SettingsProvider 之CachePrefetchThread

转载请注明出处:http://blog.csdn.net/droyon/article/details/35558595

1、总结:每一个表都有一个SettingsCache,例如:sSystemCaches.get(userHandle)、sSecureCaches.get(userHandler),然后检索system、secure表中内容,将这写内容写入cache中,最多无限制

class CachePrefetchThread extends Thread {
        private int mUserHandle;

        CachePrefetchThread(int userHandle) {
            super("populate-settings-caches");
            mUserHandle = userHandle;
        }

        @Override
        public void run() {
            fullyPopulateCaches(mUserHandle);
        }
    }
2、重要的成员变量
// 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);

3、填充内容:

private void fullyPopulateCaches(final int userHandle) {
        DatabaseHelper dbHelper = mOpenHelpers.get(userHandle);
        // Only populate the globals cache once, for the owning user
        if (userHandle == UserHandle.USER_OWNER) {
            fullyPopulateCache(dbHelper, TABLE_GLOBAL, sGlobalCache);
        }
        fullyPopulateCache(dbHelper, TABLE_SECURE, sSecureCaches.get(userHandle));
        fullyPopulateCache(dbHelper, TABLE_SYSTEM, sSystemCaches.get(userHandle));
    }

4、

// Slurp all values (if sane in number & size) into cache.
    private void fullyPopulateCache(DatabaseHelper dbHelper, String table, SettingsCache cache) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor c = db.query(
            table,
            new String[] { Settings.NameValueTable.NAME, Settings.NameValueTable.VALUE },
            null, null, null, null, null,
            "" + (MAX_CACHE_ENTRIES + 1) /* limit */);
        try {
            synchronized (cache) {
                cache.evictAll();
                cache.setFullyMatchesDisk(true);  // optimistic
                int rows = 0;
                while (c.moveToNext()) {//一直在插入,有多少,缓冲多少
                    rows++;
                    String name = c.getString(0);
                    String value = c.getString(1);
                    cache.populate(name, value);
                }
                if (rows > MAX_CACHE_ENTRIES) {
                    // Somewhat redundant, as removeEldestEntry() will
                    // have already done this, but to be explicit:
                    //有些多余,因为 removeEldestEntry() 会已经这样做,但是要做到明确:
                    cache.setFullyMatchesDisk(false);
                    Log.d(TAG, "row count exceeds max cache entries for table " + table);
                }
                if (LOCAL_LOGV) Log.d(TAG, "cache for settings table '" + table
                        + "' rows=" + rows + "; fullycached=" + cache.fullyMatchesDisk());
            }
        } finally {
            c.close();
        }
    }


你可能感兴趣的:(SettingsProvider 之CachePrefetchThread)