public static final class Secure extends NameValueTable {
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/secure");
}

上面的代码中，分别声明了Global、Secure、System三个静态内部类，分别对应SettingsProvider中的Global、Secure、System三种数据类型。Global、Secure、System三个静态内部类会分别持有NameValueCache的实例变量，进而通过AIDL远程调用IContentProvider。

查询数据需要经过NameValueCache的getStringForUser()方法，插入数据需要经过putStringForUser()方法。

（7）操作SettingsProvider

由于Settings.java对SettingsProvider进行了封装，所以，使用起来相当简单简洁。Global、Secure、System三种数据类型的使用是几乎相同。

//查询数据
String globalValue = Settings.Global.getString(getContentResolver(), Settings.Global.AIRPLANE_MODE_ON);
//插入数据
boolean isSuccess = Settings.System.putInt(getContentResolver(), Settings.Global.AIRPLANE_MODE_ON, 1);