user login

Hello, I need to do an app that the user can change some values only if he login. The app works offline. It's not important to the user creat a login or not. I'm thinking in something that i can set the password on the code, the user just need to know this code. Can someone help me?

hi friends, i want to put a login screen to my simple ios and android app.i want to limited and filtered user should login.what do you offer me and any example ? thanks