SettingsProvider

本文主要是介绍SettingsProvider，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

Android Settings 系列文章：

Android Settings解析
SettingsIntelligence
SettingsProvider

首语

为啥要聊到这个模块呢？因为Settings里存在大量的设置项，这些设置项的状态需要保存，它们就是通过SettingsProvider来处理的。以状态栏显示电量百分比菜单为例（Battery->Battery percentage）,分析下它的状态保存。
本文以Android 13 SettingsProvider源码进行分析。

Settings模块调用

这个菜单的核心实现在BatteryPercentagePreferenceController.java中，可以发现菜单的状态保存实现在Settings类中，状态读取通过getInt方法，状态保存通过putInt方法，

public class BatteryPercentagePreferenceController extends BasePreferenceController implementsPreferenceControllerMixin, Preference.OnPreferenceChangeListener {@Overridepublic void updateState(Preference preference) {//菜单状态保存读取int setting = Settings.System.getInt(mContext.getContentResolver(),SHOW_BATTERY_PERCENT, 0);((SwitchPreference) preference).setChecked(setting == 1);}@Overridepublic boolean onPreferenceChange(Preference preference, Object newValue) {boolean showPercentage = (Boolean) newValue;//菜单状态保存Settings.System.putInt(mContext.getContentResolver(), SHOW_BATTERY_PERCENT,showPercentage ? 1 : 0);FeatureFactory.getFactory(mContext).getMetricsFeatureProvider().action(mContext, SettingsEnums.OPEN_BATTERY_PERCENTAGE, showPercentage);return true;}
}

Settings类分析

在Settings中可以看到，getInt最终实现是通过ContentProvider的query方法去查询数据，putInt方法同理。mProviderHolder通过NameValueCache构造函数传入，uri为"content://settings/system"。mCallGetCommand为CALL_METHOD_GET_GLOBAL，调用ContentProvider的call方法。mContentProvider是authority为settings的ContentProvider。这里其实就知道为啥跟SettingsProvider相关联了。

因为在SettingsProvider中，定义了一个SettingsProvider，authority为settings。

继续分析下Settings类，可以发现它只能保存int，float，string等基本类型的数据，同时以键值对的形式保存，Settings中定义了大量的设置项KEY。其次除了System类外还有Global，Secure，Config，Bookmarks类分别构造了不同URI操作数据。因为Settings对数据进行了分类。

System。包含各种系统设置。
Global。包含各种对用户公开的系统设置，第三方应用程序可以读取，不可以写入。
Secure。包含各种安全系统设置。第三方应用程序可以读取，不可以写入。
Config。配置系统设置。只有Android可以读取，特定的配置服务可以写入。
Bookmarks。用户定义的书签和快捷方式。每个书签的目标是一个 Intent URL，允许它是网页或特定的应用程序活动。

修改数据需要权限：

android.permission.WRITE_SETTINGS
android.permission.WRITE_SECURE_SETTINGS

public final class Settings {public static final class System extends NameValueTable {public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/system");public static int getInt(ContentResolver cr, String name, int def) {return getIntForUser(cr, name, def, cr.getUserId());}/** @hide */@UnsupportedAppUsagepublic static int getIntForUser(ContentResolver cr, String name, int def, int userHandle) {String v = getStringForUser(cr, name, userHandle);return parseIntSettingWithDefault(v, def);}  public static String getStringForUser(ContentResolver resolver, String name,int userHandle) {return sNameValueCache.getStringForUser(resolver, name, userHandle);}}public static final class Global extends NameValueTable {public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/global");  private static final NameValueCache sNameValueCache = new NameValueCache(CONTENT_URI,CALL_METHOD_GET_GLOBAL,CALL_METHOD_PUT_GLOBAL,CALL_METHOD_DELETE_GLOBAL,sProviderHolder,Global.class);}public static final class Secure extends NameValueTable {public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/secure");                } public static final class Config extends NameValueTable {public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/config");                       }    private static class NameValueCache {<T extends NameValueTable> NameValueCache(Uri uri, String getCommand,String setCommand, String deleteCommand, ContentProviderHolder providerHolder,Class<T> callerClass) {this(uri, getCommand, setCommand, deleteCommand, null, null, providerHolder,callerClass);}public String getStringForUser(ContentResolver cr, String name, final int userHandle) {IContentProvider cp = mProviderHolder.getProvider(cr);...if (mCallGetCommand != null) {b = cp.call(cr.getAttributionSource(),mProviderHolder.mUri.getAuthority(), mCallGetCommand, name,args);String value = b.getString(Settings.NameValueTable.VALUE);return value;}if (Settings.isInSystemServer() && Binder.getCallingUid() != Process.myUid()) {final long token = Binder.clearCallingIdentity();try {c = cp.query(cr.getAttributionSource(), mUri,SELECT_VALUE_PROJECTION, queryArgs, null);} finally {Binder.restoreCallingIdentity(token);}} else {c = cp.query(cr.getAttributionSource(), mUri,SELECT_VALUE_PROJECTION, queryArgs, null);}...}private static final class ContentProviderHolder {private final Object mLock = new Object();private final Uri mUri;private IContentProvider mContentProvider;public ContentProviderHolder(Uri uri) {mUri = uri;}public IContentProvider getProvider(ContentResolver contentResolver) {synchronized (mLock) {if (mContentProvider == null) {mContentProvider = contentResolver.acquireProvider(mUri.getAuthority());}return mContentProvider;}}
}

