同时打开两个db。

public static String MAIN_DB_PATH = "/data/data/cdc.workshopapps.BowersMfgHelper/databases/";

// database control
private DatabaseHelper mDbHelper;
private static SQLiteDatabase mDb;
private static Context mCtx;

private static class DatabaseHelper extends SQLiteOpenHelper {
    DatabaseHelper(Context context, String dbname, int dbversion) {
        super(context, dbname, null, dbversion);
        if (checkDataBase(dbname)) {
            openDataBase(dbname);
        } else {
            try {
                this.getReadableDatabase();
                copyDataBase(dbname);
                this.close();
                openDataBase(dbname);
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
            Toast.makeText(context,
                    "Initial " + dbname + " database has been created",
                    Toast.LENGTH_LONG).show();
        }
    }

@Override
    public void onCreate(SQLiteDatabase db) {
    }

@Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

public DBAdapter(Context ctx) {
    DBAdapter.mCtx = ctx;
}

public DBAdapter open(String dbname, int dbversion) throws SQLException {
    mDbHelper = new DatabaseHelper(mCtx, dbname, dbversion);
    mDb = mDbHelper.getWritableDatabase();
    return this;
}

public void close() {
    mDbHelper.close();
}

private static void copyDataBase(String dbname) throws IOException {
    InputStream myInput = mCtx.getAssets().open(dbname);
    String outFileName = MAIN_DB_PATH + dbname;
    OutputStream myOutput = new FileOutputStream(outFileName);

byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }

myOutput.flush();
    myOutput.close();
    myInput.close();
}

private static boolean checkDataBase(String dbname) {
    SQLiteDatabase checkDB = null;
    boolean exist = false;
    try {
        String db = MAIN_DB_PATH + dbname;
        checkDB = SQLiteDatabase.openDatabase(db, null,
                SQLiteDatabase.OPEN_READONLY);
    } catch (SQLiteException e) {
        Log.v("db log", "database does‘t exist");
    }

if (checkDB != null) {
        exist = true;
        checkDB.close();
    }
    return exist;
}

public static void openDataBase(String dbname) throws SQLException {
    String dbPath = MAIN_DB_PATH + dbname;
    mDb = SQLiteDatabase.openDatabase(dbPath, null,
            SQLiteDatabase.OPEN_READWRITE);
}

//  public Cursor fetchOffset(String part) throws SQLException {
//      Cursor mCursor = mDb.query(true, OFFSET_TABLE, new String[] {
//              OFFSET_ROWID, OFFSET_PART, SETUP_D1, SETUP_D2, SETUP_D3,
//              SETUP_D4, SETUP_D5, SETUP_D6, SETUP_D7, SETUP_D8, SETUP_D9,
//              SETUP_D10, SETUP_D11, SETUP_D12, SETUP_D13, SETUP_D14,
//              SETUP_D15, SETUP_D16, SETUP_D17, SETUP_D18, SETUP_D19,
//              SETUP_D20, SETUP_G54, SETUP_G55, SETUP_G56, SETUP_G57,
//              SETUP_G58, SETUP_G59, SETUP_G110, SETUP_G111, SETUP_G112,
//              SETUP_G113, SETUP_G114, SETUP_G115, SETUP_G116, SETUP_G117,
//              SETUP_G118, SETUP_G119, SETUP_G120, SETUP_G121, SETUP_G122,
//              SETUP_G123 }, OFFSET_PART + "= ‘" + part + "‘", null, null,
//              null, null, null);
//      if (mCursor != null) {
//          mCursor.moveToFirst();
//      }
//      return mCursor;
//  }