SettingsProvider之多用户概念

转载请注明出处：http://blog.youkuaiyun.com/droyon/article/details/35558671

1、

• // Each defined user has their own settings

    protected final SparseArray<DatabaseHelper> mOpenHelpers = new SparseArray<DatabaseHelper>();

• private static final SparseArray<SettingsCache> sSystemCaches

            = new SparseArray<SettingsCache>();

•     private static final SparseArray<SettingsCache> sSecureCaches

            = new SparseArray<SettingsCache>();

•     private static final SettingsCache sGlobalCache = new SettingsCache(TABLE_GLOBAL);
• // The count of how many known (handled by SettingsProvider)
      // database mutations are currently being handled for this user.
      // Used by file observers to not reload the database when it's ourselves
      // modifying it.
      private static final SparseArray<AtomicInteger> sKnownMutationsInFlight
              = new SparseArray<AtomicInteger>();//用户评判是否为用户操作
  

2、删除用户时，同步更新所有存储用户概念的变量

void onUserRemoved(int userHandle) {
        synchronized (this) {
            // the db file itself will be deleted automatically, but we need to tear down
            // our caches and other internal bookkeeping.
            FileObserver observer = sObserverInstances.get(userHandle);
            if (observer != null) {
                observer.stopWatching();
                sObserverInstances.delete(userHandle);
            }

            mOpenHelpers.delete(userHandle);
            sSystemCaches.delete(userHandle);
            sSecureCaches.delete(userHandle);
            sKnownMutationsInFlight.delete(userHandle);
        }
    }

3、establishDbTracking(UserHandle.USER_OWNER);

private void establishDbTracking(int userHandle) {
        if (LOCAL_LOGV) {
            Slog.i(TAG, "Installing settings db helper and caches for user " + userHandle);
        }

        DatabaseHelper dbhelper;

        synchronized (this) {
            dbhelper = mOpenHelpers.get(userHandle);//每个user有一个dbHelper，如果为null，重新创建一个
            if (dbhelper == null) {
                dbhelper = new DatabaseHelper(getContext(), userHandle);
                mOpenHelpers.append(userHandle, dbhelper);

                sSystemCaches.append(userHandle, new SettingsCache(TABLE_SYSTEM));
                sSecureCaches.append(userHandle, new SettingsCache(TABLE_SECURE));
                sKnownMutationsInFlight.append(userHandle, new AtomicInteger(0));
            }
        }

        // Initialization of the db *outside* the locks.  It's possible that racing
        // threads might wind up here, the second having read the cache entries
        // written by the first, but that's benign: the SQLite helper implementation
        // manages concurrency itself, and it's important that we not run the db
        // initialization with any of our own locks held, so we're fine.
        SQLiteDatabase db = dbhelper.getWritableDatabase();

        // Watch for external modifications to the database files,
        // keeping our caches in sync.  We synchronize the observer set
        // separately, and of course it has to run after the db file
        // itself was set up by the DatabaseHelper.
        synchronized (sObserverInstances) {
            if (sObserverInstances.get(userHandle) == null) {//FileObserver如果为null，创建一个。
                SettingsFileObserver observer = new SettingsFileObserver(userHandle, db.getPath());
                sObserverInstances.append(userHandle, observer);
                observer.startWatching();
            }
        }

        ensureAndroidIdIsSet(userHandle);

        startAsyncCachePopulation(userHandle);
    }

4、存储一个随机的AndroidId。

private boolean ensureAndroidIdIsSet(int userHandle) {
        final Cursor c = queryForUser(Settings.Secure.CONTENT_URI,
                new String[] { Settings.NameValueTable.VALUE },
                Settings.NameValueTable.NAME + "=?",
                new String[] { Settings.Secure.ANDROID_ID }, null,
                userHandle);
        try {
            final String value = c.moveToNext() ? c.getString(0) : null;
            if (value == null) {
                // sanity-check the user before touching the db
                final UserInfo user = mUserManager.getUserInfo(userHandle);
                if (user == null) {
                    // can happen due to races when deleting users; treat as benign
                    return false;
                }

                final SecureRandom random = new SecureRandom();
                final String newAndroidIdValue = Long.toHexString(random.nextLong());
                final ContentValues values = new ContentValues();
                values.put(Settings.NameValueTable.NAME, Settings.Secure.ANDROID_ID);
                values.put(Settings.NameValueTable.VALUE, newAndroidIdValue);
                final Uri uri = insertForUser(Settings.Secure.CONTENT_URI, values, userHandle);
                if (uri == null) {
                    Slog.e(TAG, "Unable to generate new ANDROID_ID for user " + userHandle);
                    return false;
                }
                Slog.d(TAG, "Generated and saved new ANDROID_ID [" + newAndroidIdValue
                        + "] for user " + userHandle);
                // Write a dropbox entry if it's a restricted profile
                if (user.isRestricted()) {
                    DropBoxManager dbm = (DropBoxManager)
                            getContext().getSystemService(Context.DROPBOX_SERVICE);
                    if (dbm != null && dbm.isTagEnabled(DROPBOX_TAG_USERLOG)) {
                        dbm.addText(DROPBOX_TAG_USERLOG, System.currentTimeMillis()
                                + ",restricted_profile_ssaid,"
                                + newAndroidIdValue + "\n");
                    }
                }
            }
            return true;
        } finally {
            c.close();
        }
    }

5、为用户将Settings中的内容，更新到SettingsCache中；

private void startAsyncCachePopulation(int userHandle) {
        new CachePrefetchThread(userHandle).start();
    }