SettingsProvider模块分析

SettingsProvider模块源码为frameworks/base/packages/SettingsProvider/，模块名为SettingsProvider，包名为com.android.providers.settings，Manifest中定义了authority为settings的ContentProvider。

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

查看下SettingsProvider的实现，首先在onCreate方法中有迁移处理，用户相关监听，添加了两个服务SettingsService，DeviceConfigService。

public class SettingsProvider extends ContentProvider {@Overridepublic boolean onCreate() {...synchronized (mLock) {//迁移处理mSettingsRegistry.migrateAllLegacySettingsIfNeededLocked();mSettingsRegistry.syncSsaidTableOnStartLocked();}mHandler.post(() -> {//用户移除停止广播注册registerBroadcastReceivers();//用户限制变更监听startWatchingUserRestrictionChanges();});ServiceManager.addService("settings", new SettingsService(this));ServiceManager.addService("device_config", new DeviceConfigService(this));}
}

SettingsService类重写onShellCommand方法来处理adb shell 命令。

final public class SettingsService extends Binder {@Overridepublic void onShellCommand(FileDescriptor in, FileDescriptor out, FileDescriptor err,String[] args, ShellCallback callback, ResultReceiver resultReceiver) {(new MyShellCommand(mProvider, false)).exec(this, in, out, err, args, callback, resultReceiver);}
}

执行 adb shell settings，打印了以下command使用信息。可以使用这些命令快速进行数据操作。

Settings provider (settings) commands:helpPrint this help text.get [--user <USER_ID> | current] NAMESPACE KEYRetrieve the current value of KEY.put [--user <USER_ID> | current] NAMESPACE KEY VALUE [TAG] [default]Change the contents of KEY to VALUE.TAG to associate with the setting.{default} to set as the default, case-insensitive only for global/secure namespacedelete [--user <USER_ID> | current] NAMESPACE KEYDelete the entry for KEY.reset [--user <USER_ID> | current] NAMESPACE {PACKAGE_NAME | RESET_MODE}Reset the global/secure table for a package with mode.RESET_MODE is one of {untrusted_defaults, untrusted_clear, trusted_defaults}, case-insensitivelist [--user <USER_ID> | current] NAMESPACEPrint all defined keys.NAMESPACE is one of {system, secure, global}, case-insensitive

SettingsService进行了adb shell命令的扩展，让我们操作数据更加方便。DeviceConfigService同理，通过adb shell device_config查看command信息。

分析了SettingsProvider的onCreate方法后，再看下insert方法是如何插入数据的，它从uri取出table，对应不同uri为system/global/secure等。以插入global数据为例分析，System，Global等实现类似。operation来判断是增删改查那种操作，通过SettingsState类的insertSettingLocked方法来进行插入操作，而SettingsState是通过ensureSettingsStateLocked方法创建的，然后保存到mSettingsStates中。

