Qustions on android

[Gunasundari]

I am new to android developement. I am stuck with mid of my development.

I am developing Login screen and Authentication screen. Once the user id is valid, then Login screen should proceed with Authentication Screen.

1. In the Login Activity, after entered the userid, this will check the userid with the backend process. For this thing, I have developed a java class with Xml parsing.
2. After xml parsing, it should route to Authentication screen for getting password.

In the xml parsing java class, i used

Intent myIntent = new Intent(context,AuthenticationActivity.class)
startActivity(myIntent);

But I got "Null Pointer Exception" at new Intent(). Please any one guide me on how to resolve this issue