decrypt a encrypted database file by sqlcipher

decrypt.java

public void decrypt() {
    if(db.isOpen()) {
        File unencFile = mContext.getDatabasePath("decrypted.db");
        if(!unencFile.exists()) {
            db.rawExecSQL(String.format("ATTACH DATABASE '%s' as plaintext KEY '';", unencFile.getAbsolutePath()));
            db.rawExecSQL("SELECT sqlcipher_export('plaintext');");
            db.rawExecSQL("DETACH DATABASE plaintext;");
            android.database.sqlite.SQLiteDatabase sqlDB = android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(unencFile, null);
            sqlDB.close();
        }
    }
}