[Mugala]

firstly you have to check if the player is registered or not (in your database)
than you must show the correct dialog with first statement (registered or not registered)
you must use DIALOG_STYLE_PASSWORD or DIALOG_STYLE_INPUT in ShowPlayerDialog.
LOGIN: at the callback OnDialogResponse you must compare output and player's password.
REGISTER: you must create player's account with the typed password (typed thing in code is 'output' in OnDialogResponse)