Android pin login activity

I would like java/xml android source for a simple PIN entry screen and example of use. This will be used for two situations in a larger project. 1) When logging in. 2) When the user has been idle for a period. Please read important additional requirement below. A PIN and a registration code will have been given to the user prior to them using the app. The PIN entry should be by a set of four (circle) icons that change appearance as the numerical pin is entered. (Soft keyboard should come up initially automatically) Importantly, if it is the first use, they need to also enter the registration code which along with the PIN will be used to retrieve their details (including a name for display, and possible later, choosing which registration). After the first use, they only need to enter a PIN to use the app. However they may enter a new registration (using a new registration code and PIN). Once there is more than one registration, they need to be able to select which registration every time they use it, but the default should be the registration used the previous time. If there is not more than one registration there is no need for the selection mechanism to be shown. I would like this to look beautiful. Selection of registration (if more than one to choose) could be via carousel or drop down with icon (with user initials) and name. The images included are of a working prototype to give an idea of what logic needs to be achieved. But obviously your solution will look way more beautiful. I would like to know your approach to this first impression which users will have.