Create Login Form / View

Hello everyone!

I'm new to vaadin and read alot of articles. Is there some tutorial how to make simple login form/view? 
I tried to follow this tutorial : https://vaadin.com/wiki/-/wiki/Main/Creating%20a%20simple%20login%20view  but nothing good happened. I always received error - "Trying to navigate to unknown state '' and error view provider not present". 

Any help will be appreciated.
 

I recommend reading through the chapter about Navigator in the book of Vaadin. I haven't tried the code example myself, but a quick glance through it doesn't reveal anything that would be wrong.

The error message you are getting, is from the navigator. You are trying to navigate to a view, that is not registered (through navigator's addView method). If the user is trying to navigate to a view that doesn't exist, then the navigator forwards the user to an error view - but in your case, you have not defined an error view at all (or an error view provider).

Are you using the code example as it is or have you done any modifications to it? A wild guess is that you've modified the NAME variable

public class SimpleLoginMainView extends CustomComponent implements View {
    public static final String NAME = "";

The view's name is an empty string, which is also the "default view name", so in case you've modified the name to something else, such as "login", then you will receive the error message that you described. Navigating to http://localhost:8080/yourapp#!login should on the other hand work