Android application identification phone dialer

Specification:

the application work as a identification phone dialer. the application will have a login screen which contain:
- a login field
- a password field
- login button
- a call button(which is unable while unlog)
- a link to register
the register is a simple form register.
when the user is logged, the number picker page show up, with :
- a text field to fill the number to call
- a button to vaidate the number(when clicked it get back to the login screen)
now the call button is enable and it can open the phone dialer with the selected number filled in.