Android N SettingsProvider的数据保存

Android M之前SettingProvider数据储存的位置在手机目录/data/data/com.Android.providers.settings/databases下

不过目前的Android版本虽然也有这个目录，其中却没有对应的文件在，本文是看下当前的数据到底存储在哪里。

代码在在frameworks/base/packages/SettingsProvider

插入流程分析

从插入代码为线索分析：

frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.Java

 public Uri insert(Uri uri, ContentValues values) {
     ...
     switch (table) {
         ...
         case TABLE_SYSTEM: {
             if (insertSystemSetting(name, value, UserHandle.getCallingUserId())) {
                 return Uri.withAppendedPath(Settings.System.CONTENT_URI, name);
             }
         } break;
     ...
 }

只看system表的插入：

 private boolean insertSystemSetting(String name, String value, int requestingUserId) {
     ...
     return mutateSystemSetting(name, value, requestingUserId, MUTATION_OPERATION_INSERT);
 }

 private boolean mutateSystemSetting(String name, String value, int runAsUserId,
          int operation) {
       ...
              case MUTATION_OPERATION_INSERT: {
                  validateSystemSettingValue(name, value);
                  return mSettingsRegistry
                          .insertSettingLocked(SettingsRegistry.SETTINGS_TYPE_SYSTEM,
                                  owningUserId, name, value, getCallingPackage());
              }
       ...
  }

SettingsRegistry是内部类

 public boolean insertSettingLocked(int type, int userId, String name, String value,
     ...
     final boolean success = settingsState.insertSettingLocked(name, value, packageName);
     ...
 }

SettingsState是另一个文件

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

 public boolean insertSettingLocked(String name, String value, String packageName) {
     ...
     updateMemoryUsagePerPackageLocked(packageName, oldValue, value);
     scheduleWriteIfNeededLocked();
     ...
 }

 private void scheduleWriteIfNeededLocked() {
     if (!mDirty) {
         mDirty = true;
         writeStateAsyncLocked();
     }
 }

 private void writeStateAsyncLocked() {
     final long currentTimeMillis = SystemClock.uptimeMillis();

     if (mWriteScheduled) {
         mHandler.removeMessages(MyHandler.MSG_PERSIST_SETTINGS);

         // If enough time passed, write without holding off anymore.
         final long timeSinceLastNotWrittenMutationMillis = currentTimeMillis
                 - mLastNotWrittenMutationTimeMillis;
         if (timeSinceLastNotWrittenMutationMillis >= MAX_WRITE_SETTINGS_DELAY_MILLIS) {
             mHandler.obtainMessage(MyHandler.MSG_PERSIST_SETTINGS).sendToTarget();
             return;
         }

         // Hold off a bit more as settings are frequently changing.
         final long maxDelayMillis = Math.max(mLastNotWrittenMutationTimeMillis
                 + MAX_WRITE_SETTINGS_DELAY_MILLIS - currentTimeMillis, 0);
         final long writeDelayMillis = Math.min(WRITE_SETTINGS_DELAY_MILLIS, maxDelayMillis);

         Message message = mHandler.obtainMessage(MyHandler.MSG_PERSIST_SETTINGS);
         mHandler.sendMessageDelayed(message, writeDelayMillis);
     }
     ...
 }

两条分支，不过最终都是发送了个消息，消息处理中会调用doWriteState

 private void doWriteState() {
      ...
      AtomicFile destination = new AtomicFile(mStatePersistFile);
      ...
      FileOutputStream out = null;
      try {
          out = destination.startWrite();

          XmlSerializer serializer = Xml.newSerializer();
          serializer.setOutput(out, StandardCharsets.UTF_8.name());
          serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
          serializer.startDocument(null, true);
          serializer.startTag(null, TAG_SETTINGS);
          serializer.attribute(null, ATTR_VERSION, String.valueOf(version));

          final int settingCount = settings.size();
          for (int i = 0; i < settingCount; i++) {
              Setting setting = settings.valueAt(i);

              writeSingleSetting(mVersion, serializer, setting.getId(), setting.getName(),
                      setting.getValue(), setting.getPackageName());

              if (DEBUG_PERSISTENCE) {
                  Slog.i(LOG_TAG, "[PERSISTED]" + setting.getName() + "=" + setting.getValue());
              }
          }

          serializer.endTag(null, TAG_SETTINGS);
          serializer.endDocument();
          destination.finishWrite(out);
          ...
  }

一看到xml就终于知道，是写到了一个xml文件中，并不是写到sqlite中。

文件地址确认

SettingsState中的成员

 private final File mStatePersistFile;

这个成员是xml的写入文件

在SettingsProvider中

 private void ensureSettingsStateLocked(int key) {
     if (mSettingsStates.get(key) == null) {
         final int maxBytesPerPackage = getMaxBytesPerPackageForType(getTypeFromKey(key));
         SettingsState settingsState = new SettingsState(mLock, getSettingsFile(key), key,
                 maxBytesPerPackage);
         mSettingsStates.put(key, settingsState);
     }
 }

这个方法负责SettingsState的初始化

 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);
     } else if (isSecureSettingsKey(key)) {
         final int userId = getUserIdFromKey(key);
         return new File(Environment.getUserSystemDirectory(userId),
                 SETTINGS_FILE_SECURE);
     } else {
         throw new IllegalArgumentException("Invalid settings key:" + key);
     }
 }

从getSettingsFile中可以看到SettingsProvider三个表global，system和secure的文件，它们的路径是相同的，通过Environment.getUserSystemDirectory确立

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

 public static File getUserSystemDirectory(int userId) {
     return new File(new File(getSystemSecureDirectory(), "users"), Integer.toString(userId));
 }

 public static File getSystemSecureDirectory() {
     if (isEncryptedFilesystemEnabled()) { //加密文件系统分支，默认是关闭的
         return new File(SECURE_DATA_DIRECTORY, "system");
     } else {
         return new File(DATA_DIRECTORY, "system");
     }
 }

 private static final File DATA_DIRECTORY
         = getDirectory("ANDROID_DATA", "/data");

依据ANDROID_DATA环境变量获取路径，获取不到的话就默认为/data。

获取到DATA_DIRECTORY后，后续还要添加"/ " + "system" + "/" + "users" + "/" + userId的值

例如我测试的手机上是/data/system/users/0，该目录的settings_global.xml，settings_secure.xml和settings_system.xml三个xml文件就是SettingsProvider中的数据文件。