public class SettingsProvider extends ContentProvider {public static final String TABLE_SYSTEM = "system";@Overridepublic Uri insert(Uri uri, ContentValues values) {...String table = getValidTableOrThrow(uri);switch (table) {case TABLE_GLOBAL: {if (insertGlobalSetting(name, value, null, false,UserHandle.getCallingUserId(), false, /* overrideableByRestore */ false)) {return Uri.withAppendedPath(Settings.Global.CONTENT_URI, name);}} break;}}private boolean insertGlobalSetting(String name, String value, String tag,boolean makeDefault, int requestingUserId, boolean forceNotify,boolean overrideableByRestore) {return mutateGlobalSetting(name, value, tag, makeDefault, requestingUserId,MUTATION_OPERATION_INSERT, forceNotify, 0, overrideableByRestore);}private boolean mutateGlobalSetting(String name, String value, String tag,boolean makeDefault, int requestingUserId, int operation, boolean forceNotify,int mode, boolean overrideableByRestore) {switch (operation) {//插入操作case MUTATION_OPERATION_INSERT: {return mSettingsRegistry.insertSettingLocked(SETTINGS_TYPE_GLOBAL,UserHandle.USER_SYSTEM, name, value, tag, makeDefault,callingPackage, forceNotify,CRITICAL_GLOBAL_SETTINGS, overrideableByRestore);}}}final class SettingsRegistry {private static final String SETTINGS_FILE_GLOBAL = "settings_global.xml";public boolean insertSettingLocked(int type, int userId, String name, String value,String tag, boolean makeDefault, String packageName, boolean forceNotify,Set<String> criticalSettings, boolean overrideableByRestore) {return insertSettingLocked(type, userId, name, value, tag, makeDefault, false,packageName, forceNotify, criticalSettings, overrideableByRestore);}public boolean insertSettingLocked(int type, int userId, String name, String value,String tag, boolean makeDefault, boolean forceNonSystemPackage, String packageName,boolean forceNotify, Set<String> criticalSettings, boolean overrideableByRestore) {...SettingsState settingsState = peekSettingsStateLocked(key);if (settingsState != null) {success = settingsState.insertSettingLocked(name, value,tag, makeDefault, forceNonSystemPackage, packageName, overrideableByRestore);}}@Nullableprivate SettingsState peekSettingsStateLocked(int key) {...if (!ensureSettingsForUserLocked(getUserIdFromKey(key))) {return null;}return mSettingsStates.get(key);}public boolean ensureSettingsForUserLocked(int userId) {...if (userId == UserHandle.USER_SYSTEM) {final int globalKey = makeKey(SETTINGS_TYPE_GLOBAL, UserHandle.USER_SYSTEM);ensureSettingsStateLocked(globalKey);}}private void ensureSettingsStateLocked(int key) {...if (mSettingsStates.get(key) == null) {final int maxBytesPerPackage = getMaxBytesPerPackageForType(getTypeFromKey(key));SettingsState settingsState = new SettingsState(getContext(), mLock,getSettingsFile(key), key, maxBytesPerPackage, mHandlerThread.getLooper());mSettingsStates.put(key, settingsState);}}private File getSettingsFile(int key) {if (isGlobalSettingsKey(key)) {final int userId = getUserIdFromKey(key);return new File(Environment.getUserSystemDirectory(userId),SETTINGS_FILE_GLOBAL);} else if (isSystemSettingsKey(key)) {final int userId = getUserIdFromKey(key);return new File(Environment.getUserSystemDirectory(userId),SETTINGS_FILE_SYSTEM);...}}}
}

继续分析SettingsState类的insertSettingLocked方法，先将数据保存到mSettings，创建了一个Handler延时加锁进行写数据操作，核心写数据操作在doWriteState方法里。mStatePersistFile是从SettingsState传递过来的，由创建SettingsState的ensureSettingsStateLocked方法可知，通过getSettingsFile创建mStatePersistFile，文件路径为用户系统目录(/data/system/users/0/)，文件名为settings_global.xml，然后在xml中进行写数据。

