/**
  * Close assets database
  *
  * @param dbfile, the assets file which will be closed soon
  * @return, the status of this operating
  */
 public boolean closeDatabase(String dbfile) {
   if (databases.get(dbfile) != null) {
     SQLiteDatabase db = (SQLiteDatabase) databases.get(dbfile);
     db.close();
     databases.remove(dbfile);
     return true;
   }
   return false;
 }
 /** Close all assets database */
 public static void closeAllDatabase() {
   if (SQLiteDebug.isDebug) {
     Log.i(TAG, "closeAllDatabase");
   }
   if (mInstance != null) {
     Set<String> set = mInstance.databases.keySet();
     Iterator<String> iterator = set.iterator();
     while (iterator.hasNext()) {
       String key = iterator.next();
       SQLiteDatabase db = mInstance.databases.get(key);
       if (db.isOpen()) {
         db.close();
       }
       iterator.remove();
     }
   }
 }