android database rekey throws exception

    i have two database in my project 

    Database1 db1;
    db1.open();
    String newKey= "newKey";
    db1.rekey(currentKEy, newKey);
    db1.close();


    DataBase2 db2;
    db2.rekey(currentKEy, newKEy);

it is this for DB1 it is working fine, but for DB2 it throws Exception is it compulsory to open database before doing rekey....