final class SettingsState {public boolean insertSettingLocked(String name, String value, String tag,boolean makeDefault, boolean forceNonSystemPackage, String packageName,boolean overrideableByRestore) {...mSettings.put(name, newState);scheduleWriteIfNeededLocked();}private void scheduleWriteIfNeededLocked() {...writeStateAsyncLocked();}private void writeStateAsyncLocked() {...Message message = mHandler.obtainMessage(MyHandler.MSG_PERSIST_SETTINGS);mHandler.sendMessageDelayed(message, writeDelayMillis);}private final class MyHandler extends Handler {@Overridepublic void handleMessage(Message message) {switch (message.what) {case MSG_PERSIST_SETTINGS: {Runnable callback = (Runnable) message.obj;doWriteState();if (callback != null) {callback.run();}}private void doWriteState() {synchronized (mLock) {version = mVersion;settings = new ArrayMap<>(mSettings);namespaceBannedHashes = new ArrayMap<>(mNamespaceBannedHashes);mDirty = false;mWriteScheduled = false;}synchronized (mWriteLock){AtomicFile destination = new AtomicFile(mStatePersistFile, mStatePersistTag);FileOutputStream out = null;try {out = destination.startWrite();TypedXmlSerializer serializer = Xml.resolveSerializer(out);serializer.startDocument(null, true);serializer.startTag(null, TAG_SETTINGS);serializer.attributeInt(null, ATTR_VERSION, version);final int settingCount = settings.size();for (int i = 0; i < settingCount; i++) {Setting setting = settings.valueAt(i);if (setting.isTransient()) {if (DEBUG_PERSISTENCE) {Slog.i(LOG_TAG, "[SKIPPED PERSISTING]" + setting.getName());}continue;}if (writeSingleSetting(mVersion, serializer, setting.getId(), setting.getName(),setting.getValue(), setting.getDefaultValue(), setting.getPackageName(),setting.getTag(), setting.isDefaultFromSystem(),setting.isValuePreservedInRestore())) {}}}serializer.endTag(null, TAG_SETTINGS);serializer.startTag(null, TAG_NAMESPACE_HASHES);for (int i = 0; i < namespaceBannedHashes.size(); i++) {String namespace = namespaceBannedHashes.keyAt(i);String bannedHash = namespaceBannedHashes.get(namespace);if (writeSingleNamespaceHash(serializer, namespace, bannedHash)) {}}}serializer.endTag(null, TAG_NAMESPACE_HASHES);serializer.endDocument();destination.finishWrite(out);}}

到这里，才知道数据是保存在xml文件中的，而并非数据库里。Global类型数据保存在settings_global.xml中，System类型数据保存在settings_system.xml中，Secure类型数据保存在settings_secure.xml中，都在用户系统目录(/data/system/users/0/)下保存，截取部分内容如下：

<settings version="213">
<setting id="127" name="adb_wifi_enabled" value="0" package="android" defaultValue="0" defaultSysSet="true" />
<setting id="44" name="low_battery_sound_timeout" value="0" package="android" defaultValue="0" defaultSysSet="true" />
<setting id="95" name="wear_os_version_string" value="" package="android" defaultValue="" defaultSysSet="true" />...
</settings>

查看时可能乱码，这是因为Android13保存的xml文件使用的是一种二进制格式，通过以下命令修改：

adb shell setprop persist.sys.binary_xml false

xml配置文件的格式就变为ASCII 码格式文件，就不会乱码可以正常查看了。

对于其它的query，update，delete方法，也不需赘述了，都是对mSettings进行操作，根据mSettings变化重新写入xml。核心实现都在SettingsState类中，通过锁来确保多个修改以原子方式持久保存到内存和磁盘中。

再看下call方法，前面Settings类中getStringForUser方法就调用了call方法去获取数据。method是区分各种类型数据操作的,不同类型数据操作有不同的method定义，之后的数据操作流程就和增删改查方法中的一致。

public class SettingsProvider extends ContentProvider {@Overridepublic Bundle call(String method, String name, Bundle args) {case Settings.CALL_METHOD_GET_GLOBAL: {Setting setting = getGlobalSetting(name);return packageValueForCallResult(setting, isTrackingGeneration(args));}case Settings.CALL_METHOD_PUT_GLOBAL: {String value = getSettingValue(args);String tag = getSettingTag(args);final boolean makeDefault = getSettingMakeDefault(args);final boolean overrideableByRestore = getSettingOverrideableByRestore(args);insertGlobalSetting(name, value, tag, makeDefault, requestingUserId, false,overrideableByRestore);break;}}
}

