I am creating a login page which will have forgot password right now:
I would suggest using a
Fragment per page, so one for "Login" and one for "Forgot Password", and one
Activity that handles the async http request. You would then be able to use the fragment methods such as
fragment.replace() to swap out the screens without each fragment having to have a callback listener. The activity then can also parse the callback listener once instead of twice in each separate activity. Also, the way Android is heading, Fragments are better to use for UI elements than separate Activities as it makes UI updates quicker and smoother then starting a new activity.
There is an Android Developer API Guide loaders available to every Activity and Fragment. Why not check it out. On that same site you can also find guides to use fragments in your activity.