using findviewbyid in a class that does NOT extend Activity in android

you should pass the instance of your Activity to your Second Class on the constructor like this :

In your Activity Instanciate your Class like this :

MyClass instance = new MyClass(this);

And in your second Class , the constructor will be like this :

public class MyClass {

public Activity activity; 
//.... other attributes 

public MyClass( Activity _activity){

   this.activity = _activity;
//other initializations...

}
}

and then when you want to use the findViewById() method , you can do like this :

EditText txt = (EditText)this.activity.findViewById(R.id.txt);