对SettingsProvider的基本方法分析以后，我们分析下数据迁移方法migrateLegacySettingsForUserIfNeededLocked，它在onCreate方法中调用。通过DatabaseHelper类获取数据库实例来操作数据库，在TABLE_GLOBAL表内查询name 、value列，然后通过SettingsState的insertSettingLocked方法将数据插入到xml，插入完成后删除数据库。

public class SettingsProvider extends ContentProvider {private static final boolean DROP_DATABASE_ON_MIGRATION = true;public static final String TABLE_GLOBAL = "global";private void migrateLegacySettingsForUserIfNeededLocked(int userId) {// Every user has secure settings and if no file we need to migrate.final int secureKey = makeKey(SETTINGS_TYPE_SECURE, userId);File secureFile = getSettingsFile(secureKey);if (SettingsState.stateFileExists(secureFile)) {return;}DatabaseHelper dbHelper = new DatabaseHelper(getContext(), userId);SQLiteDatabase database = dbHelper.getWritableDatabase();migrateLegacySettingsForUserLocked(dbHelper, database, userId);}private void migrateLegacySettingsForUserLocked(DatabaseHelper dbHelper,SQLiteDatabase database, int userId) {...if (userId == UserHandle.USER_SYSTEM) {final int globalKey = makeKey(SETTINGS_TYPE_GLOBAL, userId);ensureSettingsStateLocked(globalKey);SettingsState globalSettings = mSettingsStates.get(globalKey);migrateLegacySettingsLocked(globalSettings, database, TABLE_GLOBAL);// If this was just createdif (mSettingsCreationBuildId != null) {globalSettings.insertSettingLocked(Settings.Global.DATABASE_CREATION_BUILDID,mSettingsCreationBuildId, null, true,SettingsState.SYSTEM_PACKAGE_NAME);}globalSettings.persistSyncLocked();}// 已经迁移，删除数据库if (DROP_DATABASE_ON_MIGRATION) {dbHelper.dropDatabase();} else {dbHelper.backupDatabase();}private void migrateLegacySettingsLocked(SettingsState settingsState, SQLiteDatabase database, String table) {SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();queryBuilder.setTables(table);Cursor cursor = queryBuilder.query(database, LEGACY_SQL_COLUMNS,null, null, null, null, null);try {if (!cursor.moveToFirst()) {return;}final int nameColumnIdx = cursor.getColumnIndex(Settings.NameValueTable.NAME);final int valueColumnIdx = cursor.getColumnIndex(Settings.NameValueTable.VALUE);settingsState.setVersionLocked(database.getVersion());while (!cursor.isAfterLast()) {String name = cursor.getString(nameColumnIdx);String value = cursor.getString(valueColumnIdx);//插入数据到xmlsettingsState.insertSettingLocked(name, value, null, true,SettingsState.SYSTEM_PACKAGE_NAME);cursor.moveToNext();}} finally {cursor.close();}}}
}

那看下DatabaseHelper实现，数据库名为settings.db，onCreate方法中创建了多张表，还是以Global为例，其它同理。在global表插入数据，KEY一般都是在Settings中定义，VALUE则一般都是本地资源。给这些KEY对应的设置项添加了初始值。可以在res/values/defaults.xml文件中看到定义了大量菜单的初始值。

class DatabaseHelper extends SQLiteOpenHelper {private static final String DATABASE_NAME = "settings.db";@Overridepublic void onCreate(SQLiteDatabase db) {//创建表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);...//加载数据// Load initial volume levels into DBloadVolumeLevels(db);// Load inital settings valuesloadSettings(db);}private void loadSettings(SQLiteDatabase db) {loadSystemSettings(db);loadSecureSettings(db);// The global table only exists for the 'owner/system' userif (mUserHandle == UserHandle.USER_SYSTEM) {loadGlobalSettings(db);}}private void loadGlobalSettings(SQLiteDatabase db) {SQLiteStatement stmt = null;final Resources res = mContext.getResources();try {//插入sqlstmt = db.compileStatement("INSERT OR IGNORE INTO global(name,value)"+ " VALUES(?,?);");loadBooleanSetting(stmt, Settings.Global.AIRPLANE_MODE_ON,R.bool.def_airplane_mode_on);loadStringSetting(stmt, Settings.Global.AIRPLANE_MODE_TOGGLEABLE_RADIOS,R.string.airplane_mode_toggleable_radios);loadIntegerSetting(stmt, Settings.Global.WIFI_SLEEP_POLICY,R.integer.def_wifi_sleep_policy);...}private void loadBooleanSetting(SQLiteStatement stmt, String key, int resid) {loadSetting(stmt, key,mContext.getResources().getBoolean(resid) ? "1" : "0");} private void loadSetting(SQLiteStatement stmt, String key, Object value) {stmt.bindString(1, key);stmt.bindString(2, value.toString());//执行sqlstmt.execute();}
}